Inheritance and linkage of isozyme loci in almond

Abstract

The segregation of seven isozyme marker genes was investigated using eight controlled crosses in almond. The cultivar lsquoNonpareilrsquo was the maternal parent in all crosses. Pollination was achieved using eight different cultivars, and a total of 3200 individual kernels were assessed. For each isozyme the goodness-of-fit test was used to test for departure from the expected frequencies assuming Mendelian inheritance. Given a higher than expected number of significant results for individual isozymes, independent segregation between pairs of isozymes was tested using the chi-square statistic on the resulting two-way contingency tables. In all crosses a highly significant association (P value< 0.001)="" was="" observed="" between="" (1)="" the="">AAT- 1 and IDH isozymes loci and (2) the LAP-1 and PGM-2 isozymes loci, which leads to the conclusion that the respective isozyme pairs are linked. In addition, a significant association (P value < 0.001)="" was="" observed="" between="">LAP-1 and GPI-2 when the pollen sources were lsquoFritzrsquo, lsquoMissionrsquo, or lsquoPricersquo, but this could not be tested for the remaining five pollen sources, lsquoCarmelrsquo, lsquoGrantrsquo, lsquoKeanersquo, lsquoNe plus Ultrarsquo, lsquoPeerlessrsquo, because they are homozygous at these loci. If LAP-1 is linked with GPI-2 and PGM-2, it might be expected that we should find evidence of linkage between GPI-2 and PGM-2. The lack of a significant association between these two isozymes suggests that LAP-1 is located centrally on the chromosome. These three pairs of linked loci are the first to be reported in almond.