Dissecting interactions of rice major and minor blast resistance genes with yield related components
Yulin Jia: USDA ARS, Dale Bumpers National Rice Research Center
<div>A large recombinant inbred line (RIL) mapping population consisting of 800 individuals was developed to investigate functional interactions of blast <em>R</em> genes, <em>Pi-ta</em> with <em>Pi-b</em>, other minor blast resistance QTL, and yield related components with US long grain tropical japonica rice varieties Cybonnet (CYBT) and Saber (SB). CYBT is known to contain <em>Pi-ta</em> (avirulent on blast races, IB1, IB17, and IB49 and virulent on IE1K) and <em>Pi-km</em> (virulent on IB1, IB17, IB49, and IE1k) and SB has <em>Pi-b</em> (avirulent on IB1, IB49, IE1k and partial avirulent on IB49). The entire population was evaluated with <em>Pi-ta</em> and <em>Pi-b</em> using gene specific PCR, and with their differential blast isolates/races under greenhouse conditions. A subset of this population (243 individuals) was used to construct a linkage map with 186 single nucleotide polymorphism (SNP) marker for mapping blast R/QTL, and QTL for 1000 grain weight, number of branches of panicle, panicle length, and weight. A total of seven blast resistance QTL were mapped on chromosomes 2, 3, 8, 9, 10, 11, and 12. Among them, qBR12 (Q1) on chromosome 12 was mapped at the <em>Pi-ta</em> locus accounted for 28.64 to 53.46% of disease reactions whereas qBR2 (Q2) was located at the <em>Pi-b</em> locus accounted 16.85 to 78.37% of disease reactions. There was a positive additive-by-additive epistatic interaction between <em>Pi-ta</em> and <em>Pi-b</em> suggesting that <em>Pi-ta</em> interacts positively with <em>Pi-b</em> in triggering a robust defense response. The remaining five minor resistance QTL have also been identified in other studies with different mapping parents suggesting that these five resistance QTL have coevolved and become domesticated. Relationship of resistance effects of blast <em>R</em> genes/QTL with yield related components will be presented.</div>
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