Pseudomonas azotogensis—an associate symbiont of Bajra (Pennisatum americanum)

Summary Bajra (Pennisatum americanum) — a millet crop grown in the semi-arid, subtropical region of India, was surveyed for associative nitrogen-fixing bacteria in roots. Out of 20 root samples collected from 10 locations, 15 showed a high population ofPseudomonas azotogensis. The bacterium produced mucoid colonies with a greenish tinge on nitrogen-free malate medium and showed appreciable nitrogenase activity in pure culture.     

Pathogenicity of Rhizoctonia solani and Phytophthora nicotianae to Brassicaceae cover crops

Soil-borne diseases can reduce nursery crop performance and increase costs to nursery producers. In particular, soil-borne diseases caused by Phytophthora nicotianae and Rhizoctonia solani are the most economically important problems of Southeastern United States nursery producers. Methyl bromide was widely used as a standard treatment for management of soil-borne diseases until the implementation of the Montreal protocol. Since then, many chemical and non-chemical soil-borne disease management methods have been tested, but are not yet providing effective and consistent results like methyl bromide. Cover crops that belonged to the Brassicaceae family can be incorporated into the soil to control soil-borne diseases and this process is widely known as biofumigation. But, the use of Brassicaceae cover crops has not been widely explored as a method of controlling soil-borne diseases in woody ornamental nursery production. The objective of this study was to evaluate Brassicaceae cover crops for susceptibility to most destructive soil-borne pathogens of nursery production, P. nicotianae and R. solani, to identify effective cover crops that can be used in the biofumigation process in woody ornamental nursery production. Brassica species intended to be used in the fresh market or biofimigation were screened for their susceptibility to R. solani and P. nicotiane in an environmentally controlled greenhouse. At the end of experiments, plant growth data (plant height, width and fresh weight), total damping-off were recorded, and cover crop root systems were assessed for disease severity using a scale of 0–100% roots affected. Among the tested 15 cover crops in the Brassicaceae family, oilseed radish (Raphanus sativus L.), yellow mustard “White Gold” (Sinapis alba L.), turnip “Purple Top Forage” (Brassica rapa L.), arugula “Astro” (Eruca vesicaria (L.) Cav. ssp. sativa (Mill.) Thell.), mighty mustard^® “Pacific Gold” (B. juncea (L.) Czern.), brown mustard “Kodiak” (B. juncea (L.) Czern.), rape “Dwarf Essex” (B. napus L.) and mustard green “Amara” (B. carinata A. Braun) showed numerically lower root rot disease severity and total damping-off in topsoil which had pre-existing populations of R. solani or P. nicotinanae compared to other cover crops. Since these above mentioned Brassicaceae crops shows the ability to withstand the higher disease pressure from R. solani and P. nicotinanae under the greenhouse conditions they can be used in the further experiments to evaluate their ability in biofumigation. Further research is necessary to evaluate the performance of these cover crops under the field conditions.     

Effect of Sodium Alginate Addition on Physical Properties of Rennet Milk Gels

Effect of addition of sodium alginate (alginate) to milk on the storage modulus (G′), water holding capacity (WHC) and hardness of rennet gels was evaluated as a function of alginate (0–0.25 g/100 g) and fat (0.5–3.0 g/100 g) concentrations. There was a significant effect of alginate addition on ionic calcium in milk and whey (Ca²⁺), and particle size distribution in alginate added milk. Results showed a positive correlation of alginate with WHC; negative correlation of alginate and positive correlation of fat with G′; and negative correlation of interaction of fat and alginate with gel hardness of rennet gels. Hence, the rennet gels with lower fat content and higher added alginate tended to be softer due to the high water holding capacity of the alginate particles.     

Silver Nanoparticles Decrease the Viability of Cryptosporidium parvum Oocysts

Oocysts of the waterborne protozoan parasite Cryptosporidium parvum are highly resistant to chlorine disinfection. We show here that both silver nanoparticles (AgNPs) and silver ions significantly decrease oocyst viability, in a dose-dependent manner, between concentrations of 0.005 and 500 μg/ml, as assessed by an excystation assay and the shell/sporozoite ratio. For percent excystation, the results are statistically significant for 500 μg/ml of AgNPs, with reductions from 83% for the control to 33% with AgNPs. For Ag ions, the results were statistically significant at 500 and 5,000 μg/ml, but the percent excystation values were reduced only to 66 and 62%, respectively, from 86% for the control. The sporozoite/shell ratio was affected to a greater extent following AgNP exposure, presumably because sporozoites are destroyed by interaction with NPs. We also demonstrated via hyperspectral imaging that there is a dual mode of interaction, with Ag ions entering the oocyst and destroying the sporozoites while AgNPs interact with the cell wall and, at high concentrations, are able to fully break the oocyst wall.     

Spatial metabolomics reveal divergent cardenolide processing in the monarch (Danaus plexippus) and the common crow butterfly (Euploea core)

Although being famous for sequestering milkweed cardenolides, the mechanism of sequestration and where cardenolides are localized in caterpillars of the monarch butterfly (Danaus plexippus, Lepidoptera: Danaini) is still unknown. While monarchs tolerate cardenolides by a resistant Na⁺/K⁺-ATPase, it is unclear how closely related species such as the nonsequestering common crow butterfly (Euploea core, Lepidoptera: Danaini) cope with these toxins. Using novel atmospheric-pressure scanning microprobe matrix-assisted laser/desorption ionization mass spectrometry imaging, we compared the distribution of cardenolides in caterpillars of D. plexippus and E. core. Specifically, we tested at which physiological scale quantitative differences between both species are mediated and how cardenolides distribute across body tissues. Whereas D. plexippus sequestered most cardenolides from milkweed (Asclepias curassavica), no cardenolides were found in the tissues of E. core. Remarkably, quantitative differences already manifest in the gut lumen: while monarchs retain and accumulate cardenolides above plant concentrations, the toxins are degraded in the gut lumen of crows. We visualized cardenolide transport over the monarch midgut epithelium and identified integument cells as the final site of storage where defences might be perceived by predators. Our study provides molecular insight into cardenolide sequestration and highlights the great potential of mass spectrometry imaging for understanding the kinetics of multiple compounds including endogenous metabolites, plant toxins, or insecticides in insects.     

Effect of different concentrations of some ammonium fertilizers on the germination ofPennisetum typhoides Stapf & Hubb. andSorghum vulgare Pers

Summary Germination experiments were carried out with varying but equivalent amounts of NH₄Cl, (NH₄)₂SO₄, and NH₄NO₃, while in one experiment urea was included. It could be stated that the inhibitory effect on germination was ionic in nature, the effect of urea being rather small, while it was safer to use NH₄Cl or (NH₄)₂SO₄ than NH₄NO₃, especially under dry conditions.