Search Results (10)

Ascochyta blight (AB) is a major threat to Kabuli-type chickpea production worldwide. This study aimed to identify AB-resistant Kabuli-type chickpea lines through combined phenotypic and genotypic screening. Twenty-six Kabuli-type chickpea lines were phenotyped at the seedling stage using spray inoculation with conidial suspension. Genotyping employed marker-aided selection (MAS) with markers linked to quantitative trait loci (QTL) for AB resistance. The allele-specific marker, CaETR, closely linked to QTLAR1, and the sequence-tagged microsatellite (STMS) markers GAA47, TAA146, and TA194 linked to QTLAR1, QTLAR2, and QTLAR3 were used to assess their utility in distinguishing between resistant and susceptible chickpea lines. The study revealed that none of the lines tested were completely resistant (R) phenotypically. However, some lines, such as AVTCPK#6 and AVTCPK#14, were found to be moderately resistant (MR). Of the two MR lines identified phenotypically, only AVTCPK#6 was found to have bands linked to QTLs for adult plant resistance. The other MR line for AB showed the presence of bands in only one or two of the four markers used. These MR lines can be further utilized in chickpea breeding programs for the development of AB-resistant chickpea cultivars. It is recommended that these results be verified through repeat experiments, using more diverse isolates, and including additional chickpea lines as reference checks for resistance and susceptibility. The allele-specific marker, CaETR, closely linked to QTL_AR1 and sequence-tagged microsatellite (STMS) markers GAA47, TAA146 and TA194 linked to QTL_AR1, QTL_AR2, and QTL_AR3 were used to explore these markers’ utility in discriminating between resistant and susceptible chickpea lines. The study showed that phenotypically, none of the lines tested are completely resistant (R). However, some lines, namely AVTCPK#6 and AVTCPK#14, were found to be moderately resistant (MR). Of the two MR lines identified phenotypically, only AVTCPK#6 was identified to have bands linked to QTLs for adult plant resistance. The other MR line for AB showed the presence of bands in only one or two markers among the four markers used. These MR lines can be exploited further in chickpea breeding programs for the development of AB-resistant chickpea cultivars. It is recommended that these results are verified by repeat experiments, using more as well as diverse isolates alongside additional chickpea lines for resistant and susceptible reference checks. Full article

The endophytic fungal biodiversity of unique plants like Peperomia argyreia (Miq.) É. Morren (Piperaceae) has antimicrobial properties and can be employed for infection treatment. Fungal isolates were obtained from appropriately treated plant tissues cultured in solid media, characterized by morphology, and identified by molecular biology using ITS and NL primers. The antimicrobial properties of fungal extracts were analyzed by combining microdilution and bioautographic assays complemented with metabolic profiling by automated thin-layer chromatography and ¹H NMR techniques. Thirty-one filamentous fungi were isolated and characterized by ITS and/or D1/D2 region amplification of rDNA, identified as Thermothielavioides, Trichoderma, Cyphellophora, Cladosporium, Arcopilus, Plectosphaerella; Chaetomium, Sporothrix, Alboefibula, and Penicillium. Thermothielavioides spp. inhibited Staphylococcus aureus ATCC 25923; moreover, Penicillium westlingii P4 showed inhibitory activity on Ascochyta rabiei AR2. The bioactivity-guided fractionation of the EtOAc extract (MIC = 62.5 μg/mL) of P. westlingii P4 allowed the purification of citrinin as the main inhibitory compound (MIC = 62.5 μg/mL). Peperomia argyreia harbors a rich and diverse endophytic community able to produce bioactive molecules. Citrinin, with a minor influence of volatile compounds biosynthesized by P. westlingii P4, was responsible for the inhibition of A. rabiei AR2. Full article

The molecular mechanism involved in chickpea (Cicer arietinum L.) resistance to the necrotrophic fungal pathogen Ascochyta rabiei is not well documented. A. rabiei infection can cause severe damage in chickpea, resulting in significant economic losses. Understanding the resistance mechanism against ascochyta blight can help to define strategies to develop resistant cultivars. In this study, differentially expressed genes from two partially resistant cultivars (CDC Corinne and CDC Luna) and a susceptible cultivar (ICCV 96029) to ascochyta blight were identified in the early stages (24, 48 and 72 h) of A. rabiei infection using RNA-seq. Altogether, 3073 genes were differentially expressed in response to A. rabiei infection across different time points and cultivars. A larger number of differentially expressed genes (DEGs) were found in CDC Corinne and CDC Luna than in ICCV 96029. Various transcription factors including ERF, WRKY, bHLH and MYB were differentially expressed in response to A. rabiei infection. Genes involved in pathogen detection and immune signalings such as receptor-like kinases (RLKs), Leucine-Rich Repeat (LRR)-RLKs, and genes associated with the post-infection defence response were differentially expressed among the cultivars. GO functional enrichment and pathway analysis of the DEGs suggested that the biological processes such as metabolic process, response to stimulus and catalytic activity were overrepresented in both resistant and susceptible chickpea cultivars. The expression patterns of eight randomly selected genes revealed by RNA-seq were confirmed by quantitative PCR (qPCR) analysis. The results provide insights into the complex molecular mechanism of the chickpea defence in response to the A. rabiei infection. Full article

