Response of Desi and Kabuli chickpea genotypes to Ascochyta rabiei isolates and their association with molecular markers in Guanajuato, Mexico

Background/Objective. Ascochyta blight of chickpea (Cicer arietinum), caused by Ascochyta rabiei, can result in yield losses of up to 100% under favorable environmental conditions. In Mexico, particularly in Guanajuato, symptoms consistent with this disease have been observed; however, few scientific reports have documented the presence of the pathogen and the level of resistance in national germplasm. Given that genetic resistance represents a viable and costeffective alternative for disease management, identifying germplasm with favorable responses and evaluating tools that support its selection are of particular importance. Therefore, the objective of this study was to determine the response of 68 Desi and Kabuli chickpea genotypes to A. rabiei isolates and to evaluate the association between molecular markers and resistance in Guanajuato, Mexico. Materials and Methods. During 2015–2016, chickpea plants exhibiting typical symptoms of Ascochyta blight, including necrotic lesions with pycnidia, were collected from five municipalities in Guanajuato, Mexico. The isolates were purified using the single-conidium technique and identified as A. rabiei based on their cultural and morphological characteristics. Virulence was evaluated using the detached-leaf assay, and the most virulent isolate was used to inoculate 68 chickpea genotypes under greenhouse conditions. DNA was analyzed using the molecular markers SCY17, CaETR, TR-19, TA-59, and TA-72. Associations between molecular markers and phenotypic resistance were assessed using the chi-square test. Sensitivity, specificity, positive predictive value, and the Matthews correlation coefficient were also calculated. Results. Five isolates of A. rabiei were obtained. The isolates from Celaya and Salvatierra exhibited the highest virulence. Of the 68 genotypes evaluated, 29 were resistant, all belonging to the Desi type; none of the Kabuli genotypes showed resistance. The CaETR marker had the highest positive predictive value (PPV = 68.8%) and showed a significant association with resistance (p = 0.0012), whereas SCY17 exhibited a lower PPV (47.1%), although its association was also significant (p = 0.0206). The STMS markers (TR-19, TA-59, and TA-72) showed no significant association (p > 0.05). Conclusion. This study provides phytopathological evidence of the presence of at least five isolates of A. rabiei in Guanajuato, Mexico. Of the 68 genotypes evaluated, 29 were resistant and belonged to the Desi type (brown-seeded; severity ≤3), five were intermediate (severity 4–6), and 34 were susceptible (severity ≥7). The CaETR marker (1034-bp allele) showed the best relative performance among the markers evaluated, making it a candidate for further validation and potential application in marker-assisted selection of Desi chickpea germplasm.