Effects of copper concentration in soil on prolife ration and survival of rhizobia, nodulation and biological nitrogen fixation in beans, cowpeas and soybeans

A study was conducted in which two strains of the fast – growing bean rhizobia- PV 1 and PV 2 and two others of the slow – growing bradyrhizobia for cowpeas and soybean- CP 1 & GM 8 , respectively, were used to test their ability to: - (a) proliferate in copper contaminated liquid media, (b) survive in copper contaminated soil, (c) nodulate respective host legumes and (d) fix nitrogen under increasing copper levels both in vitro and in vivo. Known population sizes of each of the strains were exposed to copper concentrations in the range: 0, 20, 40 60, 80 and 100 ppm in either Yeast - extract Mannitol Broth or in modified Leonard Jar assemblies or potted soil. Most Probable Number (MPN) studies were also done to estimate populations of the native strains of the fast - and slow - growing rhizobia in a Cu -contaminated soil. Results indicated that copper was more toxic to the slow – growing bradyrhizobia than to the fast – growing rhizobia. Reduction in population sizes in vitro was more significant (p = 0.05) for bradyrhizobial than for rhizobial strains. Reductions in fresh nodule volume, fresh nodule mass and total shoot nitrogen were more significant (p = 0.05) in the bradyrhizobial – than in rhizobial – legume associations. Copper depressed the populations of slow – growing strain CP 1 and GM 8 in vivo more than those of the fast – growing strains PV 1 and PV 2 . There was no statistically significant (p = 0.05) effect of 82.5 mg Cu/kg soil on numbers (MPN) of native rhizobial strains, probably due to adsorption of Cu by soil colloids. This study showed that based on the solution culture, potted soil and soil survival experiments, slow - growing rhizobia were more susceptible to Cu toxicity than were the fast - growing rhizobia.Association of African Universities (AAU

Effects of copper concentration in soil on prolife ration and survival of rhizobia, nodulation and biological nitrogen fixation in beans, cowpeas and soybeans

A study was conducted in which two strains of the fast – growing bean rhizobia- PV 1 and PV 2 and two others of the slow – growing bradyrhizobia for cowpeas and soybean- CP 1 & GM 8 , respectively, were used to test their ability to: - (a) proliferate in copper contaminated liquid media, (b) survive in copper contaminated soil, (c) nodulate respective host legumes and (d) fix nitrogen under increasing copper levels both in vitro and in vivo. Known population sizes of each of the strains were exposed to copper concentrations in the range: 0, 20, 40 60, 80 and 100 ppm in either Yeast - extract Mannitol Broth or in modified Leonard Jar assemblies or potted soil. Most Probable Number (MPN) studies were also done to estimate populations of the native strains of the fast - and slow - growing rhizobia in a Cu -contaminated soil. Results indicated that copper was more toxic to the slow – growing bradyrhizobia than to the fast – growing rhizobia. Reduction in population sizes in vitro was more significant (p = 0.05) for bradyrhizobial than for rhizobial strains. Reductions in fresh nodule volume, fresh nodule mass and total shoot nitrogen were more significant (p = 0.05) in the bradyrhizobial – than in rhizobial – legume associations. Copper depressed the populations of slow – growing strain CP 1 and GM 8 in vivo more than those of the fast – growing strains PV 1 and PV 2 . There was no statistically significant (p = 0.05) effect of 82.5 mg Cu/kg soil on numbers (MPN) of native rhizobial strains, probably due to adsorption of Cu by soil colloids. This study showed that based on the solution culture, potted soil and soil survival experiments, slow - growing rhizobia were more susceptible to Cu toxicity than were the fast - growing rhizobia.Association of African Universities (AAU

Effects of elevated copper levels on biological nitrogen fixation and occurrence of rhizobia in a Tanzanian coffee-cropped soil

