Strain selection of growth promoting Herbaspirillum spp. in rice

Abstract

Endophytic bacteria of the genus Herbaspirillum spp. are able to fix nitrogen and produce plant growth promoting compounds. The combination of these mechanisms can contribute to optimizing the efficiency of nitrogen fertilizers in crops of agricultural importance The aim of this work was to select strains of diazotrophic bacteria Herbaspirillum spp. to promote growth in rice plants. 113 diazotrophs were isolated from aerial tissue of different varieties and phenological stages. Eleven isolates were characterized as presumptive Herbaspirillum spp. Of these, two isolates obtained from the vegetative stage (9.4 and 4.2) produced significant increases in shoot dry matter under controlled conditions. Both isolates were tested in rice plants grown in greenhouse in the absence and presence of urea. The root biomass of plants inoculated with isolate 4.2 was significantly higher both in the presence and absence of 50% of the dose of urea used by farmers (100 kg/ha). Plant growth-promoting effect of strain 4.2 was reflected in plant yield. Inoculated and non inoculated treatments were carried out with different doses of nitrogen fertilization in field conditions. A 15% increase in plant yield was obtained for inoculated plants in comparison with non inoculated. The 16S rRNA gene sequence indicated that 4.2 strain belongs to the genus Herbaspirillum spp. Therefore, we conclude that Herbaspirillum spp. 4.2 strain has potential as biofertilizer in rice, maximizing the efficiency in the use of resources and sustainability.