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Abstract：
Sheath blight (ShB) is the most serious disease of rice (Oryza sativa L.), caused by the soil-borne fungus Rhizoctonia solani Kühn (R. solani). It poses a significant threat to global rice productivity, resulting in approximately 50% annual yield loss. Managing ShB is particularly challenging due to the broad host range of the pathogen, its necrotrophic nature, the emergence of new races, and the limited availability of highly resistant germplasm. In this study, we conducted QTL mapping using an F2 population derived from a cross between a partially resistant accession (IRGC81941A) of Oryza nivara and the susceptible rice cultivar Punjab rice 121 (PR121). Our analysis identified 29 QTLs for ShB resistance, collectively explaining a phenotypic variance ranging from 4.70 to 48.05%. Notably, a cluster of four QTLs (qRLH1.1, qRLH1.2, qRLH1.5, and qRLH1.8) on chromosome 1 consistently exhibit a resistant response against R. solani. These QTLs span from 0.096 to 420.1 Kb on the rice reference genome and contain several important genes, including Ser/Thr protein kinase, auxin-responsive protein, protease inhibitor/seed storage/LTP family protein, MLO domain-containing protein, disease-responsive protein, thaumatin-like protein, Avr9/Cf9-eliciting protein, and various transcription factors. Additionally, simple sequence repeats (SSR) markers RM212 and RM246 linked to these QTLs effectively distinguish resistant and susceptible rice cultivars, showing great promise for marker-assisted selection programs. Furthermore, our study identified pre-breeding lines in the advanced backcrossed population that exhibited superior agronomic traits and sheath blight resistance compared to the recurrent parent. These promising lines hold significant potential for enhancing the sheath blight resistance in elite cultivars through targeted improvement efforts.
摘要：
纹枯病（ShB）是水稻（OryzasativaL.）最严重的疾病，由土壤传播的真菌SolaniKühn引起（R.solani）。它对全球水稻生产力构成重大威胁，导致大约50%的年产量损失。由于病原体的宿主范围很广，因此管理ShB尤其具有挑战性。它的坏死性质，新种族的出现，和高抗性种质的有限可用性。在这项研究中,我们使用F2种群进行了QTL定位，该种群来自Oryzanivara的部分抗性基因（IRGC81941A）和易感水稻品种旁遮普水稻121（PR121）之间的杂交。我们的分析确定了29个抗ShB的QTL，共同解释了从4.70到48.05%的表型差异。值得注意的是,1号染色体上的一组四个QTL（qRLH1.1，qRLH1.2，qRLH1.5和qRLH1.8）始终表现出对R.solani的抗性反应。这些QTL在水稻参考基因组上的跨度从0.096到420.1Kb，包含几个重要的基因，包括Ser/Thr蛋白激酶，生长素响应蛋白，蛋白酶抑制剂/种子储存/LTP家族蛋白，含有MLO结构域的蛋白质，疾病反应蛋白，Thaumatin-likeprotein,Avr9/Cf9-elicitingprotein,和各种转录因子。此外,与这些QTL链接的简单序列重复（SSR）标记RM212和RM246可有效区分抗性和易感水稻品种，为标记辅助选择计划显示出巨大的希望。此外，我们的研究确定了高级回交群体中的预交系，与轮回亲本相比，它们表现出优异的农艺性状和纹枯病抗性。这些有前途的品系通过有针对性的改进努力，在提高优良品种的纹枯病抗性方面具有巨大的潜力。
