Intercropped red beet and radish with green bean affected microbial communities and nodulation by indigenous rhizobia

Abstract

The impact of intercropping green bean (Phaseolus vulgaris L.) with red beet (Beta vulgaris L. var. rubra) and radish (Raphanus sativus L.), two non-legume plants, on the plants' yields, as well as the effect on occurrence and enumeration of microorganisms in the rhizosphere was studied. The intercrop efficacy evaluation, using Land equivalent ratio, revealed values above 1.0 for all intercropped treatments. Diversity of rhizobia from green bean nodules under different intercropping and fertilizing conditions was observed. On the basis of morphological and biochemical characteristics, 67 out of 158 isolates from green bean roots were selected as rhizobia (42.4%), confirmed by detection of 780 bp nifH gene fragments in nifH-PCR, and then clustered in 27 phenotype patterns. Production of exopolysaccharide succinoglycan was observed in 23 rhizobial isolates, while 6 were detected to solubilize tricalcium phosphate. Screening of genetic diversity using (GTG)(5)-PCR fingerprinting showed presence of six different patterns on the 92% similarity level.