Genetics of allozyme variants in loblolly pine

Abstract

' 4 Applications of isozymes in breeding programs also have been demonstrated' 9 . However, we must understand how isozyme variants are inherited to fully realize their value in genetic investigations. Furthermore, we must look at as many loci as possible if results are to be more representative of the entire genome' 0 To date, few reports have been published on the inheritance of isozymes in forest trees, and fewer still have involved more than two or three loci ' .1 8.22 The presence of the haploid (In) megagametophyte tissue in seeds has greatly facilitated isozyme studies in conifers. Each megagametophyte, representing a single meiotic product, has the same genetic constitution as the female gamete. Thus, the Mendelian genetics of allozyme (allelic isozyme) variants can be confirmed without making crosses because allozymes are expected to segregate in 1:1 ratios in the megagametophytes of heterozygous mother trees. In addition, when allozymes are expressed clearly in both embryo and megagametophyte tissues, the male contribution to the embryo' genotype can be separated from that of the female. This unique feature of conifers has proven useful for studying pollen migration 7 and mating systems in forest trees ' ' 6 In this paper, we describe allozyme variants of 10 enzyme systems occurring in megagametophyte and embryo tissues of loblolly pine (Pinus taeda L.) seeds and provide evidence for their inheritance. Linkage relationships among the loci coding these allozymes are reported elsewhere 2