Interrelationships among Three Major Loci Controlling Heading Date of Spring Barley when Grown under Short Daylengths1

Abstract

Early maturing cultivars of barley (Hordeum vulgare L.) would enhance yield stability in lowland, low rainfall areas of Morocco. The objective of this work was to study the inheritance of heading date in crosses involving six spring barleys developed in the Sacramento Valley of California, USA and the Yaqui Valley of Sonora, Mexico. Data were gathered under short daylengths at 32° 15′ N Lat with December sowing in Morocco. Frequency distributions of parental, F1, F2, and backcross generations indicated a three‐locus model with recessive and duplicate dominant epistasis accounting for most of the phenotypic variability. Recessive gene interaction resulted in plants that were about 19 to 35 days earlier than later counterparts with the dominant allele present. Among the later genotypes, the presence of a dominant allele at either of the duplicate loci in the genotypes not homozygous for extreme earliness resulted in increased earliness of 5 to 14 days over the duplicate double recessive depending upon modifiers. A genotype for each parent was suggested; however, the three‐locus model did not account for the 4‐ to 6‐day differences between two pairs of parents. Apparently, modifying loci or different alleles were present in some parents.