Identification and performance of endophytic actinobacteria Ahn65 with functions of growth promotion and disease resistance for rice

Abstract

With positive effects on growth and disease resistance of plants, endophytes play a key role in effective crop production. In this study, actinobacteria resources with functions of growth promotion and disease resistance for rice were explored, and endophytic actinobacteria were isolated from rice. Then, growth promotion and disease resistance of the isolated endophytic actinobacteria were investigated, followed by analysis of phenotype and cultivation characteristics, as well as molecular identification. Additionally, the functions of growth promotion and disease resistance for rice of isolated endophytic actinobacteria were explored. Ahn65, a strain of endophytic actinobacteria, was isolated from rice and purified. It exhibited various growth-promoting functions, including nitrogen fixation, iron carrier generation, potassium solubilization and secretion of indole-3-acetic acid (IAA), and could significantly inhibit the mycelium growth of Magnaporthe oryzae(M.oryzae). It grew well under 26–34 °C, pH 5–9, and salt concentration of 0–5%, and the optimized conditions were as follows: temperature 28 °C, pH 9, salt concentration of 1 %. The results of stress test revealed good UV resistance of Ahn65. Both hydroponics and pot experiment indicated that Ahn65 had significantly positive effects on seed germination, root development and stem growth of rice, wherein the seed germination rate was enhanced by 27.87 %. After 21-day culture, root length, stem length and number of lateral roots of the treated group were 39.50 %, 15.80 % and 11.54 % higher than those of the control group, respectively. In pot experiment, after 60-day culture, root length, stem length and tiller number of the treated group were 12.01 %, 18.00 % and 16.00 % higher than those of the control group, respectively; rice yield at maturation stage of the treated group was 12.18 % higher than that of the control group; application of spore suspension of Ahn65 can effectively reduce the incidence rate of rice neck blast, with a biological prevention efficacy of 36.12 %. Overall, Ahn65 is highly promising as it exhibited significant functions of growth promotion and disease resistance for rice.