Intergeneric protoplast fusion between Calocybe indica (milky mushroom) and Pleurotus florida aids in the qualitative and quantitative improvement of sporophore of the milky mushroom

Abstract

This article primarily focuses on the production of somatic hybrid sporophores through PEG-mediated protoplast fusion between Calocybe indica var. APK2 and Pleurotus florida. To screen the hybrid strains a selection strategy was followed based on the differential tolerance of NaCl level by the two parental genera. Basidiocarps could be successfully generated from eight out of fourteen hybrid lines that were maintained in culture. Hybridity of the fusant lines was established on the basis of their colony morphology, mycelial growth rate and hyphal traits, while the fruit-body-generating lines were demarcated on the basis of nature of sporophores, isozyme and RAPD markers. The degree to which the hybrid population differed among themselves and from their parents was assessed by analysing each of these morphological variables by one-way analysis of variance (ANOVA). RAPD bands of the fusant lines were similar to either parental bands or were new non-parental bands, which classified them into the microgenome and macrogenome insertion types. A dendrogram created with the help of UPGMA method of clustering and Euclidean distance exhibited three major clusters, in which the Pleurotus-Calocybe hybrids showed intra-cluster variations. Notably, P. florida was genetically distant from the hybrid lines, while C. indica was phylogenetically the dominant parent. Significant increase in bio-efficiency and gamma-linoleic acid content in these hybrid lines indicated quantitative as well as qualitative improvement of the newly developed somatic hybrids.