The Developmental Genetics of the Calcarozdes Gene

REVIOUS studies carried out in the laboratory of the senior author (WIJEIp WANTHA and STEBBINS 1964, STEBBINS and YAGIL 1966. YAGIL and STEBBINS 1969, GUPTA and STEBBINS 1969, STEBBINS and GUPTA 1969) have shown that in barley, the action of genes having a pronounced effect on external morphology of the reproductive spike can be first recognized by characteristic differences in meristematic activity, which divert the course of development into a different epigenetic sequence, so that a single alteration of the frequency or orientation of mitoses at an early stage can have many effects on the adult phenotype. Moreover, these differences are accompanied or preceded by significant differences in the activity of peroxidase and/or other enzymes. Although the relationship of these phenomena to the primary action of the genes concerned is as yet far from clear, the results obtained have served to establish with some precision the stages of development that must be studied in order to obtain critical information about primary gene action. Furthermore, they suggest that this action is of a regulatory nature, perhaps affecting the action of other genes that are concerned more directly with cell metabolism, or with the production and transport of growth substances. The present series of contributions is an analysis, along the same lines, of a radiation-induced mutation, calcaroides, which was produced in the Swedish tworowed barley variety bonus by GUSTAFSSON (1947 and oral communications). This mutation is particularly interesting because its effect on the awn of the mature lemma simulates that of hooded, although, as is stated below, the resemblance between the two is only superficial. Furthermore, the calcaroides locus is on a different chromosome from the hooded locus, and the allele is recessive to that for a normal awn, while hooded is dominant to awned. Hybridizations carried out in our laboratory have shown that calcaroides is not complementary to the gene subjacent hooded, described by TAKAHASHI and HAYASHI (1 966). Consequently these two genes, which have essentially the same morphological effects, are probably allelic to each other. These results will be published at a later date. According to TAKAHASHI and HAYASHI, subjacent hooded is on chromosome 2, while hooded is on chromosome 4 (NILAN 1964).