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1.
Disease symptoms typical of anthracnose were observed in cucumber, pumpkin and squash after infiltrating leaves with a conidial suspension ofColletotrichum lagenarium, but symptoms developed only in cucumber when droplets of the conidial suspension were applied to the leaf surface. There was no difference in the germination of conidia or in appressorium formation on leaf surfaces of cucumber, pumpkin or squash plants; however, penetration was markedly reduced into pumpkin and squash with or without systemic acquired resistance (SAR) and into cucumber with SAR. Little β-1,3-glucanase and chitinase activities were detected in challenged pumpkin and squash leaves without symptoms even 5 days after inoculation in leaf surfaces. However, the enzymes were detected in pumpkin and squash leaves with symptoms, and activities of the enzymes were greater than those in cucumber. These results suggest that β-1,3-glucanase and chitinase activities are not primary initial defence compounds associated with non-host resistance of pumpkin and squash toC. lagenarium. 相似文献
2.
Zucchini squash is host to Cucurbit yellow stunting disorder virus (CYSDV), a member of the genus Crinivirus, and Cucumber vein yellowing virus (CVYV), a member of the genus Ipomovirus, both transmitted by the whitefly Bemisia tabaci. Field observations suggest the appearance of new symptoms observed on leaves of zucchini squash crops when both viruses were present. When infected during controlled experiments with CYSDV only, zucchini plants showed no obvious symptoms and the virus titer decreased between 15 and 45 days postinoculation (dpi), after which it was no longer detected. CVYV caused inconspicuous symptoms restricted to vein clearing on some of the apical leaves and the virus accumulated progressively between 15 and 60 dpi. Similar accumulations of virus followed single inoculations with the potyvirus Zucchini yellow mosaic virus (ZYMV) and plants showed severe stunting, leaf deformation, and mosaic yellowing. However, in mixed infections with CYSDV and CVYV, intermediate leaves showed chlorotic mottling which evolved later to rolling, brittleness, and complete yellowing of the leaf lamina, with exception of the veins. No consistent alteration of CVYV accumulation was detected but the amounts of CYSDV increased ≈100-fold and remained detectable at 60 dpi. Such synergistic effects on the titer of the crinivirus and symptom expression were not observed when co-infected with ZYMV. 相似文献
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Silverleaf syndrome on squash ( Cucurbita pepo ) is characterized by vein clearing, and leaf whitening, and has been associated with the presence of nymphs of Bemisia tabaci (sweetpotato whitefly), and the presence of two double-stranded RNAs (4·2 and 4·6 kb) in symptomatic leaves. However, the aetiology of the disorder remains unknown. Anatomical studies using transverse and paradermal sections from symptomatic leaves of C. pepo cv. Dixie showed turgescent, aligned adaxial epidermal cell layer, flat cuticle and the presence of sub-epidermal spaces. Histochemical studies failed to reveal any breakdown in the cellulose cell walls; however, the cuticular layer, the pectin layer and cellulose wall of epidermal cells formed a fiat compact structure. Some changes were observed in the lipid content, with the presence of lipid bodies near cell wall membranes. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of preparations of symptomatic squash leaves, partially purified by differential centrifugation, revealed a protein with a molecular mass of about 48 k Da that was not found in comparable preparations of asymptomatic leaves. This protein was localized by immunological staining in the spongy mesophyll cells and in the layer of bundle sheath associated with sieve elements and companion cells of the leaf phloem. 相似文献
5.
Yueping Zheng Mantri Nitin Lanlan Wang Yongming Ruan Bo Jiang Zonggen Shen 《国际虫害防治杂志》2013,59(1):10-19
Squash silverleaf induced by the geographical variant Middle East-Asia Minor 1 (MEAM1) of Bemisia tabaci (Gennadius) is an economically important disease of Cucurbita pepo L. in tropical and warm temperate regions of the world. Therefore, both early detection of disease severity and judicious use of insecticides are important for minimizing economic losses. Therefore, the aims of this study were to use chlorophyll fluorescence to detect squash silverleaf early and determine the best protocol for imidacloprid application. The results showed that chlorophyll fluorescence was positively correlated with disease severity of whitefly-infested plants. Foliar spraying was suitable for application to control MEAM1 in the high risk region because it could be rapidly implemented against whitefly infestations and because it has a high knockdown rate. Soil application was slow-acting but had a long-lasting effect and was suitable for implementation during the initial stage of a whitefly outbreak. Considering the overall insect control potential and the risks to the environmental contamination and human health, 0.3 g L?1 imidacloprid is the recommended concentration using the two application methods. 相似文献
6.
