Aislamiento De Bacterias Endófitas Fijadoras De Nitrógeno En Plantas De Arroz Cultivadas En Diferentes Suelos

Abstract

Rice (Oryza sativa) is a major agricultural product exported by Uruguay. It is imperative to find new tools to increase the yield and to improve the crop nutrient utilization keeping sustainable and healthy conditions of production. Endophytic bacteria grow in internal vegetal tissues without causing symptoms of damage to the plant. They can have a major impact on the cereal productivity by stimulating plant growth by mechanisms such as hormone production, antagonism of pathogens or atmospheric nitrogen fixation (diazotrophic bacteria). The use of biological inoculants instead of chemical nitrogen fertilizers is a strategy that reduces the environmental impact of agrochemicals. The objective of this work is to isolate endophytic diazotrophyc bacteria in rice planted in different soils from Uruguay. The assay was performed in controlled conditions sowing sterilized seeds in soils of different origin and characteristics. Plants yield was evaluated after 20 days of incubation. Diazotrophic bacteria were isolated from roots and aerial tissues of the plants. Different culture media and incubation conditions were used to recover aerobic, anaerobic sporulated and anoxigenic phototrophic bacteria. More than 50 isolates were obtained and tested for the diazotrophic activity and for the amplification of nifH gene. The diversity of the isolates was analyzed by ARDRA (Amplified Ribosomal DNA Restriction Analysis). The identification was performed by 16S rRNA gene sequencing. The main species detected were Azospirillum lipoferum, Herbaspirillum seropedicae, Enterobacter cloacae and Paenibacillus graminis. These strains could be good tools to develop inoculants to promote the growth in rice plants.