Opportunistic endophytism of Trichoderma species in rice Pusa Basmati-1 (PB1)

Abstract

Microbes that colonize internal tissues of plants are called endophytes, andare known for their functional role against biotic/abiotic stress and growth promotion activity in plants. The ascomyceteous fungus Trichoderma spp. (Teleomorph: Hypocrea) are well known antagonists cum biocontrol agents. In this study, a total of five Trichoderma isolates from two different species viz., T. asperellum (TaR1, TaR2 and TaR3) and T. asperelloides (TaR4 and TaR5) collected from different agro-climatic zones in Rajasthan, India were evaluated for their endophytism in rice variety Pusa Basmati-1 (PB-1) through soil and seed treatment. An attempt was made to re-isolate the fungus from rice roots (seed and soil treated) and further subjected to microscopic and molecular analysis. Re-isolation results revealed that culture growth of Trichoderma spp. isolated was similar to that of the inoculated ones. The microscopic analysis (light and scanning electron microscopy) results also confirmed that the re-isolated endophytic fungus were identical to the inoculated ones. These results were further confirmed by polymerase chain reaction (PCR) amplification of the rDNA region (18SrRNA, ITS1, 5.8SrRNA, ITS2 and 28SrRNA) and translation elongation factor 1 (Tef1) with the re-isolated Trichoderma asperellum and T. asperelloides isolates. In this study, it has been confirmed that Trichoderma asperellum and T. asperelloides turns endophytic in rice after introduction through seed and soil treatment.