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1.
The maize weevil Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) is a worldwide pest on stored products, as maize, wheat and rice grains. However, in South Brazil, these weevils have been found attacking fruits in field conditions. It was reported that adults attack fruits to feeding, but there was no information of oviposition and larval development on these hosts. Furthermore, due to monitoring apple orchards, was observed that some fruits showed distinct kind of punctures, suggesting a oviposition by these weevils. The present study reports first record an unusual behavior of S. zeamais by oviposition and larval development in peach and apple fruits. The study was conducted in laboratory conditions (temperature: 25?±?1 °C, RH: 70?±?10% and photophase of 14 h). Peach and apple fruits were offered to S. zeamais females. The oviposition and duration of immature stages in peach were measured in fruits and in corn grains, used as control observation. The oviposition and larval development occurred in peach and apple fruits, with a development until to adult. The average of egg-to-adult was 47.4 d in peach and and 45.1 d apple fruits, respectively, while in corn grains, its natural host, the duration was 38.2 d. These results show that the damage caused by S. zeamais in peach and apple fruits may be due to oviposition and the development of immature stages. So, the novelty is in demonstrating that the maize weevil does not just feed as an adult opportunistically on the fruits, but can complete a full life cycle using fresh fruits.  相似文献   

2.
为明确生产栽培小麦品种对玉米象Sitophilus zeamais(Motschulsky)的抗性机制,采用选择性和非选择性试验法系统评估了9个小麦品种对玉米象的抗性,并分析了小麦籽粒营养物质和次生物质含量与其抗性的关系。结果显示,不同小麦品种对玉米象的抗性存在显著差异,其中陕麦139和西农88的不选择性和抗生性较弱,小偃22、周麦16和周麦11较强;玉米象成虫对西农165选择性最强,虫口数为152.00头,而卵至子代成虫发育历期最长,为35.06 d,子代成虫数、重量损失率和敏感系数均较低,分别为19.67头、5.37%和8.30;对周麦18选择性最差,敏感性居中。玉米象成虫对不同小麦品种的选择性与各物质含量,以及总酚、蛋白质含量与各抗性指标均无显著相关性,但阿魏酸含量与子代成虫数、敏感系数及重量损失率显著负相关;可溶性糖含量与子代成虫数、敏感系数及重量损失率显著正相关,与卵至子代成虫发育历期显著负相关。表明小麦品种对玉米象的抗生性与其籽粒中阿魏酸和可溶性糖含量相关,阿魏酸含量越高、可溶性糖含量越低,小麦对玉米象的抗性越强。  相似文献   

3.
稻谷在储藏期对玉米象的抗虫机制研究   总被引：2，自引：0，他引：2       下载免费PDF全文
本文选用抗、感各类的水稻品种(品系)22个,就所考察的13个稻谷物理化学因素彼此相互影响,刚逐步回归分析,研究稻谷在储藏期对玉米象的抗虫机制。结果表明,稻谷开裂率愈大,千粒重越重,则品种就愈有利于玉米象取食;开裂率愈大,谷粒愈宽,谷粒表面颊毛数愈少就愈有利于玉米象的产卵;直链淀粉含量越高,开裂率越大,品种的抗生性就愈低,愈有利于玉米象生长发育;相反,品种粗蛋白含量和粗脂肪含量越高,就愈不利于玉米象的生长发育。其它被测试的6个稻谷物理化学因素:谷粒长,谷粒长/宽,谷壳表面突起数,谷壳内、外颖壳厚度和总糖含量对稻谷在储藏期对玉米象的抗性无显著影响。  相似文献   

