排序方式: 共有19条查询结果,搜索用时 15 毫秒
1.
2.
In vitro assays investigated the responses of Alternaria brassicicola and A. brassicae isolates towards two crucifer phytoalexins and two isothiocyanates (ITC) by evaluating their potential toxic effects on different fungal growth parameters. Although variable responses towards each compound was observed within the species A. brassicicola , the results obtained confirmed the antifungal effects of camalexin, brassinin, allyl- (AlITC) and benzyl- (BzITC) isothiocyanates, at different developmental stages of both Alternaria species. Irrespective of the tested isolate, the phytoalexin camalexin exhibited the greater inhibitory effect with mean EC50 values ranging from 34 µ m (germ-tube elongation) to 183 µ m (mycelial growth). Germ-tube elongation was more sensitive compared to conidial germination and mycelial growth, with mean EC50 values of the former of 81 µ m , 520 µ m and 870 µ m for brassinin, BzITC and AlITC, respectively. 相似文献
3.
The toxicities of fenvalerate (20% EC) to the 3rd instar larvae of diamondback moth (DBM), Plutella xylostella (L.), reared on three host plants viz., radish, oilseed rape, and cabbage were tested. The LC50 values of fenvalerate to the 3rd instar larvae of DBM varied with host plants, however, there wasn't any significant difference among them (P〉 0.05). Similarly, DBM fed on three host plants had same pupal weight, pupal period, pupation rate, adult emergence rate, female ratio, and fecundity. The activity of juvenile hormone esterase (JHE, EC 3.1.1.1) in the 3rd instar larvae of DMB did not significantly vary with host plants, either. These suggested that DBM had similar fitness on the three host plant species. When fed on the host plants pretreated with fenvalerate at the concentrations equivalent to LC20, LC50 and LC50, the pupation rate, pupal weight, adult emergence rate, female ratio, fecundity, and JHE activity of the tested insects were declined as compared with insects in control treatments fed on the same host plant species. Furthermore, the pupal period of the tested insects was extended after fenvalerate treatment. The decrease in JHE activity after fenvalerate treatment in the tested insects could partly explain the changes in the mentioned growth parameters. Whether the role of fenvalerate in the inhibition of JHE activity could serve as a new way to control DBM needs further investigation. 相似文献
4.
Xanthomonas campestris is a seedborne bacterium that causes black rot of crucifers. Substantial crop losses may result from the rapid spread of the bacteria under favourable conditions, especially those occurring during seedling production. A PCR-based method has been developed for the rapid and sensitive detection of the pathovars of X. campestris that affect crucifers. Primers were designed to specifically amplify a 619 bp fragment of the hrpF gene from X. campestris . Amplification products were not detected from other Xanthomonas species, or from other pathogenic or epiphytic bacteria occurring on these plants. To avoid false-negative results arising from the presence of amplification inhibitors in plant extracts, primers targeting a 360 bp section of the internal transcribed spacer (ITS) region from Brassica spp. were included in a multiplex PCR. The assay readily detected X. campestris pv. campestris infections in diseased plants and from bacterial colonies isolated on growth media, and was more sensitive and specific than traditional plating methods and a commercially available ELISA. A seed-washing protocol was optimized to allow the detection of a single artificially infected seed among 10 000 healthy seeds using the multiplex PCR. 相似文献
5.
6.
南宁市十字花科蔬菜害虫天敌群落结构分析 总被引:4,自引:0,他引:4
南宁市十字花科蔬菜害虫天敌群落物种有70种(类),隶属7目26科。主要有青翅隐翅虫(Paederus fuseipes),长足虻(Dolichopodidae)、小菜蛾绒茧蜂(Cotesta plutellae)、八斑鞘蛛(Coleoserma octumaculalum)、食虫沟瘤蛛(Ummeliata insecticeps)、浅斑近微蛛(Eperigone fredeorum)和肖蛸(Tetragnatha)。蜘蛛的种类和数量皆为无公害和常规栽培两类菜地天敌之最。群落的多样性和均匀度偏低,优势种突出。文中揭示了两类菜地天敌群落的相似性及其结构特点和时间动态。认为占两类菜地节肢动物群落物种的53.44%和占个体数量的24.96%的菜地害虫天敌资源,是值得进一步研究和保护利用的自然生物控制因素。 相似文献
7.
The cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) is a generalist species and an important pest of Brassicaceae worldwide. Egg parasitoids are a feasible alternative for the control of this species. We evaluated the suitability of T. ni eggs as hosts for three Trichogramma Westwood (Hymenoptera: Trichogrammatidae) species and their tolerance to survive and develop within a range of temperatures between 15 and 30°C under laboratory conditions. The species evaluated were Trichogramma pretiosum Riley, Trichogramma atopovirilia Oatman and Platner, and Trichogramma acacioi Brun, Moraes and Soares. Parasitism rate was affected by temperature, parasitoid species, and by the interaction between these two factors. Parasitoids developed and reproduced in the range of temperatures evaluated, but Trichog. acacioi failed to parasitize T. ni eggs at 30°C. The highest parasitism rates of Trichog. atopovirilia and Trichog. pretiosum occurred at 20 and 25°C and Trichog. acacioi at 25°C, with parasitism rate above 70% in the three species. Parasitoid emergence was not affected by temperature or species. The estimated thermal constant and lower temperature threshold were 134.6 DD and 10.6°C for Trichog. pretiosum and 130.1 DD and 11.2°C for Trichog. atopovirilia. The results demonstrated that Trichog. pretiosum and Trichog. atopovirilia are the most suitable species for the control of T. ni, as they can remain active throughout the year in subtropical regions. 相似文献
8.
9.
十字花科蔬菜昆虫群落的组成及动态 总被引:2,自引:0,他引:2
通过田间观察、室内饲养和鉴别等方法,利用 1995 年9 月至1997 年3 月在福州市郊区和福建农业大学的调查资料,研究十字花科蔬菜昆虫群落的种类组成、生境分化和时间动态.共记载昆虫58 种(类),其中植食性昆虫39 种(类),占昆虫67.24% ;肉食性昆虫 19 种(类),占32.76% .发现昆虫群落的结构及 Sim pson 优势集中性指数与蔬菜种类、生境条件及生育期等有关. 相似文献
10.
通过以甘蓝、苤兰、青花、油菜植物上的甘蓝蚜喂食大灰食蚜蝇幼虫,研究了这4种十字花科植物次生物质对大灰食蚜蝇生物学习性的影响,结果表明产生的差异是明显的。幼虫历期最短的和最长的是青花与油菜,为9.5d和11.06d。蛹期最短和最长的是甘蓝和油菜,为8.81d和9.68d。蛹重以苤兰的处理最轻,为26.46mg。产卵期以甘蓝和油菜最短,分别为10d和10.5d。产卵量以青花的处理为少,为214.6粒,甘蓝最多,达364.4粒。而成虫寿命、产卵前期、卵孵化率差异都不显著。大灰食蚜蝇幼虫可以取食死亡的甘蓝蚜。对高温致死的取食量是8.3~10.5头,低温致死的是8.3~12.7头,机械致死的为19.7~22.7头。带蚜植物与涂抹蚜虫体液植物均能使其产卵,而无蚜植物则不会产卵。 相似文献