Biochemical defense mechanism in groundnut genotypes against rust caused by Puccinia arachidis Speg.

Abstract

Biochemical defense response in groundnut genotypes infected with Puccinia arachidis (Speg.) causing rust at different growth stage was studied in present investigations. Twelve genotypes viz. ICG 13165, ICG 13160 (wild resistant), RHRG-6083, GPBD-4, KDG-128, ICG-11426, ICG-12672, ICGV-86590, ICGV-94118, ICGV-96283 (cultivated resistant) and SB- XI and JL- 24 (highly susceptible) were selected. The results revealed that all the genotypes showed variable disease severity. It was observed that in all stages of pathogen infection, disease severity and characteristic symptoms were more prominent in susceptible genotype than the other ten. The biochemical analysis of leaves of different varieties of groundnut revealed the content of chlorophyll, phenol and the activity of peroxidase and polyphenol oxidase were found maximum in resistant genotypes while total sugar content was found maximum in susceptible genotypes than in resistant at all the growth stages. There was reduction in chlorophyll and reducing sugar content and the level of reduction of these biochemical constituents were less in resistant genotypes than susceptible genotypes, while total sugar and total phenol and the activity of peroxidase and polyphenol oxidase increased after inoculation in all the groundnut genotypes and were more in resistant genotypes than susceptible ones. The results indicated that factors conditioning the host response to P. arachidis might be the outcome of complex biochemical changes operated in host genotypes.