Identification of QTLs and Environmental Interactions Associated with Agronomic Traits on Chromosome 3A of Wheat

some substitution lines between two parental lines for complex traits allows for the identification of single Genetic analyses of complex traits in wheat (Triticum aestivum L.) chromosomes containing QTLs for those traits (Berke are facilitated by the availability of unique genetic tools such as chroet al., 1992a,b; Cantrell and Joppa, 1991). Single recipromosome substitution lines and recombinant inbred chromosome lines cal chromosome substitution lines can be targeted for (RICLs) which allow the effects of genes on single chromosomes to be studied individually. Chromosome 3A of ‘Wichita’ is known to development of RICLs that segregate only for genes on contain alleles at quantitative trait loci (QTLs) that influence variation that chromosome (Shah et al., 1999a,b; Joppa et al., in grain yield and agronomic performance traits relative to alleles of 1997). RICL populations present a powerful tool to ‘Cheyenne’. To determine the number, location, and environmental conduct QTL studies, especially in wheat, which has interactions of genes related to agronomic performance on chromothe largest genome size of the cereals at 16 000 Mbp some 3A, QTL and QTL environment analyses of 98 RICLs-3A (Arumuganathan and Earle, 1991). Kaeppler (1997) were conducted in seven locations across Nebraska from 1999 through documented the advantage of using RICL populations 2001. QTLs were detected for seven of eight agronomic traits meato detect QTLs in wheat, by showing the statistical sured and generally localized to three regions of chromosome 3A. power of 50 RICLs was equal to that of 200 recombinant QTL environment interactions were detected for some QTLs and inbred lines, when considering a Type I error rate of these interactions were caused by changes in magnitude and crossover interactions. Major QTLs for kernels per square meter and grain yield 5%. The power of 100 RICLs (0.98) exceeded that of were associated within a 5-centimorgan (cM) interval and appeared 200 recombinant inbred lines (0.41) by a factor of 2.4 to represent a single QTL with pleiotropic effects. This particular QTL times, when considering a Type I error rate of 1%. displayed environmental interactions caused by changes in magnitude, Because of these advantages, RICL populations have wherein the positive effect of the Wichita QTL allele was larger in been created to study grain yield, grain protein, and higher yielding environments. other agronomic traits in wheat (Araki et al., 1999; Joppa et al., 1997; Kato et al., 1999, 2000; Shah et al., 1999a,b). G yield and agronomic performance are the The analysis of grain yield and agronomic traits conmost commonly measured, but poorly understood trolled by genes on chromosome 3A in Nebraska was crop traits. Modern strategies for investigating the geinitiated in the 1980s. Berke et al. (1992a,b) evaluated netic basis of grain yield and agronomic performance a full set of reciprocal chromosome substitution lines were first established in the 1980s with the use of molecbetween cv. Cheyenne (CNN) and cv. Wichita (WI) for ular markers to construct genetic linkage maps in disgrain yield and other agronomic traits and reported that crete populations (Edwards et al., 1987; Lander and chromosome 3A from WI increased grain yield 12 to Botstein, 1989; Stuber et al., 1987; Tanksley et al., 1982). 15% when placed in CNN background. This research Information from genetic linkage maps and agronomic led to the development of a set of 50 chromosome 3A data collected from field experiments allowed the identirecombinant inbred chromosome lines (RICLs-3A), defication of QTL associated with agronomic trait variabilrived from a cross between CNN and CNN (WI3A) ity. The aim of QTL studies is to provide a framework (Shah et al., 1999a,b). Shah et al. (1999a,b) evaluated for understanding complex traits by identifying and the 50 RICLs-3A lines for anthesis date, plant height, measuring the relative impact of alleles at a mapped grain volume weight, grain yield, 1000-kernel weight, chromosomal region. The identified QTLs can also be spikes per square meter, and kernels per spike. Anthesis used by plant breeders using marker assisted selection date (Eps) was mapped as a single gene on the short (MAS) to increase breeding efficiency (Dudley, 1993). arm of chromosome 3A and explained significant variaScientists conducting QTL experiments in wheat have tion for 1000 kernel weight, kernels per spike, and plant access to unique genetic resources, including chromoheight. Additional QTLs were detected for yield composome substitution lines. Evaluating reciprocal chromonents and plant height elsewhere on the chromosome. However, QTLs for grain yield per se were not detected. The inability to map QTLs for grain yield could be B.T. Campbell, Rice Exp. Station, Calif. Coop. Rice Res. Foundation, attributed to the interaction of yield component QTLs, Biggs, CA 95917; P. S. Baenziger, H. Budak, M. Erayman, I. Dweikat, Dep. of Agronomy and Horticulture, Univ. of Nebraska, Lincoln, NE hence no single grain yield locus could be identified. 68583; K. S. Gill, Dep. of Crop and Soil Sciences, Washington State QTL E interactions (QEI) of the crossover type could Univ., Pullman, WA 99164; K. M. Eskridge, Dep. of Biometry, Univ. of Nebraska, Lincoln, NE 68583; Y. Yen, Dep. of Biology and MicrobiAbbreviations: AD, anthesis date; cM, centimorgan; GEI, genotype ology, South Dakota State Univ., Brookings, SD 57007. Research environment interaction; GVWT, grain volume weight; GYLD, grain partially funded by USDA, NRICGP 00-353000-9266. Nebraska Agyield; KPS, kernel number spike 1; KPSM, kernel number m 2; PHT, ricultural Research Division, Journal Series No. 13824. Received 28 plant height; QTL, quantitative trait locus; QEI, QTL environment Sept. 2002. *Corresponding author ([email protected]). interaction; RICLs, recombinant inbred chromosome lines; SPSM, spike number m 2; TKWT, 1000-kernel weight. Published in Crop Sci. 43:1493–1505 (2003).