Genetic Variation in Component Traits of Heading Date in Hordeum vulgare subsp. spontaneum Accessions Characterized in Controlled Environments

Ancestral germplasm may be a useful source of genetic variation for crop improvement. Genetic variation in developmental traits that contribute to heading date may be useful in developing varieties that are uniquely tailored to specific stress environments. Hordeum vulgare subsp. spontaneum (K. Koch) A. & Gr. is the ancestor of cultivated barley and useful developmental trait alleles may have been lost in the domestication process. Accordingly, we surveyed a sample of 16 subsp. spontaneum accessions for vernalization requirement, photoperiod sensitivity, photoperiod response, and relative earliness. We compared the subsp. spontaneum accessions to four H. vulgare L. subsp. vulgare accessions representing spring, facultative, and winter growth habit. Thirteen subsp. spontaneum accessions originating from the Fertile Crescent and the one subsp. spontaneum accession from the Caucasus region required vernalization; they were responsive to long photoperiods and most were very early. Two subsp. spontaneum accessions from the Himalayan region had no vernalization requirement but were extremely sensitive to short photoperiods. We used a clustering procedure to define two groups of subsp. spontaneum accessions, a group of subsp, spontaneum that included the two subsp. vulgare accessions of spring and facultative growth habit, and a fourth group comprised of the two subsp. vulgare winter habit cultivars. These data indicate that subsp. spontaneum may be a source of novel alleles for growth habit.