Rekha G, Abhilash Kumar V, Gokulan C G, Koushik M B V N, Laxmi Prasanna B, Kulkarni Swapnil, Aleena D, Harika G, Hajira S K, Pranathi K, Punniakoti E, Kale R R, Dilip Kumar T, Ayyappa D, Anila M, Sinha Pragya, Manohara K K, Padmavathi G, Subba Rao L V, Laha G S, Srinivas Prasad M S, Fiyaz R A, Suneetha K, Balachandran S M, Patel Hitendra Kumar, Sonti Ramesh V, Senguttuvel P, Sundaram R M
Department of Biotechnology, ICAR-Indian Institute of Rice Research, Rajendranagar, Hyderabad, India.
Rallis India Limited, Seeds/Biotech R&D Division, Bangalore, India.
Rice (N Y). 2022 Aug 17;15(1):45. doi: 10.1186/s12284-022-00591-3.
Improved Samba Mahsuri (ISM) is an elite, high-yielding, bacterial blight resistant, fine-grained rice variety with low glycaemic index. It is highly sensitive to salt stress, particularly at seedling stage, which significantly reduces its yield potential in coastal areas. A salinity tolerant QTL, Saltol, associated with seedling stage tolerance was previously mapped on chromosome 1 (10.6-11.5 Mb) from the Indian landrace, Pokkali and is effective in different genetic backgrounds. The objective of this study was to enhance salinity tolerance of ISM by incorporating the Saltol QTL through marker-assisted backcross breeding using the breeding line, FL478 (Pokkali/IR29).
Foreground selection was carried out at each generation using five Saltol-specific markers and three bacterial blight resistance genes, Xa21, xa13 and xa5. Background selection was conducted using 66 well distributed polymorphic SSR markers and at the BCF generation, a single plant with maximum recurrent parent genome recovery (95.3%) was identified and advanced to the BCF generation. Based on bacterial blight resistance, seedling stage salinity tolerance and resemblance to ISM, four advanced breeding lines were selected for testing in replicated experiments near Hyderabad, India. A promising near-isogenic line, DRR Dhan 58, was evaluated in multi-location trials-coastal salinity and it showed significant salinity tolerance, resistance to bacterial blight disease, high yield and excellent grain quality during the 2019 and 2020 trials. DRR Dhan 58 was 95.1% similar to ISM based on genotyping with the 90 K SNP chip. Whole genome resequencing analysis of Pokkali and FL478 which were salinity tolerant checks, ISM and DRR Dhan 58 showed a high degree of relatedness with respect to the candidate gene loci for Saltol and OsSKC1 (Shoot K Concentration 1).
DRR Dhan 58, possessing Saltol and three bacterial blight resistance genes (Xa21, xa13 and xa5) in the genetic background of the Indian mega-variety of rice, Samba Mahsuri, was developed for potential cultivation in areas prone to seedling stage salinity, as well as areas with endemic bacterial blight disease. This entry had a 24% yield advantage over the recurrent parent ISM under coastal saline conditions in multi-location trials and was recently released for commercial cultivation in India.
改良桑巴马苏里（ISM）是一种优质、高产、抗白叶枯病、细粒且血糖指数低的水稻品种。它对盐胁迫高度敏感，尤其是在幼苗期，这显著降低了其在沿海地区的产量潜力。一个与幼苗期耐盐性相关的耐盐QTL，Saltol，先前已定位在印度地方品种Pokkali的第1号染色体（10.6 - 11.5 Mb）上，并且在不同遗传背景下均有效。本研究的目的是通过使用育种系FL478（Pokkali/IR29），通过标记辅助回交育种导入Saltol QTL来提高ISM的耐盐性。
在每一代使用五个Saltol特异性标记和三个抗白叶枯病基因Xa21、xa13和xa5进行前景选择。使用66个分布均匀的多态性SSR标记进行背景选择，在BCF代，鉴定出一个具有最大轮回亲本基因组恢复率（95.3%）的单株并推进到BCF代。基于对白叶枯病的抗性、幼苗期耐盐性以及与ISM的相似性，选择了四个高级育种系在印度海得拉巴附近进行重复试验测试。一个有前景的近等基因系DRR Dhan 58在多地点试验——沿海盐度试验中进行了评估，在2019年和2020年的试验中，它表现出显著的耐盐性、对白叶枯病的抗性、高产和优良的谷物品质。基于90K SNP芯片基因分型，DRR Dhan 58与ISM的相似度为95.1%。对耐盐对照Pokkali和FL478、ISM以及DRR Dhan 58进行的全基因组重测序分析表明，它们在Saltol和OsSKC1（地上部钾离子浓度1）的候选基因位点方面具有高度相关性。
DRR Dhan 58在印度超级水稻品种桑巴马苏里的遗传背景中拥有Saltol和三个抗白叶枯病基因（Xa21、xa13和xa5），被开发用于在易受幼苗期盐害的地区以及白叶枯病流行地区进行潜在种植。在多地点试验的沿海盐渍条件下，该品种比轮回亲本ISM具有24%的产量优势，最近已在印度发布用于商业种植。
