The bionomics ofLiriomyza Trifolii on Gypsophila and Bean Leaves

A study was carried out to determine the distribution of feeding and oviposition punctures made byLiriomyza trifolii Burgess on gypsophila(Gypsophila paniculata ) and bean(Phaseolus vulgaris) leaves, and the development times of the immature stages on these plants. The absolute number of punctures per leaf area was much greater on bean leaves than on gypsophila leaves. The number of mines per leaf was also higher on beans than on gypsophila, but the ratio of mines/punctures was higher on gypsophila. Gypsophila leaves were punctured on both sides, but most of the punctures were on the distal third of the upper leaf side. On beans the punctures were dispersed uniformly on the upper side of the leaf. The larval period (±SE) at temperatures of 20, 25 and 30°C was 9.9±0.2, 4.4±0.1 and 3.7±0.1, and 5.5±O. l, 3.7±0.1 and 2.4±0.1 days, on gypsophila and bean, respectively. The pupal period at 17, 20, 25 and 30°C lasted 19.9±0.2, 14.7±0.1, 10.4±0.1 and 7.8±0.1 days, respectively.     

蚕豆黄化卷叶病的药剂防治

喷药治蚜防病试验中,溴氰菊酯和久效磷对豆蚜(Aphis craccivora)的防效分别达到96.7%和67.1%。两次和三次施用溴氰菊酯的防病效果分别达到84.1%和86.1%,蚕豆产量分别比未施药对照增产17.7%和21.9%。施药也影响蚕豆黄化卷叶病的时间分布型,三次施药小区的病株始终为泊松分布,病害没有再次扩散;未施药小区早春病株就出现负二项分布,越冬前病害已经扩散。豆蚜蚜害率与蚕豆黄化卷叶病发病率密切相关。     

川化-018在水稻白叶枯病综防中的应用

1982—1984年在安徽进行的研究表明,川化-018用于秧苗处理预防白叶枯病最为经济有效,纯收益合投资的30倍。早稻和中稻本田用该药喷洒可获得较好的防治和较高的产量,纯收益分别合投资的2.55倍及2.2倍。本田发病中心用该药处理获得满意的效果。因此,在白叶枯病的综防中,对中抗和中感的栽培品种扩大秧苗处理而减少本田防治面积是合理可行的。     

新疆大蒜叶疫病的研究:Ⅱ病菌越冬致病性病害流行因素及防治

 试验结果表明,本菌(Stemphylium vesicarium(Wallr.) Simons)以病残体上分生孢子和菌丝体在田间和冷藏室越冬,9月至翌年6月检查,分生孢子萌发率为16.4~41.3%。人工接种试验指出,不论有无伤口,病菌均可侵染大蒜,但洋葱与大葱在伤口接种条件下病情较重。在自然条件下,大蒜的斑点型病状出现于6月下旬,7月为病情高峰期。影响病情的天气因素,主要是7月份温度和7月中旬的降水量(r=0.69)。如果7月雨次多、雨时长,病情即极为严重,可导致蒜田绝收。化学防治试验结果,以腐霉利防效最佳。从7月上旬开始,每间隔10~13天喷药1次。喷药2~3次即可取得较好的防治效果。     

Accessions of Australian Nicotiana species suitable as indicator hosts in the diagnosis of plant virus diseases

When screening the genusNicotiana for sensitive and differential hosts for a group of mechanically transmissible plant viruses with narrow host ranges, development of systemic symptoms was alsmost exclusively observed in species of three closely related sections of the subgenusPetunioides. These species wereN. miersii (sectionAcuminatae),N. bigelovii andN. clevelandii (Bigelovianae) andN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata andN. rotundifolia (Suaveolentes). Except forN. benthamiana andN. clevelandii, which are already known for their large virus ranges, they are new experimental hosts that appeared very useful for detection of viruses and for differentiation of viruses that closely resemble each other in host range. Accessions of the same species often varied largely in local and systemic viral response. EspeciallyN. benthamiana-9,N. miersii-33 andN. occidentalis-37B (code numbers given by Tobacco Research Laboratory, Oxford, N.C., USA) are recommended for routine inoculation tests. The sensitiveSuaveolentes species mentioned are native to the arid parts of Australia. Collections of these species deserve attention in studies on virus diseases of unknown etiology where experimental hosts are lacking.Samenvatting In het genusNicotiana werden vatbare, gevoelige en differentiële toetsplanten opgespoord door toetsing van vooral de collectie van het Tobacco Research Laboratory (Oxford, N.C., VS) met een aantal virussen waarvoor weinig of geen bruikbare toetsplanten bekend waren. Systemische reacties werden bijna uitsluitend in soorten van drie nauw verwante secties van het subgenusPetunioides waargenomen. Deze soorten warenN. miersii (sectieAcuminatae),N. bigelovii enN. clevelandii (Bigelovianae) enN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata enN. rotundifolia (Suaveolentes). Behalve voor virusvermeerdering bleken deze soorten ook zeer geschikt te zijn voor differentiatie van virussen of virusstammen met een bijna gelijke waardplantenreeks.Collectienummers van één en dezelfde soort konden sterk in lokale en systemische reactie verschillen. VooralN. benthamiana-9,N. miersii-33 enN. occidentalis-37B kunnen voor routine-inoculaties worden aanbevolen. Met uitzondering vanN. benthamiana enN. clevelandii zijn de genoemde soorten of genotypen nieuwe experimentele waardplanten voor de virologie. De soorten die van de sectieSuaveolentes worden genoemd, zijn inheems in de woestijnachtige gebieden van Australië. Verzamelingen daarvan verdienen nadere aandacht bij de diagnostiek van virusziekten waarvoor nog geen experimentele waarplanten voorhanden zijn.     

