对2005年水稻褐飞虱大发生的思考

针对我国2005年水稻褐飞虱暴发成灾,从药剂使用角度分析了我国褐飞虱成灾的原因。外来虫源大量迁入、种植制度和水肥管理对褐飞虱有利、农药的诱导作用是3大主要因子。农药诱导褐飞虱猖獗主要包括对非靶标生物的杀伤、施药技术不尽合理、药剂品种使用不当、耐药性或抗药性增加等因子。     

Genetic Linkage Maps and Genomic Organization in Leptosphaeria maculans

Leptosphaeria maculans is a haploid outcrossing ascomycete with a genome size of about 34 Megabases (Mb) which is predicted to have between 10,000 and 12,000 genes. The chromosomes of L. maculans are of a size range (0.7–3.5 Mb) and number (15–16) that can be readily resolved by pulsed field gel electrophoresis. Chromosome length polymorphisms are generated by meiosis giving rise to size differences as high as 57%, in the case of the ribosomal DNA-harbouring chromosome whose size varies between 1.8 and 4.2 Mb. Genetic maps are characterised by linkage groups comprising an accumulation of markers based on retrotransposon sequences. This, along with sequencing of pericentromeric regions and stretches of ORF-rich regions, suggest that the genome of L. maculans consists of a mosaic of GC-equilibrated coding regions with no or few transposons, and of stretches of highly degenerated and truncated retrotransposons, encompassing very few genes. Chromosome length polymorphisms are linked with the loss of dispensable regions. We suggest that the degree of length polymorphism for a particular chromosome correlates to the amount of dispensable retrotransposons, and that some gene-rich chromosomes may be less prone to undergo chromosome length polymorphisms than other chromosomes.     

芦竹内生真菌F0238对烟草赤星病的防治作用

从黄海岸芦竹(Arundo donax)中分离得到一株木霉属的内生真菌F0238，在皿内及盆栽苗上对该菌防治烟草赤星病(Alternarina alternate)的作用进行了试验研究。皿内的对峙培养结果表明，F0238对烟草赤星病菌有较强的营养竞争作用；盆栽试验表明，F0238在10^10个／ml孢子浓度下对烟草赤星病的预防能力达90％以上，10^8-10^9个／ml孢子浓度下对烟草赤星病的治疗效果达50％以上，表明该菌具有潜在的防治烟草赤星病的能力。     

新型肥料海生源对甘蔗耐寒性的影响

为研究不同施肥处理对甘蔗耐寒性的影响,以甘蔗品种新台糖22、滇蔗01-58为供试材料,通过6种不同施肥处理（D1、D2、H1、H2、DH1、DH2）,在甘蔗苗期进行低温（3℃）胁迫,同时测定与耐寒性相关的各项生理生化指标。结果显示：（1）通过极点排序法计算得到电导率、可溶性糖含量、可溶性蛋白含量、丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性的权重系数分别为0.190、0.203、0.096、0.341、0.170,其中,可溶性糖含量和MDA含量的权重系数较大,说明这两个指标对甘蔗耐寒性的影响较大。（2）不同施肥处理对甘蔗耐寒性影响表现为DH1>DH2>H2>D2>H1>D1,说明不同施肥处理对甘蔗耐寒性影响不同,但总体趋势是一致的,即新型肥料海生源与普通复合肥配合施用可显著提高甘蔗品种的耐寒性。     

耐氨固氮菌对黄瓜种子萌发、幼苗素质和保护酶活性的影响

采用耐氨固氮菌浸种处理黄瓜种子.结果表明,用2%菌液浸处理黄瓜种子,黄瓜种子发芽势、幼苗素质及子叶保护酶活性均有显著提高,幼苗子叶抗氧化功能增强,其中以浸种时间为3、4 h的效果尤为明显.     

“白雪公主”草莓茎尖组培快繁体系研究

为了建立草莓品种"白雪公主"的组织培养快速繁殖体系,取匍匐茎的茎尖为外植体,对MS(蔗糖25g/L,琼脂5.5g/L)添加不同浓度的6-BA和IBA用于诱导培养和增殖培养的效果,对诱导培养前暗处理的作用,对1/2MS(蔗糖20g/L,琼脂5.5g/L)添加IBA(0.5mg/L)用于再生芽生根培养的效果等进行了研究。结果表明,暗处理3d能够促进茎尖萌发,提高萌发速度;MS+6-BA 0.5mg/L+IBA 0.1mg/L为适宜的诱导培养基,诱导率达82%以上;MS+6-BA 0.5mg/L+IBA 0.1mg/L为适宜的增殖培养基,增殖系数为8.0;不添加IBA的1/2MS是适宜的生根培养基,培养5d后生根率达100%,平均生根数为10条,平均根长为5.00cm。     

三白草AP1基因的表达和进化选择压力分析

为了探究选择压力对三白草AP1基因进化的影响,本研究在已克隆三白草AP1基因的基础上,对AP1a和AP1b两个同源基因做RT-PCR分析,并对AP1a和AP1b 2个同源基因和29个AP1同源基因做多序列比对,通过生物信息学软件包PAML 4.9中的codeml程序对三白草AP1基因和29个供试物种的AP1基因的CDS序列进行了进化选择压力分析。结果显示,AP1a和AP1b基因在花中的表达明显高于叶;所有的31个CDS序列的选择压力测度参数ω均小于1,表明AP1基因所承受的选择压力总体趋势为纯化选择。而多序列比对结果表明AP1基因在不同品种植物间有所保守,但在同一个物种中AP1基因又存在着分化。     

Yield loss caused by huanglongbing in different sweet orange cultivars in São Paulo,Brazil

Citrus huanglongbing (HLB) reduces an affected orchard’s economic life. This work aimed to characterize yield loss due to HLB for different sweet orange cultivars and determine the relationship between disease severity and yield. Disease severity and yield were assessed on 949 individual trees distributed in 11 different blocks from sweet orange cultivars Hamlin, Westin, Pera and Valencia. In each block, plants showing a range of HLB severity levels and asymptomatic plants were selected. Total yield (weight of harvested fruit), mean weight of asymptomatic and symptomatic fruit, relative yield (symptomatic tree yield/mean yield of asymptomatic trees from the same block) and relative number of fruits (fruit number from symptomatic tree/mean number of fruits from asymptomatic trees from the same block) were determined. The weight of symptomatic fruit was lower than the weight of asymptomatic fruit, but the weights of asymptomatic and symptomatic fruit were not correlated with disease severity, indicating that the effects of HLB were restricted to symptomatic branches. The relationship of the relative yield with HLB severity can be satisfactorily described by a negative exponential model. The rates of yield decrease as a function of disease severity were similar for all assessed cultivars. A relative yield (up to 19%) was observed even for trees where disease severity was 100%. The strong linear relationship between relative number of fruits per tree and the relative yield per tree suggested that the yield reduction was due primarily to early fruit drop or lack of fruit set on affected branches.