|CHEN, XINGLONG - China Agricultural University|
|WANG, XUEYAN - University Of Arkansas|
|WU, BOMING - China Agricultural University|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2018
Publication Date: 4/19/2018
Citation: Chen, X., Jia, Y., Jia, M.H., Pinson, S.R., Wang, X., Wu, B. 2018. Functional interactions of major rice blast resistance genes Pi-ta with Pi-b and minor blast resistance QTLs. Phytopathology. https://doi.org/10.1094/PHYTO-02-18-0032-R.
Interpretive Summary: Rice blast disease caused by the fungus Magnaporthe oryzae is the one most damaging rice diseases worldwide. Major blast resistance (R) genes play important roles in preventing rice blast disease. However, the genetic mechanism of interactions of two R genes has not been clearly documented. In the present study, we used M. oryzae strains/races that differentiate the effects of blast R genes Pi-ta and Pi-b with rice varieties Cybonnet, carrying Pi-ta and Pi-km, and Saber, carrying Pi-b, and evaluated their 243 progeny for disease reactions using two phenotyping methods. The resistance effect of Pi-km was excluded by using virulent isolates toward Pi-km, and noticeable significant increase of resistance responses were observed in progenies with both Pi-ta and Pi-b. These findings suggest that Pi-ta interacts with Pi-b by triggering more effective defense responses. This knowledge is important for stacking both Pi-ta and Pi-b to develop blast resistant rice varieties worldwide.
Technical Abstract: Major blast resistance (R) genes confer resistance in a gene-for-gene manner. However, little information is available on interactions between R genes. In this study, interactions between two rice blast R genes, Pi-ta and Pi-b, and other minor blast resistance quantitative trait locus (QTLs) were investigated in a recombinant inbred line (RIL) population comprising of 243 RILs from a ‘Cybonnet’ (CYBT) × ‘Saber’ (SB) cross. CYBT has the R gene Pi-ta and SB has Pi-b. Ten differential isolates of four Magnaporthe oryzae races (IB-1, IB-17, IB-49, and IE-1K) were used to evaluate disease reactions of the 243 RILs under greenhouse conditions. Five resistance QTLs were mapped on chromosomes 2, 3, 8, 9, and 12 with a linkage map of 179 single nucleotide polymorphism (SNP) markers. Among them, qBR12 (Q1), was mapped at the Pi-ta locus and accounted for 45.41% of the phenotypic variation while qBR2 (Q2) was located at the Pi-b locus and accounted for 24.81% of the disease reactions. The additive-by-additive epistatic interaction between Q1 (Pi-ta) and Q2 (Pi-b) was detected; they can enhance the disease resistance by an additive 0.93 using the 0 to 9 standard phenotyping methods. These results suggest that Pi-ta interacts synergistically with Pi-b.