Identifying the Genes of Blast Resistance in Rice (Oryza sativa L.) Using Line X Tester Analysis

Abstract

The present study investigation was carried out at the Experimental Farm of Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, during the three successive growing seasons of 2014, 2015 and 2016. Four rice genotypes namely; Sakha 101, Sakha 102, Sakha103 and Sakha 104 were used as Lines and four monogenic lines; i.e., IRBLKS-S, IRBL3-CP4, IRBL5-M and IRBL7-M, were used as Testers, which cried blast resistance genes Pik-s, Pi3, Pi5(t) and Pi7(t). Under field condition, the results showed that the varieties Sakha 102 and Sakha 103 were resistant to blast under the three locations, Sakha, Gemmiza and Zarzoura. On the contrary, the other two Egyptian varieties Sakha 101 and Sakha104 were susceptible. Moreover, the monogenic lines (IRBLKS-S, IRBL3-CP4, IRBL5-M and IRBL7-M) were blast resistant under natural infection conditions. On the other hand, under five artificial inoculations races IA-77, IG-1, ID-15, IC-17 and IB-45 of Magnaporthe grisea, the results revealed that Sakha 102 and Sakha 103 variety were resistant to all races, except IB-45 race, which were susceptible. While, the two Egyptian varieties, Sakha 101 and Sakha 104 were susceptible to blast of the five races. For monogenic rice genotypes, results showed that IRBLKS-S, IRBL3-CP4 and IRBL5-M which carried (Pik-s, Pi3 and Pi5) blast resistance genes were resistant to all races, except EG-5 race, which were susceptible and the other rice monogenic line IRBL7-M which carry Pi7(t) was resistant against IG-1, 367 and 374 races and susceptible under EG-5 and IB-45 races of M. grisea. The results also suggested that the six major genes; Pi-i, Pi-sh, Pik-s, Pi3, Pi5, Pi7 (t) were effective under Egyptian conditions and can be used for improving blast resistance character in breeding program. The results of the inheritance of blast resistance using sixteen F1 and F2 rice populations showed that all F1s were resistant to blast. Among the F2 segregating generation eight populations showed resistant and non-segregation ratio, four rice crosses gave segregations 15 resistant (R) : 1 susceptible (S), while the segregating ratio of another four crosses were 3 R : 1 S for blast. In addition, the analysis of variance revealed significant differences among genotypes, lines, testers and line x tester interactions for blast reaction, duration, plant height, panicle length and weight, flag leaf area, number of panicles/plant and primary branches/panicle, 1000-grain weight and spikelet fertility % traits, indicated that the genotypes had wide genetic diversity for the studied traits. However, significant differences due to interactions of line x tester for the above mentioned traits, indicating the importance of both additive and non-additive gene action in the inheritance of these traits. Highly significant and desirable heterosis and heterobeltiosis were recorded in Sakha 103 X IRBL5-M for improving blast resistance, plant height, flag leaf area, number of panicles/plant and spikelet fertility %. In addition, Sakha 102 X IRBLKS-S rice hybrid was the best cross combinations for early maturity, shortness, area of flag leaf, number of panicles/plant and 1000-grain weight traits and it could be used in breeding program to improving these characters in rice