Identification of qBK2.1, a novel QTL controlling rice resistance against Fusarium fujikuroi

Szu-Yu Chen; Ming-Hsin Lai; Yi-Ling Chu; Dong-Hong Wu; Chih-Wei Tung; Yue-Jie Chen; Chia-Lin Chung

doi:10.1186/s40529-023-00375-y

Identification of qBK2.1, a novel QTL controlling rice resistance against Fusarium fujikuroi

Bot Stud. 2023 Apr 20;64(1):11. doi: 10.1186/s40529-023-00375-y.

Authors

Szu-Yu Chen¹, Ming-Hsin Lai², Yi-Ling Chu¹, Dong-Hong Wu², Chih-Wei Tung³, Yue-Jie Chen¹, Chia-Lin Chung⁴

Affiliations

¹ Department of Plant Pathology and Microbiology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd, Taipei City, 106319, Taiwan.
² Crop Science Division, Taiwan Agricultural Research Institute, No. 189, Zhongzheng Rd., Wufeng Dist, Taichung City, 413008, Taiwan.
³ Department of Agronomy, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd, Taipei City, 106319, Taiwan.
⁴ Department of Plant Pathology and Microbiology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd, Taipei City, 106319, Taiwan. clchung@ntu.edu.tw.

Abstract

Background: 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.

Results: A population of F_2:9 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.

Conclusions: 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.

Keywords: Bakanae resistance; Budda; Fusarium fujikuroi; Genotyping-by-sequencing (GBS); Molecular markers; Quantitative trait loci (QTLs); Recombinant inbred lines (RILs); Taikeng 16; qBK1.8; qBK2.1.

Grants and funding

108AS-8.4.4-BQ-B1(1);109AS-8.4.2-BQ-B3(1);110AS-5.3.2-BQ-B2(1), 111AS-5.3.2-BQ-B1(1), 112AS-5.3.2-BQ-B1(1)/Council of Agriculture