Genetic Structure of Peruvian Populations of Phytophthora infestans

ABSTRACT Isolates of the late blight pathogen Phytophthora infestans (n = 327) from the central to southern Peruvian Andes were systematically collected in 1997 to 1999 and analyzed to determine the pathogen's population structure at its host's center of diversity. No isolates of the A2 mating type were detected. Cluster analysis of DNA fingerprinting data indicated that the collection consisted of five major groups that were interpreted to be clonal lineages. Two of the lineages (US-1 and EC-1) have been previously described, and three (PE-3, 5, and 6) are described here for the first time. Collections from three areas in the central Peruvian Andes, including two key sites used in an international potato breeding program, consisted of isolates of the EC-1 lineage, which has been reported to dominate the pathogen population in Andean countries to the north of Peru. The collections from Cusco and Puno were more diverse. More than one lineage was detected in 10 of the 20 fields sampled in Cusco. Data on virulence, metalaxyl sensitivity, and band data for allozymes, mitochondrial DNA, and ipiB1 suggested that PE-3 may have been produced through recombination events between US-1 and EC-1. Restriction fragment length polymorphism and amplified fragment length polymorphism marker data were not consistent with this hypothesis.     

Taenia solium oncosphere antigens induce immunity in pigs against experimental cysticercosis

Immunity to Taenia solium infection was investigated using an experimental intramuscular oncosphere infection assay (IMOA) model in pigs. Three naturally infected pigs with cysticercosis were treated with oxfendazole (OFZ), a drug demonstrated to kill cysts in porcine muscle. These animals were then challenged with oncospheres but did not develop any cysts while three uninfected pigs that were similarly challenged, did develop intramuscular cysts. In another study, two groups of three pigs each were immunized with crude T. solium oncosphere and metacestode antigens, respectively, and tested with the IMOA. Immunization with crude oncosphere antigens (OAs) induced 100% protection, while metacestode antigens provided only partial protection. Immunoblots showed that pigs with complete immune protection to oncosphere intramuscular challenge had antibodies to two OAs at 31.3 and 22.5 kDa, respectively. Antibody to these two antigens was absent in pigs immunized with metacestodes or in uninfected control pigs. This study demonstrated the presence of two antigens that are unique to the oncosphere. Although, antibody to these two antigens is consistently present in pigs that are protected from an oncosphere intramuscular challenge their role in preventing infection by T. solium larval cysts is still hypothetical.     

盐碱胁迫对芨芨草种子萌发的影响

研究了5种盐碱(NaCl、Na2SO4、NaHCO3、Na2CO3及该4种盐按1:9:9:1的物质的量比例配置成的混合溶液)及其在不同浓度处理下对芨芨草(Achnatherum splendens)种子萌发的影响.结果表明,在不同盐碱处理下,随着浓度的增加,种子发芽率、发芽势、发芽指数适渐降低,种子萌发抑制作用逐渐增强...     

Variations in the secondary metabolite camptothecin in relation to tissue age and season in Camptotheca acuminata

We investigated variation in concentration of the secondary metabolite, camptothecin (CPT), in relation to leaf, branch and tree age, season, and leaf drying method in Camptotheca acuminata Decaisne saplings. Younger leaves contained higher CPT concentrations than older leaves. Within a branch, there was a linear decline in CPT concentration from leaves at the apex of the branch down to Leaf 7. Comparing leaves of similar age, those from younger trees had higher CPT concentrations than those from older trees. Over the course of the growing season, there was a steady decline of 11% per month in leaf CPT concentration. Branches showed a similar seasonal decline in CPT concentration to leaves; however, the rate of decline was threefold greater in leaves than in branches. Freeze-dried tissues had a 27% higher CPT concentration than oven- or air-dried tissues, suggesting that oven- and air-drying caused degradation of CPT. The decline in CPT concentration with tissue aging may reflect a genetically determined mechanism whereby, in young trees, chemicals serve as a first line of defense against attacks by herbivores and pathogenic microorganisms until other mechanisms are developed and deployed. We hypothesize that chemical defense mechanisms are programmed for early ontogenic stages, whereas they are induced by biotic and abiotic factors during later ontogenic stages.     

