Production and characterization of somatic hybrids raised through protoplast fusion between edible mushroom strains Volvariella volvacea and Pleurotus florida

Twelve somatic hybrid lines were raised through polyethylene glycol-mediated intergeneric protoplast fusion between Volvariella volvacea and Pleurotus florida using a double selection method. Four hybrid lines belonging to two distinct colony morphology types could be maintained in culture. Basidiocarps could be generated from two hybrid lines, one of which showed resemblance to the P. florida parent while the other showed intermediate parental morphology. Hybridity of the fusant lines was established on the basis of colony morphology, mycelial growth rate, hyphal traits, fruit body morphology, isozyme and RAPD analysis. Four isozyme activities were analyzed to provide biochemical criteria for detection of polymorphism among the hybrids and their parents. Using 20 random decamers a total of 203 RAPD bands ranging from 0.09 to 1.6 kb were observed. The UPGMA method of clustering exhibited two major phylogenetic clusters, the first of which comprised of the parents, two fruit body generating hybrid lines and their subsequent fruit body derived lines, while the two non-fruit body generating hybrid lines formed the out group of the first major cluster. Screening of a Pleurotus type hybrid line having high biological efficiency and generation of a temperature tolerant Pleurotus type line through backcross mating between a non-fruit body generating somatic hybrid and V. volvacea parent are the key achievements of this fusion programme.