首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Cotton leaf curl virus (CLCuV) (Geminiviridae : Begomovirus), the causative agent of leaf curl disease in cotton plants (Gossypium hirsutum), is exclusively transmitted by whitefly species Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). CLCuV transmission occurs in Sriganganagar (Rajasthan), an area endemic with cotton leaf curl disease. The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. To further understand these relationships, fecundity and life history parameters of an indigenous non- b (Asia II genetic group) biotype whitefly, B. tabaci, were compared on 10, 25, and 40 days post-inoculation (DPI), in CLCuV-infected and healthy cotton plants to determine the effect of virus on its vector. The development time of the immature stages of whiteflies was significantly reduced on CLCuV-infected plants. The development time of the immature stages did not change with severity of symptoms at 25 and 40 DPI (45- and 60-d-old plants). Cotton leaf curl virus infection increased percent egg viability of B. tabaci. Whiteflies deposited significantly fewer eggs on virus-infected plants than on healthy plants. Whiteflies had better egg viability on younger plants than older plants, whereas plant age did not affect the fecundity. Male and female whiteflies had shorter longevity on CLCuV-infected plants than on healthy plants.  相似文献   

2.
A destructive leaf spot disease was found onNymphaea alba in the lakes near Kortenhoef, Netherlands. After comparison of fresh material and herbarium specimens the causal agent is namedColletotrichum nymphaeae (Pass.) van der Aa, comb. nov. Synonymy, morphology and cultural characters of the fungus are described and discussed. Some remarks on the relationship with several host plants are given and the provisional conclusion is that the species is a widespread parasite, but that the destructive attack in the Kortenhoef region is probably caused by a combination of various factors.  相似文献   

3.
Stemphylium lycopersici (Enjoji) W. Yamam was initially described from tomato and has been reported to infect different hosts worldwide. Sequence analyses of the internal transcribed spacer (ITS) regions 1 and 2, including 5.8S rDNA (ITS-5.8S rDNA) and glyceraldehyde-3-phosphate dehydrogenase (gpd) gene, random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), as well as virulence studies were conducted to analyze 46?S. lycopersici isolates. Stemphylium lycopersici isolates used in this study were obtained from diseased tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), pepper (Capsicum annuum L.) and lettuce (Lactuca sativa L.) from major vegetable growing regions of Malaysia, including the three states of Pahang, Johor and Selangor between 2011 and 2012. Phylogenetic analysis of a combined dataset of the ITS-5.8S rDNA and gpd regions indicated that all isolates were clustered in the sub-cluster that comprised S. lycopersici, and were distinguished from other Stemphylium species. Cluster analyses using the UPGMA method for both RAPD and ISSR markers grouped S. lycopersici isolates into three main clusters with similarity index values of 67 and 68 %. The genetic diversity data confirmed that isolates of S. lycopersici are in concordance to host plants, and not geographical origin of the isolates. All S. lycopersici isolates were pathogenic on their original host plants and showed leaf spot symptoms; however, virulence variability was observed among the isolates. In cross-inoculation assays, the representative isolates were able to cause leaf spot symptoms on eggplant, pepper, lettuce and tomato, but not on cabbage.  相似文献   

4.
Tomato yellow leaf curl virus (TYLCV) causes huge losses to tomato production worldwide. In July 2011 and July–August 2012, we screened for potential TYLCV hosts in a tomato-growing area in Shandong Province, the core vegetable-producing region in China. PCR detection showed that 5 species of plants, Zinnia elegans, Acalypha australis, Gossypium hirsutum, Abutilon theophrasti, and Nicotiana tabacum, were infected. Full genomic sequences of the new TYLCV isolates were obtained and submitted for sequence analysis. Sequence alignment and similarity analysis showed that they all belonged to the TYLCV-IL strain.  相似文献   

5.
Copper fungicides applied via low head sprinklers, reduced brown rot (caused byPhytophthora spp.) on oranges and grapefruit. The most effective fungicide was Bordeaux mixture, which reduced the disease rate to the same level as that obtained by standard spraying with this fungicide. Copper oxychloride was moderately effective and captan was ineffective. A field method for brown rot rating was devised.  相似文献   

