Genetic diversity in populations of the Pleurotus eryngii complex in Israel

Random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was u sed to assess the genetic diversity in twelve populations (a total of 144 i solates) of the Pleurotus eryngii complex, sampled in Israel. Our results s how a higher level of diversity of RAPD polymorphism in the populations, es pecially in the drier, stressful climates. Twelve primers used in this stud y amplified 164 scorable RAPD loci, of which 163 (99.4%) were polymorphic a nd only I monomorphic, Out of the 164 loci, 123 (75%) varied significantly (P < 0.05) in allele frequencies among populations. This total proportion ( 75%) of significant polymorphic loci far exceeds the 5% level expected by c hance (binomial test, P < 0.000001). The levels of polymorphism and gene di versity appeared to be highly significantly different between the populatio ns. Sixty-eight per cent of the RAPD diversity was within populations and 3 2% was between populations. Inter-population genetic distances showed posit ive association with geographic distance, which was confirmed with spatial autocorrelation analysis of RAPD frequencies. Spearman rank correlation rev ealed a strong positive association between high polymorphism and the aridi ty index. In multiple regression, the coefficient of determination of polym orphism and gene diversity was explained by climatic variables linked to te mperature and humidity. Our findings further demonstrate the validity of th e 'environmental theory of genetic diversity' hypothesis within P. eryngii populations in Israel. We suggest that natural selection develops a high le vel of RAPD polymorphism as adaptation to cope with stressful and temporall y heterogeneous environments.