Chickpea (Cicer arietinum L.), one of the most cultivated legumes worldwide, is crucial for the economy of several countries and a valuable source of nutrients. Yields may be severely affected by Ascochyta blight, a disease caused by the fungus Ascochyta rabiei. Molecular and pathological studies have not yet managed to establish its pathogenesis, since it is highly variable. Similarly, much remains to be elucidated about plant defense mechanisms against the pathogen. Further knowledge of these two aspects is fundamental for the development of tools and strategies to protect the crop. This review summarizes up-to-date information on the disease’s pathogenesis, symptomatology, and geographical distribution, as well as on the environmental factors that favor infection, host defense mechanisms, and resistant chickpea genotypes. It also outlines existing practices for integrated blight management. Full article

Chickpea (Cicer arietinum) is a globally important food legume but its yield is negatively impacted by the fungal pathogen Ascochyta blight (Ascochyta rabiei) causing necrotic lesions leading to plant death. Past studies have found that Ascochyta resistance is polygenic. It is important to find new resistance genes from the wider genepool of chickpeas. This study reports the inheritance of Ascochyta blight resistance of two wide crosses between the cultivar Gokce and wild chickpea accessions of C. reticulatum and C. echinospermum under field conditions in Southern Turkey. Following inoculation, infection damage was scored weekly for six weeks. The families were genotyped for 60 SNPs mapped to the reference genome for quantitative locus (QTL) mapping of resistance. Family lines showed broad resistance score distributions. A late responding QTL on chromosome 7 was identified in the C. reticulatum family and three early responding QTLs on chromosomes 2, 3, and 6 in the C. echinospermum family. Wild alleles mostly showed reduced disease severity, while heterozygous genotypes were most diseased. Interrogation of 200k bp genomic regions of the reference CDC Frontier genome surrounding QTLs identified nine gene candidates involved in disease resistance and cell wall remodeling. This study identifies new candidate chickpea Ascochyta blight resistance QTLs of breeding potential. Full article

The Protected Geographical Indication (PGI) Fuentesaúco-Chickpea (F-C) includes a legume crop developed in the south of the province of Zamora (Spain), of great agronomic, economic, and cultural importance for the area, as well as gastronomically on a global scale. Its cultivation is mainly affected by the fungal diseases called fusariosis (caused by Fusarium oxysporum f. sp. ciceri) and rabies (caused by Ascochyta rabiei). Through an in vitro antagonism study, we were able to select the species Trichoderma atroviride, T. hamatum, T. harzianum, and T. koningii as the most effective against both pathogens, thanks to mechanisms of action such as mycoparasitism, antibiosis, and/or competition for space and/or nutrients. Subsequently, these four species were used in studies with F-C plants and both pathogens, inoculating Trichoderma radicularly. Using this methodology, we described how T. atroviride and T. koningii were able to control F. oxysporum f. sp. ciceri both directly and by activating plant defenses, in the case of T. koningii. On the other hand, the species T. hazianum and T. koningii were able to significantly reduce foliar infection with A. rabiei, by activating systemic plant defense responses. Regarding the productivity of F-C, the species T. hamatum and T. koningii were able to significantly increase the formation of grains in each plant. Therefore, T. koningii is capable of controlling both pathogens under greenhouse conditions, in addition to increasing their productivity. Full article

Ascochyta blight, also known as chickpea blight, which is caused by the fungal pathogen, Didymella rabiei, is an important disease affecting chickpea (Cicer arietinum L.) in many countries. We studied the genetic diversity and population structure of 96 D. rabiei isolates collected from three geographic populations in Ethiopia using simple sequence repeat (SSR) markers. We confirmed the genetic identity of 89 of the D. rabiei isolates by sequencing their rRNA internal transcribed spacer region genes. The chickpea blight pathogen isolates were genetically diverse, with a total of 51 alleles identified across 6 polymorphic SSR loci, which varied from 3 to 18 (average 8.5) alleles per SSR marker. The observed heterozygosity and expected heterozygosity ranged from 0.01 to 0.92 and 0.19 to 0.86, respectively. The mean polymorphic information content value of the D. rabiei populations was 0.58, with a mean gene diversity of 0.61 among loci. Gene flow (Nm = number of migrants) for the three populations of D. rabiei isolates ranged from 1.51 to 24.10 (average 6.2) migrants/cluster. However, the genetic variation between the D. rabiei populations was small (8%), with most of the variation occurring within populations (92%). Principal component analysis to visualize genetic variation showed that the D. rabiei isolates obtained from most of the chickpea samples formed roughly three groups on a two-dimensional coordinate plane. Similarly, the clustering of individuals into populations based on multi-locus genotypes (using Clumpak) grouped isolates into three clusters but with individual isolate admixtures. Hence, no clear geographic origin-based structuring of populations could be identified. To our knowledge, this is the first report of D. rabiei diversity in Ethiopia. Virulence studies should be conducted to develop chickpea varieties that are resistant to more aggressive pathogen populations. Full article

