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<p>White rust, caused by the obligate biotroph <i>Albugo candida</i>, is one of the most devastating diseases of Indian mustard (<i>Brassica juncea</i>), with nearly all cultivated varieties becoming highly susceptible under changing climatic conditions, resulting in substantial yield losses. Development of immune or highly resistant cultivars without a yield penalty offers a sustainable strategy to mitigate these losses. However, effective immunity against white rust is currently unavailable within cultivated Brassica species. In the present study, 23 genes from <i>Sinapis alba</i> were successfully introgressed into the <i>B. juncea</i> background using two stable allohexaploid Brassica lines (H1 and H2) and their derived set of 94 backcross introgression lines (BC₂F₇₋₈, BCILs). These BCILs segregated into immune to highly susceptible responses against a virulent isolate of <i>A. candida</i>. Ten BCILs consistently exhibited immunity across two consecutive crop seasons (2022–23 and 2023–24) under artificial inoculation. Genotyping of the BCILs with 277 mono-allelic <i>S. alba</i>-specific SSR markers enabled construction of a genetic linkage map spanning 1866.17 cM across 12 linkage groups. QTL mapping using Inclusive Composite Interval Mapping (ICIM-ADD) identified a stable QTL (WRRS-1) on linkage group LG-3 at 30.00 cM that explained 11.30% and 8.40% of the phenotypic variance in the first and second crop seasons, respectively. An additional QTL (WRRS-2) was detected on LG-12 at 94.00 cM, explaining 10.63% of the phenotypic variance. Collectively, the two QTLs accounted for 19.03% of the total phenotypic variation in the second season. These QTL regions harbor multiple putative NBS-LRR class resistance genes. The identified stable QTL and candidate genes provide valuable genomic resources for marker-assisted breeding and genetic transformation to develop durable white rust-resistant, high-yielding Indian mustard varieties.</p>

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Introgression of a Stable Locus for White Rust Resistance Harboring Putative NBS-LRR Class R Genes in Backcross Progeny of Allohexaploid Brassica

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Kaushal Pratap Singh,
  • Prajjwal Rai,
  • Pramod Kumar Rai,
  • Preetesh Kumari

摘要

White rust, caused by the obligate biotroph Albugo candida, is one of the most devastating diseases of Indian mustard (Brassica juncea), with nearly all cultivated varieties becoming highly susceptible under changing climatic conditions, resulting in substantial yield losses. Development of immune or highly resistant cultivars without a yield penalty offers a sustainable strategy to mitigate these losses. However, effective immunity against white rust is currently unavailable within cultivated Brassica species. In the present study, 23 genes from Sinapis alba were successfully introgressed into the B. juncea background using two stable allohexaploid Brassica lines (H1 and H2) and their derived set of 94 backcross introgression lines (BC₂F₇₋₈, BCILs). These BCILs segregated into immune to highly susceptible responses against a virulent isolate of A. candida. Ten BCILs consistently exhibited immunity across two consecutive crop seasons (2022–23 and 2023–24) under artificial inoculation. Genotyping of the BCILs with 277 mono-allelic S. alba-specific SSR markers enabled construction of a genetic linkage map spanning 1866.17 cM across 12 linkage groups. QTL mapping using Inclusive Composite Interval Mapping (ICIM-ADD) identified a stable QTL (WRRS-1) on linkage group LG-3 at 30.00 cM that explained 11.30% and 8.40% of the phenotypic variance in the first and second crop seasons, respectively. An additional QTL (WRRS-2) was detected on LG-12 at 94.00 cM, explaining 10.63% of the phenotypic variance. Collectively, the two QTLs accounted for 19.03% of the total phenotypic variation in the second season. These QTL regions harbor multiple putative NBS-LRR class resistance genes. The identified stable QTL and candidate genes provide valuable genomic resources for marker-assisted breeding and genetic transformation to develop durable white rust-resistant, high-yielding Indian mustard varieties.