宁夏银川地区甘蓝蚜的发生规律及防治

甘蓝蚜在银川地区1 a发生15代左右,危害较为严重。以2.5%高效氯氟氰菊酯水乳剂对大白菜(‘津绿75’)甘蓝蚜的田间药效进行了试验。结果表明:2.5%高效氯氟氰菊酯水乳剂对大白菜甘蓝蚜的防治效果较好,平均防效在90.9%以上,最佳使用剂量7.5 ga.i./hm2以上。     

Survival of pathogens of Brussels sprouts (Brassica oleracea Gemmifera Group) in crop residues

Mycosphaerella brassicicola (ringspot), Alternaria brassicicola and A. brassicae (dark leaf spot) and Xanthomonas campestris pv. campestris (black spot) can infect leaves of Brussels sprouts resulting in yield losses. Infections of outer leaves of sprouts cause severe losses in quality. Crop residues can be a major primary inoculum source of the pathogens. Their population dynamics were followed in residues of leaves and stalks of crops of Brussels sprouts during 24 months using real‐time PCR assays. Leaf residues on the soil surface or buried in soil decomposed within 4 months. However, residues of stalks were present in the field after 24 months. In such residues, M. brassicicola populations increased during the first 2 months, but decreased thereafter and the pathogen was found only occasionally in the second year. Alternaria brassicicola multiplied on stalks exposed on the surface of field soil and was present on such residues after 24 months. Survival was less on residues buried in soil. Alternaria brassicae population increased in stalks exposed on the soil surface during the first months but decreased thereafter under the detection limit. Xanthomonas campestris cv. campestris populations fluctuated in time but 1 × 10⁴ cells mg^?1 stalk residue were still found after 24 months. Additionally, the four pathogens were present in residues of 11 commercial rapeseed crops that were analysed. The observed variation in population sizes of the pathogens between individual pieces of crop residues indicates a stochastic spread of pathogens. Unravelling the underlying processes will support the development of novel methods for sustainable disease prevention.     

种植油菜诱集飘虫防治竹蚧的研究

在竹林周围或幼林内空地种植油菜繁殖菜蚜,以增加瓢虫种群数量。油菜收获后,瓢虫转迁入竹林捕食竹蚧,对竹蚧的控制效果可达90％以上。     

龟纹瓢虫选择取食行为的研究

通过室内实验初次研究了龟纹瓢虫取食5种蚜虫行为及其食蚜量;比较了取食5种蚜虫对幼虫生长发育及成虫生殖产卵的影响。结果表明:龟纹瓢虫成虫和幼虫对同种蚜虫的嗜食程度基本相同。初龄幼虫无选择适宜猎物蚜虫的能力。幼虫随龄期的增大,选择能力渐趋明显,以成虫和大龄幼虫选择力更强。该种瓢虫明显选择取食棉蚜、桃蚜和白杨毛蚜,洋槐蚜为不甚适宜的猎物,而甘蓝蚜最不适宜。因此认为,龟纹瓢虫具有一定程度的食物专化性,可作为棉蚜和桃蚜的有效天敌,应充分加以保护与利用。     

Effects of R gene‐mediated resistance in Brassica napus (oilseed rape) on asexual and sexual sporulation of Pyrenopeziza brassicae (light leaf spot)

The phenotype of the R gene‐mediated resistance derived from oilseed rape (Brassica napus) cv. Imola against the light leaf spot plant pathogen, Pyrenopeziza brassicae, was characterized. Using a doubled haploid B. napus mapping population that segregated for resistance against P. brassicae, development of visual symptoms was characterized and symptomless growth was followed using quantitative PCR and scanning electron microscopy on leaves of resistant/susceptible lines inoculated with suspensions of P. brassicae conidia. Initially, in controlled‐environment experiments, growth of P. brassicae was unaffected; then from 8 days post‐inoculation (dpi) some epidermal cells collapsed (‘black flecking’) in green living tissue of cv. Imola and from 13 to 36 dpi there was no increase in the amount of P. brassicae DNA and no asexual sporulation (acervuli/pustules). By contrast, during this period there was a 300‐fold increase in P. brassicae DNA and extensive asexual sporulation in leaves of the susceptible cv. Apex. However, when leaf tissue senesced, the amount of P. brassicae DNA increased rapidly in the resistant but not in the susceptible cultivar and sexual sporulation (apothecia) was abundant on senescent tissues of both. These results were consistent with observations from both controlled condition and field experiments with lines from the mapping population that segregated for this resistance. Analysis of results of both controlled‐environment and field experiments suggested that the resistance was mediated by a single R gene located on chromosome A1.     