N. L. Robertson 《Plant pathology》2004,53(5):569-576
A new virus named Nootka lupine vein-clearing virus (NLVCV) was isolated from Lupinus nootkatensis plants that were confined to a relatively small area in the Talkeetna mountains of south-central Alaska. Annual surveys (2000–03) consistently found leaf symptoms of pronounced vein clearing and mosaic on 3- to 4-week-old plants in late June. Spherical particles ≈30 nm in diameter were isolated from these leaves. Virions contained a single-stranded RNA of ≈4·0–4·2 kb and one species of capsid protein estimated to be ≈40 kDa. The double-stranded RNA profile from naturally infected leaves consisted of three major bands ≈4·2, 1·9 and 1·5 kbp. Protein extractions from either sap or virions of diseased plants reacted to polyclonal antiserum made against the virions in Western blot assays. A predicted PCR product ≈500 bp was synthesized from virion RNA using primers specific to the carmovirus RNA-dependent RNA polymerase (RDRP) gene. The nucleotide sequence of the amplified DNA did not match any known virus, but contained short regions of identity to several carmoviruses. Only species belonging to the Fabaceae were susceptible to NLVCV by mechanical inoculation. Based on dsRNA profile, size of virion RNA genome and capsid protein, and similarity of the RDRP gene to that of other carmoviruses, it is suggested that NLVCV is a member of the family Tombusviridae , and tentatively of the genus Carmovirus . As the host range, RDRP gene and dsRNA profile of NLVCV are different from those of known viruses, this is a newly described plant virus. 相似文献
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Tomato plants infected with Potato spindle tuber viroid (PSTVd) had severe leaf curling and vein necrosis. The disease symptoms began to diminish during the late stages of infection, however, and almost healthy-looking leaves began to appear on the upper portion of the plants. PSTVd concentrations reached their highest levels in leaves with severe symptoms and decreased in upper leaves recovering from severe symptoms. PSTVd-specific short interfering RNAs (siRNAs), characteristic of RNA silencing, accumulated in all leaves in which PSTVd reached a detectable level, suggesting that recovery from severe disease was induced by RNA silencing via sequence-specific degradation of PSTVd. 相似文献
8.
BACKGROUND: The potato psyllid, Bactericera cockerelli, is a vector of Candidatus Liberibacter solanacearum, causing several diseases in solanaceous crops. Laboratory and field no‐choice and choice experiments were conducted to evaluate the repellency of kaolin particle film on adults of B. cockerelli on tomato plants that had been sprayed with kaolin particle film on the upper surface only, on the lower surface only and on both leaf surfaces. RESULTS: In no‐choice tests in the laboratory, the numbers of adults on leaves were not different between the kaolin particle film and the water control, regardless of which leaf surface(s) were treated, but numbers of eggs were lower on the leaves treated with kaolin particle film than on those treated with water. In choice tests on plants treated with water/plants treated with kaolin particle film at ratios of 1:1, 6:3 or 8:1, fewer adults and eggs were found on the leaves treated with kaolin particle film than on leaves treated with water. Under field conditions, in caged no‐choice or choice tests, fewer adults, eggs and nymphs were found on plants treated with kaolin particle film than on plants treated with water. In an uncaged test under field conditions, plants sprayed with kaolin particle film had fewer psyllids than those sprayed with water. CONCLUSION: Even though potato psyllid adults could land on plants treated with kaolin particle film when no choice was given, fewer eggs were laid. When given a choice, the psyllids avoided plants treated with kaolin particle film under laboratory and field conditions. Kaolin particle film treatment may be a useful alternative for management of potato psyllids under field conditions. Copyright © 2011 Society of Chemical Industry 相似文献
9.
R. Aly F. Mansour F. A. Moch M. Edelstein D. Libman E. Meiri Y. M. Shiboleth A. Gal-On 《Phytoparasitica》2005,33(2):177-186
Control of the spider miteTetranychus cinnabarinus Boisduval is problematic, and there is a pressing need for efficient, non-hazardous and inexpensive strategies for limiting
the damage it causes. The gene for the anti-bacterial peptide sarcotoxin IA of the flesh flySarcophaga peregrina was cloned into the nonpathogenic potyvirus-based vector system ZYMV-AGII (Zucchini yellow mosaic virus-AGII). Expression of this peptidevia the AGII vector was detected in infected squash leaves and was not deleterious to the host plant. Leaf discs of squash infected
with the recombinant virus AGII-sarcotoxin IA were tested for spider mite control under laboratory conditions. Spider mite
egg production on plants expressing the sarcotoxin IA gene was decreased by a factor of two or three compared with that on
AGII-infected plants or healthy leaf discs, respectively. In contrast to its effect on oviposition, sarcotoxin IA expressing
squash did not significantly affect the mortality and the ability to repel spider mites. Crude extract from squash leaves
infected with AGII-sarcotoxin IA was also found to cause a significant decrease of mite fecundity compared with extracts from
AGII-treated or healthy plants and also caused a rise in mite mortality. Our results demonstrate that sarcotoxin IA affects
mite fecundity and, to a lesser degree, mortality, and shows potential for controlling spider mites in the field. 相似文献
10.
