Call Prefix : PR-T

Call Suffix : 1994

Call Cutter : T - SoSc 16

Location : SEARCA Library

Format : TD

Publisher : University of the Philippines Los Baños,

Publication Date : November 1994

Publication Place : Los Baños, Laguna, the Philippines :

Summary : Changes in rhizobia population in acid soil and in the mung bean rhizosphere were assessed in pot experiments. Acid tolerant M79-17-19 and acid sensitive M79-20-124 mung bean cultivars grown in unlimed (pH 4.6) and limed pH 6.2) Luisiana clay were inoculated with antibiotic resistant mutants of Bradyrhizobium sp. (Vigna): BVr 9 (acid-tolerant) and TAL 209 (acid-sensitive). In the unlimed soil, regardless of cultivars and strain, total population of rhizobia in the soil and rhizosphere was depressed at two and five weeks after planting (WAP), but it was significantly increased by liming. The total population of rhizobia either in the soil or in the rhizosphere tended to decrease from 2 WAP to 5 WAP. In general, inoculum strain population was higher in the limed than in the unlimed soil. However, higher numbers were observed at 5 WAP than at 2 WAP. Regardless of cultivar, the rhizosphere population of Bvr 9 was similar with or without lime. TAL 209 had a significantly lower number in the rhizosphere without lime application. The interaction of lime application, strain, and cultivar had significant influenced nodule occupancy by the inoculum strain in the primary and secondary roots. Without lime, more nodules were formed by the inoculum strains on the acid tolerant cultivar than on the acid-sensitive cultivar. A separate pot experiment showed that in unlimed and limed Luisiana clay, inoculation with mycorrhiza resulted in higher population of Bvr 9 in the mung bean rhizosphere than phosphorus application. In the presence of mycorrhiza, Bvr 9 formed 100 percent of the nodules in both secondary and primary roots while the average nodule occupancy of 80 percent by 6 WAP. In the absence of the host plant, Bvr 9 showed better survival than TAL 209 in unlimed and limed soil.