Search

Microsatellite marker locus Xgwm 261 has been associated with reduced plant height attributed to the linked gibberellic acid (GA) sensitive Rht8c allele in wheat (Triticum aestivum L.). Our objective was to determine effects of allelic variation at the Xgwm 261 and Rht-B1 loci in two winter wheat recombinant inbred line (RIL) populations. 'Longhorn'/'Akron' and Longhorn/'Yuma' RIL populations were evaluated in controlled environments for GA sensitivity and coleoptile length and were grown in Colorado at five locations for 2 yr for agronomic evaluation. Microsatellite markers were used to identify alleles at the Xgwm 261 and Rht-B1 loci. In both populations, the Rht-B1b class showed reduced plant height (8.9% average), GA sensitivity (average 73.5%), coleoptile length (average 11.3%), and test weight (average 1.9%) relative to the Rht-B1a class. In the Longhorn/Yuma population, Rht-B1b and Xgwm 261 165-bp classes were shorter than the Xgwm 261 210-bp and Rht-B1a classes. Increased GA sensitivity and coleoptile length of the Xgwm 261 165-bp class were observed, although only in the Rht-B1a background. Plant height of the Xgwm 261 165-b p + Rht-B1a combination was intermediate to the shorter Xgwm 261 165-bp + Rht-B1b and the taller Xgwm 261-210-bp + Rht-B1a combinations. No negative associations attributed to the Xgwm 261 165-bp allele were observed. Our results suggest that the Xgwm 261 165-bp allele may provide reduced plant height, increased coleoptile length, and increased test weight when combined in a background with the Rht-B1a allele.

White mold disease (WM) of common bean (Phaseolus vulgaris L.), caused by Sclerotinia sclerotiorum (Lib.) de Bary, reduces crop yield and quality throughout the United States. The development of cultivars with resistance to WM would be facilitated by the identification and use of molecular markers linked to resistance genes. The objectives of this research were (i) to characterize WM reaction in a recombinant inbred line (RIL) population derived from a cross between resistant and susceptible germplasm, (ii) to validate the effect of a previously reported quantitative trait locus (QTL) for WM resistance, and (iii) to locate additional QTL associated with WM resistance. A RIL population that consisted of 94 lines was derived from a cross between G122 (resistant) and CO72548 (susceptible). The population was evaluated for WM reaction in three greenhouse tests and one field environment, and for molecular markers throughout the genome. Two RIL were identified with higher resistance levels (P < 0.05) than the resistant parent G122. A previously reported QTL on linkage group B7 was significant (P < 0.01) n single-factor analysis of variance, but not with composite interval mapping. Five QTL for resistance to WM were found (likelihood odds ratio [LOD] > 2.7) on linkage groups B1, B2b, B8, and B9. The QTL were contributed from both parents and together accounted for 48% of the phenotypic variation ([R.sup.2]). For field resistance, one QTL ([R.sup.2] = 12%) on linkage group B8 was detected. These results confirm polygenic resistance to WM in common bean.