Enhancement of growth and yield of upland rice (Oryza sativa L.) by actinomycetes
2014
Cruz, J. | Lantican, N.B. | Delfin, E.F. | Paterno, E.S.
Growth room and greenhouse experiments examined the potential of actinomycetes as microbial inoculant to improve the yield of upland rice. Fifty-nine isolates from rice and corn rhizosphere and existing collection of the National Institute of Molecular Biology and Biotechnology (BIOTECH) were for growth promoting activities. Thirty-two isolates produced indole acetic acid (IAA), fourteen of which showed 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity while twenty-four solubilized bound phosphate in vitro. Five isolates were selected from among 59 isolates evaluated for further study. In the growth room, the selected actinomycetes increased root dry weight of upland rice by 24 to 71% at 14 days after sowing (DAS). All five isolates were rhizosphere competent as indicated by the root colonization study. Actinomycetes colonized the roots of upland rice with population densities ranging from 5.9 x 10 sup 5 to 1.2 x 10 sup 7 CFU/g rhizosphere soil with R:S ratios of 0.8 to 1.1. At 30 DAS, actinomycete isolate NB sub 3 population in the rhizosphere increased 100-fold with R:S ratio of 1.08. In the greenhouse, NB sub 3 combined with full rate of fertilization, had the highest shoot biomass. At full rate of fertilization, inoculation with NB1, AVermi7, YB6y and NB sub 3 and AVermi7 significantly increased grain yield by 62% and 48% respectively, relative to uninoculated treatment. The significant increase in grain yield by NB sub 3 and Avermi7 and their inability to colonize the rhizosphere demonstrate the potential of these actinomycetes as plant growth-promoting inoculants for upland rice. However, field assessment is recommended to determine the effect of biotic and abiotic stresses in the performance of promising actinomycetes.
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