Search Results (14)

Sugarcane, a key cash crop in tropical and subtropical regions, is primarily cultivated for sucrose and bioethanol. However, Sugarcane Leaf Scald Disease, caused by the Gram-negative bacterium Xanthomonas albilineans, significantly threatens global sugarcane production. This review examines the disease cycle, epidemics, host–pathogen interactions, integrated management strategies, and future prospects for combating leaf scald. It highlights advancements in understanding pathogenicity, immune responses, and sustainable management of bacterial plant diseases to enhance control and prevention efforts. An analysis of GenBank data revealed 21 strains of X. albilineans, with some featuring complete genome maps and varying guanine-cytosine (GC) content. Advanced genomic tools, including clustered regularly interspaced short palindromic repeats (CRISPR), and molecular techniques, such as polymerase chain reaction (PCR), enable accurate pathogen detection and facilitate the identification of resistance genes, aiding breeding programs. Recent progress in whole-genome sequencing and reduced costs have enabled the assembly of multiple X. albilineans genomes, enhancing bioinformatics analysis. Despite these advancements, research on the global genetic diversity of X. albilineans remains limited. Addressing this gap is crucial for developing more sustainable strategies to manage leaf scald, ensuring stable sugarcane yields and supporting global production. Further studies will strengthen efforts to mitigate this significant agricultural challenge. Full article

Plants must adapt to the complex effects of several stressors brought on by global warming, which may result in interaction and superposition effects between diverse stressors. Few reports are available on how drought stress affects Xanthomonas albilineans (Xa) infection in sugarcane (Saccharum spp. hybrids). Drought and leaf scald resistance were identified on 16 sugarcane cultivars using Xa inoculation and soil drought treatments, respectively. Subsequently, four cultivars contrasting to drought and leaf scald resistance were used to explore the mechanisms of drought affecting Xa–sugarcane interaction. Drought stress significantly increased the occurrence of leaf scald and Xa populations in susceptible cultivars but had no obvious effect on resistant cultivars. The ROS bursting and scavenging system was significantly activated in sugarcane in the process of Xa infection, particularly in the resistant cultivars. Compared with Xa infection alone, defense response via the ROS generating and scavenging system was obviously weakened in sugarcane (especially in susceptible cultivars) under Xa infection plus drought stress. Collectively, ROS might play a crucial role involving sugarcane defense against combined effects of Xa infection and drought stress. Full article

Selecting appropriate donors and acquiring information about the genetic basis of inheritance is essential for breeding programs. In this study, a diallel cross was produced by crossing 15 progenies with five commercial lines of wide diversity for different rice traits (grain yield, plant height, days to flowering, panicle blast, brown spots, leaf scald, and grain discoloration) in an incomplete crossing design. The 20 parents and the 25 F₂ crosses constituting the diallel cross were evaluated in a triple lattice design for different traits in a field test. The analysis of variance revealed significant differences between parents and their crosses for all traits, showing high variability. The general combining ability ($GCA$) and the specific combining ability ($SCA$) were significant, with a greater contribution of the $SCA$ compared to $GCA$ for the variation among crosses, indicating that non-additive effects were more prevalent for the traits evaluated. The results suggested that commercial lines such as IRGA 424 and BRS Catiana can be used to improve CNA 12T population. Full article

Leaf scald caused by Xanthomonas albilineans (Xa) is a major bacterial disease in sugarcane that represents a threat to the global sugar industry. Little is known about the population structure and genetic evolution of this pathogen. In this study, 39 Xa strains were collected from 6 provinces in China. Of these strains, 15 and 24 were isolated from Saccharum spp. hybrid and S. officinarum plants, respectively. Based on multilocus sequence analysis (MLSA), with five housekeeping genes, these strains were clustered into two distinct phylogenetic groups (I and II). Group I included 26 strains from 2 host plants, Saccharum spp. hybrid and S. officinarum collected from 6 provinces, while Group II consisted of 13 strains from S. officinarum plants in the Zhejiang province. Among the 39 Xa strains, nucleotide sequence identities from 5 housekeeping genes were: ABC (99.6–100%), gyrB (99.3–100%), rpoD (98.4–100%), atpD (97.0–100%), and glnA (97.6–100%). These strains were clustered into six groups (A–F), based on the rep-PCR fingerprinting, using primers for ERIC2, BOX A1R, and (GTG)5. UPGMA and PCoA analyses revealed that group A had the most strains (24), followed by group C with 11 strains, while there was 1 strain each in groups B and D–F. Neutral tests showed that the Xa population in S. officinarum had a trend toward population expansion. Selection pressure analysis showed purification selection on five concatenated housekeeping genes from all tested strains. Significant genetic differentiation and infrequent gene flow were found between two Xa populations hosted in Saccharum spp. hybrids and S. officinarum. Altogether, these results provide evidence of obvious genetic divergence and population structures among Xa strains from China. Full article

