Abstract
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.
Highlights
Wheat ranks first as a cultivated cereal in the world (>200 mha annually) and is the most important crop with respect to sustaining food security [1]
Out of 15,944 bread wheat (T. aestivum) accessions screened, 29% were resistant to leaf rust, 65% were resistant to stripe rust and 91% were resistant to stem rust (Fig 4)
At the end of the evaluation, as many as 244 bread wheat and 253 durum wheat accessions conserved in the Indian Genebank were either resistant or moderately resistant to stripe rust pathotypes occurring across both hotspots, Wellington and Gurdaspur (Table 3)
Summary
Wheat ranks first as a cultivated cereal in the world (>200 mha annually) and is the most important crop with respect to sustaining food security [1]. Enhancing the production in the face of changing climate inter alia requires protection against biotic stresses [3, 4] that cause huge yield loss. Three rust diseases (stem rust, leaf rust and stripe rust) are the major threats to wheat production globally [5]. These pathogens are known to occur in India and cause varying degrees of economic losses. The disease is gradually extending towards the North-West, the major wheat growing areas in the country with an average of about 15–20% yield loss [12, 13]. A severe rust and spot blotch disease outbreak in India’s wheat-dependent agro-economy will lead to a serious loss in production as well as huge monetary cost in undertaking control measures. Considering the high demand relative to production, such situations can potentially lead to food-insecurity with global political implications
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