Chen Szu-Yu, Lai Ming-Hsin, Chu Yi-Ling, Wu Dong-Hong, Tung Chih-Wei, Chen Yue-Jie, Chung Chia-Lin
Department of Plant Pathology and Microbiology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd, Taipei City, 106319, Taiwan.
Crop Science Division, Taiwan Agricultural Research Institute, No. 189, Zhongzheng Rd., Wufeng Dist, Taichung City, 413008, Taiwan.
Bot Stud. 2023 Apr 20;64(1):11. doi: 10.1186/s40529-023-00375-y.
Bakanae disease caused by Fusarium fujikuroi is an increasing threat to rice production. The infected plants show symptoms such as elongation, slenderness, chlorosis, a large leaf angle, and even death. Bakanae disease is traditionally managed by seed treatment. However, fungicide-resistant F. fujikuroi isolates have emerged in several Asian areas, including Taiwan. This study aimed to identify new bakanae resistance quantitative trait loci (QTLs) and provide molecular markers to assist future breeding.
A population of F recombinant inbred lines (RILs) was derived from the cross between an elite japonica Taiwanese cultivar 'Taikeng 16 (TK16)' and an indica variety 'Budda'. 'Budda' was found highly resistant to all 24 representative isolates of the F. fujikuroi population in Taiwan. For the RIL population, 6,492 polymorphic single nucleotide polymorphisms (SNPs) spanning the rice genome were obtained by genotyping-by-sequencing (GBS) technique, and the disease severity index (DSI) was evaluated by inoculation with a highly virulent F. fujikuroi isolate Ff266. Trait-marker association analysis of 166 RILs identified two QTLs in 'Budda'. qBK2.1 (21.97-30.15 Mb) is a novel and first bakanae resistance QTL identified on chromosome 2. qBK1.8 (5.24-8.66 Mb) partially overlaps with the previously reported qBK1.3 (4.65-8.41 Mb) on chromosome 1. The log of odds (LOD) scores of qBK1.8 and qBK2.1 were 4.75 and 6.13, accounting for 4.9% and 8.1% of the total phenotypic variation, respectively. 64 RILs carrying both qBK1.8 and qBK2.1 showed lower DSI (7%) than the lines carrying only qBK1.8 (15%), only qBK2.1 (13%), or none of the two QTLs (21%). For the future application of identified QTLs, 11 KBioscience competitive allele-specific PCR (KASP) markers and 3 insertion-deletion (InDel) markers were developed.
Compared to other important rice diseases, knowledge of bakanae resistance has been insufficient, which limited the development and deployment of resistant cultivars. The discovery of qBK2.1 has provided a new source of bakanae resistance. The resistant RILs inheriting good plant type, good taste, and high yield characteristics from 'TK16' can be used as good resistance donors. Our newly developed markers targeting qBK2.1 and qBK1.8 can also serve as an important basis for future fine-mapping and resistance breeding.
由藤仓镰孢菌引起的水稻恶苗病对水稻生产的威胁日益增大。受感染的植株会出现植株伸长、细弱、黄化、叶角增大甚至死亡等症状。传统上，水稻恶苗病通过种子处理进行防治。然而，包括台湾地区在内的多个亚洲地区已出现对杀菌剂具有抗性的藤仓镰孢菌分离株。本研究旨在鉴定新的水稻恶苗病抗性数量性状位点（QTL），并提供分子标记以辅助未来的育种工作。
一个重组自交系（RIL）群体由优良粳稻台湾品种‘台梗16（TK16）’与籼稻品种‘菩提’杂交产生。发现‘菩提’对台湾藤仓镰孢菌群体的所有24个代表性分离株均具有高度抗性。对于该RIL群体，通过简化基因组测序（GBS）技术获得了覆盖水稻基因组的6492个多态性单核苷酸多态性（SNP），并通过接种高毒力藤仓镰孢菌分离株Ff266来评估病情严重程度指数（DSI）。对166个RIL进行性状 - 标记关联分析，在‘菩提’中鉴定出两个QTL。qBK2.1（21.97 - 30.15 Mb）是在第2号染色体上鉴定出的一个新的且首个水稻恶苗病抗性QTL。qBK1.8（5.24 - 8.66 Mb）与先前在第1号染色体上报道的qBK1.3（4.65 - 8.41 Mb）部分重叠。qBK1.8和qBK2.1的对数优势（LOD）分数分别为4.75和6.13，分别占总表型变异的4.9%和8.1%。同时携带qBK1.8和qBK2.1的64个RIL表现出比仅携带qBK1.8（15%）、仅携带qBK2.1（13%）或不携带这两个QTL（21%）的株系更低的DSI（7%）。为了所鉴定QTL的未来应用，开发了11个KBioscience竞争性等位基因特异性PCR（KASP）标记和3个插入缺失（InDel）标记。
与其他重要的水稻病害相比，对水稻恶苗病抗性的了解不足，这限制了抗性品种的开发和推广。qBK2.1的发现提供了一个新的水稻恶苗病抗性来源。从‘TK16’继承了良好株型、优良口感和高产特性的抗性RIL可作为优良的抗性供体。我们新开发的针对qBK2.1和qBK1.8的标记也可作为未来精细定位和抗性育种的重要基础。
