INHERITANCE AND LINKAGE OF ISOZYME LOCI IN ALMOND

The segregation of seven isozyme marker genes was investigated using e ight controlled crosses in almond. The cultivar 'Nonpareil' was the ma ternal parent in all crosses. Pollination was achieved using eight dif ferent cultivars, and a total of 3200 individual kernels were assessed . For each isozyme the goodness-of-fit test was used to test for depar ture from the expected frequencies assuming Mendelian inheritance. Giv en a higher than expected number of significant results for individual isozymes, independent segregation between pairs of isozymes was teste d using the chi-square statistic on the resulting two-way contingency tables. In all crosses a highly significant association (P value < 0.0 01) was observed between (1) the AAT-1 and IDH isozymes loci and (2) t he LAP-1 and PGM-2 isozymes loci, which leads to the conclusion that t he respective isozyme pairs are linked. In addition, a significant ass ociation (P value < 0.001) was observed between LAP-I and GPI-2 when t he pollen sources were 'Fritz', 'Mission', or 'Price', but this could not be tested for the remaining five pollen sources, 'Carmel', 'Grant' , 'Keane', 'Ne plus Ultra', 'Peerless', because they are homozygous at these loci. If LAP-1 is linked with GPI-2 and PGM-2, it might be expe cted that we should find evidence of linkage between GPI-2 and PGM-2. The lack of a significant association between these two isozymes sugge sts that LAP-1 is located centrally on the chromosome. These three pai rs of linked loci are the first to be reported in almond.