The Nature of the Virido-albina/striata Mutant Induced During Storage in Barley Seeds

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Abstract
A single striata mutant (green and yellowish-white striped leaves) was observed in first generation (A1) barley plants grown from aged seeds. In the following generation (A2) normal, striata and virido-albina (yellowish-white leaves and pale yellowish-green tips) phenotypes were observed. The segregation of the progeny was examined in A2 and A3 and it was found that the large majority of normal and virido-albina phenotypes bred true, whereas most of the A2 striata phenotypes segregated normal, striata and virido-albina phenotypes in variable ratios. The expression of both mutant phenotypes is temperature-dependent and normally only observed when the initial temperature for seedling growth is about 5 °C. In the vast majority of individuals the symptoms disappear on transfer to 7 °C or more. Even at 5 °C the expression of the striata phenotype is variable, ranging from seedlings which are little different from the normal phenotype to those which are difficult to distinguish from the virido-albina phenotype. The genetical status of this mutant is discussed in relation to these observations and previous reports of the anomolous behaviour of the striata character. It is suggested that the symptoms could be the result of a single gene mutation showing incomplete dominance, and that the anomalous segregation ratios result mainly from difficulties in categorizing the heterozygous genotype at the extremes of its phenotypic expression. However, there is insufficient evidence to exclude the possibility that the symptoms derive from a cytoplasmically inherited extrachromosomal mutation.

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