Time-course differential expression of transcripts in resistant and susceptible groundnut genotypes challenged with Sclerotium rolfsii Sacc

Abstract

Groundnut stem rot is one of the most devastating fungal diseases caused by Sclerotium rolfsii, resulting in significant yield loss. A transcriptome approach based on the cDNA-RAPD technique was employed to further understand the specific response of groundnut challenged with S. rolfsii. 35 cDNA-RAPD primers were employed to analyze the expression profiles of ICGV 86590 (resistant) and Narayani (susceptible) genotypes over a time course (0, 24, 48, 72 and 96 h after inoculation). The expression analysis found 3499 Transcript Derived Fragments (TDFs), of which 1431 TDFs with a qualitative difference and 128 quantitative differences (28, 27 up and 30, 43 down-regulated) in resistant and susceptible genotypes. A sharp increase in differentially expressed transcripts (DETs) in ICGV 86590 compared to susceptible Narayani at 24 h after inoculation indicated early recognition and timely activation of defense-related genes. A delayed response to pathogen infection was observed in susceptible genotype and also in the expression of a distinct set of DETs at different time intervals. However, more TDFs were differentially expressed in the resistant genotype compared to the susceptible genotype. As a result, these DETs were the responsible factors for the stem rot resistance and can be employed as functional markers in the development of stem rot resistant groundnut varieties. This study also reveals transcriptome changes before and after stem rot infection in groundnut, signifying the complex nature of stem rot resistance.