Variations in nodulation and nitrogen-fixing characteristics of slow-growing rhizobia isolates on pigeon-pea [Cajanus cajan (L.) Millsp.]
2002
Ramsubhag, Adash | Donawa, Alfred L. | Umaharan, Pathmanathan
Studies were conducted to determine the variation in nodulation and nitrogen-fixing characteristics of rhizobia isolates on two contrasting genotypes of pigeonpea [Cajanus cajan (L.) Millsp.] under greenhouse conditions. Significant isolate effects were noted for all nodulation and nitrogen-fixing parameters, except nodule number and specific acetylene reduction under pure-culture experimental conditions using the Leonard Jar system. Genotype effects were significant for all parameters except hydrogen evolution, specific hydrogen evolution, and relative efficiency of nodules. There was no significant genotype x isolate interaction for any of the characteristics evaluated. Linear regression analysis indicated that nodule weight alone accounted for variations in shoot nitrogen in Genotype ICPL88027, but both nodule weight and hydrogenase uptake activity were important in Genotype A-8-2. Results of 15N experiments on Piarco Fine Sand (Aquoxic Tropudults) showed that the performance of the isolates was generally related to pure-culture conditions. However, as the relative average performance of the isolates increased, the increases were greater in Genotype ICPL88027 than in Genotype A-8- 2. The implications of these results to rhizobia inoculations and breeding of pigeonpea for nitrogen fixation are discussed.
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