Selection of multi-purpose native rhizobia from a new red clover cultivar developed in Brazil

Abstract

Red clover is an important forage legume in the livestock sector in southern Brazil, but regional climatic conditions compromise its management. Therefore, UFRGS and EMBRAPA have developed the cultivar URS BRS Mesclador adapted to the southern region of Brazil, but efficient rhizobia for it is still missing. This study aimed to select symbiotic rhizobia for the URS BRS Mesclador and evaluate their efficiency in biological nitrogen fixation in red clover and growth promotion in the rye. Seven rhizobia isolates from red clover nodules of the new cultivar and nine strains from the SEMIA Rhizobia Culture Collection were evaluated for their ability to promote plant growth. Certain strains exhibited notable abilities among the studied rhizobia, such as Rhizobium changzhiense Tp46 producing indole compounds (5.33 μg ml−1), Semia 2076 with a phosphate solubilization index of 2.4, and R. leguminosarum Tp57 and Tp34, SEMIA 2038, and SEMIA 276 with high siderophore production index. Isolates Tp46 and Tp34 demonstrated potential by displaying high biological nitrogen fixation efficiency in red clover and promoting rye growth. These promising results warrant further investigation for field studies with a long-term goal of developing inoculants for red clover cultivation in Brazil.