6.
In 1987 a new disease, called pseudostem rot, was observed on 3–5-month-old banana plants(Musa sp.) cv. ’Robusta’. The pathogen was isolated in pure culture and identified asCorticium rolfsii (Sacc.) Curzi, teleomorph ofSclerotium rolfsii Sacc. The teleomorphic stage of the fungus was observed inside the pseudostem sheath. The pathogen produced leaf spot diseases (by basidiospores) on 16 tested host plants from various families.  相似文献   

7.
In 2017, leaf spots were found on lettuce growing in fields in Songkhla Province, southern Thailand. The fungus isolated from the spot lesions on the leaves was identified as Curvularia aeria (Bat., J.A.Lima and C.T.Vasconc.) Tsuda based on morphological characteristics and DNA sequences of the ITS region of the rRNA gene. After a conidial suspension of the isolate was sprayed on lettuce seedlings, the leaf spots developed on lettuce seedlings, and the fungus was reisolated; leaves of plants inoculated with water did not develop spots. This is the first report of C. aeria causing leaf spot on lettuce.  相似文献   

8.
In 2014 and 2015, an unknown leaf spot disease was found on tobacco in Guangxi, China. The fungus isolated from these spots was identified as Fusarium proliferatum based on morphological characteristics and sequence analysis of translation elongation factor 1 alpha (tef1α). This fungus also reproduced leaf spot symptoms after inoculation and was reisolated from the symptomatic lesions. This is the first report of a new leaf spot caused by Fusarium proliferatum on tobacco.  相似文献   

9.
Bacterial blight (BB) incited by Xanthomonas citri subsp. malvacearum (Xcm) is an important bacterial disease occurring in all cotton growing areas throughout the world, including parts of Western Kenya, that are characterized by a hot and humid climate. The disease causes seedling blight, angular leaf spot, boll rot and black arm on petioles and branches leading to a loss of fruiting branches with yield losses of up to 35 %. Fifty- one Kenyan cotton genotypes (Gossypium hirsutum L.) were established in the two counties of Siaya and Busia famous for their cotton cultivation in the western region. The BB symptoms caused by natural Xcm infection in the field were scored for each cotton accession. In addition artificial inoculation with the same strains was done to confirm the status under controlled greenhouse conditions. The results of BB disease scoring revealed that some accessions (e.g. T 24A and T 24B) possess a reasonable level of resistance. However, most of the Kenyan genotypes surveyed showed medium to severe symptoms of BB, including KSA 81 M, the only commercially grown cultivar in the region of Western Kenya. Overall, 71 % of the genotypes showed susceptibility and 29 % were classified as either resistant or moderately resistant. There is therefore need to improve the local commercial genotypes by introducing new genetic resources with a more durable BB resistance to ensure a successful revitalization of the Kenyan cotton sector.  相似文献   

10.
Several golf courses established with hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) were surveyed from April 2011 through April 2015 in Hainan Province, China. The hybrid bermudagrass in these golf courses showed a new leaf spot disease, and a filamentous fungus was consistently recovered from the infected leaves. Based on the morphological characteristics of colony color and appearance, shapes of conidiophores and conidia as well as sequences of internal transcribed spacer regions (ITS) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), the fungus was identified as Bipolaris peregianensis. The pathogenicity test conducted on healthy hybrid bermudagrass produced leaf spot symptoms one week post inoculation. B. peregianensis mycelia grew in a temperature range of 5 to 35 °C with the optimum temperature being 28 °C.  相似文献   

