MOLECULAR CHARACTERIZATION OF RHIZOBIA STRAINS ASSOCIATED WITH MUNGBEAN (VIGNA RADIATA), IN SOILS OF SUDANO-GUINEAN AND SAHELIAN AGROECOLOGICAL ZONES OF MALI

Abstract

In the Sudano-Guinean and Sahelian zones of Mali, the decline in soil fertility is a key challenge for a sustainable enhancement of agricultural productivity. In addition, studies on the diversity of bacteria associated with Mungbeans are rare, with very few studies conducted on their identification and molecular characterization in the soils of the major agricultural production basins in the Sudano-Guinean and Sahelian Guinean zones of Mali. This study was therefore motivated not only by these different challenges of productivity and soil fertility, but also by the numerous nutritional and agronomic interests of mung beans and the possibility of using its associated bacteria as bio-fertilizers. It aims at contributing to the improvement of mung bean (Vigna radiata L) productivity and the promotion of its cultivation using inocula based on indigenous and efficient bacteria. To achieve this objective, soil samples were taken from various farmers' fields in the two studied areas. The Physico-chemical characteristics of the soils were determined, and trapping trials were conducted in the greenhouse on these soils with Mung bean as the trap plant. The nodules formed on the plants were harvested, the rhizobia contained in these nodules were isolated, the IGS of the 16S-23S rDNA of the isolates was analyzed using PCR-RFLP, and an inoculation test was carried out in a growth chamber to verify the infectivity of the isolates. Eighty-three (83) isolates divided into two groups according to their color (whitish, yellowish) and three (03) IGS types (I, II, III) were encountered with a large dominance of IGS type I in the Guinean zone and that of IGS types I and II in the Sahel zone. Two (02) isolates of type IGS I showed a higher infectivity. These results show a low diversity of rhizobium strains associated with Mung bean in the studied soils. It would be interesting to extend this study to other areas of Mali for strains that associate with Mung bean.