Sugarcane leaf scald is a systemic disease caused by Xanthomonas albilineans that limits sugarcane yield and quality. Previous research has shown that exogenous application of copper hydroxide to plants is effective in controlling this disease. However, long-term bactericide use causes serious “3R” problems: resistance, resurgence, and residue. It is therefore urgent to discover new methods for the improvement of bactericide efficiency and efficacy. In the present study, disease index values for leaf scald were measured in sugarcane seedlings over time to determine the effects of different concentrations of copper hydroxide, types of silicon additive, and treatment timing after inoculation with X. albilineans on controlling sugarcane leaf scald disease. Our results show copper hydroxide mixed with organosilicon additive could improve the bactericide efficiency and efficacy and reduce the growth of pathogenic bacteria, even at a reduced concentration in both laboratory and field conditions. This study provides an important practical model for controlling sugarcane leaf scald disease by reducing the concentration of bactericide and increasing its efficacy in sugarcane fields. Full article

Rice is considered one the most important plants globally because it is a source of food for over half the world’s population. Like other plants, rice is susceptible to diseases that may affect the quantity and quality of produce. It sometimes results in anywhere between 20–40% crop loss production. Early detection of these diseases can positively affect the harvest, and thus farmers would have to be knowledgeable about the various disease and how to identify them visually. Even then, it is an impossible task for farmers to survey the vast farmlands on a daily basis. Even if this is possible, it becomes a costly task that will, in turn, increases the price of rice for consumers. Machine learning algorithms fitted to drone technology combined with the Internet of Things (IoT) can offer a solution to this problem. In this paper, we propose a Deep Convolutional Neural Network (DCNN) transfer learning-based approach for the accurate detection and classification of rice leaf disease. The modified proposed approach includes a modified VGG19-based transfer learning method. The proposed modified system can accurately detect and diagnose six distinct classes: healthy, narrow brown spot, leaf scald, leaf blast, brown spot, and bacterial leaf blight. The highest average accuracy is 96.08% using the non-normalized augmented dataset. The corresponding precision, recall, specificity, and F1-score were 0.9620, 0.9617, 0.9921, and 0.9616, respectively. The proposed modified approach achieved significantly better results compared with similar approaches using the same dataset or similar-size datasets reported in the extant literature. Full article

Barley is one of the most important cereal crops globally. In Ukraine, it is grown on an area of 2.4–2.8 million hectares annually and is the second largest grain crop in Ukraine after wheat. Barley grain export is about 4.3 million tons p.a. At the same time, one of the limiting factors for obtaining a high-quality yield is diseases, in particular leaf spots. In recent decades, there have been significant changes in the technology of cultivation, the composition of varieties and the pathogenic complex. Net blotch (Pyrenophora teres Drechsler) in net and spot forms and spot blotch (Bipolaris sorokiniana Shoem.) remain the most common among the diseases of barley leaves. They occur in all regions where barley is grown. Barley scald (Rhynchosporium secalis (Oudem.) Davis) is distributed mainly in the forest zone and western part of the forest-steppe zone and has become more widespread in recent years with rainy summers. Outbreaks of stripe spot (Pyrenophora graminea S. Ito & Kurib.) occur sporadically. Ascochyta leaf spot (Ascochyta spp.) was found in the Lviv and Dnipropetrovsk regions in 2020, and in the Lviv, Donetsk and Zaporizhia regions in 2021. In the field, spots can be misdiagnosed as barley scald, so their prevalence may be much higher. In 2021, during the seed ripening period, ramularia leaf spot was found in the Kherson and Vinnytsia regions. The disease was diagnosed in the laboratory by obtaining a typical conidial sporulation of the fungus Ramularia collo-cygni B. Sutton & J.M. Waller on affected tissues (wet chamber). Therefore, in recent years, the composition of the barley leaf spot pathogens has become wider and requires further investigation. Full article

