Identification and quantification of resistance against Ascochyta blight complex in garden pea (Pisum sativum L.)

Abstract

One hundred elite pea genotypes were evaluated under natural as well as artificial epiphytotic conditions for three consecutive seasons to determine their relative resistance to the three predominant concurrently infecting pathogens associated with blight complex, Didymella pinodes, D. pinodella and Ascochyta pisi. Disease reaction under natural epiphytotic conditions varied with percent disease incidence and severity ranging from 38.45 to 89.45% and 11.59 to 55.14%, respectively, among test genotypes. Among the test genotypes, wide variation in the susceptibility index (Sx), area under disease progress curve (AUDPC), and relative area under disease progress curve (RAUDPC), apparent rate of infection (r), disease incidence, disease severity, percent stem girdling (%HTM) and incubation period (IP50) was recorded under artificial epiphytotic field conditions. Field trials conducted both under natural and artificial epiphytic conditions, five genotypes, namely, Eddy, PS-24, Arya Veer, CHPMR-2 and PS-19, showed consistent resistance with susceptibility index (Sx) values less than 2 and r between 0.06 to 0.08. CHPMR-2 showed a maximum incubation period of 7.46 days and a minimum percent stem girdling of 7.03%. A positive correlation between AUDPC and stem girdling, as well as disease severity, whereas AUDPC was negatively correlated with IP50, was recorded. It is the first report in Punjab that evaluated disease resistance under simultaneous stress caused by three different pathogens that cause pea blight. The identified resistant sources have the potential to provide impetus to pea disease resistance breeding.