Relative susceptibility of four species of African mahogany to the shoot borer Hypsipyla robusta (Lepidoptera: Pyralidae) in the moist semideciduous forest of Ghana

We examined the relative susceptibility of four mahogany species, Khaya ivorensis, Khaya anthotheca, Entandrophragma angolense, and E. utile, to Hypsipyla robusta attack. Seeds were obtained from one to three parent trees for each species. The research was conducted in the moist semideciduous forest zone in Ghana and used a randomized complete block design. Tree height and diameter and height to first branch were measured until 24 months after out-planting in the field. H. robusta damage was assessed by counting the numbers of shoots attacked, branches, and dead shoots. Khaya spp. grew better but experienced more attack than Entandrophragma spp. The relative susceptibility to H. robusta attack, from most to least, of the four species was: K. anthotheca > K. ivorensis > E. angolense > E. utile. At 24 months, the mean number of shoots attacked per tree ranged from 1.0 for an E. utile seed source to 3.6 on for a K. anthotheca seed source. At 15 months, K. anthotheca and K. ivorensis started branching at about 1.5 m, but height of clear trunk increased over time due to self-pruning. As K. anthotheca grew taller, the number of H. robusta attacks per tree declined. This suggested that selection of genotypes and species that are tolerant of H. robusta attack based on infestation of young plants may not be appropriate. Genetic factors more completely reflecting the response of different species and genotypes to H. robusta attack may manifest themselves at later growth stages.     

两株芽孢杆菌的鉴定

通过对2株芽孢杆菌的形态学、生理生化试验及16S rDNA序列同源性分析,发现B02号菌株与Ba-cillus cereus的同源性为100%,系统发育树分析与Bacillus cereus遗传关系最近,确定该菌株为Bacillus ce-reus。而B03号菌株与Bacillus cereus的同源性为98%,要确定其种还需进一步DNA杂交;该2株芽孢杆菌的芽胞数在1.0×1012个/kg体重以下安全无毒。2株芽孢杆菌的药敏性试验和拮抗性试验结果表明,参试菌对5类抗菌药物大多数都很敏感;对4种动物肠道病原菌无明显拮抗作用。通过酶系测定,参试菌都具有一定SOD酶活性。喂养实验结果表明,2株菌对雏鸡具有一定的防病治病效果。以上结论初步证明该菌株的抑病促生机理主要是生物夺氧和有益代谢产物的作用,而非优势种群、生物拮抗作用。     

小麦收获前种子发芽敏感性配合力的研究

选用5个收获前穗发芽敏感性不同的白皮小麦亲本品种,进行双列杂交,研究了发芽敏感性的配合力。结果表明:小麦收获前种子发芽敏感性同时受加性和非加性基因效应影响,而加性基因效应起主导作用;亲本品种发芽敏感性的一般配合力存在极显著差异,杂交组合的特殊配合力和反交效应方差则有时显著,有时不显著;白皮小麦杂交当代种子,以     

甘蓝蚜对杀虫剂的敏感性测定

采用微量点滴法,测定了甘蓝蚜对杀虫剂的敏感性。研究结果表明:不同地形条件菜园甘蓝蚜种群对药剂敏感性存在差异,山区种群对药剂的敏感性高于平原种群,在供试药剂中各种群对齐螨素、吡虫啉和辛硫磷的敏感性表现较高;油菜上的甘蓝蚜种群对药剂的敏感性较高,其中对啶虫脒、吡虫啉、马拉硫磷、齐螨素、辛硫磷、氯氰菊酯存在显著的差异;甘蓝结球期甘蓝蚜种群对药剂敏感性高于甘蓝莲座期,对啶虫脒、吡虫啉、马拉硫磷、齐螨素、辛硫磷、氯氰菊酯存在显著的差异。     

Characterization of Leptospira infection in suckling and weaning rat pups

Rats are known to be the most important reservoirs of Leptospira spp. However, the leptospiral dose and age at which rats become resistant to Leptospira infection are not yet well elucidated. Aimed to characterize leptospirosis in rat pups, we found that suckling pups (4-, 7-, and 14-day old) are susceptible to leptospires and resistance starts from the weaning age (23-day old). Susceptibility of rat pups was also affected by the infecting dose of the organisms. Jaundice, decrease in body weight, and neurological symptoms prior to moribundity was evident in infected suckling pups. However, 23-day-old infected pups did not manifest any pathological changes and were able to survive the infection similar to adult rats. Based on these results, we propose the suckling rat pup as a novel animal model of human leptospirosis to investigate pathogenesis, development of host resistance, and the mechanisms involved in rats becoming maintenance hosts for leptospires.     

