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The direct cross-hybridization approach between 16 Aegilops tauschii (AT) and 10 bread wheat (W) lines was carried out in reciprocal directions. W (♀) x AT (♂) yielded no embryo formation whereas embryo formation ranging from 34.09 to 43.33% was obtained in AT (♀) x W (♂) crosses in all 160 combinations. The major bottleneck of low plant regeneration in AT (♀) x W (♂) crosses was cleared by adopting detached tiller culture and embryo rescue medium adjuvants such as casein hydrolysate (200 mg/L) and activated charcoal (2 g/L). The regeneration frequency as a result of these two interventions increased from 3.61 to 19.29 per cent. Two innovative methods of chromosome doubling included in situ colchicine (0.05%) treatment with cotton swab method and pre-regeneration colchicine treatment (0.1 and 0.2%) to pollinated ovaries were found to be effective. The findings of the study make successful exploitation of direct cross approach (AT (♀) x W (♂)) possible in wheat improvement.

Limited backcrossing was followed to introgress useful variability, needed for improving grain morphology and milling traits, from wild Oryza species into two indica cultivars PR114 and Pusa44.These alien introgressions lines (ILs), having similar grain quality parameters to the recurrent parent, were used for developing rice hybrids to assess the effect of these introgressions in the heterozygous state and to assess their grain quality parameters, as most of the hybrids commercialized in the tropics have inferior grain quality. These ILs and their recurrent parents, possessing fertility restoration ability for wide abortive cytoplasm, were crossed with CMS line PMS 17A to generate introgressions line hybrids (ILHs). Hybrids developed from recurrent parents were used as a check to compare the performance of ILHs. Based on yield and phenotypic acceptability, six ILHs having enriched genome of O. rufipogon and O. nivara were selected and analyzed for grain quality traits. All six hybrids observed significant improvement in milled rice recovery (up to 10%), head rice recovery (up to 25%) over ILs and check hybrids. Introgressions were analyzed using polymorphic SSR markers. The majority of O. rufipogon and O.nivara alleles identified in the study seems to be effective across recipient genotypes and could be used effectively in quality breeding programs.

Cytoplasmic ( Triticum timopheevii -based) and chemically induced (CH9832- based) male sterility systems were compared for hybrid performance in wheat. A total of 40 genotypes including 10 CMS-based hybrids, 10 CHA-based hybrids, 10 B lines and 10 R lines were included in the experiment. analysis of variance revealed significant differences between the genotypes for all the characters studied. Differences between the hybrids and their parents were significant for all the characters. There were also significant differences between the hybrids resulting from the two systems of sterility. This study of 10 comparable hybrids showed, on average, midparent heterosis of 30.2 and 7.3% for CMS- and CHA-derived hybrids, respectively. Generally, the CMS-based hybrids were superior to their CHA-based equivalents for grain yield performance. In spite of the incomplete fertility the higher grain yield in CMS-based hybrids was attributed to the profuse tillering and high thousand-grain weight. On the other hand, the CHA-based hybrids had lower yield performance due to the lower thousand-grain weight and tillering. The lower grain weight and tillering in these hybrids compared with their CMS-based equivalents might be due to the toxic effect of the CHA, which was carried over to the hybrid and affected vigour. As a whole the CMS system was found to be better than the CHA system (based on the particular CHA used in this study) for hybrid performance in wheat.

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat-Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011-14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.

Stripe rust (Puccinia striiformis f.sp. tritici) is the most devastating disease of wheat (Triticum aestivum L.) accounting huge economical losses to the industry worldwide. HD 2329 was a widely grown wheat cultivar which had become highly susceptible to stripe rust and was used to understand the biochemical aspects of the host pathogen interaction through characterization of superoxide dismutase (SOD). In the present study, two types of SOD, ionically or covalently bound to the particulate fraction were found in the stripe rust infected and uninfected wheat leaves of susceptible cultivar HD 2329. Cell walls of leaves contained a high level of SOD, of which 41-44% was extractable by 2 M NaCl and 10-13% by 0.5% EDTA in infected and uninfected leaves. The NaCl-released SOD constituted the predominant fraction. It exhibited maximum activity at pH 9.0, had a Km value of 1.82-2.51 for uninfected and 1.77-2.37 mM for infected, respectively with pyrogallol as the substrate, and a Vmax of 9.55-21.4 and 12.4-24.1 delta A min(-1)g(-1)FW. A temperature optimum of 20 degrees C was observed for SOD of both uninfected and infected leaves. SOD showed differential response to metal ions, suggesting their distinctive nature. Inhibition of wall bound SOD by iodine and its partial regeneration of activity by mercaptoethanol suggested the involvement of cysteine in active site of the enzyme. These two forms showed greater differences with respect to thermodynamic properties like energy of activation (Ea) and enthalpy change (delta H), while entropy change (delta S) and free energy change (delta G) were similar. The results further showed that pathogen infection of the leaves of susceptible wheat cultivar induced a decrease in the SOD activity and kinetics which might be critical during the response of plant cells to the infection.