4.
Plasmodiophora brassicae, causal agent of clubroot of crucifers, poses a serious threat to Canadian canola production. The effects of fallow (F) periods and bait crops (clubroot‐susceptible canola (B) and perennial ryegrass (R)) on clubroot severity and P. brassicae resting spore populations were evaluated in five sequences: R–B, B–R, R–F, B–F and F–F. Both host and non‐host bait crops reduced clubroot severity in a subsequent crop of a susceptible canola cultivar compared with fallow. Resting spore and P. brassicae DNA concentrations decreased in all treatments, but were lowest for the R–B and B–R bait crop sequences. In addition, two studies were conducted in mini‐plots under field conditions to assess the effect of rotation of susceptible or resistant canola cultivars on clubroot severity and P. brassicae resting spore populations. One study included three crops of susceptible canola compared with a 2‐year break of oat–pea, barley–pea, wheat–wheat or fallow–fallow. The other study assessed three crops of resistant canola, two crops of resistant canola with a 1‐year break, one crop of resistant canola and a 2‐year break, and a 3‐year break with barley followed by a susceptible canola. The rotations that included non‐host crops of barley, pea or oat reduced clubroot severity and resting spore concentrations, and increased yield, compared with continuous cropping of either resistant or susceptible canola. Growing of a susceptible canola cultivar contributed 23–250‐fold greater gall mass compared with resistant cultivars.  相似文献   

5.
BACKGROUND: In a screening programme for new agrochemicals from Chinese medicinal herbs, Chenopodium ambrosioides L. was found to possess strong fumigant activity against the maize weevil Sitophilus zeamais (Motsch.). Essential oil of C. ambrosioides was obtained by hydrodistillation, and the constituents were determined by GC‐MS analysis. The active compounds were isolated and identified by bioassay‐directed fractionation. RESULTS: Five active compounds [(Z)‐ascaridole, 2‐carene, ρ‐cymene, isoascaridole and α‐terpinene] were isolated and identified from the essential oil from Chinese C. ambrosioides. The LC50 values (fumigation) of the crude essential oils and the active compound (Z)‐ascaridole against S. zeamais adults were 3.08 and 0.84 mg L?1 air respectively. The LD50 values (contact toxicity) of the crude essential oil and (Z)‐ascaridole against S. zeamais adults were 2.12 and 0.86 µg g?1 body weight respectively. CONCLUSION: The findings suggested that the essential oil of Chenopodium ambrosioides and its main active constituent, (Z)‐ascaridole, may be explored as a natural potential fumigant. Copyright © 2011 Society of Chemical Industry  相似文献   

6.
The population dynamics of Xanthomonas arboricola pv. pruni (Xap) and X. citri subsp. citri (Xcc) was assessed on over three dozen plant species/genotypes under field and greenhouse conditions. Both Xap and Xcc multiplied on red nightshade, black nightshade, bindweed, Chenopodium, common bean and wheat up to 20 days post‐inoculation (dpi) under greenhouse conditions. A high bacterial growth rate was observed on all (alfalfa, bindweed, Chenopodium, field mustard, millet and prickly lettuce) but one (liquorice) plant species tested under field conditions. Xap successfully proliferated on both lemon and sweet lemon up to 140 dpi, attaining a population density even higher than that of Xcc. The latter showed an increased growth rate on GxN, GF677, Ghisella 6 and Mariana 2624 rootstocks up to 140 dpi. While Xap and Xcc did not grow on pomegranate and common fig, they had a steady population growth on apple and pear plants up to 140 dpi, although the final population sizes were smaller than those observed on lemon and sweet lemon plants. The results suggest that a large number of non‐host plant species could support epiphytic populations of Xap or Xcc, which may have implications for plant disease epidemiology.  相似文献   

7.
辣椒花象甲Anthonomus eugenii是一种毁灭性害虫,原产于中美洲,可为害至少35种商业辣椒品种,对辣椒为害严重,可使其减产33%～90%。该害虫于1993年入侵加拿大,并于2014年进入欧洲。频繁的全球贸易及国际运输将加速该害虫的传播和扩散,并有入侵我国的风险。该文对辣椒花象甲的生物学特性、寄主植物、为害特征、分布范围及传播进行总结,分析其对我国的入侵风险及对我国辣椒产业造成的潜在损失,并提出风险管理措施。  相似文献   

