Piriformospora indica: A Novel Plant Growth-Promoting Mycorrhizal Fungus

Piriformospora indica, a member of the newly created order Sebacinales, is extremely versatile in its mycorrhizal associations and its ability to promote plant growth. P. indica is widely distributed as a symptomless root endophyte, and it colonizes members of bryophytes, pteridophytes, gymnosperms and angiosperms. P. indica and allied members of Sebacinales have been reported to occur in four continents. The existing literature suggests that the multitude of mycorrhizal interactions in Sebacinales may have arisen from an ancestral endophytic habitat by specialization. Considering their proven beneficial influence on plant growth and their ubiquity, endophytic P. indica may have been a previously unrecognized universal hidden force in plant ecosystems. Root colonization by P. indica results in an increase in plant growth, early flowering, higher seed yield, alteration in the secondary metabolites, and adaptation to abiotic and biotic stresses. The colonization of roots begins with a biotrophic growth phase, in which living cells are colonized, and continues with a cell death-dependent phase, in which root cells are actively killed by the fungus. The complexity of sebacinalean symbiosis is further enhanced by the presence of endocellular bacteria which may represent significant determinants for a successful outcome of the symbioses. P. indica is shown to have enormous bioprotective potential against plant pathogens and insect pests of agricultural and horticultural crops. Recently, decoding of P. indica's genome has revealed its potential for application as a plant growth-promoting mycorrhizal fungus for realizing the targeted improvement in the production of crop plants.