Evaluation of phenetic characters ·and growth Performance of native wood ear mushrooms (Auricularia species) on partially composted Agricultural wastes

Abstract

Wood ear mushrooms (Auricularia species) are a group of jelly fungi which occur as saprophytes on stumps or at the bases of dead or dying woody trees found in tropical regions. They have an ear shaped fruiting body from which they derive their common name. In other parts of the world, wood ear mushrooms have been domesticated and are valued for their nutritional and medicinal properties. Kenyan indigenous wood ear ~nushrooms which occur abundantly in Kakamega Forest have not been studied to evaluate their cultivation potential. Currently, the indigenous wood ear mushrooms face a threat of depletion due to over harvesting by the rural populace and rampant forest destruction. There is need to investigate their domestication potential in order to conserve their genetic resource. The objectives of this study were to evaluate the genetic diversity and to develop cultivation protocols for the indigenous wood ear mushrooms on malt extract agar, millet and sorghum grains and partially composted agricultural wastes. Mushroom germplasm collection was done at 3 different forest reserves within Kakamega Forest in Western Kenya. Mycelia growth was done through culturing of collected fruiting bodies on malt extract agar. External and internal mycelia and fruiting body features were evaluated and used to develop a descriptor for phenetic characterization of the wood ears. Data obtained from nine randomly selected accessions were used to calculate genetic similarity and to construct a dendogram. Some mycelia were used to raise spawns, which were used to inoculate the agricultural wastes. The agricultural wastes were treated to a short composting procedure, packed in heat resistant polypropylene bags and sterilized before inoculation. Inoculated substrates were kept in enclosed cabinets to allow mycelia propagation. They were then transferred to a cultivation room for mushroom growth. The cultivation experiment was set up as a two factorial Randomized Complete Block Design (RCBD) with variations in selected mushroom strains, different substrates and supplements. Three wood ear mushroom strains (Brown, Black, and White), four partially composted substrates (Wheat straws, Sugarcane bagasse, Grass straws and Corn cobs) and two supplements (Wheat bran and Rice bran) were used as treatments. Agronomic factors such as mycelia colonization rate, primordia initiation, yield and fruiting body quality were measured. Data collected were subjected to Analysis of Variance (ANOV A) to determine differences due to treatment effects. Mean separation was done using Least Significant Difference (LSD) at pSO.OS. Con-elation analysis was done to compare some of the variables. The results demonstrated significant genetic and agronomic variations between the strains. A significant dichotomy separating three (all white strains) out of the nine accessions at dissimilarity index of 0.318 was observed. The other two groups (black and brown strains) separated at a narrower dissimilarity index indicating that they were more closely related. From the cultivation experiment, no significant differences occurred between the strains on their mycelia growth on malt extract agar. The treatment 40% millet, 40% sorghum and 20% wheat bran gave the shortest duration of 10 days for spawn production. Averagely, the black strains gave the best performance on corn cobs supplemented with wheat bran giving values of3.7, 21, 318 g and 79% for fruiting body quality, number of fruiting bodies, fresh weight and biological efficiency respectively. The second best production was observed in wheat straw supplemented with wheat bran. Corn cobs and wheat straw supplemented with wheat bran were recommended to rural growers. Whereas morphological and productivity traits significantly separated the strains, further differentiation using molecular markers was recommended. Further investigation on their growth performance on other agricultural wastes and in different environmental conditions is necessary.