Evaluation of activation tagged rice mutants for variability in response to Meloidogyne graminicola under challenged inoculation

Abstract

Activation tagging is one of the most preferred strategies in functional genomics. The major advantage of the technique is the development of variability to a particular character(s) in a single genetic background based on the site of T-DNA integration. The understanding of resistance/ susceptibility mechanism portrayed by the mutants and identification of the genes responsible for the respective trait has always been a lucrative option for crop improvement. In rice, Meloidogyne graminicola has emerged as one of the major nematode pests and a main constraint for yield losses. The activation tagged rice mutants developed depicted a range of phenotypic variations with respect to panicles, height, flowering time, seed colour etc. Further, evaluation of the response of selected 16 activation tagged rice mutants to deliberate challenging with M. graminicola under pot culture studies showed a large variation in the ability of the nematode to infect these mutants. Among them, five mutants (lines 8, 9, 10, 11 and 15) portrayed a resistant response by producing least number of galls ranging from 1.5 to 2.6 galls per plant whereas wild type and other mutants were moderately susceptible (5 to 8.10 galls per plant) to M. graminicola. Corroborately, the multiplication factor of M. graminicola in resistant mutants was significantly less ranging from 0.64 to 1.71 as against 6.36 to 17.43 in wild type and other susceptible mutants due to reduction in total endoparasites and nematode fecundity. This variability towards the nematode challenge can be very useful in deciphering the molecular mechanisms of underlying responses, which can be exploited for breeding resistant rice varieties against this serious pest.