Suma S. Biradar

Molecular and Phenotypic Characterization for Leaf Rust Resistance in Bread Wheat (Triticum aestivum L.)

Bread wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide (second after maize), providing staple food for 35 % of the world population. Leaf rust caused by the fungus Puccinia triticina Eriks. is one of the most common foliar diseases of wheat worldwide (Oelke and Kolmer, 2004; Mebrate et al., 2008). Severe leaf rust epidemics can cause yield losses up to 40% (Knott, 1989). Use of resistant wheat cultivars is the most economic and environmentally safe way to reduce losses caused by leaf rust. Till date 71 genes for resistance to leaf rust have been cataloged in wheat (Singh et al., 2012). Most Lr genes confer race-specific seedling resistance and are vulnerable to defeat by new virulent races. Greater durability of resistance could be achieved through combinations of race-specific genes (Kolmer et al., 2008a, 2008b).

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.

Improvement of leaf rust resistance in bread wheat variety DWR162 (Triticum aestivum L.) through marker assisted selection

SCAR markers SCS1302 and SCS421 linked to leaf rust resistance genes Lr24 and Lr28 used in the present study genetically improved a bread wheat variety DWR162 using marker assisted selection. Evaluation of BC1F2 generation under field conditions indicated that plants with both Lr24 and Lr28 were superior in yield and its components and leaf rust resistance. Twenty six DUS characters used for identification of plants showed close resemblance with recipient variety DWR 162. The availability of a combination of the two major leaf rust resistance genes in desirable background would encourage the genetically enhanced DWR 162 with leaf rust resistance for its cultivation in a large area.