11.
The effect of azadirachtin and salannin, two triterpenoids isolated from seeds of neem (Azadirachta indica A. Juss), on the feeding response ofSpodoptera littoralis (Boisd.) andEarias insulana (Boisd.) larvae, was investigated. Styropor (foamed polystyrene) lamellae were painted on both sides with a mixture of 5% sucrose with different concentrations of either azadirachtin or salannin dissoled in methanol-water (3∶7). Azadirachtin strongly suppressed feeding inS. littoralis larvae even at 0.001%, whereas salannin showed some antifeedant activity at 0.005% and above. Larvae ofE. insulana were deterred from feeding on azadirachtin-treated lamellae even at 0.005%, whereas salannin was effective only at 0.01% and above. Azadirachtin applied on cotton leaves deterred larvae ofS. littoralis from feeding at all concentrations ranging between 0.001 and 0.02%.  相似文献   

12.
Drimia maritima (squill) is a historically important medicinal plant. During the spring of 2016, small, yellow leaf spots, which became brown and finally necrotic, were observed on squill plants in Kohgiluyeh and Boyer-Ahmad Provinces in Iran. A fungus was consistently isolated from infected leaves and identified as Alternaria alternata based on morphological and phylogenetic analyses. Pathogenicity tests confirmed A. alternata to be the causal agent of the newly observed leaf spot disease. This is the first report of leaf spot on D. maritima caused by A. alternata in the world.  相似文献   

13.
Macrophomina phaseolina (Tassi) Goid. is the most important pathogen of jute and primarily causes seedling blight, leaf spot and stem rot. The pathogen was detected from field samples by a simple method of direct PCR (dPCR) which obviates the steps of DNA extraction. The leaf bits were treated with a lysis buffer at 65°C for 25 min, whereas the stem pieces were initially incubated at 65°C for 5 min followed by incubation at 60°C for 25 min and the lysate was used as PCR template. Based on the type of tissue, the composition and concentration of lysis buffer systems were optimized. For leaf samples the optimized buffer system composed of 20 mmol l -1 tris (hydroxymethyl aminomethane (Tris)-Cl (pH 8.0), 1.5 mmol l -1 ethylene diamine tetra acetate (EDTA) (pH 8.0), 1.4 mol l -1 sodium acetate and 200 μg/ml proteinase K. Further, 3% PVP (w/v) and β-mercaptoethanol (1% w/v) were added into the buffer. In case of stem samples, PVP was not applied and higher concentrations were used for other components. M. phaseolina could be detected from both leaf and stem samples generating amplicon of 350 bp. This is the first report of detecting M. phaseolina by a direct PCR method without DNA extraction.  相似文献   

14.
A method was developed for estimating the number of surviving tobacco whitefly (TWF),Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), nymphs after insecticide applications, based on the number of honeydew droplets ejected by TWF nymphs in 30 minutes. Honeydew droplets excreted by live TWF nymphs on a water-sensitive paper (Ciba-Geigy) stained blue and could easily be observed and counted. To estimate the number of live nymphs on an infested cotton leaf, the number of droplets ejected during 30 min was divided by a factor of 1.29.  相似文献   

15.
A quick and easy method for estimating the number of surviving nymphs of the tobacco whitefly (TWF),Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), after spray applications was developed in the laboratory. The method is based on the number of honeydew droplets ejected by TWF immatures during 30 minutes. Since the nymphs ofB. tabaci feed on the lower leaf surfaces, the honeydew excreted falls downward. In this study infested cotton leaves were placed with their lower side up, forcing the nymphs to eject the honeydew droplet upwards. Inverted plastic petri dish covers were placed over infested cotton leaves and after 30 minutes the droplets deposited on the inner side of each cover were counted and the average number of droplets per nymph was calculated. To estimate the number of live nymphs on an infested cotton leaf, the number of droplets ejected during 30 minutes was divided by the average number of droplets per nymph (factor of 1.23).  相似文献   

16.
In September 2014, Phytophthora rot on wasabi plants [Wasabia japonica (Miq.) Matsum.] was found for the first time in the city of Okutama, Tokyo, Japan. A Phytophthora sp. strain was constantly isolated from brown stem bases and rhizomes of infected plants. The same symptoms as those observed in the field were produced in vitro through inoculation of test plants with the isolated Phytophthora sp. The fungus was identified as Phytophthora drechsleri based on morphological and DNA sequence comparison. Phytophthora rot, “eki-byo” in Japanese, is proposed for this disease common name.  相似文献   

