Biochemical defense response and genetic basis of resistance against Ascochyta blight (Ascochyta rabiei (Pass.) Labr.) in chickpea (Cicer arietinum L.)
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Date
2024
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Punjab Agricultural University
Abstract
Chickpea (Cicer arietinum L.), the second-largest global pulse crop, is under threat from highly variable nature of Ascochyta rabiei, causing widespread disease damage under favourable environmental conditions. This disease, Ascochyta blight is a major concern worldwide, with insufficient resistant sources and frequent breakdowns due to rapid pathogen evolution. This study evaluated 238 kabuli chickpea genotypes for resistance to Ascochyta blight (AB) over the growing seasons from 2019-2022 at Punjab Agricultural University under artificial epiphytotic conditions, identifying 18 resistant lines (GLK 10-40, GLK 20054, GLK 20055, FLIP 10-298C-IFC-S2, FLIP 10298C-IFC-S1, CS-3-E-24, FLIP 09 256C-55, FLIP 07-314C-57, FLIP 10-243C, FLIP 09-194C, FLIP 08-104C, FLIP 04-219C, ICCV 55233, ICCV 55215, ICCV 55135, ICCV 55108 and ICCV 155141) belonging to different genetic backgrounds with disease scores of 1.0 to 3.0, whereas seventy-three (73) lines demonstrated a moderate level of disease resistance with a disease rating of 3.1-5.0. The activities of defense-related enzymes (PAL, TAL, PPO, POD) associated with phenol metabolism along with lignin and total phenol content were compared among six kabuli chickpea lines, viz., five resistant (GLK 10-40, GLK 20055, FLIP-09-194C, FLIP-04-219C, ICCV 55215) and one susceptible (GLK 17301) treated lines that exhibited differential responses to Ascochyta blight at tested time intervals of 48, 96, 144 and 240 hr post-inoculation respectively. The perusal of data showed increased activity of all enzymes (PAL, TAL, PPO, POD) till 96 hr after inoculation, whereas the non-enzymatic contents such as lignin and total phenols showed the maximum enzyme activity till 144 hr after inoculation. However, enzyme and non-enzymatic activity remained almost constant with no significant difference in all control/untreated resistant and susceptible line(s) at different time intervals. For understanding the genetic basis of resistance, the F2 population comprising of 162 plants derived from the cross, GLK 24096 (resistant) and L 556 (susceptible) was assessed under artificially epiphytotic conditions against local isolate of Ascochyta rabiei. Of 162 plants evaluated, 39 plants were grouped in resistant (R ) category (disease score ≤ 5.0 ) and 123 were classified as susceptible (S) with score of five and above. Consequently, the F2 plants exhibited a segregation ratio of 1R:3S, suggesting that a monogenic recessive gene governed resistance to Ascochyta blight. Of thirty four SSR markers associated with Quantitative Trait Loci (QTLs)/genes were used for confirmation of resistance in identified eighteen resistant and six susceptible lines, only 19 SSR markers depicted polymorphism. Notably, SSR markers, STMS11, TA194, TS12, TA146, and TA2 exhibiting significant polymorphism, indicated tight linkage to Ascochyta blight resistance. Phylogenetic analysis showcased distinct clustering based on resistance, offering insights into the genetic basis of resistance. These findings informed about targeted resistance breeding and sustainable disease management with defence-related enzymes/identified markers holding promise for developing superior, resistant and resilient chickpea varieties contributing to crop sustainability and productivity.
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Abassy, Omer (2024). Biochemical defense response and genetic basis of resistance against Ascochyta blight (Ascochyta rabiei (Pass.) Labr.) in chickpea (Cicer arietinum L.) (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.