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Spot blotch (causative pathogen the fungus Bipolaris sorokiniana) is a damaging disease of wheat in warm and humid environments, which are prevalent in the Indian subcontinent. Genetic analyses have indicated that resistance is mediated by a number of independent genes, each contributing a small to intermediate size effect, meaning that combinations of three to five genes are required to ensure a high level of resistance. Near-immunity to spot blotch is not known. Hence, in order to seek further genetic gain on resistance, populations were developed from four simple crosses between the resistance donors “Yangmai#6” and either “Mon/Ald”, “Chirya#3”, “Tia#1” or “Ning#8201” with the aim of stacking resistance genes for resistance in order to generating lines showing near-immunity to the disease. The strategy was evaluated by genotyping the selections at 14 microsatellite loci linked to spot blotch resistance genes. The resistance locus most frequently retained by the selections maps to chromosome 6D; the second most frequently retained one maps to chromosome 2B. The use of a donor × donor crossing strategy was effective for developing lines with near-immunity to spot blotch disease.

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