High temperature, pH, and salt stresses in tropical alkaline soils limit nodulation and dinitrogen fixation by strains of Rhizobium from the root nodules of nitrogen fixing trees (NFTs). This study was conducted to determine the variability among Rhizobium strains isolated from different NFTs in growth response to high temperature, pH, and salt concentrations. Variable response to increases in temperature, pH, and salt concentrations was observed. Rhizobium strain isolated from Albizia lebbek survived at 50 °C, while Rhizobium strains isolated from Sesbania formosa, Acacia farnesiana, and Dalbergia sissoo were well adapted to grow on pH 12.0. All the Rhizobium strains tolerated salt concentrations up to 5.0%. Strains were further characterized with respect to utilization of 27 carbon sources and for their effectiveness in substrate utilization at pH 7.0 and 9.0. Generally higher rates of O2 consumption were observed at pH 7.0 compared with pH 9.0.Key words: Rhizobium, leguminous trees, root nodules, stress tolerance.

A field experiment was carried out during therabiseason of 2004-05 to find out the effect ofRhizobiumand phosphate solubilizing bacterial (PSB) inoculants on symbiotic traits, nodule leghemoglobin, and yield of five elite genotypes of chickpea. Among the chickpea genotypes, IG-593 performed better in respect of symbiotic parameters including nodule number, nodule fresh weight, nodule dry weight, shoot dry weight, yield attributes and yield. Leghemoglobin content (2.55 mg g−1of fresh nodule) was also higher under IG-593. Among microbial inoculants, theRhizobium+ PSB was found most effective in terms of nodule number (27.66 nodules plant−1), nodule fresh weight (144.90 mg plant−1), nodule dry weight (74.30 mg plant−1), shoot dry weight (11.76 g plant−1), and leghemoglobin content (2.29 mg g−1of fresh nodule) and also showed its positive effect in enhancing all the yield attributing parameters, grain and straw yields.

Carbon partitioning in plants may be viewed as a dynamic process composed of the many interactions between sources and sinks. The accumulation and distribution of fixed carbon is not dictated simply by the sink strength and number but is dependent upon the source, pathways, and interactions of the system. As such, the study of carbon partitioning through perturbations to the system or through focus on individual traits may fail to produce actionable developments or a comprehensive understanding of the mechanisms underlying this complex process. Using the recently published sorghum carbon-partitioning panel, we collected both macroscale phenotypic characteristics such as plant height, above-ground biomass, and dry weight along with microscale compositional traits to deconvolute the carbon-partitioning pathways in this multipurpose crop. Multivariate analyses of traits resulted in the identification of numerous loci associated with several distinct carbon-partitioning traits, which putatively regulate sugar content, manganese homeostasis, and nitrate transportation. Using a multivariate adaptive shrinkage approach, we identified several loci associated with multiple traits suggesting that pleiotropic and/or interactive effects may positively influence multiple carbon-partitioning traits, or these overlaps may represent molecular switches mediating basal carbon allocating or partitioning networks. Conversely, we also identify a carbon tradeoff where reduced lignin content is associated with increased sugar content. The results presented here support previous studies demonstrating the convoluted nature of carbon partitioning in sorghum and emphasize the importance of taking a holistic approach to the study of carbon partitioning by utilizing multiscale phenotypes.

Carbon partitioning in plants may be viewed as a dynamic process composed of the many interactions between sources and sinks. The accumulation and distribution of fixed carbon is not dictated simply by the sink strength and number but is dependent upon the source, pathways, and interactions of the system. As such, the study of carbon partitioning through perturbations to the system or through focus on individual traits may fail to produce actionable developments or a comprehensive understanding of the mechanisms underlying this complex process. Using the recently published sorghum carbon-partitioning panel, we collected both macroscale phenotypic characteristics such as plant height, above-ground biomass, and dry weight along with microscale compositional traits to deconvolute the carbon-partitioning pathways in this multipurpose crop. Multivariate analyses of traits resulted in the identification of numerous loci associated with several distinct carbon-partitioning traits, which putatively regulate sugar content, manganese homeostasis, and nitrate transportation. Using a multivariate adaptive shrinkage approach, we identified several loci associated with multiple traits suggesting that pleiotropic and/or interactive effects may positively influence multiple carbon-partitioning traits, or these overlaps may represent molecular switches mediating basal carbon allocating or partitioning networks. Conversely, we also identify a carbon tradeoff where reduced lignin content is associated with increased sugar content. The results presented here support previous studies demonstrating the convoluted nature of carbon partitioning in sorghum and emphasize the importance of taking a holistic approach to the study of carbon partitioning by utilizing multiscale phenotypes.

Jatropha (Jatropha curcas L.) is an oil bearing crop growing in tropical and subtropical parts of the world. The present study was undertaken to investigate the effects of different plant growth regulators on in vitro callus induction in physic nut (J. curcus). In the present study, it was observed that all the explants viz., leaf lamina, petioles, nodal segments and cotyledonary nodes showed good callus induction responses on various culture media thus tried. Leaf lamina and petioles showed 100.0% callus induction responses on different MS media supplemented with auxins and cytokinins alone or in combinations whereas, nodal segments and cotyledonary nodes showed maximum 89.6% and 83.9% callus induction respectively. The presence of 2, 4-D in culture media with auxins or cytokinins was essential for good callus growth. Among different explants tried, leaf lamina was the best responding explants and MS-13 media supplemented with 5×10-6 M NAA and 10-5 M 2, 4-D is the best callusing and growth supporting medium. However, the regenerative competence of the callus tissues can differ depending on the type of explants used because certain types of plant tissues have more favorable regeneration responses than others. Callus induction rate from all explant types was highest than other reports. The results obtained in the present study would facilitate the high callus induction and regeneration responses in J. curcus for its improvement using biotechnological tools.