Ascochyta blight caused by Ascochyta rabiei is an important disease of chickpea. By using systems analysis, we retrieved and analyzed the published information on A. rabiei to develop a mechanistic, weather-driven model for the prediction of Ascochyta blight epidemics. The ability of the model to predict primary infections was evaluated using published data obtained from trials conducted in Washington (USA) in 2004 and 2005, Israel in 1996 and 1998, and Spain from 1988 to 1992. The model showed good accuracy and specificity in predicting primary infections. The probability of correctly predicting infections was 0.838 and the probability that there was no infection when not predicted was 0.776. The model’s ability to predict disease progress during the growing season was also evaluated by using data collected in Australia from 1996 to 1998 and in Southern Italy in 2019; a high concordance correlation coefficient (CCC = 0.947) between predicted and observed data was obtained, with an average distance between real and fitted data of root mean square error (RMSE) = 0.103, indicating that the model was reliable, accurate, and robust in predicting seasonal dynamics of Ascochyta blight epidemics. The model could help growers schedule fungicide treatments to control Ascochyta blight on chickpea. Full article

In many plant–pathogen interactions, the host resistance is governed by a combinatorial action of multiple genes termed as quantitative disease resistance (QDR). Three decades of genetic research on economically important interaction of chickpea (Cicer arietinum L.) and Ascochyta rabiei has revealed quantitative nature of host resistance. Despite various genomic studies in chickpea-Ascochyta system, identification of narrowed QTL/gene remains elusive. We utilized a next-generation genomic tool, namely multiple quantitative trait loci sequencing (mQTL-seq), to trounce the hurdles in revealing QDR genes against Ascochyta blight (AB). The mQTL-seq analysis revealed two major QTLs (qABR4.1 and qABR4.2) and a novel minor QTL (qABR4.3) on assembled Ca4 chickpea chromosome that provides resistance against AB. Under the major qABR4.1, a transcriptional regulator CaAHL18 was identified as a candidate gene and CaNIP8 marker was developed from its polymorphic cis-regulatory region for molecular breeding. We are further fine-mapping the major qABR4.2 (27.55–33.49 Mb) and novel minor qABR4.3 (38.78–39.48 Mb) to elucidate the candidate genes and their molecular mechanism of resistance. Up until now, the second major QTL, qABR4.2 is narrowed to ~1.41 Mb from 5.41 Mb region via utilizing bi-parental CRIL-7 population genotyping and association analysis in various chickpea accessions. Further, to translate the obtained genetic information from our AB resistance study, we intend to introgress multiple fungal resistance loci (for AB and FW resistant desi accessions) in few selected higher yielding cultivated chickpea varieties. Our combinatorial approaches have helped in overcoming the chickpea-AB genetic mapping associated problems of AB resistance loci fine-mapping and their utilization in molecular breeding. Consequently, our work will provide landmark information on chickpea AB resistance for the convenience of biotechnologists and breeders. Full article

Ascochyta blight (AB) caused by Ascochyta rabiei (Pass.) Labr. is an important and widespread disease of chickpea (Cicer arietinum L.) worldwide. The disease is particularly severe under cool and humid weather conditions. Breeding for host resistance is an efficient means to combat this disease. In this paper, attempts have been made to summarize the progress made in identifying resistance sources, genetics and breeding for resistance, and genetic variation among the pathogen population. The search for resistance to AB in chickpea germplasm, breeding lines and land races using various screening methods has been updated. Importance of the genotype × environment (GE) interaction in elucidating the aggressiveness among isolates from different locations and the identification of pathotypes and stable sources of resistance have also been discussed. Current and modern breeding programs for AB resistance based on crossing resistant/multiple resistant and high-yielding cultivars, stability of the breeding lines through multi-location testing and molecular marker-assisted selection method have been discussed. Gene pyramiding and the use of resistant genes present in wild relatives can be useful methods in the future. Identification of additional sources of resistance genes, good characterization of the host–pathogen system, and identification of molecular markers linked to resistance genes are suggested as the key areas for future study. Full article