Isoperoxidase pattern and internode length genotype in Pisum

Abstract

Inbred Pisum sativum lines of known constitution for the intemode length genes Le, La and Cry, and representing four height phenotypes, were grown to the 7-intemode stage in the light. Six cationic isoperoxidases, making up ca. 90% of the activity of stem extracts, were resolved by concave gradient elution from Dowex 50 columns and shown to run as single peroxidase bands on starch gel electrophoresis. They were all able to oxidise IAA in the presence of 2,4-dichlorophenol, but fell into two groups with widely differing IAA oxidase/peroxidase ratios. The isoperoxidase patterns were independent of both genotype and phenotype for internode length, thus making it unlikely that these loci exert their effect on internode extension via control of synthesis of a particular isoperoxidase. Amongst the lines screened polymorphism was detected involving two of the isoperoxidases, and limited F 2 data suggest that these two variants fire determined by alleles of a single gene. Isoperoxidase patterns of stem extracts of 6 other Pisum species did not differ significantly from the two found in P. sativum.