Breeding Application Of Three Sheath Blight Resistant Quantitative Genes And Two Rice Blast Resistant Genes In Japonica Rice

Sheath blight(SB)and rice blast are two of the most serious fungal diseases in rice production in China.In the practice of disease resistant breeding,developing resistant genes and develop resistant varieties are the most economical,effective and feasible strategies to control disease.Combine with the molecular marker-assisted selection(MAS),we can directly select the target resistant genes and introduce them into the elite varieties,which can greatly improve the efficiency of breeding.Previously,our research group found three major SB-resistant quantitative locus(QTLs)named qSB-9TQ,qSB-11HJX and qSB-12YSBRI,which were from the 9th chromosome of Teqing(TQ),the 11th chromosome of Huajingxian(HJX)and the 12th chromosome of YSBR1,respectively.Pi40 and Pigm are two broad-spectrum rice blast resistance genes,but few studies reported their potential on improving the resistance of japonica rice in Jiangsu Province.In this study,the three SB-resistant QTLs and two rice blast resistance genes were introduced into different japonica varieties through MAS to analyze their resistance effects and evaluate their breeding application values in resistance improvement of japonica varieties,which will provide theoretical basis and intermediate materials for future molecular breeding of resistance to SB and rice blast.1.Three SB-resistant QTLs,qSB-9TQ,qSB-11HJX and qSB-12YSBRI,were introduced into 7 japonica rice varieties,Lianjing 6,Nanjing 9108,Nanjing 44,Nanjing 5055,Lindao 10,W030 and Liaojing lines,respectively,and the corresponding introgression lines were obtained.Then the resistance levels to SB were evaluated and the agronomic traits were investigated for these introgression lines.The results showed that under the same background,the disease grades of the introgression lines with different SB-resistantQTLs were significantly lower than those of the corresponding receptor parents There was a slight difference among the disease grades reduced by different SB-resistant QTLs,and qSB-12YSBR1 decreased the disease grade the most.The trends of the effects of the threeSB-resistance QTLs on different background were the same.It was found that the introduction of the three SB-resistant QTLs had no adverse effect on the agronomic traits of improved japonica rice lines.2.qSB-9TQ and qSB-11HJX were pyramided into two japonica rice backgrounds,Lianjing 6 and Nanjing 9108,though MAS to evaluate polymerization effect of the two QTLs.The results showed that under the background of Lianjing 6,when qSB-9TQ or qSB-11HJX existed alone,the disease grades can be reduced by 0.99 or 1.04,respectively.However,the pyramiding of the two QTLs can reduce the disease grade by 1.55,and showed the interaction effect of 0.48 grade,which was not statistically significant.The pyramiding effect of the two QTLs in the background of Nanjing 9108 was the same as that in Lianjing 6.Through the investigation of agronomic traits of the pyramiding lines,it was found that pyramiding qSB-9TQ and qSB-11HJX had no adverse effect on the agronomic traists.In conclusion,the three SB-resistant QTLs,qSB-9TQ、qSB-11HJX and qSB-12YSBRI,have great breeding value in japonica rice breeding and pyramiding two resistance QTLs is a more favorable choice for improving the resistance to SB.3.Though MAS,the rice blast resistance genes Pi40 and Pigm were introduced into the background of Wuyunjing 32,Yanjing 16,Huajing 8,Sidao 17 and Huaidao 1309,respectively,and the corresponding introgression lines were obtained.The results of the identification of resistance to ear neck rice blast showed that the rice blast grades of the introgression lines carrying Pigm were between 0 and 1,but the corresponding lineswithout Pigm were between 7 and 9.The introgression lines carrying Pi40 werebetween 7 and9,which was consistent with the corresponding receptor parents.The results of natural identification showed that the rice blast disease grades of lineswith Pigm were significantly lower than the corresponding lines without Pigm,and there were no significant differences between the rice blast disease grades of lines with Pi40 and the corresponding receptor parents.We obtained four introgression lines,HJ8Pg,WYJ32Pg,WYJ32Pi40 and YJ16Pi40,by introduced Pi40 and Pigm into Huajing 8,WYJ32 and YJ16,respectively,then used 109 rice blast strains to identify the resistance spectrums at seedling stage.The results showed that the resistance spectrums of lines carrying Pigm was broader than those of recurrent parents.The above results suggested that Pigm has higher value in rice blast resistance breeding of japonica rice.