8.
BACKGROUND: Isothiocyanates (ITCs) extracted from Armoracia rusticana Gaertn., May & Scherb. have been shown previously to have insecticidal activity. Allyl isothiocyanate (AITC), a major component of ITCs with high volatility, was therefore extracted using different methods and tested as a fumigant against four major pest species of stored products, maize weevil Sitophilus zeamais (Motsch.), lesser grain borer Rhizopertha dominica (F.), Tribolium ferrugineum (F.) and book louse Liposcelis entomophila (Enderlein). RESULTS: Whereas there was no significant difference between hydrodistillation and supercritical carbon dioxide fluid extraction in extraction rate for AITC from A. rusticana, both methods resulted in higher extraction efficiency than water extraction. AITC fumigation showed strong toxicity to the four species of stored‐product pests. Adult mortality of 100% of all four pest species, recorded after 72 h exposure to AITC fumes at an atmospheric concentration of 3 µg mL?1, showed no significant difference from that of insects exposed to phosphine at 5 µg mL?1, the recommended dose for phosphine. CONCLUSIONS: The results suggest good insecticidal efficacy of AITC against the four stored‐product pests, with non‐gaseous residuals on stored products. AITC obtained from A. rusticana may be an alternative to phosphine and methyl bromide against the four pest species. Copyright © 2009 Society of Chemical Industry  相似文献   

9.
Reactive oxygen species (ROS) play dual roles in plant–microbe interactions in that they can either stimulate host resistance or enhance pathogen virulence. Innate resistance in peach (Prunus persica) to the brown rot fungal pathogen Monilinia fructicola is very limited, and knowledge of the mechanism of virulence is rudimentary. In this study, production of hydrogen peroxide, a major component of ROS, was determined in peach flower petals in response to M. fructicola (a host pathogen) and Penicillium digitatum (a non‐host pathogen). Monilinia fructicola was able to infect flower petals while P. digitatum was not. During the host‐specific interaction, M. fructicola induced hydrogen peroxide accumulation in flower petals. Application of exogenous antioxidants significantly reduced hydrogen peroxide accumulation as well as the incidence of brown rot disease. Application of M. fructicola spores to the surface of intact flower petals induced gene expression and increased enzyme activity of NADPH oxidase and cell wall peroxidase in host tissues, resulting in the production of hydrogen peroxide. Petals inoculated with M. fructicola exhibited high levels of protein carbonylation and lipid peroxidation. No significant response in gene expression, enzyme activity or hydrogen peroxide levels was observed in peach flower petals treated with P. digitatum. These results suggest that M. fructicola, as with other necrotrophic fungi, uses the strong oxidative response as part of a virulence mechanism.  相似文献   

10.
BACKGROUND: The polyphagous cotton‐melon aphid Aphis gossypii Glover is structured into geographically widespread host races comprising a few clones specialised on Cucurbitaceae, cotton, eggplant or pepper. To assess insecticide resistance among and within host races, leaf disc bioassays were conducted on aphid clones collected from Cucurbitaceae (genotypes C4 and C9), cotton (genotypes Burk and Ivo), eggplant (genotype Auber) and pepper (genotype PsP4). Molecular diagnostic (PCR‐RFLP) and enzyme assays were also performed to detect the basic mechanisms underlying insecticide resistance. RESULTS: All six clones were susceptible to acetamiprid (neonicotinoid) or carbosulfan (carbamate). Conversely, all clones were resistant to dimethoate (organophosphate) (RF = 4.1–38.1) and carried mutation S431F in the acetylcholinesterase gene. Auber, PsP4 and Burk also carried mutation A302S in this gene, which possibly conferred moderate resistance (RF = 3.7–6.8) to profenofos and monocrotophos (organophosphates). Auber and Burk were highly resistant (RF = 41.2 and 473 respectively) to cypermethrin (pyrethroid). This resistance was likely associated with point mutation super‐kdr (M918L) in the voltage‐gated sodium channel gene (para gene) or metabolic detoxification mediated by esterase and oxidase enzymes. CONCLUSION: Multiple resistance to a broad range of insecticides and multiple mechanisms of resistance in some clones could explain to some extent the low genetic diversity observed within A. gossypii host races. Copyright © 2009 Society of Chemical Industry  相似文献   

