The Diversity of Culture-Dependent Gram-Negative Rhizobacteria Associated with Manihot esculenta Crantz Plants Subjected to Water-Deficit Stress

There is a lack of studies on the root-associated bacterial microbiome of cassava plants. The identification and characterization of rhizobacteria can contribute to understanding the adaptation of the agriculturally important crop plants to abiotic stress. Rhizobacteria play a significant role in plants, as they can alleviate the drought stress by various mechanisms that enhance the plant growth under these stressor conditions. In this study, Gram-negative bacterial strains from the plant rhizosphere of cassava Manihot esculenta Crantz CIAT MCOL1734 variety subjected to water deprivation were isolated, characterized according to their morphological properties, and then identified by VITEK® 2. An increase in the diversity, abundance, and species richness of Gram-negative rhizobacterial community was found in cassava plants subjected to water-deficit stress. In total, 58 rhizobacterial strains were isolated from cassava plants. The identification process found that the bacteria belonged to 12 genera: Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas. Interestingly, Pseudomonas luteola and Ocrhobactrum anthropi were rhizobacteria isolated exclusively from plants submitted to drought conditions. The cassava roots constitute a great reservoir of Gram-negative bacteria with a remarkable potential for biotechnological application to improve the drought tolerance of plant crops under water-deficit conditions.


Introduction
Cassava (Manihot esculenta Crantz) is widely grown in subtropical and tropical areas worldwide, including Africa, Asia, Latin America, and the Caribbean [1,2]. In these regions, the cassava root is one of the most essential sources of calories after rice and corn and provides staple food to an estimated 800 million people [1]. In addition, the top biomass including leaves and immature stems may be used as the cassava hay for animal feeding [2,3].
The cassava crops are well adapted to several agroecological conditions; even its potential to adapt well to climate change is a factor that favors the increased production of cassava [1]. However, several factors, such as salinity and drought, may cause crop yield losses of more than 50% worldwide [4,5]. Despite these reasons, cassava can withstand relatively prolonged periods of drought during the first three months; however, after planting, the cassava crop is very sensitive to the soil water deficit [1, [5][6][7]. At any time during this early establishment period, the water-deficit stress may affect the root system development, significantly reducing the growth of roots and shoots and, subsequently, the storage roots [1,8]. After this time, a water-deficit causes turgor loss, diminished water potential, disruption of membrane integrity along with protein denaturation, and stomatal

Identification (VI-TEK ® 2)
cp-c-1 cp-c-1. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables 1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report. The Pielou evenness index was derived from the Shannon diversity index and was calculated as follows: were H' is the Shannon diversity index, pi is the relative impo1rtance value of species i, J' is the Pielou evenness index, H'max = ln(S), and S is the total number of species in ith plot. Statistically significant differences of the bacterial diversity in cp-c and cp-ds, comparing independently T0 and T20, were analyzed and compared using Shannon diversity index through the Hutcheson t-test [49]. p-values ≤ 0.05 were considered statistically significant. All calculations were performed with the R-Project free software Version 1.1.463.

Strain Isolation, Morphological Characterization, and Biochemical Identification
In total, 58 rhizobacterial strains were obtained from the rhizoplane and endorhizosphere of casava roots, and most of them were grown on different media (Tables 1 and 2). Based on the colony morphology on NA, AMA, KAB, and EMB media, all isolates had different morphological characteristics, including round-to-irregular colonies with flat and raised elevations, smooth and irregular surfaces, and diversity of size (Tables 1 and  2). Several isolates produced pigments, with colonies that were white, off-white, milky white, purple, pink-purple, reddish, and yellowish in color, but some isolates did not produce any pigmentation (Tables 1 and 2). All isolates reacted negatively to Gram staining but reacted positively and negatively to the catalase and oxidase tests, respectively (Tables  1 and 2). VITEK ® 2 identification showed that the isolates were mainly the members of genus Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas (Tables 1 and 2). The probability levels of discrimination for all strains were ≥95% according to the VITEK ® 2 system report.

Strains Diversity at the Beginning of the Drought Stress Assay (T0)
In total, 18 strains were isolated from the rhizoplane and endorhizosphere of cassava roots at T0, with 33.3% and 66.6% of bacteria isolated from roots of cp-c and cp-ds plants, respectively (Table 1). All isolates were identified at the species level using VITEK ® 2. Concerning to identified isolates from the control plants, six rhizobacterial strains were the members of genus Pseudomonas, including four of Pseudomonas fluorescens, one of Pseudomonas putida, and one of Pseudomonas mendocina (Table 1). Contrariwise, 12 isolates were identified from the roots of cp-ds plants at the beginning of the assay. Members of the identified rhizobacteria in these plants were dominated by the genus Pseudomonas (50%), including species such as P. putida (n = 5) and P. fluorescens (n = 1). Moreover, species such as Sphingomonas paucimobilis (n = 4), Achromobacter xylosoxidans (n = 1), and Rhizobium radiobacter (n = 1) were also identified ( Table 1). All the isolates produced colonies with different morphological characteristics (Table 1). According to the relative abundances, Pseudomonas and Sphingomonas were the predominant bacterial genera found in roots of cp-c and cp-ds plants at T0 (Figure 1).

