Isozyme variability in mature seeds of U.S. peanut cultivars and collections.

Abstract The mature seeds of 61 U. S. peanut (Arachis hypogaea L.) cultivars, one breeding and six exotic peanut lines representing three botanical types were surveyed for 25 enzyme systems using horizontal starch gel electrophoresis. The genotypes assayed showed no variation for most of the enzymes. For catalase and malate dehydrogenase, variability was present but not reproducibly within genotypes. Only three enzymes—glutamate oxaloacetate transaminase (GOT), isocitrate dehydrogenase (IDH), and phosphohexose isomerase (PHI)—were consistently polymorphic. Each of the three enzymes displayed two different banding patterns. With three exceptions, the distribution of the zymograms for GOT and PHI reflected the taxonomic relatedness of Spanish and Valencia botanical type peanuts which are members of the subspecies A. hypogaea L. ssp. fastigiata Waldron when compared with Virginia botanical varieties which belong to the subspecies hypogaea. IDH showed only one banding pattern for the Spanish- and valencia-type peanuts (one exception), whereas the virginia-type cultivars varied for this enzyme reflecting the narrow genetic base of most Spanish cultivars and the broader germplasm base used for the development of Virginia cultivars. The limited amount of variability appears to restrict the applicability of isozymes as genetic markers in the cultivated peanut.