Rice Genetics IV - IRRI books - International Rice Research Institute

Table 5. The percentage of three types of epistatic QTL pairs affecting 13 traits in the fiverelated rice mapping populations from the Lemont/Teqing cross.TraitRecombinant inbredFour backcross/testcrosspopulationF 1populationsn Type I Type II Type III n Type I Type II Type IIIHeading date 8 12.5 50.0 37.5 21 4.8 28.6 66.7Plant height 8 0.0 12.5 87.5 20 10.0 45.0 45.0Flag leaf length 8 0.0 25.0 75.0 14 7.1 35.7 57.1Flag leaf width 4 0.0 25.0 75.0 18 5.6 27.8 66.7Panicle length 9 0.0 11.1 88.9 15 0.0 33.3 66.7Floret density 12 0.0 16.7 83.3 25 0.0 28.0 72.0Spikelets per panicle 12 0.0 41.7 58.3 27 0.0 44.4 55.6Spikelet sterility 12 0.0 16.7 83.3 19 5.3 21.1 73.7Panicles per plant 12 8.3 8.3 83.3 25 8.0 20.0 72.0Grains per panicle 12 0.0 25.0 75.0 21 0.0 42.9 57.11,000-grain weight 12 0.0 16.7 83.3 29 0.0 24.1 75.9Biomass 12 0.0 16.7 83.3 28 7.1 50.0 42.9Grain yield 14 0.0 35.7 64.3 26 15.4 38.5 46.2Mean 10.4 1.6 23.2 75.2 22.2 4.9 33.8 61.3SD a 2.8 4.0 12.5 14.4 4.9 4.8 9.8 11.5aSD = standard deviation.cating that the trait values are more properties of the digenic genotypes than differentalleles at the two loci. In cases of type III epistasis, both alleles at an E-QTL pair canbe favorable depending on which allele is fixed at the other locus. This type of incompatibleinteraction between alleles at uncomplementary loci has been shown to be animportant genetic basis underlying hybrid sterility and inbreeding depression in theprogenies from the Lemont/Teqing cross (Li et al 1997a,b, 2001a, Luo et al 2001).QE interactionsGenotype × environment (GE) interactions are a common property of most quantitativetraits and the subject of extensive investigation. However, results from numerousclassical GE studies provide little information regarding the QE interactions underlyingGE interactions. To address this important issue, QTL mapping was performed ona DH population from the IR64/Azucena cross, evaluated in nine diverse environments.These environments cover a wide geographical range from 13.5° to 31.5° Nand from 76° to 121.5° E at seven locations in four Asian countries (Philippines,China, India, and Thailand) and two different growing seasons at two of the locations(Li et al 2001b). Tables 6–8 summarize several important results on the QE interactionsaffecting plant height and heading date in the DH population.First, GE interactions of quantitative traits are reflected in two aspects: inconsistentQTL detection across environments and the presence of significant QE effects. Inthe former case, some undetectable QTLs appear to result from non- or weak geneexpression in certain environments, as suggested by variation in QTL main effectsand their corresponding test statistics (Tables 6 and 7).QTL mapping in rice: . . . 159