Allele variation in loci for adaptive response in Bulgarian wheat cultivars and landraces and its effect on heading date

Abstract

Allele composition at the major growth habit (Ppd-D1,Vrn-1, Rht-1andRht8) loci was determined in 52 Bulgarian bread wheat cultivars and landraces, using recently developed diagnostic molecular markers. The study showed that Bulgarian wheat germplasm varies for photoperiod, vernalization and height-reducing genes. The photoperiod-sensitive allele (Ppd-D1b)was the most frequent one in the old cultivars and landraces (90.9%), while the photoperiod-insensitive allele (Ppd-D1a) showed the highest frequency in the modern cultivars (96.71%). The alleles conferring winter growth habit (vrn-A1,vrn-B1andvrn-D1) were more common in both the old (72.7%) and the modern (93.3%) wheat genotypes. The spring alleleVrn-A1cwas not detected in Bulgarian germplasm, while the spring alleleVrn-B1was found only in the old genotypes (13.6%). The semi-dwarfing alleleRht-B1bwas observed in several modern cultivars. Seven allele variants were found in the microsatellite locusXgwm261, closely located to theRht8gene. Among them, alleles of 164, 212 and 216 bp length were specific for the old genotypes studied, while alleles of 192 and 202 bp length were specific for the modern ones. The allele combinationRht-B1b//192 or 202 bp allele (Xgwm261locus)//Ppd-D1a//vrn-A1/vrn–B1/vrn-D1was detected in most of the early-heading modern cultivars. Our study emphasizes on the plasticity of the adaptive response of bread wheat cultivars sown in Bulgaria, as well as on the effect of variation for major growth habit on some yield and reproductive characteristics.