Identification of quantitative trait loci for blast resistance in Taiwan rice variety Tainung 84
Date Issued
2015
Date
2015
Author(s)
Chang, Wei-Bin
Abstract
Rice blast, caused by Magnaporthe oryzae, is a serious constraint to rice production. The use of resistance varieties, in combination with proper fertilizer management and pesticide application, is a widely adopted strategy for effective control of this disease. Through years, breeders in Taiwan have developed several cultivars possessing high level of blast resistance. However, mechanisms underlying the resistance remain unknown. Besides, the resistance can often be overcome after a few years of widespread cultivation. This is mainly due to the complex genetic diversity of M. oryzae populations and their high mutation rates at avirulence loci. This study aimed to uncover the resistance/susceptibility genetics of “Tainung 84” (TNG84, a resistant cultivar released in 2010) and “Tainan 11” (TN11, a most widely cultivated rice varirty in Taiwan, moderately susceptible to blast) using quantitative trait loci (QTL) mapping approach. Three field isolates of M. oryzae belonging to different Pot2 groups and physiological races, D41-2, 12CY-MS1-2, and 12IL-TT4-1, were used to inoculate the F2 and F2:3 progeny from “TN11 x TNG84”. A total of 7,742 single-nucleotide polymorphism (SNPs) were identified for 122 F2 individuals by using genotyping by sequencing (GBS) analysis. Composite interval mapping revealed that TNG84 harbors a major-effect QTL conferring resistance to all the three isolates. The QTL was located at ~52 cM on chromosome 12 (physical map position: 9,547,082-15,160,145 bp on IRGSP 1.0 map, logarithm of odds score: 20.553-31.687, R2 = 54.3-69.8%). A population consisting of 665 F2:4 individuals from 16 F2:3 families was phenotyped by inoculation with D41-2 and genotyped by five newly-developed cleaved amplified polymorphic sequences (CAPS) markers. Trait-marker association delineated the major QTL to a region between 10,012,254-13,020,487 bp. Sequence variations of several candidate genes in the region, together with the reaction patterns of different M. oryzae isolates, suggested that the superior resistance of TNG84 is likely conferred by the previously-cloned Pita gene and another gene (s) in the neighboring region.
Subjects
QTL mapping
Magnaporthe oryzae
physiological races
differential lines
resistance genetics
Type
thesis
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