Powdery mildew, net blotch, scald, spot blotch, barley stripe, and leaf rust are important foliar fungal pathogens of barley. Fungal leaf pathogens negatively affect the yield and quality in barley plant. Virulence changes, which can occur in various ways, may render resistant plants to susceptible ones. Factors such as mutation, population size and random genetic drift, gene and genotype flow, reproduction and mating systems, selection imposed by major gene resistance, and quantitative resistance can affect the genetic diversity of the pathogenic fungi. The use of fungicide or disease-resistant barley genotypes is an effective method of disease control. However, the evolutionary potential of pathogens poses a risk to overcome resistance genes in the plant and to neutralize fungicide applications. Factors affecting the genetic diversity of the pathogen fungus may lead to the emergence of more virulent new pathotypes in the population. Understanding the factors affecting pathogen evolution, monitoring pathogen biology, and genetic diversity will help to develop effective control strategies. Full article

Malt barley is one of the promising crops in Greece, mainly due to high yields and contract farming, which have led to an increase in malt barley acreage. Net form net blotch (NFNB), caused by Pyrenophora teres f. teres, and barley leaf scald, caused by Rhynchosporium secalis, are among the most important barley diseases worldwide and particularly in Greece. Their occurrence in malt barley can exert a significant negative effect on malt barley grain yield and quality. An experimental trial across two growing seasons was implemented in Greece in order (i) to estimate the epidemiology of NFNB and leaf scald in a barley disease-free area when the initial inoculation of the field occurs through infected seeds, (ii) to explore the spatial dynamics of disease spread under the interaction of the nitrogen rate and genotype when there are limited sources of infected host residues in the soil and (iii) to assess the relationship among the nitrogen rate, grain yield, quality variables (i.e., grain protein content and grain size) and disease severity. It was confirmed that both NFNB and leaf scald can be carried over from one season to the next on infected seed under Mediterranean conditions. However, the disease severity was more pronounced after the barley tillering phase when the soil had been successfully inoculated, which supports the hypothesis that the most important source of primary inoculum for NFNB comes from infected host residue. Increasing the rate of nitrogen application, when malt barley was cultivated in the same field for a second year in a row, caused a non-significant increase in disease severity for both pathogens from anthesis onwards. However, hotspot and commonality analyses revealed that spatial and genotypic effects were mainly responsible for hiding this effect. In addition, it was found that the effect of disease infections on yield, grain size and grain protein content varied in relation to the genotype, pathogen and stage of crop development. The importance of crop residues in the evolution of both diseases was also highlighted. Full article

Leaf scald (caused by Xanthomonas albilineans) is an important bacterial disease affecting sugarcane in most sugarcane growing countries, including China. High genetic diversity exists among strains of X. albilineans from diverse geographic regions. To highlight the genomic features associated with X. albilineans from China, we sequenced the complete genome of a representative strain (Xa-FJ1) of this pathogen using the PacBio and Illumina platforms. The complete genome of strain Xa-FJ1 consists of a circular chromosome of 3,724,581 bp and a plasmid of 31,536 bp. Average nucleotide identity analysis revealed that Xa-FJ1 was closest to five strains from the French West Indies and the USA, particularly to the strain GPE PC73 from Guadeloupe. Comparative genomic analysis between Xa-FJ1 and GPE PC73 revealed prophage integration, homologous recombination, transposable elements, and a clustered regulatory interspaced short palindromic repeats (CRISPR) system that were linked with 16 insertions/deletions (InDels). Ten and 82 specific genes were found in Xa-FJ1 and GPE PC73, respectively, and some of these genes were subjected to phage-related proteins, zona occludens toxin, and DNA methyltransferases. Our findings highlight intra-species genetic variability of the leaf scald pathogen and provide additional genomic resources to investigate its fitness and virulence. Full article

Sugarcane can suffer severe yield losses when affected by leaf scald, a disease caused by Xanthomonas albilineans. This bacterial pathogen colonizes the vascular system of sugarcane, which can result in reduced plant growth and plant death. In order to better understand the molecular mechanisms involved in the resistance of sugarcane to leaf scald, a comparative proteomic study was performed with two sugarcane cultivars inoculated with X. albilineans: one resistant (LCP 85-384) and one susceptible (ROC20) to leaf scald. The iTRAQ (isobaric tags for relative and absolute quantification) approach at 0 and 48 h post-inoculation (hpi) was used to identify and annotate differentially expressed proteins (DEPs). A total of 4295 proteins were associated with 1099 gene ontology (GO) terms by GO analysis. Among those, 285 were DEPs during X. albilineans infection in cultivars LCP 85-384 and ROC20. One hundred seventy-two DEPs were identified in resistant cultivar LCP 85-384, and 113 of these proteins were upregulated and 59 were downregulated. One hundred ninety-two DEPs were found in susceptible cultivar ROC20 and half of these (92) were upregulated, whereas the other half corresponded to downregulated proteins. The significantly upregulated DEPs in LCP 85-384 were involved in metabolic pathways, the biosynthesis of secondary metabolites, and the phenylpropanoid biosynthesis pathway. Additionally, the expression of seven candidate genes related to photosynthesis and glycolytic pathways, plant innate immune system, glycosylation process, plant cytochrome P450, and non-specific lipid transfer protein was verified based on transcription levels in sugarcane during infection by X. albilineans. Our findings shed new light on the differential expression of proteins in sugarcane cultivars in response to infection by X. albilineans. The identification of these genes provides important information for sugarcane variety improvement programs using molecular breeding strategies. Full article