Susceptibility of hairy root lines of Brassica species to Plasmodiophora brassicae and in an in vitro subculture system

To investigate the susceptibility of hairy root lines of Brassica species to Plasmodiophora brassicae, hairy roots were induced in a number of Brassica species with Agrobacterium rhizogenes. Turnip hairy root was highly susceptible to P. brassicae; infection rates were high and large galls formed. In contrast, the rates of root hair infection and gall formation on intact Brassica plants did not differ significantly from the control. To induce resting spore formation, turnip hairy roots were incubated at 15°, 20°, or 25°C after 3 weeks of incubation at 25°C. The number and fresh mass of the galls per hairy root were higher and formation of resting spores was greatest after a 7-week incubation at 20°C. To subculture P. brassicae using turnip hairy root, turnip hairy roots were reinoculated with resting spores and gall with resting spores then formed on the hairy roots. In this way, P. brassicae using hairy roots could be subcultured in vitro two or three times on three single-spore isolates of P. brassicae. This is the first report of in vitro subculture of P. brassicae using hairy root.     

芸薹根肿菌及油菜根肿病分子检测与早期诊断

近年来芸薹根肿菌引起的根肿病已成为我国油菜的主要病害,严重影响油菜及其它十字花科作物的产量及品质。为建立一套在土壤、植物组织和种子中精准检测根肿菌的高效分子方法,利用根肿菌ITS(internal transcribed spacer)序列,设计一对特异性引物(Pb ITS1),通过PCR反应优化体系进行根肿菌的分子检测及病害评估。结果表明,该引物及方法能够特异性检测根肿菌DNA,不受土传病原真菌、细菌、线虫及寄主植物内生菌的DNA干扰。灵敏性检测表明,模板DNA最低浓度达1pg·μL^-1,土壤带菌量最低为1×10^3个孢子/g土,种子带菌量最低1×10^5个孢子/g种子。此外,该体系能够用于检测油菜及其它十字花科寄主植物(如组织、种子)和土壤类型。同时,可用于田间油菜不同生长阶段油菜根部及周围土壤的根肿菌检测。本研究建立的检测体系操作简便、适用范围广、灵敏度高、特异性强,可检测样品种类丰富,可为油菜及其它十字花科根肿病的早期诊断、流行监测与预警、综合防控等提供科学依据。     

Growth and movement of secondary plasmodia of Plasmodiophora brassicae in turnip suspension-culture cells

Growth of secondary plasmodia of the clubroot pathogen Plasmodiophora brassicae was studied in dual culture of P. brassicae and turnip suspension cells. Suspension culture of P. brassicae -infected turnip cells was achieved by using P. brassicae -infected callus in Murashige and Skoog medium supplemented with 0·1 mg 2,4-D L⁻¹ and 0·02 mg kinetin L⁻¹. The shape of secondary plasmodia in suspension cells was spherical-to-subspherical. A few young plasmodia divided and became numerous spherical, small plasmodia which eventually formed a plasmodial cluster. The plasmodia fused and became vegetative plasmodia. Infected cells were significantly larger than noninfected cells. Secondary plasmodia moved within transformed turnip suspension host cells by cytoplasmic streaming of the host cells. Secondary plasmodia divided in synchrony with the transformed turnip cells.     

四川省根肿菌的分布和生理小种及品种抗性评估

为探究四川省根肿菌Plasmodiophora brassicae分布、生理小种及品种抗性,于2014-2016年向各县(区、市)植保站问卷调研了解四川省根肿病分布,并利用Williams体系对采自四川省不同病田的22个根肿菌样进行生理小种鉴定,利用其中18个对9个普通十字花科作物品种进行室内抗性评估。结果表明,根肿病分布于四川省19市(州)89个县(区、市),占总调查数的50%。按照极高、高、中等、低、极低、无分布6个根肿病分布密度等级依次划分为23、7、11、16、32和0个县(区、市),其中11个县(区、市)根肿病病史较长,大部分根肿病极高和高密度分布以及长病史县(区、市)都在地理位置上相对集中。22个根肿菌样共鉴定出2、4、7和11号4个生理小种,其中4号为优势生理小种,占77%。四川省表现出明显生理小种地域分布差异。抗性评估发现供试品种对绝大多数供试菌都表现感病,且73%的供试组合病情指数在75以上。     

Cabbage aphid control on commercial farms in the Thames Valley, UK

Cabbage aphid control on June/July-planted cabbages was studied on four commercial vegetable farms in the Thames Valley and compared with an untreated crop at Silwood Park. At the four commercial sites, where growers followed their normal control practices, counts were made of aphids, their predators and parasites, throughout the cropping season and following the application of foliar insecticide sprays. Although natural enemies appear to be important in producing a mid-season trough in aphid numbers, they are unable to cope with the increase in aphid numbers later in the crop season. This problem of late aphid control is made worse because the effectiveness of foliar treatment also declines. At present, as the use of action thresholds does not seem feasible, it is suggested that improvements should be sought in more effective techniques of granular or foliar application.