← Back to Search
LEAF ISOZYMES AS GENETIC MARKERS IN CITRUS
Published 1978 · Biology
Reduce the time it takes to create your bibliography by a factor of 10 by using the world’s favourite reference manager
Time to take this seriously.
The genetic control of isozymes from Citrus and its near relatives was determined for three gene/ enzyme systems: glutamate oxaloacetate transaminase, phosphoglucose isomerase and phosphoglucose mutase. These enzymes are controlled by four genes having 19 codominant alleles, 12 of which occur in Citrus subg Citrus. Formal genetic studies were carried out with F1 biotypes and F1 populations of known origin. When biotypes were grouped into traditionally recognized species to examine genetic affinities within and between species, a remarkable pattern of uniformity of genotype combinations was found within a species, and every species had an unique combination. Because many economically important cultivars produce asexual(nucellar) as well as sexual(zygotic) embryos, a central problem of the breeder is to distinguish these when plants are young, long before fruiting. Isozyme markers can be used with varying degrees of efficiency, depending on the genotypes of the particular parents, to distinguish nucellar seedlings from those of zygotic origin. THERE have been several attempts to render a taxonomy reflecting species relationships in Citrus, a diverse and difficult group comprised of two subgenera, Citrus and Papeda (Swingle, 1943; Swingle and Reece, 1967). The former includes all the edible cultivars. Papeda includes six species with non-edible fruits. The number of species to be recognized in Citrus subg Citrus, and which biotypes to include in which species, constitute the central problems in Citrus taxonomy. The best known taxonomies, those of Swingle (1943) and Tanaka (1969), differ widely in the number of admitted species. Swingle recognized 16 in Citrus, Tanaka, 159. At another extreme, Scora (1975) and independently, Barrett and Rhodes (1976), recognized just three basic species exclusive of those of the subgenus