11.
S. Ekesi 《Phytoparasitica》2000,28(4):305-310
The effect of volatiles and aqueous extracts of black pepper,Piper guineense; neem seed,Azadirachta indica; garlic bulb,Allium sativum; and onion bulb,Allium cepa on egg viability ofMaruca vitrata Fab. (Lepidoptera: Pyralidae) andClavigralla tomentosicollis Stål (Heteroptera: Coreidae) was evaluated in laboratory experiments. Compared with the other treatments, volatiles of black pepper and garlic bulb were superior in reducing hatch of freshly laid (12-h-old) eggs of both species of insects. Volatiles of onion bulb and neem seed had no effect on egg hatch. When aqueous extracts of the various plant materials were tested at 5%, 10% and 15%, extracts of black pepper, neem seed and garlic bulb caused a severe reduction in egg hatch, with black pepper and garlic bulb providing the highest reduction at all concentrations tested in both insects. When black pepper and garlic bulb were compared at 5% for their activity in relation to egg age, the effect of black pepper decreased with increasing egg age but the performance of garlic was consistent across the various age groups tested in both insects. This result is indicative of the potential of using these plant materials and especially garlic for the management ofM. vitrata andC. tomentosicollis.  相似文献   

12.
This study aimed to elucidate the relationship between plant hosts and root‐colonizing fungi recovered from apple orchard soils that had been replanted over multiple generations. Functional relationships of three groups of filamentous fungi (Ceratobasidium sp., Cylindrocarpon‐like group and Fusarium acuminatum) with apple rootstocks were evaluated in plant growth bioassays. The Cylindrocarpon‐like group and Ceratobasidium sp. showed a relationship with the host plant varying from pathogenic to commensal through to mutualistic for the latter group, while that of F. acuminatum tended to be mutualistic. Seven fungal isolates of each group, which induced the highest plant growth in bioassays, were evaluated for auxin (IAA) and gibberellin (GA3 and GA4) production in culture filtrate. All isolates of F. acuminatum as well as most of those of the Ceratobasidium sp. and Cylindrocarpon‐like groups produced IAA in culture filtrate. IAA production was evaluated for additional isolates of endophytic fungal species from fruit tree orchards and the functionality of IAA was confirmed by growing in vitro micropropagated plantlets of apple rootstock on MS medium supplemented with fungal culture filtrate. Findings from this study may explain the difficulty in defining the precise role of diverse root‐colonizing fungal populations in replant disease aetiology of fruit tree orchards. However, the results demonstrate the presence of a positive and widely available biotic component of the orchard soil biology that may be exploited for the benefit of tree growth and production.  相似文献   

13.
Striga hermonthica is a major biotic constraint to sorghum production in Nigeria, sometimes causing total yield loss. Recommendations for Striga management often include the use of cultural and agronomic practices, herbicides and host plant resistance when available. The use of biological control has not been commercialized. Fusarium oxysporum (isolate PSM 197)‐based mycoherbicide was used in combination with selected sorghums (the Striga‐resistant cultivar Samsorg 40, and the Striga tolerant landrace Yar'ruruka) as an Integrated Striga Management strategy (ISM) in on‐farm trials in the Sudano‐Sahelian savanna of Nigeria. Crop stands were significantly (P = 0.05) higher in ISM compared with non‐ISM plots on which the mycoherbicide was not applied. Similarly, ISM plots had significantly (P = 0.05) lower Striga counts than non‐ISM plots. Striga emergence was reduced by ISM by around 95%. Sorghum yields were 49.6% higher where integrated management was used. Cost benefit analysis of the ISM package shows that use of the mycoherbicide increased the profitability of sorghum production on Striga‐infested soils. Farmers’ preferences monitored during and after the trials highlighted the need for careful selection and integration of control components into an ISM package.  相似文献   

14.
To assess its response to the herbicide, tribenuron‐methyl, samples of Nasturtium officinale were exposed to 0, 0.01, 0.05, 0.1, and 0.5 mg L?1 of tribenuron‐methyl for 1, 2, 4 and 7 days. The influence of this herbicide on the relative growth rate, electrolyte leakage, lipid peroxidation, photosynthetic pigmentation, protein content, and performance of anti‐oxidant enzymes, such as superoxide dismutase (SOD), catalase, and ascorbate peroxidase (APX), was examined. The results indicated that tribenuron‐methyl, applied at 0.5 mg L?1, affected plant growth negatively. It also was determined that chlorophyll a is the most responsive photosynthetic pigment to tribenuron–methyl exposure. Under stress conditions, the anti‐oxidant enzymes were up‐regulated compared to the control. The SOD activity was significantly stimulated, while the activity of APX was inhibited. A significant correlation was found between lipid peroxidation and SOD activity. The exposure period and herbicide concentration had significant effects on the biological responses against tribenuron‐methyl stress. These results may be useful for clarifying the effect of herbicides on non‐target aquatic plants.  相似文献   

