Marker-assisted breeding of the rice restorer line Wanhui 6725 for disease resistance, submergence tolerance and aromatic fragrance

Abstract

BackgroundRice is a staple food crop in the world. With the increase in world population and economic development, farmers need to produce more rice in limited field. However, the rice production is frequently affected by biotic and abiotic stresses. The use of natural disease resistance and stress tolerance through genetic breeding is the most efficient and economical way to combat or acclimate to these stresses. In addition, rice with aromatic fragrance can significantly increase market value for its good grain quality. Mianhui 725 (MH725) is an elite restorer line that has been widely used to produce three-line hybrid rice in China. We previously introduced rice bacterial blight resistance genes Xa4 and Xa21 into MH725 and obtained an introgression rice line Wanhui 421 (WH421), which theoretically possesses 96.9% genetic background of MH725.ResultsHere we report the introduction and pyramiding of disease resistance genes Xa27 and Pi9, submergence tolerance gene Sub1A and aromatic fragrance gene badh2.1 in WH421 through backcrossing and marker-assisted selection. The newly developed introgression rice line was designated as Wanhui 6725 (WH6725), which theoretically possesses 95.0% genetic background of MH725. WH6725 and its hybrid rice conferred disease resistance to both blast and bacterial blight diseases and showed tolerance to submergence for over 14 days without significant loss of viability. Compared with non-aromatic rice MH725, WH6725 has strong aromatic fragrance. The major important agronomic traits and grain quality of WH6725 and its hybrid rice obtained in field trials were similar to those of MH725 and the control hybrid rice, indicating that WH6725 is as good as MH725 when it is used as a restorer line for three-line hybrid rice production.ConclusionWe have successfully developed a new restorer line WH6725 with disease resistance to rice blast and bacterial blight, tolerance to submergence and aromatic fragrance, which can be used to replace MH725 for hybrid rice production.

Genotyping for Blast (Pyricularia oryzae) Resistance Genes in F2 Population of Supa Aromatic Rice (Oryza sativa L.)

“…The badh2 gene for aroma was detected in 84 F 2 plants in both allele or on one allele which demonstrate the inheritance of aroma from parent and segregation. In the present study, there were plants which had both the aroma and blast resistance genes, similar to the findings by Luo et al [24] who reported a successful development of WH6725 resistant line to blast disease which possessed both genes. In the present study, the presence of Pita gene in resistant or moderately resistant plants may be attributed to the fact that Pita gene has been found to confer a medium-spectrum resistance [25].…”

Distribution of Bacterial Blight Resistance Genes in the Main Cultivars and Application of Xa23 in Rice Breeding

“…Recently, Xu et al (2019) and Oliva et al (2019) created new germplasms with robust and broad-spectrum resistance to BB using CRISPR/Cas9-mediated genome editing to introduce mutations in three effector-triggered susceptibility-associated SWEET genes, namely, Xa13 / OsSWEET11 , Xa25 / OsSWEET13 , and Xa41 / OsSWEET14 , successively. Therefore, pyramiding of multiple R genes is one of the more conducive and effective approaches to enhancing the horizontal resistance of rice varieties and achieving broad-spectrum and durable resistance ( Luo et al, 2012 ; Suh et al, 2013 ; Pradhan et al, 2015 ; Luo et al, 2016 ; Oliva et al, 2019 ; Xu et al, 2019 ). In the present study, the improved lines, YXYZ2, YTYZ, and Tai S, pyramided Xa23 and Xa4 at least ( Figures 3A, B ), which could have been better than the Xa23 alone for disease resistance and durability, although Xa4 alone was unable to meet the current requirements for rice disease resistance breeding.…”

Functional Marker Assisted Improvement of Stable Cytoplasmic Male Sterile Lines of Rice for Bacterial Blight Resistance

“…The rice gene Xa21 has got its own significance in breeding practices for developing rice varieties with bacterial blight resistance due to its wide range of resistance against bacterial blight disease (Huang et al, 1997; Li et al, 2001; Pradhan et al, 2015; Luo et al, 2016). …”