Breeding and Application of a New Thermo-Tolerance Rice Germplasm R203

The global warming has led to the increasingly serious heat damage on the heading and flowering stage of rice. To reduce the impact of heat damage on rice production and to ensure food security in China and even the world, new rice germplasms with thermo-tolerance on heading stage should be identified and new thermo-tolerance varieties need be bred.

Guanghui 128 (Qiguizao/Ce64//Minghui 63) was used as the heat resistant parent, through hybridization, multiple crossing and pedigree selection, the lines with high seed setting rate and small variation on heading and flowering stage during the high temperature were screened out for several generations’ breeding process. Then the selected higher generation lines were identified to create new thermos-tolerance rice germplasms in artificial climate chamber (The treated plants will be moved into the chamber on the flowering day, high temperature treatment is 9:00-15:00, 38℃, 15:01-8:59 28℃, the relative humidity is 75%, and the treatment lasts for 7 days), with analysis of agronomic trait.

The new germplasm R203 has stronger thermo-tolerance and higher seed setting rates under both normal and high temperature conditions (94.5% at normal temperature, 81.9% at high temperature, and 86.7% at relative). Its agronomic traits, quality and comprehensive resistance all meet the production standards. Above all, R203 has the potential to breed new thermos-tolerance hybrid rice varieties. The seed setting rates of 7 hybrid combinations with R203 as the male parent and seven three-line male sterile lines as the female parent were between 83.4%-99.4% under natural high temperature conditions. Among them, Taiyou 203, a new three-line medium indica hybrid rice has good qualities, the seed setting rate was 87.9%, the comprehensive relative heat resistance coefficient was 1.11, and the heat resistance reached level 1. In the production test, the yield increased by 5.36% compared with the control, and the yield increase point accounted for 85.71%. It has good high and stable yield, and the rice quality reached the second level of the ministerial standard. Thus Taiyou 203 has good promotion and application value.

Currently, basic research on heat resistance is not enough to support the breeding of new practical heat resistant varieties, the rice resources in areas prone to high temperature and humidity are preferred as materials for breeding new heat tolerance lines, a new heat-resistant rice variety R203 was created by phenotypic selection, and a practical heat-resistant rice variety Taiyou 203 was developed by using heterosis.