Journal of Agricultural Science and Applications (J. Agric. Sci. Appl.)A study was conducted to investigate the effects of increasing copper concentration in soil on rhizobial occurrence and the process of biological nitrogen fixation. Two slow-growing bradyrhizobial strains CP, and GM, and two fast-growing rhizobial strains PV, and PV2 were studied by comparing their performance under increasing copper concentrations in greenhouse-based assays involving modified Leonard jar assemblies and potted-soil experiments. Additionally, field samples from soils grown to coffee and subjected to long-term use of copper-based fungicides were analyzed for their total indigenous rhizobial populations using the most probable number-plant infection technique. Results indicated that elevated copper levels in the growth medium had inhibitory effects on nodulation, biological N2 fixation and overall rhizobial numbers in soil. Significant (p= 0.05%) reductions in fresh nodule mass, fresh nodule volume and total shoot nitrogen were recorded when copper concentration was increased from 0 to 100 ppm in both modified Leonard jar assemblies and potted-soil trials. Effective decrements in all the three parameters of fresh nodule mass, fresh nodule volume and total shoot nitrogen were more pronounced with the slow-growing bradyrhizobial strains of CP, and GM, than with the fast-growing PV, and PV2. The MPN-plant infection technique results showed a non-significant (p=0.05) but substantial decrement in rhizobial and bradyrhizobial numbers when the copper-contaminated field soil (82.5 mgCu/g soil) was compared to a control soil (1.8 mgCu/g soil). The study concludes, therefore, that elevated levels of copper in soil could be harmful to free-living rhizobia and their abilities to fix N2 in respective symbiotic associations with legume species. Such negative effects were more pronounced in the slow-growing bradyrhizobial than rhizobial species used

Effects of elevated copper levels on biological nitrogen fixation and occurrence of rhizobia in a Tanzanian coffee-cropped soil

Journal of Agricultural Science and Applications (J. Agric. Sci. Appl.)A study was conducted to investigate the effects of increasing copper concentration in soil on rhizobial occurrence and the process of biological nitrogen fixation. Two slow-growing bradyrhizobial strains CP, and GM, and two fast-growing rhizobial strains PV, and PV2 were studied by comparing their performance under increasing copper concentrations in greenhouse-based assays involving modified Leonard jar assemblies and potted-soil experiments. Additionally, field samples from soils grown to coffee and subjected to long-term use of copper-based fungicides were analyzed for their total indigenous rhizobial populations using the most probable number-plant infection technique. Results indicated that elevated copper levels in the growth medium had inhibitory effects on nodulation, biological N2 fixation and overall rhizobial numbers in soil. Significant (p= 0.05%) reductions in fresh nodule mass, fresh nodule volume and total shoot nitrogen were recorded when copper concentration was increased from 0 to 100 ppm in both modified Leonard jar assemblies and potted-soil trials. Effective decrements in all the three parameters of fresh nodule mass, fresh nodule volume and total shoot nitrogen were more pronounced with the slow-growing bradyrhizobial strains of CP, and GM, than with the fast-growing PV, and PV2. The MPN-plant infection technique results showed a non-significant (p=0.05) but substantial decrement in rhizobial and bradyrhizobial numbers when the copper-contaminated field soil (82.5 mgCu/g soil) was compared to a control soil (1.8 mgCu/g soil). The study concludes, therefore, that elevated levels of copper in soil could be harmful to free-living rhizobia and their abilities to fix N2 in respective symbiotic associations with legume species. Such negative effects were more pronounced in the slow-growing bradyrhizobial than rhizobial species used

Methods for Monitoring Autophagy in Silkworm Organs

In holometabolous insects, various larval organs are remodeled by autophagy during metamorphosis. Although moths and butterflies are among the first animal models in which this self-eating process was described, only in recent years autophagy has been analyzed in detail in these insects. In particular, the silkworm Bombyx mori, which represents a well-studied model among Lepidoptera, provides a wide repertoire of cellular and molecular tools useful for studying the occurrence of autophagy and for evaluating its role in postembryonic development. Here, we describe some morphological, biochemical, and molecular methods to monitor autophagy in silkworm organs