Studies on strain improvement in Agaricus bisporus

Abstract

Agaricus bisporus (J.E. Lange) Imbach, the white button mushroom, is highly nutritious edible fungus cultivated industrially worldwide, which has a unique taste and medicinal properties. The present investigations entitled Studies on strain improvement in Agaricus bisporus were conducted to isolate and evaluate the single spore cultures and selected generated hybrids from parental strains U3 and A15 for quality traits including other aspects like physiological studies and molecular characterization. Based on mycelial growth type i.e. fluffy, appressed and strandy, 500 single spore isolates from parental strains were evaluated for the selection of homokaryons and heterokaryons. Among these SSIs, 30 (twenty from parent strain U3 and ten from A15) were selected on the basis of fast mycelial growth rate (and#8805;2.0 mm per day) and strandy colony morphology for the evaluation of their fertility status. On the other hand, 16 single spore isolates (nine from U3 and seven from A15) having slow appressed mycelial growth (and#8804;1.2 mm per day) were selected and put to fruiting test in order to confirm their identity as homokaryons. The yield studies showed that among single spore isolates of strain U3 and A15, isolates U3-1 and A15-5 were identified as high yielders with yield of 22.3 kg/100 kg and 14.95 kg/100 kg compost, respectively. Out of one hundred thirty six (136) crosses, only five crosses were found compatible. Among five hybrids, Hb-2, produced highest average yield (22.2 kg/100kg compost) and also exhibited better morphological characteristics. The physiological studies on four selected high yielding single spore isolates viz., U3-1, U3-7, U3-8 and one hybrid (Hb-2) showed that among various solid media studied compost extract agar media supported maximum average mycelial growth. The optimum temperature and pH for the growth of single spore isolates, hybrid along with parent strain were found to be 25°C and 6.5, respectively. RAPD studies showed that the percentage of polymorphism detected in high yielding isolates and hybrids was 56.9 and 53.8 per cent, respectively. Maximum numbers of bands were produced by OPP-12 primer among high yielding single spore isolates, while primer OPQ-14 yielded maximum bands among developed hybrids. In all, total of six variants of high yielding SSIs along with three variants of hybrids were genetically characterized at 73 per cent similarity coefficient. newline newline newline