Genetic effect of differentially regulated fungal response genes on resistance to necrotrophic fungal pathogens in chickpea ( Cicer arietinum L.)

Abstract

Plant resistance to pathogen infection can be achieved by systemic regulation of the defense-related genes that respond to specific systemic signals. To elucidate defense responses in chickpea ( Cicer arietinum L.) against fungal pathogens, Ascochyta rabiei (Pass.) Labr. causing ascochyta blight and Fusarium oxysporum f.sp. ciceri causing fusarium wilt, expression patterns of defense-related genes in chickpea after pathogen inoculation and exogenous treatments with systemic signals such as SA and Me-JA were investigated. Two blight differentia germplasm lines, FLIP84-92C(2) (blight resistant and SA- and Me-JA-sensitive) and PI359075(1) (blight susceptible and SA- and Me-JA-insensitive) showed significant differential expression patterns of the defense-related genes after A. rabiei inoculation and exogenous treatment with SA and Me-JA. However, blight resistance in the recombinant inbred lines generated from the cross of the two germplasm lines did not cosegregate with the expression of the genes induced either by pathogen inoculation or by signal chemicals. Fusarium wilt resistance in chickpea also did not require induction of the defense-related genes after Fusarium infection. These results indicated that systemic regulation of the defense-related genes at transcription level which is reportedly associated with disease resistance in other model plant species such as Arabidopsis might not confer resistance in chickpea against two necrotrophic fungal pathogens, A. rabiei (Pass.) Labr and F. oxysporum f.sp. ciceri. Further studies focused on constitutive or unknown defense systems independent of SA- and JA-mediated systemic resistance mechanisms are required to understand fungal resistance mechanisms in chickpea.