15.
BACKGROUND: The granary weevil, Sitophilus granarius (L.), is one of the most damaging pests of stored grains, causing severe quantitative and qualitative losses. Sustainable control means, alternative to the commonly used fumigants and broad‐spectrum contact insecticides, are urgently needed owing to legislative limits, the development of resistant insect strains and increasing consumer demand for safe food. Short‐chain aliphatic ketones, known to be emitted by cereal grains and previously identified as repellents to adult granary weevils, were evaluated for their ability to disrupt insect orientation towards wheat grains and as possible natural fumigants. RESULTS: In behavioural bioassays, 2‐pentanone, 2‐hexanone, 2‐heptanone and 2,3‐butanedione significantly reduced insect orientation towards odours of wheat grains, with 2‐hexanone and 2‐heptanone being the most active. In fumigation tests, all compounds were effective in killing weevil adults, but they performed differently according to chemical structure, speed of action and presence of wheat grains. In the presence of grains, the highest fumigant toxicity was shown by 2‐pentanone (LC50 = 8.4 ± 1.0 mg L?1) after 24 h exposure, and by 2‐pentanone (LC50 = 4.5 ± 0.3 mg L?1), 2‐heptanone (LC50 = 7.1 ± 0.3 mg L?1) and 2‐hexanone (LC50 = 8.1 ± 0.6 mg L?1) 1 week after the treatment end. CONCLUSION: Short‐chain aliphatic ketones have potential for applications in IPM programmes for the granary weevil because of their behaviour‐altering activity and fumigant toxicity. Copyright © 2011 Society of Chemical Industry  相似文献   

16.
Pyrenophora tritici‐repentis (Ptr) is a destructive fungal pathogen of wheat worldwide. In addition to wheat, Ptr has been isolated from various other hosts in the family Poaceae, yet the nature of its interaction with those hosts is unknown. The Ptr–barley relationship was explored and the existence of a specific interaction between Ptr and barley is described for the first time; symptom development on several barley genotypes was evaluated in bioassays and by toxin infiltration into barley leaves. Ptr ToxB‐producing isolates of the fungus were able to cause significant damage when inoculated onto certain barley genotypes, and Ptr ToxB was able to induce chlorosis in a highly selective manner when infiltrated into those same genotypes. Ptr–barley specificity is subtle and can break with slight changes in temperature after infection. To understand the infection process in barley, a cytological analysis and in planta fungal biomass estimation using quantitative PCR were performed. The fungus penetrates through the host epidermal cells and advances to colonize the mesophyll layer intercellularly, with the infection process on barley closely resembling that on wheat. Here, evidence is provided for a specific interaction between barley and Ptr, expanding understanding of Ptr host specificity and breaking the assumption that the highest level of specificity seen with Ptr is restricted to particular genotypes of the wheat host.  相似文献   

17.
The miniature tomato (Solanum lycopersicum) cultivar Micro‐Tom (MT) has become an important platform to investigate plant–pathogen interactions. In the case of the witches' broom disease of Theobroma cacao (cacao), the existence of Moniliophthora perniciosa isolates pathogenic to Solanaceae (S‐biotype) may enable the use of MT to circumvent limitations of the cacao host, whereas the availability of a non‐infective cacao C‐biotype allows the evaluation of contrasting responses of MT. Infection of MT by the S‐biotype led to stem swelling and axillary shoot growth to form broom‐like symptoms similar to the biotrophic phase in cacao, but the infected tissues did not progress to necrosis. Conversely, inoculation with the C‐biotype did not cause typical symptoms, but reduced plant height, appearing as a non‐host interaction. Histopathological characterization of the S‐biotype infection of MT by light and electron microscopy indicated limited germ tube penetration, preferentially through wounds at the base of trichomes or actively through the epidermis. No intracellular mycelium was observed, corroborating the lack of the necrotrophic stage of the pathogen. The analysis of gene expression during the interaction between the S‐ or C‐biotype with MT indicated that expression of plant defence‐associated genes differs for kinetics and intensity between a compatible or incompatible M. perniciosa–MT interaction. The pattern of spore germination and low rate of mycelia penetration suggests that the S‐biotype is not a fully adapted tomato pathogen, but possibly a case of broken non‐host resistance, and evidence suggests the occurrence of a non‐host MT response against the C‐biotype.  相似文献   

