Diaporthe species associated with dieback on Cyclopia (honeybush)

European Journal of Plant Pathology - The formal honeybush tea industry in South Africa is relatively new, and has tremendous growth potential. However, as with other cultivated crops, production...     

Native maize landraces from Los Tuxtlas, Mexico show varying mycorrhizal dependency for P uptake

Different degrees of dependency on the activity of arbuscular mycorrhizal fungi (AMF) exist between native maize landraces and hybrids. In Los Tuxtlas, Mexico, the Popoluca people maintain a traditional polycultural land management with more than 15 native landraces of maize; however, it is not known whether the recent substitution of local maize for improved hybrids and fertilization has affected the integrity of the mycorrhizal symbiosis in these naturally phosphorus-poor systems. A greenhouse experiment was conducted to evaluate the response of four Popoluca maize landraces and the hybrid Texcoco to the presence of native AMF in conditions of low and medium P input (5 and 65 mg kg^?1, respectively). After 120 days in both P treatments, the native landraces Black and Yellow presented higher colonization and had acquired more P in their shoot biomass than the hybrid. The moderate fertilization did not appear to have affected the integrity of the mycorrhizal symbiosis, since all of the maize types presented a positive mycorrhizal dependency (2–14 %). Under low P conditions, the Texcoco hybrid maize presented one of the highest mycorrhizal dependencies; however, unlike the local landraces, this was not reflected in a higher tissue P concentration. The results obtained indicate that the native maize Black was the best at capturing symbiotic and direct P, which makes this landrace an important genetic and cultural heritage for the Popoluca and for the world.     

Suspected citrus pulp toxicosis in dairy cattle.

Thirteen lactating dairy cows from a herd of 650 died over a 6-week period. Most animals were down in milk production at 1 milking and were found dead at the next milking. Two cows had elevated heart rate and enlarged mandibular lymph nodes. Two others had azotemia, elevated heart rate, hyperglycemia, and weight loss. Necropsy of 10 cows revealed hemorrhages on the intestinal serosa and epicardium, lymphadenopathy, interstitial nephritis, small intestinal hemorrhage, and interstitial pneumonia. Histopathology showed lymphocytic to lymphogranulomatous inflammation in the heart, spleen, kidney, lymph nodes, liver, lung, pancreas, and adrenal gland. Phlebitis was present in 2 livers. The lesions resembled those of hairy vetch toxicosis, but no vetch was being fed. Similar lesions have been reported with the feeding of citrus pulp. Citrus pulp was being fed to the lactating cows and had been added to the diet 6 weeks before the first death. The syndrome resolved with elimination of citrus pulp from the diet.     

Grass and legume seeding on a scarified coastal alluvial site in northwestern British Columbia: response of native non-crop vegetation and planted Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings

The success of various grass-legume mixtures in controlling competing vegetation, and their effect on subsequent survival and growth of Sitka spruce seedlings was studied on a coastal alluvial site in northwestern British Columbia. Mechanically scarified (bladed) strips were hand seeded to pure and combined mixtures of legumes, bunchgrasses, and sodforming grasses. An unseeded control (bladed but not seeded) was also established.Alsike clover (Trifolium hybridum L.) was the most successful legume species. Orchardgrass (Dactylis glomerata L.), big bluegrass (Poa ampla Merr.), and creeping red fescue (Festuca rubra L.) were the most successful grass species. Red alder (Alnus rubra Bong.) density and height were lower in legume-seeded treatments. Red elderberry (Sambucus racemosa L.) and salmonberry (Rubus spectabilis Pursh.) were effectively reduced by blading and have reestablished slowly. A combination of blading and early establishment of either sodforming grasses or bunchgrasses effectively decreased reinvasion by thimbleberry (Rubus parviflorus Nutt.).Growth of Sitka spruce was best in the unseeded control treatment or in the treatments with legumes but no sodforming grasses. Presence of sodforming grasses decreased both diameter and height growth. Sitka spruce diameter decreased with increasing red alder density. After 5 growing seasons, spruce has outgrown all competitors except red alder.     

Iron-rich post-perovskite and the origin of ultralow-velocity zones

The boundary layer between the crystalline silicate lower mantle and the liquid iron core contains regions with ultralow seismic velocities. Such low compressional and shear wave velocities and high Poisson's ratio are also observed experimentally in post-perovskite silicate phase containing up to 40 mol% FeSiO3 endmember. The iron-rich post-perovskite silicate is stable at the pressure-temperature and chemical environment of the core-mantle boundary and can be formed by core-mantle reaction. Mantle dynamics may lead to further accumulation of this material into the ultralow-velocity patches that are observable by seismology.     

Distribution and activity of hypolithic soil crusts in a hyperarid desert (Baja California, Mexico)

Widespread and ecologically important, biological soil crusts include those microbial communities living on the surface of the soil and those that live beneath semitranslucent rocks (a.k.a. hypolithic crusts). We examined the distribution, abundance, physiology, and potential soil N contributions of hypolithic, biological crusts in hyperarid ecosystems of the Baja California peninsula and islands in the midriff region of the Gulf of California, Mexico (Sonoran desert). Crusts were limited in distribution to areas with translucent quartz rocks less than 3 cm thick, were not found on areas of islands with seabird guano deposition, but covered as much as 1% (12,750 m²) of the surface area of one island. The percent of available rocks colonized by crusts was similar between the mainland (38%) and islands without seabird guano (26%). Carbon fixation rates in the field, which have not been previously reported, ranged between 0 and 1.23 μmol m⁻² s⁻¹, and in the lab ranged between 0.66 and 0.94 μmol m⁻² s⁻¹. Evidence of low rates of N fixation was inferred from δ ¹⁵N values of crust and soil. Hypolithic crusts were found to have minimal, if any, influence on soil salinity, pH, and , but may represent up to 14% of the biomass of primary producers on these islands and provide C and N to the belowground and possibly aboveground heterotrophic communities where crusts exist. The results of this study suggest a limited but potentially important contribution of hypolithic soil crusts to hyperarid ecosystems.     

Field dissipation and environmental hazard assessment of clomazone, molinate, and thiobencarb in Australian rice culture

The fates of clomazone [2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone], molinate (S-ethyl hexahydro-1-H-azepine-1-carbothioate), and thiobencarb {S-[(4-chlorophenyl)methyl]diethylcarbamothioate} applied to rice were studied at two locations in New South Wales (Australia). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the three herbicides from water and soil can be best explained by a first-order decay process. DT(50) values for clomazone, molinate, and thiobencarb were 7.2, 5.1, and 3.5 days, respectively, in water and 14.6, 23.9, and >46 days, respectively, in surface soil. Maximum measured concentrations of clomazone, molinate, and thiobencarb in floodwaters were 202, 1042, and 148 microg/L, respectively, taking 18.4, 26.4, and 21.4 days to dissipate to concentrations set to protect aquatic ecosystems. A hazard assessment identified clomazone as presenting a low environmental hazard while molinate and thiobencarb presented a medium environmental hazard when used at registered field rates.