Effectiveness of Coniothyrium minitans and Trichoderma atroviride in suppression of sclerotinia blossom blight of alfalfa

The effects of the mycoparasites Coniothyrium minitans and Trichoderma atroviride on the suppression of alfalfa blossom blight caused by Sclerotinia sclerotiorum were evaluated under indoor and field conditions. When T. atroviride (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) were applied to detached young alfalfa florets, T. atroviride effectively inhibited saprophytic growth of S. sclerotiorum, whereas C. minitans showed no inhibition under the same conditions. When T. atroviride (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) was applied to young alfalfa petals in vivo just after pollination, the percentage of pod formation was higher for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum, and the percentage of pod rot was lower for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum. However, when they were applied to senescent petals attached to developing pods of alfalfa at 9·2 × 10⁴ conidia/floret together with S. sclerotiorum at 4·5 × 10³ ascospores/floret at 14 days after pollination, C. minitans was more effective than T. atroviride in suppressing sclerotinia pod rot and seed rot of alfalfa. Field experiments showed that three applications of C. minitans (5·4 × 10⁶ conidia mL⁻¹) or T. atroviride (5·4 × 10⁶ conidia mL⁻¹) at a 7-day interval to blossoms of alfalfa effectively suppressed sclerotinia pod rot in two out of three annual trials. Coniothyrium minitans effectively suppressed sclerotinia seed rot in all three years, whereas T. atroviride was not effective against seed rot in any of the trial years. The efficacy of C. minitans was not significantly different (P > 0·05) from benomyl (250 µg ai mL⁻¹). This study suggests that C. minitans has potential as a biocontrol agent to control blossom blight of alfalfa caused by S. sclerotiorum.     

小麦白粉病纯化菌种保存方法

利用经初选确定的5种具有较好保鲜能力的配方,采用离体叶段滤纸保存法、离体叶段琼脂保存法和试管苗保存法对小麦白粉病菌纯化菌系保存效果进行了研究.结果表明,对小麦幼苗第一叶叶段保鲜效果最好的配方是沈保6号,当使用40～60μg/mL最适浓度时,第25天叶段绿色仍可达到90%以上.保存菌种的最适环境条件研究结果表明,在4℃冰箱中,以离体叶片沈保6号琼脂保存和离体叶沈保6号浸润滤纸保存效果最佳,在第40天叶片绿色仍分别达到78.0%和68.0%,孢子萌发率可达26.7%和26.8%.     

桃红叶植原体检测及鉴定

对表现红叶的桃植株进行植原体16SrRNA基因PCR扩增,得到1.2kb的特异片段.将此片段与pGEM T Easy载体连接并转化到大肠杆茵DH5α感受态细胞中.通过酶切、PCR鉴定,对筛选得到的重组阳性克隆进行序列测定及同源性比较分析,确定该株系属于翠菊黄化植原体组(Aster yellows group,16SrI).在国内首次报道了翠菊黄化组中的植原体侵染桃树.     

Growth Complementation of hrpXo Mutants of Xanthomonas oryzae pv. oryzae by Virulent Strains in Rice Cultivars Resistant and Susceptible to the Parental Strain

Xanthomonas oryzae pv. oryzae (X. o. pv. oryzae) T7174 is virulent on rice cultivar IR24 and avirulent on IR-BB2. From recent reports, some virulence and avirulence factors of plant pathogenic bacteria are transferred to plant cells through the hrp-dependent type III secretion system. In this study, we investigated the involvement of hrp genes in the compatible and the incompatible interactions between rice and X. o. pv. oryzae after co-inoculation with hrpXo mutants derived from T7174 and virulent strains. Growth of the mutants, named 74ΔHrpXo and 76ΔHrpXo, was repressed in IR24 when the mutants were applied alone. However, growth of the mutants was complemented by co-inoculation with virulent strains. Growth of bioluminescent hrpXo mutant 76ΔHrpXo in IR24 and its growth in IR-BB2 after co-inoculation with T7133, which is virulent on both cultivars, was equally complemented, as detected by bioluminescence from the mutant. On the other hand, only partial complementation of growth of T7174L76, which is a bioluminescent and pathogenic derivative of T7174, by T7133 was observed in IR-BB2. Thus, growth of the hrpXo mutant of X. o. pv. oryzae was complemented by virulent strains in both susceptible and resistant rice leaves with the parental strain. Received 21 July 2000/ Accepted in revised form 26 October 2000     

Genetic Structure of Melampsora Epitea Populations in Swedish Salix Viminalis Plantations

Amplified fragment length polymorphism (AFLP) was used to study the genetic structure of populations of the willow leaf rust, Melampsora epitea, in Swedish willow plantations. In total, 197 isolates collected from Salix viminalis clones in three locations in Sweden were analysed. AFLP profiles based on 83 markers were used to compute genetic distances between pairs of individuals. High levels of gene and genotypic diversity were detected in all populations, with 96% of the AFLP loci being polymorphic and with normalized Shannon's diversity indices ranging from 0.977 to 1.0. Analysis of molecular variance (AMOVA) showed small significant differences among locations, although most of the molecular variability was found within locations (97.5%). Five isolates from one willow clone in one location differed markedly from the common pattern. When these five exceptional isolates were excluded, no significant differences among willow clones were found with AMOVA. Sexual reproduction and spore migration appear to be important factors for the population genetic structure of this pathogen.