Drought mitigation in cocoa (Theobroma cacao L.) through developing tolerant hybrids

Background Cocoa, being a shade loving crop cannot withstand long periods of water stress. Breeding for drought tolerance is the need of the hour due to change in climatic condition and extension of crop to non-traditional areas. Hybrids were produced by crossing four tolerant genotypes in all possible combination. The cross GV1 55 x M 13.12 didn’t yield any fruit due to cross incompatibility between these genotypes. Various biochemical parameters act as the true indicators to select tolerant and susceptible types. The major biochemical parameters considered after imposing stress included proline, nitrate reductase activity, superoxide dismutase content and glycine betaine. Results The drought tolerant hybrids were having high amount of proline, superoxide dismutase enzyme and glycine betaine content. Normally, plants having drought stress show low amount of nitrate reductase activity. However, in case of hybrids, the drought tolerant hybrids were having higher NR activity than the susceptible hybrids. The highest amount of NR was found in the control plants kept at fully irrigated conditions. Conclusions This experiment showed the role of different biochemical enzymes and osmolytes in giving tolerance to plants during drought stress. Logistic regression analysis selected proline and nitrate reductase as the two biochemical markers for identifying efficient drought tolerant genotypes in the future breeding programmes.

Biosynthesis, Characterization and Antimicrobial Activity of Silver Nanoparticles by Aspergillus niger Isolated from the Rotten Onion

Present day, researchers turn to natural processes such as using biological microorganisms in order to develop reliable and ecofriendly methods for the synthesis of metallic nanoparticles. In this research, we had investigated extracellular biosynthesis of silver nanoparticles using A. niger, isolated from the rotten onion. The formation of silver nanoparticles in the cell filtrates was confirmed by change in the color of filtrates of cell, absorption peak between 300-600 nm in UV-VIS spectra. There was a logical relationship in the efficiencies of studied A. niger in the production of silver nanoparticles and their nitrate reductase activity. The microscopic analysis of the colonies of A. niger was done by using 0.1% congo red dye. It effectively showed the morphological structure of the fungus with Conidia and Conidiophores. Hence, 0.1% congo red dye was used to stain the fungal smear and study it under the microscope. The present study showed that A. niger have potential for the biosynthesis of silver nanoparticles depending on their nitrate reductase activity.

Attenuation of Mercury Phytotoxicity with a High Nutritional Level of Nitrate in Alfalfa Plants Grown Hydroponically

Background and aims Mercury (Hg) is one of the most dangerous pollutant heavy metals to the environment, which causes several toxic effects in plants upon accumulation, such as induction of oxidative stress. Nitrogen (N) is one of the most limiting macronutrient for plants, being mostly assimilated as NO3─ which is reduced to NO2─ by the enzyme nitrate reductase (NR), prior its reduction to NH4+.Methods We studied the physiological alterations caused by Hg (0, 6 and 30 µM) in alfalfa plants grown at two different levels of NO3─: low, (2 mM; LN), and high (12 mM; HN) for one week using a semi-hydroponic culture system.Results Several parameters of oxidative stress such as lipid peroxidation, chlorophyll content, biothiol concentration and, ascorbate peroxidase (APX) and glutathione reductase (GR) activity showed that HN plants were less affected by Hg. Nitrate reductase activity and NO3─ concentration was altered under Hg stress, with lower impact in plants nourished with high NO3─. Conclusions Our results highlight the importance of the nitrogen nutritional status to improve tolerance to toxic metals like Hg.

Physiological screening of ruderal weed biomonitors of atmospheric nitrogen deposition

Background: Plants take up various species of reactive nitrogen and their different physiological responses to the increase of nitrogen availability can be useful in biomonitoring. Questions: Does atmospheric nitrogen deposition affect the physiology of ruderal weeds? Which species are most responsive to the nitrogen deposition? Studied species: Eleven ruderal weeds. Study site and dates: Morelia, Michoacán, Mexico. 2019. Methods: Under scenarios of 10, 20, 40 and 80 kg N ha-1year-1, we quantified plant responses of biomass production, nitrate reductase activity, chlorophyll content, photosynthetic efficiency, δ15N, nitrogen and carbon content. Results: Total biomass production increased with the rate of nitrogen deposition for Bidens pilosa, Chloris gayana,Lepidium virginicum, and Pennisetum setaceum, as chlorophyll content in B. pilosa, C. gayana, and L. virginicum. In turn, the below- to above-ground biomass ratio decreased for B. pilosa and C. gayana, as photosynthetic efficiency in C. gayana, L. virginicum, and Chloris pycnothrix. Nitrate reductase activity was only affected in L. virginicumm, C. gayana, and T. officinale. With the exception of C. pycnothrix, the nitrogen content increased, while the carbon augmented in C. gayana, C. pycnothrix, and P. setaceum. The C/N ratio was reduced in B. pilosa, C. gayana, Chloris virgata, P. setaceum, and T. officinale. The δ15N was increased in B. pilosa, C. gayana, C. virgata and P. setaceum. Conclusions: Bidens pilosa, C. gayana, L. virginicum, and P. setaceum were the species with more affected variables to nitrogen deposition, which could be useful in the biomonitoring.

NITROGEN AND PHOSPHORUS METABOLISM OF ANABAENA DOLIOLUM UNDER UV-B AND PESTICIDE STRESS

The effects of UV-B and pesticides (Butachlor and Carbofuran) on nitrogen and phosphorus metabolism have been studied on filamentous, nitrogen-fixing cyanobacterium, Anabaena doliolum. The study showed a decrease in the uptake of NH4+, PO4-3, activities of nitrogenase, glutamine synthetase, and alkaline phosphatase, when the cells were exposed to UV-B and pesticides. The interaction of two stresses showed the additive type of behavior for the studied parameters. In contrast, a significant increase in NO3- uptake and nitrate reductase activity was seen when Anabaena cells were exposed to different doses of UV-B.

Drought Mitigation in Cocoa (Theobroma Cacao L.) Through Developing Tolerant Hybrids

Background:Cocoa, being a shade loving crop cannot withstand long periods of water stress. Breeding for drought tolerance is the need of the hour due to change in climatic condition and extension of crop to non traditional area. Hybrids were produced by crossing four tolerant genotypes in all possible combination. The cross GVI 55 x M 13.12 didn’t yield any fruit due to cross incompatibility between these genotypes. Various biochemical parameters act as the true indicators to select tolerant and susceptible types. The major biochemical parameters considered after imposing stress included proline, nitrate reductase activity, superoxide dismutase content and glycine betaine. Results: The drought tolerant hybrids were having high amount of proline, superoxide dismutase enzyme and glycine betaine content. Normally, plants having drought stress shows low amount of nitrate reductase activity. However, in case of hybrids, the drought tolerant hybrids were having higher NR activity than the susceptible hybrids. The highest amount of NR was found in the control plants kept at fully irrigated conditions.Conclusions: This experiment showed the role of different biochemical enzymes and osmolytes in giving tolerance to plants during drought stress. Logistic regression analysis selected proline and nitrate reductase as the two biochemical markers for identifying efficient drought tolerant genotypes in the future breeding programmes.