Characterization of Isozyme Variability in Apricots

Abstract

Seven enzyme systems were examined in 69 apricot [Prunus armeniaca L. and P. mandshurica (Maxim.) Koehne] clones. Three enzymes (6-phosphogluconate dehydrogenase, phosphoglucose isomerase, and phosphoglucomutase) were polymorphic at five loci. Only seven clones were characterized uniquely by their isozyme phenotypes and 56% fell into two of the 15 phenotypic groups found. Isozyme variability in apricot was greater than in peach, but less than that reported in plum or almond.

Inheritance of Five Isozyme Loci in Apricot

“…For the PGM-1 loci, each homozygous form (78/78 or 70/70) results in two bands, and the het erozygous form (78/70) has a three-banded pattern. Three presumptive alleles were re ported for PGM-2 (Byrne and Littleton, 1989). The segregation ratios from PGM-2 segre gation are consistent with two codominant alleles (100 and 83).…”

“…Given that NJA62 is a complex hybrid in volving both self-compatible and self-in compatible apricot races, it is expected to have a relatively high outcrossing rate. Con sequently, the " 100" phenotypes are due to outcrossing to the surrounding plants that were mostly of the " 100" phenotype (Byrne and Littleton, 1989). Although the data are not conclusive, they support the allelic basis of the presumptive null allele.…”

“…Iso zyme variability has been reported in several Prunus spp. (Hauagge et al, 1987;Durham et al, 1987;Byrne and Littleton, 1988), in cluding apricot (Byrne and Littleton, 1989). This variability is a rich source of genetic markers that can be used for cultivar and hybrid identification, the development of rapid selection schemes, the monitoring of genetic diversity in populations, and in the quanti fication of the genetic relationship among populations (Torres, 1983;Byrne, 1989).…”

“…Isozyme variability in apricot has been re ported for five presumptive loci for three en zymes: 6-phosphogluconate dehydrogenase (6PGD-2; EC 1.1.1.44), malate dehydro genase (MDH-1, MDH-2; EC 1.1.1.37), and phosphoglucomutase (PGM-1, PGM-2; EC 2.7.5.1) (Byrne and Littleton, 1989). This paper reports the results of inheritance stud ies for these five loci in the cultivated apri cot.…”

“…Phenotypes observed from peach are not eas ily interpreted as dimeric, and several studies have shown that the variation observed can be explained by the segregation of several alleles at one locus, although the origin of all the bands are not always explained (Arul sekar et al, 1986;Durham et al, 1987). Two loci, each with two putative alleles, were proposed for MDH in apricot (Byrne and Littleton, 1989). The patterns observed clearly show single-and triple-banded phenotypes in two regions of the starch gel.…”