Diazotrophy of rhizobia associated with rice plants cv. INCA LP-5 and INCA LP-7

Abstract

The rhizobia have been studied, fundamentally, for their capacity to carry out the biological nitrogen fixation, an attribute that at present has also been verified in its interaction with non-legume plants. The aim of this research was to evaluate the capacity to fix nitrogen of rhizobia strains, from the rhizosphere rice plants cultivars INCA LP-5 and INCA LP-7, cultivated in intensive monoculture. The research was carried out in 2018, at the National Institute of Agricultural Sciences from Cuba and at the Center for Genomic Sciences in Mexico. The diazotrophy of three Rhizobium strains was determined by three methods. The amplification of nifH gene, for which three sets of primers and different alignment times and temperatures were used in the PCR technique; through the growth of strains in two semi-solid nitrogen-free media and through inoculation tests with siratro and soy  plants, under controlled conditions. The nifH gene was not amplified from any of three rhizobia strains; however, they grew in nitrogen-free media and formed effective nodules on siratro and soy roots. The strain Rhizobium sp. Rpr11 produced the highest number of nodules in both legumes roots, 30 days after inoculation. This research is a first approach to understand the capacity to nitrogen fixation of rhizobia strains associated with Cuban rice cultivars under intensive monoculture.