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Wild populations of edible species are important source of genetic variability for cultivated lines that can undergo a drastic loss of diversity resulting from man's selection. The development of tools aimed at the clear-cut and safe identification and assessment of genetic variability of the wild and cultivated strains is thus a fundamental goal of molecular genetic research. In this study, we used two polymerase chain reaction (PCR)-based fingerprinting methods-amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism (RFLP) of laccase and manganese peroxidase genes-to assess genetic differences among strains and independently evolving lineages belonging to the Pleurotus eryngii complex. Both laccase RFLP and AFLP have been proved to distinguish unambiguously the three taxa studied: Pleurotus ferulae, P. eryngii, and P. eryngii var. nebrodensis. AFLP also showed enough sensitivity to detect polymorphisms among the strains, proving to be an efficient DNA fingerprinting tool in studies of strain assignment. The divergent RFLP laccase and manganese peroxidase patterns are also discussed in relation to the role played by these genes in the interaction between these fungi and their host plants.

A study using allozymes and PCR fingerprinting was conducted to estimate the genetic diversity of Italian populations of two economically important cultivated fungal taxa, Pleurotus eryngii and P. ferulae. Very little is known about the genetic diversity distribution pattern of these taxa. Heterozygote deficiency was observed at few loci; in fact the inbreeding coefficients were not high, which demonstrates that mechanisms restrain the inbreeding act at the local level. Estimates of genetic differentiation indicated a pattern of greater variation within, rather than between, populations. These results were supported by AMOVA analysis, which attributed a low proportion of the total genetic variation to large geographical scale divergence, and indicated that most of the genetic diversity was because of differences within populations. This distribution pattern of genetic variation of P. eryngii and P. ferulae populations seems to be the result of high gene flow, by efficient basidiospore dispersal, and outcrossing mechanisms, which restrain inbreeding within populations.

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With the use of isozymes and PCR-fingerprinting analysis molecular markers were found between the varieties Pleurotus eryngii var. eryngii and P. eryngii var. ferulae within the Pleurotus eryngii complex, which allowed the identification of the fruitbodies collected in Southern and Central Italy. The study of sympatric localities has shown that there is no gene exchange between them in the field. The post-mating barriers between these taxa are not yet completely efficient. However, in the field the gene pools of the two taxa appear isolated and associated with specific host plants: Eryngium campestre and Ferula communis. On the basis of the genetic and ecological differences observed and given the absence of gene exchange in sympatric localities, P. eryngii and P. ferulae are to be considered distinct biological species