Blast resistance improvement of hybrid rice restorer line Fuhui 676 by polygene polymerization

Rice is the staple food for more than half of the world's population. The success of hybrid rice in China has made outstanding contributions to global food security. Restorer line is one of the parents of hybrid rice, and its characteristics often determine the quality of a hybrid rice variety. Fuhui 676, as a restorer line parent of hybrid rice with high yield, good combining ability and excellent comprehensive characters, has been tested and bred 18 new hybrid rice varieties, which have passed the variety examination and approval at the provincial level or above. One of the varieties has been identified as a super rice variety by the Ministry of Agriculture and Rural Affairs, which with excellent performance in production. However, with the expansion of the extension area and the extension of time, the combination of the male parent was susceptible to rice blast. Studies have shown that breeding and application of disease-resistant varieties is one of the most economical and effective methods to control diseases. Long-term practice has also proved that aggregating multiple blast resistance genes with different resistance spectra into the same variety is an effective measure to cultivate varieties with durable resistance. Therefore, in order to effectively improve the blast resistance of the restorer line Fuhui 676, extend the application period of the restorer line in production and improve the efficiency of breeding, the cross was made between the high-quality restorer line Jinhui 1059 with three broad-spectrum rice blast resistance genes (Pi-1, Pi-9 and Pi-k(h)) bred by molecular marker-assisted selection and the susceptible restorer line Fuhui 676. Meanwhile, through the combination of backcross introductionbetween the restorer line Jinhui 1059 as the donor parent and the restorer line Fuhui 676 as the recurrent parent, molecular marker-assisted selection and identification of rice blast resistance in the field, five stable resistant lines were selected, of which three lines aggregated the rice blast resistance gene Pi-1, Pi-9 and Pi-k(h) in this study. The comprehensive agronomic traits, quality, and combining ability of these five lines were systematically analyzed and compared, and the resistance to rice blast was identified in the field and in the laboratory. The results showed that compared with the recurrent parent Fuhui 676, the improved lines and their hybrid F-1 with Guang8A, Quan9311A, and Guangzhan634S showed significantly enhanced resistance to rice blast. Among them, line 6 performed best in terms of agronomic traits, yield, and quality, The rice quality of the combinations with the three male sterile lines reached the national standard of third-class high-quality rice.In terms of genetic background, compared with the recurrent parents, the genetic background recovery rate of this line was 97.1%, and there was no significant difference in the main agronomic characters of the growth period and plant height with Fuhui 676, but the yield was improved and the quality was improved. In summary, the resistant parent Jinhui 1059 was used in this study to improve the blast resistance of susceptible restorer line Fuhui 676. The improved line 6 retained the excellent characteristics of Fuhui 676, such as high yield, strong resilience and good combining ability. The quality was improved and had a good production application prospect.