ARS | Publication request: Identification of two major resistance genes against race IE-1k of Magnaporthe oryzae in the indica rice cultivar ZHE733

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 6, 2009
Publication Date: June 1, 2009
Citation: Lee, S., Wasmishe, Y., Jia, Y., Liu, G., Jia, M.H. 2009. Identification of two major resistance genes against race IE-1k of Magnaporthe oryzae in the indica rice cultivar ZHE733. Molecular Breeding. 24:127-134.

Interpretive Summary: Blast disease of rice is one of the most damaging rice diseases worldwide. Spontaneous occurrence of field virulence isolates, occasionally resulting in significant yield loss, has been commonly observed in the US for the past two decades. The race IE-1K of Magnaporthe oryzae overcoming the resistance (R) gene Pi-ta has been recovered from the southern US over a period of severl years and is considered to be a new threat to rice production in the US. One of the most important tasks is to rapidly incorporate novel resistance genes. Zhe733 is a high yielding and pest resistant indica cultivar recently introduced from China. In the present study, three isolates TM2, S1, and 94071 of the race IE-1K were used to identify R genes from Zhe733 using a recombinant inbred line population of a cross of a genetic stock of the tropical japonica cultivar KBNTlpa1-1 with Zhe733. The ratios of 3:1 resistance to susceptibility in 341-344 RILs of F10-11 KBNTlpa1-1/Zhe733 population indicate that two major R genes in Zhe733 confer resistance to isolates TM2, S1, and 94071, respectively. A total of 118 polymorphic Simple Sequence Repeat (SSR) markers were further analyzed in 167 F10-11 RILs of KBNTlpa1-1/Zhe733 population using composite interval mapping. Two major R genes designated as Pi41(t) and Pi42(t), each providing complete resistance to TM2, were identified on chromosomes 8 and 11, respectively. Pi41(t) and Pi42(t) also show conferring resistance to the common races IB-1, IB-45, IB-49, IB-54, IC-17, IE-1, IE-1K, IG-1, and IH-1 of M. oryzae in the US. The Pi41(t) gene was defined by SSR marker RM72 at the genetic distance of 0.9 cM and Pi42(t) was 0.2 cM from SSR marker RM1233. Molecular markers RM72 and RM1233 identified in this study should be useful for tagging Pi41(t) and Pi42(t) and for accelerating their incorporations into advanced breeding lines by marker-assisted selection.

Technical Abstract: The race IE-1K of Magnaporthe oryzae overcoming the resistance (R) gene Pi-ta has been recovered from the southern US over a period several years. In the present study, three isolates TM2, S1, and 94071 of the race IE-1K were used to identify R genes from a newly introduced resistant indica cultivar, Zhe733, using a recombinant inbred line population of a cross of a genetic stock of the tropical japonica cultivar KBNTlpa1-1 with Zhe733. The ratios of 3:1 resistance to susceptibility in 341-344 RILs of F10-11 KBNTlpa1-1/Zhe733 population indicate that two major R genes in Zhe733 confer resistance to isolates TM2, S1, and 94071, respectively. A total of 118 polymorphic Simple Sequence Repeat (SSR) markers were further analyzed in 167 F10-11 RILs of KBNTlpa1-1/Zhe733 population using composite interval mapping method. Two major R genes designated as Pi41(t) and Pi42(t), each providing complete resistance to TM2, were identified on chromosomes 8 and 11, respectively. Pi41(t) and Pi42(t) also show the wide range of resistance to other US races IB-1, IB-45, IB-49, IB-54, IC-17, IE-1, IE-1K, IG-1, and IH-1. The Pi41(t) gene was defined by SSR marker RM72 at the genetic distance of 0.9 cM and Pi42(t) was 0.2 cM from SSR marker RM1233. RM72 and RM1233, identified in this study, should be useful for tagging Pi41(t) and Pi42(t) and facilitating their incorporation into advanced breeding lines by marker-assisted selection.