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- Author or Editor: Raymond Baptiste x
Pigeonpea [Cajanus cajan (L.) Millsp.] and cowpea [Vigna unguiculata (L.) Walp.] seeds were inoculated with broth cultures of Rhizobium strains 3278, 3458, and 3472 at a population of ≈9.5 × 10 g viable cells/ml. They were planted at three air temperature regimes: 20/10C, 30/20C, and 38/25C (day/night), which generated variable rhizosphere temperatures of 17/6C, 26/15C, and 33/20C, respectively. Seeds and/or seedling roots were sampled at 3, 7, 11, and 15 days after planting and Rhizobium survival was enumerated as viable cells on agar media. Only strain 3458 in association with pigeonpea genotype ICPL8304 had a higher population at day 15 than that at the earlier sample dates. The duration of the strains in the rhizosphere, rather than temperature, influenced population changes. No strain showed a consistent increase in cell numbers from inoculation to 15 days after planting. There was no clear pattern of population changes for any strain within or across temperatures, hence it was difficult to identify any strain as having superior growth habits over another.
Low temperatures adversely affect legume- Rhizobium symbiosis in the temperate regions. Plant growth and N-fixation of two pigeonpea and two cowpea genotypes were examined at three temperature regimes (20/10 C, 30120 C and 38/25 C day/night). Sterilized seeds were inoculated with broth culture containing approximately 1 × 109 cells ml-1 of Bradyrhizobium USDA 3278, 3458 and 3472. Nitrogen fixation by pigeonpea was inhibited at 20/10 C. Cowpea IT82E-16 inoculated with USDA 3458 at 20/10 C produced the greatest amount of nodules. Inoculation had no effect on Nitrogenase activity in pigeonpea. Pinkeye Purple Hull inoculated with USDA 3472 at 20110 C had the highest Nitrogenase activity. These results indicate a wide degree of variability among genotypes and Bradyrhizobium in their response to temperature.
The number of viable cells produced by Rhizobium on solid media gives an indication of the strains survivability when used as an inoculant. This study was conducted to determine the viability of different strains of Bradyrhizobium. and their ability to nodulate pigeonpea (Calanus calan) and cowpea (Vlgna unguiculata) genotypes at two temperature regimes: 20/10°C and 30/20°C (day/night). Bradyrhizobium strains USDA 3278, 3362 and 3458 were cultured in yeast mannitol broth for 7 days from which a 10% dilution was made. From this dilution, 0.1 ml of a further 10 dilution was allowed to grow on yeast mannitol agar plates at the test temperatures. Strains cultured at 30/20°C had a higher number of viable cells than those cultured at 20/10°C for 4 days. While there was no difference between Rhizobium strains 3278 and 3362, strain 3458 had the highest number of cells per ml of 7-day old broth culture. Pigeonpea and cowpea plants inoculated at 20/10°C with the three Rhizobium strains and those inoculated with 3362 at 30/20°C had no nodules at 30 days after planting. At 30/20°C, plgeonpea and cowpea plants Inoculated with strain 3458 produced a higher number of nodules than those inoculated with strain 3278. These results indicate that temperature Influences the Rhizobium strains and their ability to nodulate plgeonpea and cowpea.
There is an increasing number of tropical legumes presently grown under temperate conditions with varying amounts of success, This growth chamber study examines the germination, modulation and N2 fixation of two cowpea and one pigeonpea genotypes at two temperature regimes, 15/10° C and 20/10° C, day/night. Prior to planting, surface sterilized seeds were inoculated by soaking in yeast mannitol broth containing approximately 2 × 106 cells ml-1 Bradyrhizobium (USDA 3384). Uninoculated control seeds were soaked in sterile water before planting. Air temperature of 15/10°C, day/night delayed seed germination, nodule initiation, and seedling development. Inoculated cowpea seeds planted at the 20/10° C regime attained 50% germination within 9 days, while inoculated pigeonpea took 13 days under similar regime. Bradyrhizobium persistence was not significantly affected by low temperature. The results indicate that nodule development for both crops were inhibited chiefly by a lack of developing root hairs at low soil temperature,