17.
In a survey for postharvest diseases of apples and pears in the Netherlands, an unknown postharvest fruit rot was observed. The disease appeared to originate from infected lenticels. A fungus was consistently isolated from the decayed fruits. The fungal pathogen was isolated on potato dextrose agar, and at low temperatures development of a fast-growing whitish mycelium was observed. Growth of this fungus was observed between 1 and 20 °C with an optimum at 15 °C, while incubation of mycelium at 25 °C resulted in no growth. The isolates did not produce asexual or sexual spores. The isolates were characterized and identified by morphology and molecular phylogenetic analysis. Genomic DNA was isolated and amplified using ITS1-ITS4, EF1 and RPB2 primers, and BLAST searches in GenBank placed the fungus taxonomically in the genus Fibulorhizoctonia, with the highest matches to F. psychrophila. Pathogenicity of representative isolates from apple and pear fruit was confirmed under laboratory conditions. To the best of our knowledge this is the first report of F. psychrophila causing lenticel spot on apple and pear, and also the cause of a whitish mould on storage bins.  相似文献   

18.
Application of various fungicides to cotton plots (Gossypium barbadense cv. Pima) affected byAlternaria macrospora resulted in a yield increase from 3955 kg/ha in unsprayed plots to 5207 kg/ha in plots treated with fentin acetate. Pathogen, host and disease parameters were estimated by a key of grades in the field and by precise measurements of detached plants. Measurements included the number of spores present in the field and numbers and/or areas of healthy, lesioned and shed leaves and bolls. No significant differences were found between the number of healthy bolls on variously treated plants and the number of lesioned bolls on the same plants. Disease incidence was relatively low in treated plots, with no significant difference between treatments and no correlation with the size of the pathogen population or the yield level in variously treated plots. The low proportion of lesioned leaves resulted from their tendency to shed and from the emergence of new leaves, which masked the damage. Rate of shedding was correlated with the respective yield and with the size of the pathogen population in the same plot. Leaf shedding was induced by lesions occupying an average of 1 to 3% of the leaf area. Shedding was affected by leaf position on the plant, being most frequent for the lowest leaves despite their being the least lesioned, and least frequent for the upper leaves even though these were the most lesioned.  相似文献   

19.
Over 20 insecticides were screened against the tobacco whitefly,Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), on cotton. AsB. tabaci feeds only on live plants, a suitable laboratory test method incorporating young cotton plants was developed. Both cover sprays and systemic insecticides applied to the soil were tested. Triazophos, pyridaphenthion, azinphos-methyl, bendiocarb and flucythrinate were found to be effective and persistent. The best of the systemic insecticides was aldicarb, followed by butocarboxim.  相似文献   

20.
Poinsettia plants growing in ebb-and-flow irrigation systems developed wilting and root rot during the summer growing seasons of 2010 in Gifu Prefecture and 2011 in Aichi Prefecture. Pythium species were isolated from roots with rot symptoms. The isolates were identified as P. helicoides and P. myriotylum on the basis of morphological characteristics and sequence homologies in the rDNA internal transcribed spacer regions. In pathogenicity tests, these isolates caused severe wilting and root rot. This is the first report of poinsettia root rot disease caused by P. helicoides and P. myriotylum, although P. aphanidermatum was reported as a pathogen of poinsettia root rot. To better understand these diseases, we performed an epidemiological study of three high-temperature-tolerant Pythium species, P. aphanidermatum, P. helicoides and P. myriotylum. Disease incidence as a percentage of diseased plants was greatest at 35 °C for all three species. Disease severity using the rating scale of root rot was also highest at 35 °C, particularly with high zoospore inoculum densities (100.0 zoospores/mL). Although the disease incidence and severity were reduced at lower temperatures, the three Pythium species were able to cause disease at temperatures as low as 20 °C.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号