Genetic control of the nuda character complex in the genus Avena

Abstract

SummaryThe inheritance of the units of the character complex which differentiates Avena nuda from Avena sativa was studied in F1 hybrids and in the F2 generation derived from inter-crossing five cultivars of A. saliva with four cultivars of A. nuda. The 14 derived F1 hybrids could be classified into four types depending on the level of dominance of the sativa or nuda character expression. Type-I hybrids involving the cultivar Milford as parent showed a high level of dominance of the sativa-type expression, whereas the F1 hybrid from the cross, Condor × China, type IV, had the character expression typical of the A. nuda parent. Segregation in the F2 generation indicated that the entire character complex was under the control of a major gene, and supported the suggestion from previous work that modifying genes interact with the major gene to alter the expression of the homozygous nuda genotype towards the heterozygous phenotypeHomozygous nuda and heterozygous genotypes were shown to exhibit a gradient in the expression of the nuda character complex from the apex to the base of the panicle, the nuda-type characters being most pronounced in the apical spikelets. It is suggested that the variation of character expression within single panicles of homozygous nuda and heterozygous genotypes indicates the operation of an inhibitor-type gene action rather than a mutation to loss of function.