V. Rudra Naik

Induction of systemic resistance and management of safflower Macrophomina phaseolina root-rot disease by biocontrol agents.

Three biocontrol agents such as Trichoderma harizianum, Pseudomonas fluorescens and Bacillus subtilis were isolated from safflower rhizosphere soil and tested individually for their effectiveness in controlling root-rot of safflower. Talc based formulations were prepared and treated the seeds at different concentrations for assessing their ability to induce plant growth and in turn control root-rot disease. Among bioagents, P. fluorescens and T. harzianum (10 g/kg) proved to be effective in controlling disease under laboratory, greenhouse and field conditions. The efficacy of these biocontrol agents are equivalent to the standard fungicide Bavistin (Carbedazim). Other than direct action of these biocontrol agents triggered defense related enzymes involved in phenyl proponoid pathways and phenols. Higher activity of peroxidase, phenylalanine ammonia-lyase, chitinase, polyphenol oxidase and β-1,3-glucanase was observed in P. fluorescens and T. harzianum treated safflower plants after challenge inoculation with M. phaseolina. Seed treatment with these biocontrol agents enhanced the seed germination and growth parameters against root-rot disease and they also induced systemic resistance and/or physiological changes leading to plant defense mechanisms.

Phenotypic and Molecular Characterization of Alleles of Grain Quality Genes in Bread Wheat Genotypes

Grain quality is an important determinant of market value of wheat. Identification of the genes that influence grain quality traits and estimation of effects of alleles of these genes can improve the effectiveness of wheat breeding. Sixty-four bread wheat cultivars from six different agro-climatic zones of India and eleven Australian cultivars were analyzed for the prevalence of Puroindoline (Pin) hardness mutations and Storage Protein Activator (SPA) alleles for detecting allelic diversity among these varieties. Most of the Australian genotypes had soft or semi hard textured grains and amplified both Pina and Pinb genes. In Indian genotypes, most of the genotypes had hard grain texture and the null mutation of Pina and the wild type Pinb allele (Pina-D1b/Pinb-D1a) was the most frequent combination in the Indian wheat germplasm. Predominance of Spa gene was observed in both Australian and Indian genotypes and all these genotypes recorded high grain protein content as compared to genotypes which are having null allele for SpaB gene. This study can provide useful information for the improvement of wheat quality in selecting parental lines for crossing to maximize diversity at these loci and enhance the effectiveness of molecular marker assisted crop breeding.

Pyramiding of leaf rust resistance genes in bread wheat variety DWR 162 through marker assisted backcrossing

A popular widely grown but leaf rust susceptible Indian bread wheat variety was pyramided with two leaf rust resistance genes, Lr24 and Lr28 by Marker Assisted Backcrossing (MABC). The near isogenic line of PBW 343 introgressed with Lr24 and Lr28 was used as a donor. The MABC approach employed one SSR marker, Xwmc313 and one SCAR marker SCS421 with its locus linked to Lr28 and two SCAR markers, SCS719 and SCS 1302 linked to Lr24 for foreground selection to select plants carrying Lr24 and Lr28 genes. Marker assisted background selection in BC2F2 to recover the genome of recipient parent involving 42 polymorphic SSR markers dispersed throughout the genome facilitated mean recurrent parent genome (RPG) recovery of 80.3% with a range from 67.5–94.7%. BC2F2 plants were characterized for DUS (Distinctiveness Uniformity Stability) for phenotypic identification of plants that mostly resemble DWR 162 variety. Field evaluation of BC2F2 plants for yield and its component traits to assess the effect of these two genes in the background of DWR 162 revealed high yield potential of selected plants along with leaf rust resistance and no yield penalty was apparent. This study successfully demonstrate the practical utility of MABC in wheat rust resistance breeding for developing resistant lines in the background of any elite and popular wheat cultivar with relatively higher speed and precision.