Sugarcane (Saccharum spp. hybrids) is a major source of sugar and renewable bioenergy crop worldwide and suffers serious yield losses due to many pathogen infections. Leaf scald caused by Xanthomonas albilineans is a major bacterial disease of sugarcane in most sugarcane-planting countries. The molecular mechanisms of resistance to leaf scald in this plant are, however, still unclear. We performed a comparative transcriptome analysis between resistant (LCP 85-384) and susceptible (ROC20) sugarcane cultivars infected by X. albilineans using the RNA-seq platform. 24 cDNA libraries were generated with RNA isolated at four time points (0, 24, 48, and 72 h post inoculation) from the two cultivars with three biological replicates. A total of 105,783 differentially expressed genes (DEGs) were identified in both cultivars and the most upregulated and downregulated DEGs were annotated for the processes of the metabolic and single-organism categories, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the 7612 DEGs showed that plant–pathogen interaction, spliceosome, glutathione metabolism, protein processing in endoplasmic reticulum, and plant hormone signal transduction contributed to sugarcane’s response to X. albilineans infection. Subsequently, relative expression levels of ten DEGs determined by quantitative reverse transcription-PCR (qRT-PCR), in addition to RNA-Seq data, indicated that different plant hormone (auxin and ethylene) signal transduction pathways play essential roles in sugarcane infected by X. albilineans. In conclusion, our results provide, for the first time, valuable information regarding the transcriptome changes in sugarcane in response to infection by X. albilineans, which contribute to the understanding of the molecular mechanisms underlying the interactions between sugarcane and this pathogen and provide important clues for further characterization of leaf scald resistance in sugarcane. Full article

The aim of the present study was to investigate the effects of magnesium on the gas exchange and photosynthetic efficiency of Coffee seedlings grown in nutrient solution under different light levels. The experiment was conducted under controlled conditions in growth chambers and nutrient solution at the Department of Plant Pathology of the Federal University of Lavras. The treatments consisted of five different Mg concentrations (0, 48, 96, 192 and 384 mg·L⁻¹) and four light levels (80, 160, 240 and 320 µmol photon m⁻²·s⁻¹). Both the Mg concentration and light levels affected gas exchange in the coffee plants. Photosynthesis increased linearly with the increasing light, indicating that the light levels tested were low for this crop. The highest CO₂ assimilation rate, lowest transpiration, and highest water use efficiency were observed with 250 mg·Mg·L⁻¹, indicating that this concentration was the optimal Mg supply for the tested light levels. Full article

Xanthomonas albilineans is the bacterium responsible for leaf scald, a lethal disease of sugarcane. Within the Xanthomonas genus, X. albilineans exhibits distinctive genomic characteristics including the presence of significant genome erosion, a non-ribosomal peptide synthesis (NRPS) locus involved in albicidin biosynthesis, and a type 3 secretion system (T3SS) of the Salmonella pathogenicity island-1 (SPI-1) family. We sequenced two X. albilineans-like strains isolated from unusual environments, i.e., from dew droplets on sugarcane leaves and from the wild grass Paspalum dilatatum, and compared these genomes sequences with those of two strains of X. albilineans and three of Xanthomonas sacchari. Average nucleotide identity (ANI) and multi-locus sequence analysis (MLSA) showed that both X. albilineans-like strains belong to a new species close to X. albilineans that we have named “Xanthomonas pseudalbilineans”. X. albilineans and “X. pseudalbilineans” share many genomic features including (i) the lack of genes encoding a hypersensitive response and pathogenicity type 3 secretion system (Hrp-T3SS), and (ii) genome erosion that probably occurred in a common progenitor of both species. Our comparative analyses also revealed specific genomic features that may help X. albilineans interact with sugarcane, e.g., a PglA endoglucanase, three TonB-dependent transporters and a glycogen metabolism gene cluster. Other specific genomic features found in the “X. pseudalbilineans” genome may contribute to its fitness and specific ecological niche. Full article