P. Caciagli D. Bosco Lina Al-Bitar 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(2):163-170
Relationships of an Italian isolate of tomato yellow leaf curl geminivirus from Sardinia (TYLCV-S) with its whitefly vectorBemisia tabaci were studied by means of experimental transmissions from tomato to tomato plants. TYLCV-S was confirmed to be transmitted in a persistent, circulative manner. The minimum latent period in the vector was between 17 and 20 h from the beginning of the acquisition access period (AAP). The maximum retention of infectivity was 8 days from the end of the AAP. Both acquisition and inoculation feeding times influenced the detected proportion of infective insects, with patterns well described by an exponential model. Acquisition was more efficient than inoculation. Males were significantly less efficient vectors than females. Nymphs were as efficient as adults in acquiring the virus. The length of AAP influenced both the retention of infectivity, and the pattern of transmission in serial transfer transmission tests with individual females. No significant difference in transmission efficiency was detected between two colonies ofB. tabaci, one inducing typical silverleaf symptoms on squash, the other inducing only mild symptoms with more than 50 whiteflies per plant. The phenomenon of periodic acquisition was not unequivocally proved for TYLCV-S.Research supported by the National Research Council of Italy, Special Project RAISA, Sub-project N. 2. Paper N. 1961.Supported by a grant from the Istituto Agronomico Mediterraneo, Valenzano (Bari), Italy. 相似文献
11.
In this study, Tomato yellow leaf curl Sardinia virus (TYLCSV) and the strains Israel and Mild of Tomato yellow leaf curl virus (TYLCV-IL, TYLCV-Mld) were detected for the first time in four cucurbit crops in Jordan by nested polymerase chain reaction (nPCR). These viruses cause the tomato yellow leaf curl disease (TYLCD) in tomato. Cucumber, squash, melon and watermelon plants inoculated with TYLCV-IL[JO:Cuc], TYLCV-Mld, TYLCSV-IT[IT:Sar:88] and the Jordanian isolate of TYLCV (TYLCV-JV) did not show disease symptoms. However, virus-specific fragments were detected in uppermost leaves of symptomless plants by nPCR. A whitefly transmission test showed that Bemisia tabaci could transmit TYLCV-Mld from cucumber into tomato and jimsonweed plants. However, all infected tomato plants remained symptomless. In addition, results of semi-quantitative PCR (sqPCR) analysis showed that the relative amount of TYLCV-Mld DNA acquired by B. tabaci from cucumber plants was less than that acquired from tomato plants. 相似文献
12.
A high incidence (86%) of potyvirus infection was noted in tobacco plants exhibiting a form of leaf curl in South Africa. Despite leaf curl being reported in the literature to be of geminiviral aetiology, no geminiviruses were detected. Furthermore, no other virus particles were detected by virus purification, TEM and serology. Twelve species of dsRNA were consistently isolated from these tobacco plants, but were absent from other forms of leaf curl-affected and healthy tobacco. Aphid and mechanical inoculation demonstrated that the purified potyvirus(es) did not cause leaf curl symptoms, but rather mild mottle and mosaic symptoms in tobacco. Partial characterization of the potyvirus preparation showed a possible relationship to a South African strain of potato virus Y. Because potyvirus-inoculated plants did not manifest leaf curl symptoms, and because leaf curl symptoms were noted in some plants not infected with a potyvirus, it was concluded that the potyvirus is not involved in the leaf curl aetiology, but causes a latent infection, the symptoms of which are masked. The pattern of the dsRNA banding, induction of enations and lack of mechanical and seed transmission are common to plant reoviruses. The possibility of a phytoreovirus involvement in this form of leaf curl is currently being investigated. The results from this study suggest that tobacco leaf curl disease worldwide, with regard to geminiviruses, be re-evaluated. 相似文献
13.