18.
Conidial germination and differentiation, the so‐called prepenetration processes, of the barley powdery mildew fungus (Blumeria graminis f.sp. hordei) are triggered in vitro by very‐long‐chain aldehydes, minor constituents of barley leaf wax. However, until now it has not been demonstrated that these cuticle‐derived molecules also play a significant role in the initiation and promotion of the fungal prepenetration processes in vivo, on the surface of a living plant leaf. In the maize (Zea mays) wax mutant glossy11, which is completely devoid of cuticular very‐long‐chain aldehydes, germination and appressorial differentiation of B. graminis were strongly impeded. Spraying the mutant leaf surface with aldehyde‐containing wild‐type wax or pure n‐hexacosanal (C26‐aldehyde) fully restored fungal prepenetration, whereas maize wild‐type leaf surfaces coated with n‐docosanoic acid exhibited reduced conidial germination rates of 23%, and only 5% of the conidia differentiated infection structures. In vitro studies were performed to further corroborate the extensive prevention of fungal germination and differentiation in response to artificial surfaces coated with aldehyde‐deficient maize wax. Because of its phenotype affecting the B. graminis prepenetration processes, the glossy11 mutation of maize may become a valuable molecular target and genetic tool that could provide a means of developing basal powdery mildew resistance in the globally important crops wheat and barley.  相似文献   

19.
Within season gradient of wheat take‐all was measured in field experiments according to line or random sowing host spatial distribution, and two Gaeumannomyces graminis var. tritici (Ggt) isolates (G1i and G2i), representative of the G1 and G2 genotype groups in terms of aggressiveness. Root disease incidence and severity were assessed at six dates from early March to late June on plants located at regular distances from the inoculum sources. Simple models relating disease intensity at different levels of hierarchy fitted observed data well, and indicated a strong disease aggregation both within and among plants. Disease severity on source plants placed nearby the inoculum source increased over time, ranging from 5 to 46% at the first assessment, and from 55 to 98% at the last assessment, being in general larger for G2i than G1i. In line‐sown plots, disease progressed steadily along the line but did not extend beyond 20 cm, seldom reaching the neighbour line. Disease rarely reached 25 cm in the direct‐seeded crop stands. These results indicate that Ggt intensifies but does not spread to a large extent during a cropping season. Distance from the source, pathogen genotype and assessment date had a significant effect on disease severity according to mixed model analyses, disease spread being larger for G2i than G1i. However, no significant effect of host spatial distribution could be detected. Yield loss within 20 cm of the source plant ranged between 20 and 40%, and was not significantly affected by pathogen genotype or host spatial distribution.  相似文献   

20.
Ochradenus baccatus is a widely distributed shrub in desert regions of the Middle East and North Africa. This plant's nematicidal activity against the root‐knot nematode Meloidogyne javanica was evaluated because it has been found to contain exceptionally high levels of glucosinolates. In in vitro assays with aqueous extracts of the plant, 100% of second‐stage juveniles were immobilized after exposure to 4% root‐core extract for 48 h; 8% root‐core extract suppressed their hatching by 87%, whereas stem, flower and root bark showed lower activity. Incorporation of root core or bark into the soil, as fresh or dry powder at 1 and 0·5% (w/w), respectively, reduced the number of nematodes recovered from the soil by 95–100%, whereas the flower and stem were much less effective. Results from further pot experiments indicated that only the root bark consistently contains nematicidal compounds which are effective in soil, whereas the nematicidal activity of the root core in soil was inconsistent. The presence of non‐volatile lipophilic and lipophobic nematicidal compounds in the root bark was suggested by extraction with different polar solvents, but these compounds do not seem to be isothiocyanates – glucosinolate‐hydrolysed compounds with nematicidal activity. Very poor host status of Ochradenus baccatus to M. javanica, M. incognita and M. hapla, but with root‐penetration rates of juveniles similar to those in tomato roots, suggest that this plant may be used as a cover plant or trap plant to reduce nematode populations in the soil.  相似文献   

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