Allelic Variation at the Vernalization Response (Vrn-1) and Photoperiod Sensitivity (Ppd-1) Genes and Their Association With the Development of Durum Wheat Landraces and Modern Cultivars

Wheat adaptability to a wide range of environmental conditions is mostly determined by allelic diversity within genes controlling vernalization requirement (Vrn-1) and photoperiod sensitivity (Ppd-1). We characterized a panel of 151 durum wheat Mediterranean landraces and 20 representative locally adapted modern cultivars for their allelic composition atVrn-1andPpd-1gene using diagnostic molecular markers and studied their association with the time needed to reach six growth stages under field conditions over 6 years. Compared with the more diverse and representative landrace collection, the set of modern cultivars were characterized by a reduction of 50% in the number of allelic variants at theVrn-A1andVrn-B1genes, and the high frequency of mutant alleles conferring photoperiod insensitivity atPpd-A1, which resulted on a shorter cycle length.Vrn-A1played a greater role thanVrn-B1in regulating crop development (Vrn-A1>Vrn-B1). The results suggest that mutations in theVrn-A1gene may have been the most important in establishing the spring growth habit of Mediterranean landraces and modern durum cultivars. The alleleVrn-A1d, found in 10 landraces, delayed development. The relative effects of singleVrn-A1alleles on delaying the development of the landraces werevrn-A1=Vrn-A1d>Vrn-A1b>Vrn-A1c. Allelevrn-B1was present in all except two landraces and in all modern cultivars. The null allele atPpd-A1(a deletion first observed in the French bread wheat cultivar 'Capelle-Desprez') was found for the first time in durum wheat in the present study that identified it in 30 landraces from 13 Mediterranean countries. AllelePpd-A1a(GS105) was detected in both germplasm types, while the allelePpd-A1a(GS100) was found only in modern North American and Spanish cultivars. The relative effect of singlePpd-A1alleles on extending phenological development wasPpd-A1(DelCD) >Ppd-A1b>Ppd-A1a(GS105) >Ppd-A1a(GS100). SixteenVrn-1+Ppd-1allelic combinations were found in landraces and six in modern cultivars, but only three were common to both panels. Differences in the number of days to reach anthesis were 10 days in landraces and 3 days in modern cultivars. Interactive effects betweenVrn-1andPpd-1genes were detected.