Jae Yeol YoonJi San Shin Dong Young ShinKyu Hwan Hyun Nilda R. BurgosSungbeom Lee Yong In Kuk 《Pesticide biochemistry and physiology》2011,99(1):65-76
Paraquat is labeled for row-middle application on cucurbits, but drift to crop foliage is inevitable. Experiments were conducted to determine whether differential tolerance to paraquat existed among leaves of various ages in Cucurbita spp. (squash) and other plants, and to examine whether leaves tolerant to paraquat are also tolerant to other herbicides and abiotic stresses. Physiological responses to paraquat, including antioxidant activity, were investigated in squash leaves to identify mechanisms of paraquat tolerance. Although the level of paraquat tolerance differed by leaf age, cultivar, and species, the level of paraquat injury was lower in younger leaves than in older leaves in 14 of 18 squash cultivars and 5 of 12 other species tested. Cellular leakage and lipid peroxidation were consistently lower in the youngest leaf (leaf 4) than in the older leaves. Quantum yield and relative chlorophyll content were the same in all leaves of nontreated plants. Epicuticular wax content was higher in the youngest leaf than in leaves 1, 2, and 3 of cv. ‘Joongangaehobak’ and ‘Wonbiaehobak’. However, leaf cuticle content was not consistent with leaf ages. Differential leaf response to paraquat was partially correlated with the change in catalase, peroxidase, ascorbate peroxidase (APX), and glutathione reductase activities in nontreated and treated leaves. The APX activity in the youngest leaf was generally 2 times higher than in leaves 1-3 in both nontreated and treated plants. Ascorbate antioxidant levels were also higher in the youngest leaf than those in leaves 1-3. Leaves tolerant to paraquat were also tolerant to diquat and to abiotic stresses, low temperature and drought. However, tolerance to oxyfluorfen, which has a different mode of action than paraquat and diquat, was higher in older than in younger leaves. Higher tolerance to paraquat-mediated oxidative and abiotic stresses in young leaves of most squash cultivars might contribute to the differential prevention of oxidative damage in leaves of various ages. 相似文献
14.
苹果褪绿叶斑病毒生物学及生化特性研究 总被引：12，自引：1，他引：11
对从苹果和扁桃上获得2个苹果褪绿叶斑病毒的分离物ACLSV-C和ACLSV-B的主要生物学和生化特性进行了比较。人工接种5科19种草本植物,发现两者均能侵染苋色藜(Chenopodium amaranticolor)、昆诺藜(Ch.quinoa)和西方烟(Nicotiana occidentalis),产生局部侵染斑和系统褪绿斑。但症状反应存在差异,后者在这3种植物上引起叶片反卷等较强症状反应,还可潜伏侵染笋瓜(Cucurbita maxima cv.Buttercup Burgess)。经SDS-聚丙烯酰胺凝胶电泳结果显示,ACLSV-B衣壳蛋白的迁移率较ACLSV-C快。两者的RNA分子量及双链RNA数量无明显差异。根据已报道的核苷酸系列设计合成引物,采用PCR法检测ACLSV分离物,均获得特异性扩增产物。 相似文献
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A. I. Nissinen M. Haapalainen L. Jauhiainen M. Lindman M. Pirhonen 《Plant pathology》2014,63(4):812-820
Carrot psyllid Trioza apicalis was recently found to carry the plant pathogenic bacterium ‘Candidatus Liberibacter solanacearum’ (CLs). To confirm the transmission of bacteria by the psyllids and to dissect the symptoms caused in carrot plants by psyllid feeding and CLs infection, a greenhouse experiment with single psyllids feeding on separate plants was performed. A positive correlation was found between the amount of CLs bacteria in the psyllids and in the corresponding plants exposed to feeding, indicating CLs transmission. The female psyllid feeding caused more severe damage than male feeding, and resulted in a substantial decrease in the root weight. Female psyllid feeding also significantly reduced the carrot leaf weight and increased the number of curled leaves. The number of curled leaves was also increased by the nymphs when their number exceeded 10 per plant. A high titre of CLs bacteria significantly reduced root weight, while not affecting the weight or number of the leaves. However, the amount of CLs correlated with the number of leaves showing discolouration symptoms. Microscopy of infected carrot plants revealed that the phloem tubes throughout the whole plant, from leaf veins to the root tip, were colonized by bacteria. The bacterial cells appeared to be long and thin flexible rods with tapering ends and a transversally undulated surface. Microscopy also revealed collapsed phloem cells in the infected carrots. Damage in the phloem vessels is likely to reduce the sucrose transport from source leaves to the root, explaining the observed leaf discolouration and reduction in root weight. 相似文献
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Indian peanut clump virus (IPCV) infection on wheat and barley: symptoms, yield loss and transmission through seed 总被引：1，自引：0，他引：1
Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few, shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0.5–1.3%. Storage at 4°C for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms. 相似文献
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Fang Dong Tomofumi Mochizuki Satoshi T. Ohki 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(1):117-122
We analysed the kinetics of virus distribution in Tobacco ringspot virus (TRSV)-infected tobacco. Infected plants developed asymptomatic leaves above the symptomatic leaves that exhibited ringspots.
We detected virus in the shoot apical meristem (SAM). Time-course immunohistochemical microscopy showed that TRSV continuously
distributed in the centres of the SAM and in leaf primordia. In contrast, TRSV infection was transient in the root meristem.
In western blot and RT-PCR analyses, TRSV infection occurred only within and around the ringspot tissues of the symptomatic
leaf; however, TRSV was not or hardly detected in the asymptomatic leaves of inoculated tobacco plants. These results indicate
that TRSV persists in the SAM, but that TRSV infection is transient in the root meristem and asymptomatic leaves. 相似文献