罗源县茶叶低温冻害灾害风险区划探讨

本文利用罗源县气象站1986-2015 年逐日气温数据，结合罗源县以乡镇为单位的农业经济 资料，对罗源县主要农业经济作物茶叶低温冻害致灾因子危险性、孕灾环境敏感性、承灾体易损性、防 灾抗灾能力等指标分析，得出罗源低温冻害风险评估及区划，为防灾减灾规划提供依据。     

Cu离子对巴西橡胶树组织培养的影响

巴西橡胶树是重要的经济作物,微量元素Cu对巴西橡胶树组织培养成胚、生根及组培苗生根有重要影响。试验以巴西橡胶树花药为外植体,以改良MSB为基础培养基,改变其中Cu的浓度,进行试验,寻找最佳的微量元素Cu的含量。结果表明:培养基中不同铜元素的添加量,对巴西橡胶树胚状体及组培切苗的生根产生明显的促进及抑制作用。     

Clinical and radiographic findings in Corynebacterium equi pneumonia of foals

Thirty-nine foals with pneumonia were admitted to the Veterinary Medical Teaching Hospital at the University of California, Davis. Corynebacterium equi was recovered from each of them on bacteriologic culture of transtracheal aspiration specimens or lung specimens at necropsy. The foals were divided into 2 groups. Group I consisted of 20 foals that died because of C equi pneumonia and were subsequently necropsied. Group II consisted of 19 foals that were treated and discharged from the hospital. Radiography was performed on all foals. Clinical signs included increased respiratory rate, fever, cough, nasal discharge, increased bronchovesicular sounds over large airways, and wheezing over small airways. Highly significant differences were found in the mean respiratory rate (P less than 0.005) and temperature (P less than 0.001), recorded at admission, between the 2 groups; both factors were higher for group I. Hematology revealed leukocytosis with neutrophilia, monocytosis, and high plasma fibrinogen content in all foals. Significant differences were recorded in the mean total leukocyte count (P less than 0.05), mean neutrophil count (P less than 0.05), mean monocyte count (P less than 0.005), and mean fibrinogen value (P less than 0.05) between the 2 groups; values from group I were higher than those from group II. Although C equi was isolated alone from 25 of the tracheal aspirates and lung specimens, 14 cultures yielded multiple pathogens. At the time of initial examination, all foals had radiographic evidence of pneumonia. Pulmonary consolidation indicative of bronchopneumonia was identified in 31 of the 39 foals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunomodulatory Effects of Dietary β‐glucan and Vitamin C in Nile Tilapia,Oreochromis niloticus L., Subjected to Cold‐induced Stress or Bacterial Challenge

To determine the dietary β‐glucan and vitamin C levels that would enable the fish to cope with different stress, 252 tilapia (16.86 ± 0.24 g) were distributed in thirty six 250‐L aquaria and fed experimental diets for 60 d. Diets were supplemented with β‐glucan (0.1, 0.2, 0.4, and 0.8%) and vitamin C (400 and 600 mg/kg diet) and distributed in a factorial design that included a control diet (0 β‐glucan/125 mg vitamin C/kg). After growth performance analyses, a group of 108 fish were subjected to cold‐induced stress and another to Aeromonas hydrophila infection. Hematological and immunological parameters were determined before and after the stress. Growth performance was not affected. Red blood cells, hematocrit, mean corpuscular volume, total plasma protein, albumin : globulin ratio and leukocytes, lymphocytes, neutrophils, and monocytes were affected (P < 0.05) by stress and/or diets. The control diet resulted in higher post‐infection cortisol (P < 0.05). Liver vitamin C was directly proportional to dietary vitamin C (P < 0.05). The production of hydrogen peroxide and nitric oxide was also affected by diets and/or bacterial challenge (P < 0.05). In total, 0.1–0.2% β‐glucan and 600 mg/kg vitamin C increased fish resistance to stress and 0.8% β‐glucan resulted in reduced immune responses regardless of the vitamin C supplementation level.