Elucidation of gene action and identification of QTLs or genes for false smut resistance in rice Oryza sativa L

Abstract

Cyto-histological studies using SEM at one, five and 15 days after pathogen inoculation showed differences in the appearance of hyphae in the spikelets, packaging of cells in anther walls and size of anther wall opening between resistant and susceptible genotypes upon pathogen infection process. Biochemical components viz., Phenol, sugars, Phenyl alanine ammonia lyase (PAL), Peroxidase (POD) and Polyphenol oxidase (PPO) were estimated in florets before pathogen inoculation, five and 15 DAI and the defense enzymes alone quantified in shoots and roots of seedlings germinated from treated and untreated seeds at three different intervals in eight genotypes with different scales of resistance. Results revealed that, innate quantities of sugar and starch were lower in resistant genotypes, while phenol was higher and the phenomenon was vice- versa in susceptible genotypes. The defense enzymes namely, PAL, POD and PPO were at higher levels in resistant genotypes and vice- versa in susceptible genotypes. Significant differences were observed between resistant genotype RG170 and susceptible genotype CO43 in quantum production of all components at all intervals. These variations imply that, biochemical components play a crucial role in resistance mechanism. newlineEvaluation of full diallel mated population (30 F1s and 6 parents) generated using six parents with different levels of resistance to false smut and six different populations using six parameter generation mean analysis in two crosses viz., CO(R)50/RG170 and BPT5204/RG170 highlighted additive gene action for the trait number of infected grains per panicle (NIGPa) and dominance gene action for percentage of infected grains per panicle (PIGPa) and single plant yield through ratio of GCA and SCA variance. The heritability and genetic advance was high for all the three traits in diallel and F2 generation except moderate heritability for single plant yield.