Characterization ofPi-tablast resistance gene in an international rice core collection

Abstract

The Pi-ta gene in rice prevents the infections by races of Magnaporthe oryzae containing AVR-Pita. In the present study, 1790 accessions were characterized for Pi-ta, and Pi-ta independent resistance genes using marker analysis, disease evaluation with the race IB-49 carrying AVR-Pita, and IE-1k not carrying AVR-Pita and sequence analysis. A total of 183 accessions were identified using a Pi-ta-indel marker from the intron region. Sequence analysis revealed that resistance functional nucleotide polymorphism (FNP) was present in 163 accessions including reference cultivars. Among them, 89 were resistant to IB-49 and susceptible to IE-1k indicating that these accessions contain Pi-ta R alleles. Four accessions were susceptible to IB-49 suggesting that components were not intact in Pi-ta-mediated resistance. In contrast, 14 accessions with the susceptible FNP were resistant to IB-49 suggesting these 14 accessions may contain Pi-ta independent new R genes. Together, 83 accessions were identified to contain new R gene to IE-1k. These accessions were genetically distinct determined by simple sequence repeat markers. The results could impact breeding for blast resistance worldwide.

Analysis of rice blast resistance gene Pi-z in rice germplasm using pathogenicity assays and DNA markers

“…Under that assumption, if we select germplasm using a marker that lacks an association with IE1k resistance 50% of the germplasm should be resistant to IE1k and 50% Fjellstrom et al (2006) should be susceptible to IE1k. The assumption of Hardy-Weinberg equilibrium for IE1k resistance was verified by performing v 2 analysis on data published by Wang et al (2010) in which germplasm were screened for the presence of blast resistance gene Pi-ta, and pathogenicity assays were performed with both IE1k and IB49. Pi-ta confers resistance to IB49 but not IE1k.…”

Characterization of Rice Blast Resistance Gene Pi61(t) in Rice Germplasm

“…When the seedlings reached three-to four-leaf stage, they were used for pathogenicity assays and samples were collected for DNA extraction. In addition, the presence of Pi-ta in a total of 89 accessions from the 183 USDA rice core collection lines that contained the Pi-ta InDel marker associated with the presence of Pi-ta based on previous study (25) was verified. Furthermore, 136 accessions from the core collection were used for an R gene survey.…”

“…South America a M2 and S29 were co-dominant insertion-deletion (InDel) markers and flanked the Pi61(t) gene; M9 was a dominant InDel marker and co-segregated with Pi61(t). Allele sizes of M2, M9, and S29 were 620, 850, and 250 nucleotides (nt), respectively, for Nipponbare; and allele sizes of M2 and S29 were 150 and 220 nt, respectively, for 93-11. b Symbols + and -indicate the presence and absence, respectively of the Pi-ta gene, based on Wang et al (25), or Pi61(t). c Disease reaction (DR): 0 to 2 = resistant (R) and 3 to 5 = susceptible (S).…”

“…It confers resistance to the major blast races (isolates) in the United States (11). The Pi-ta gene was identified in the USDA core collection by a designed Pi-ta insertion-deletion (InDel) marker (12,25). The presence of Pi-ta was verified in 89 rice accessions using various DNA markers and also by disease reactions of M. oryzae to races IB49 and IE1K (25).…”

“…The Pi-ta gene was identified in the USDA core collection by a designed Pi-ta insertion-deletion (InDel) marker (12,25). The presence of Pi-ta was verified in 89 rice accessions using various DNA markers and also by disease reactions of M. oryzae to races IB49 and IE1K (25). These results illustrated that DNA markers linked to R genes were useful for detecting the function of R genes and, thus, could be widely used in rice improvement programs utilizing MAS.…”