Strains Diversity at the Beginning of the Drought Stress Assay (T0)
In total, 18 strains were isolated from the rhizoplane and endorhizosphere of cassava roots at T0, with 33.3% and 66.6% of bacteria isolated from roots of cp-c and cp-ds plants, respectively (Table 1). All isolates were identified at the species level using VITEK ® 2. Concerning to identified isolates from the control plants, six rhizobacterial strains were the members of genus Pseudomonas, including four of Pseudomonas fluorescens, one of Pseudomonas putida, and one of Pseudomonas mendocina (Table 1). Contrariwise, 12 isolates were identified from the roots of cp-ds plants at the beginning of the assay. Members of the identified rhizobacteria in these plants were dominated by the genus Pseudomonas (50%), including species such as P. putida (n = 5) and P. fluorescens (n = 1). Moreover, species such as Sphingomonas paucimobilis (n = 4), Achromobacter xylosoxidans (n = 1), and Rhizobium radiobacter (n = 1) were also identified ( Table 1). All the isolates produced colonies with different morphological characteristics (Table 1). According to the relative abundances, Pseudomonas and Sphingomonas were the predominant bacterial genera found in roots of cp-c and cp-ds plants at T0 (Figure 1).

Strains Diversity at the Beginning of the Drought Stress Assay (T0)
In total, 18 strains were isolated from the rhizoplane and endorhizosphere of cassava roots at T0, with 33.3% and 66.6% of bacteria isolated from roots of cp-c and cp-ds plants, respectively (Table 1). All isolates were identified at the species level using VITEK ® 2. Concerning to identified isolates from the control plants, six rhizobacterial strains were the members of genus Pseudomonas, including four of Pseudomonas fluorescens, one of Pseudomonas putida, and one of Pseudomonas mendocina (Table 1). Contrariwise, 12 isolates were identified from the roots of cp-ds plants at the beginning of the assay. Members of the identified rhizobacteria in these plants were dominated by the genus Pseudomonas (50%), including species such as P. putida (n = 5) and P. fluorescens (n = 1). Moreover, species such as Sphingomonas paucimobilis (n = 4), Achromobacter xylosoxidans (n = 1), and Rhizobium radiobacter (n = 1) were also identified ( Table 1). All the isolates produced colonies with different morphological characteristics (Table 1). According to the relative abundances, Pseudomonas and Sphingomonas were the predominant bacterial genera found in roots of cp-c and cp-ds plants at T0 (Figure 1).

Strains Diversity at the Beginning of the Drought Stress Assay (T0)
In total, 18 strains were isolated from the rhizoplane and endorhizosphere of cassava roots at T0, with 33.3% and 66.6% of bacteria isolated from roots of cp-c and cp-ds plants, respectively (Table 1). All isolates were identified at the species level using VITEK ® 2. Concerning to identified isolates from the control plants, six rhizobacterial strains were the members of genus Pseudomonas, including four of Pseudomonas fluorescens, one of Pseudomonas putida, and one of Pseudomonas mendocina (Table 1). Contrariwise, 12 isolates were identified from the roots of cp-ds plants at the beginning of the assay. Members of the identified rhizobacteria in these plants were dominated by the genus Pseudomonas (50%), including species such as P. putida (n = 5) and P. fluorescens (n = 1). Moreover, species such as Sphingomonas paucimobilis (n = 4), Achromobacter xylosoxidans (n = 1), and Rhizobium radiobacter (n = 1) were also identified ( Table 1). All the isolates produced colonies with different morphological characteristics (Table 1). According to the relative abundances, Pseudomonas and Sphingomonas were the predominant bacterial genera found in roots of cp-c and cp-ds plants at T0 (Figure 1).

Strains Diversity at the Beginning of the Drought Stress Assay (T0)
In total, 18 strains were isolated from the rhizoplane and endorhizosphere of cassava roots at T0, with 33.3% and 66.6% of bacteria isolated from roots of cp-c and cp-ds plants, respectively (Table 1). All isolates were identified at the species level using VITEK ® 2. Concerning to identified isolates from the control plants, six rhizobacterial strains were the members of genus Pseudomonas, including four of Pseudomonas fluorescens, one of Pseudomonas putida, and one of Pseudomonas mendocina (Table 1). Contrariwise, 12 isolates were identified from the roots of cp-ds plants at the beginning of the assay. Members of the identified rhizobacteria in these plants were dominated by the genus Pseudomonas (50%), including species such as P. putida (n = 5) and P. fluorescens (n = 1). Moreover, species such as Sphingomonas paucimobilis (n = 4), Achromobacter xylosoxidans (n = 1), and Rhizobium radiobacter (n = 1) were also identified ( Table 1). All the isolates produced colonies with different morphological characteristics (Table 1). According to the relative abundances, Pseudomonas and Sphingomonas were the predominant bacterial genera found in roots of cp-c and cp-ds plants at T0 (Figure 1).