Rhizobia as biofertilizers for mushroom cultivation

Mushrooms are conventionally grown with inorganic and organic nutrients added to their culture substrate. In the past, it had been reported using N balance studies that mushroom fungi such as Pleurotus spp. can fix N sub(2) biologically on natural substrates and that this might be quite commonly found among them. However, a later study showed that only associations of Pleurotus spp. and N sub(2)-fixing bacteria (diazotrophs, e.g. rhizobia) can fix N sub(2). Microbial biofilms developed by diazotrophic colonization on the fungal filaments were observed to show nitrogenase activity, and hence increased N accumulation in the hyphae. Recently, N sub(2)-fixing alpha-Proteobacteria were observed to be predominant in bacterial communities in truffles, a type of mushroom found in the soil. Based on this knowledge, it has now been shown in Iran that rhizobia can be used as biofertilizers for increasing the harvest and nutritional quality of cultivated mushrooms more efficiently.