Effectiveness Of Rhizobia Strains Isolated From South Kivu Soils On Growth Of Soybeans (glycine Max).

Abstract

Identification of effective indigenous Bradyrhizobium strains which nodulate soybean varieties could trigger development of an industry for inoculant production with use of strains adapted to local conditions. This study was conducted in South Kivu to identify and select effective rhizobial strains nodulating soybean present in South Kivu soils. One hundred and seven isolates from root nodules of legumes plants sampled in five villages of South Kivu were tested in sterile sand in the greenhouse in the modified Leonard’s jars. 10% of these isolates produced higher nodules and plant shoot dry weight (P˂0.001) compared to the commercial strain USDA110 .The effectiveness index of the isolates NAC10, NAC22, NAC37, NAC40, NAC42, NAC45, NAC46, NAC50, NAC67 and NAC75 was higher compared to the commercial isolates and were selected for further evaluation using soils in the greenhouse. From the potted soils experiment in the greenhouse the isolates NAC10, NAC22, NAC40 and NAC75 were classified as competitive and highly effective. Increments in nodule number and shoot dry weight were observed when the plant was inoculated with an effective rhizobial isolate compared to the controls. the best strains were tested also for carbon source utilization ability. Three sources of carbon were used namely mannitol, glucose and glycerol. From this experiment there was significant differences between the three carbon sources in sustaining viable counts of the tested isolates from South Kivu soils (P<0.005) with higher carbon substitution index with the glucose.