Victoria Blight,defense turned upside down

Genes that confer disease resistance to biotrophic pathogens typically encode nucleotide-binding, leucine-rich-repeat proteins (NB-LRRs). These proteins confer resistance by detecting the presence of virulence effectors secreted by biotrophic pathogens. Recognition triggers NB-LRR activation and subsequently, the defense response which often includes localized host cell death. The fungus, Cochliobolus victoriae, is a necrotrophic pathogen that causes a disease called Victoria Blight. Virulence of this fungus is dependent on its production of a peptide called “victorin” that has been traditionally described as a toxin. Only plants that respond to victorin are susceptible to Cochliobolus victoriae whereas those that do not are resistant to the fungus. Genetic and molecular analyses have revealed that victorin functions like a biotrophic effector recognized by a NB-LRR resistance protein in Arabidopsis. Further, numerous plant species express victorin sensitivity suggesting there are numerous NB-LRRs that recognize victorin. Thus, through expression of victorin, C. victoriae is able to exploit plant defense to cause disease and is capable of evoking this response in an array of different plants.     

Susceptibility of citrus species to Alternaria alternata, the causal agent of the Alternaria brown spot

Alternaria alternata, the causal agent of Alternaria brown spot (ABS), causes necrosis on leaves, twigs, and fruit, reducing the productivity and quality of fruits. Tangerines and their hybrids are highly susceptible to the disease. Species, hybrids, and cultivars of Citrus from the germplasm bank of the Estação Experimental de Citricultura de Bebedouro, São Paulo, Brazil, were evaluated in 2004 and 2005 with respect to their resistance to A. alternata, both through natural infection and by inoculation. Detached leaves were also used to demonstrate susceptibility or resistance to the disease. Ten cultivars of Satsumas (Citrus unshiu), and 14 cultivars of Clementine mandarin (C. clementina) did not show any symptoms of the disease in their leaves, either through natural infection or when inoculated in the field. The Burguess SRA-412, Wallent SRA-438, Carvalhais, Ampefy SRA-459, Ananas SRA, and Macaque SRA-426 mandarin hybrids (C. reticulata) did not show symptoms of the disease under natural or artificial infection in the field. Some cultivars of C. deliciosa, C. tangerina, C. erythrosa, and C. temple showed symptoms of the disease, even though no previous record of their susceptibility to Alternaria brown spot had been previously reported. The hybrids Fairchild, Nova, Page, Fortune, and Sunburst were susceptible to the disease. However, Fremont mandarin (a crossing between C. clementina and C. reticulata), Encore (C. nobilis × C. deliciosa), and Fallglo (C. reticulata × C. paradisi) did not show symptoms in field, and few symptoms were verified in detached leaves. These materials are promising for the cultivation of tangerines, and will enable genetic improvement for the development of cultivars resistant to Alternaria brown spot.     

柚矮化病的品种感病性调查

以特征性症状春梢叶片扭曲畸形和枝条茎陷点为诊断依据,调查结果表明,５５个柚类品种中有２２个发病,占调查品种数的４０％;２８个沙田柚砧穗组合中有２２个发病,占调查砧穗组合数的７８．５％。以沙田柚实生苗和酸柚实生苗作指示植物,对温州蜜柑上的类似矮化病的叶片扭曲症状进行鉴定的结果,指示植物上表现出与接种沙田柚矮化病病原的指示植物相似的春梢叶片扭曲及茎陷点症状。     

基于模糊评判法的长安区滑坡崩塌灾害易发性分区评价

在对长安区滑坡崩塌地质灾害发育现状及形成条件分析的基础上,结合地质灾害易发性分区评价方法,采用模糊综合评判法对长安区滑坡崩塌地质灾害进行了易发性区划评价。结果表明,长安区滑坡崩塌易发性分区分为6个高易发区域、3个中易发区、1个低易发区(C)和1个不易发区(D),高易发区总面积为190.94 km2,中易发区为382.93 km2,低易发区为299.21 km2,不易发区为707.56km2。