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1.
The Melon yellows virus (MYV), a whitefly-transmitted closterovirus, is one of the major pathogens causing crop losses in protected melons in southeastern Spain. An accession of the wild Asiatic Cucumis melo ssp. agrestis (Cma) shows resistance to MYV infection. Results indicate the participation of two resistance mechanisms in this source: firstly, an antixenotic reaction against Trialeurodes vaporariorum, the disease vector, and secondly, resistance to the virus. The combined effect of these two mechanisms confers Cma a higher level of resistance, expressed as a delayed and milder infection.The genetics of resistance to the Melon yellows closterovirus have been studied in two families derived from Cma. As under natural infection conditions, the effect of antixenosis and virus resistance cannot be distinguished, a biometrical model that permits separation of the two resistance mechanisms operating in the same resistant source, has been proposed to determine genetic control of MYV resistance.The genetic analysis has been conducted by fitting the disease progress curves of each generation to the biometrical model instead of fitting the final disease ratios. The scoring of disease incidence over time allows for the comparison of data from assays conducted in different conditions (2 years/4 transplanting dates), thus reinforcing the analysis.The results agree with a simple control of the resistance to MYV derived from Cma, with incomplete penetrance of the gene and partial dominance of resistance. The effect of antixenosis on the spread of this plant virus is highly significant in Cma, but not in segregant generations.Since there do not exist crossability barriers between this accession and the cultivated melon, Cma could be readily used in breeding programmes to obtain melon varieties resistant to MYV.  相似文献   

2.
The agent causing a yellowing disease of melon (Cucumis melo), which results in severe losses in crops under plastic on the coastal plains of southeast Spain, was shown to be transmitted in a semipersistent manner by the greenhouse whitefly (Trialeurodes vaporariorum Westwood). The agent was transmitted by grafting, but not by mechanical inoculation or through seeds. The agent was acquired in the minimum period tested (2 h) and could infect plants in an infection feeding interval of 6 h. Capsella bursa-pastoris, Cucumis melo, C. sativus, Cucurbita moschata, Cichorium endivia, Lactuca sativa andTaraxacum officinale were found susceptible.Results suggest that the yellowing disease affecting melon crops in the southeast of Spain is due to a pathogen similar to beet pseudo yellows virus, but this has to be confirmed by serology.  相似文献   

3.
BACKGROUND: Vermicompost is an organic soil amendment produced by earthworm digestion of organic waste. Studies show that plants grown in soil amended with vermicompost grow faster, are more productive and are less susceptible to a number of arthropod pests. In light of these studies, the present study was designed to determine the type of insect resistance (antixenosis or antibiosis) present in plants grown in vermicompost‐amended potting soil. Additionally, the potential role of microarthropods, entomopathogenic organisms and non‐pathogenic microbial flora found in vermicompost on insect resistance induction was investigated. RESULTS: Findings show that vermicompost from two different sources (Raleigh, North Carolina, and Portland, Oregon) were both effective in causing Arabidopsis plants to be resistant to the generalist herbivore Helicoverpa zea (Boddie). However, while the Raleigh (Ral) vermicompost plant resistance was expressed as both non‐preference (antixenosis) and milder (lower weight and slower development) toxic effect (antibiosis) resistance, Oregon (OSC) vermicompost plant resistance was expressed as acute antibiosis, resulting in lower weights and higher mortality rates. CONCLUSION: Vermicompost causes plants to have non‐preference (antixenosis) and toxic (antibiosis) effects on insects. This resistance affects insect development and survival on plants grown in vermicompost‐amended soil. Microarthropods and entomopathogens do not appear to have a role in the resistance, but it is likely that resistance is due to interactions between the microbial communities in vermicompost with plant roots, as is evident from vermicompost sterilization assays conducted in this study. Copyright © 2010 Society of Chemical Industry  相似文献   

4.
新疆哈密瓜蔓枯病及防治研究   总被引：6，自引：0，他引：6  
 本文描述了哈密瓜蔓桔病两种症状类型。自然寄主主要是哈密瓜,1996年偶见轻微侵染西葫芦及籽西瓜。人工接种可侵染梨瓜及西瓜等葫芦科作物,惟对哈密瓜致病性强,对其它瓜类则弱。哈密瓜苗及田间成株接种试验表明,地面任何组织无论有伤或无伤都能侵染。该病主要借灌溉与风雨传播,病健蔓靠接也是一种传病方式。根据菌原形态及寄主范围等特点,明确本菌无性阶段为瓜壳单隔孢菌Ascochy-ts cucumis Fautr.et Roum.有性阶段为甜瓜球腔菌Mycosp-haerellamelonis (Pass) Chiu et J.C.Walker.防治研究表明.发病初期和以后每隔8-10天连续2-3次喷洒利克菌或拌种双都有很好的预防和治疗效果。  相似文献   

5.
中国香瓜与菜瓜地方品种资源白粉病抗性评价   总被引：5，自引：0，他引：5  
春秋2个季节在温室利用风媒接种方法对搜集的102份香瓜和14份菜瓜种质资源进行了白粉病抗性评价,结果鉴定出7份香瓜和1份菜瓜高抗白粉病,其病情指数为零,1份菜瓜抗病,其病情指数0.9,表明我国香瓜和菜瓜地方品种资源中蕴涵着潜在的改良甜瓜白粉病抗性的基因资源。  相似文献   

6.
ABSTRACT The Cucumis melo accession TGR-1551 was found to be resistant to Watermelon mosaic virus (WMV, genus Potyvirus, family Potyviridae). The resistance resulted in a drastic and significant reduction of virus titer and infected plants were asymptomatic or exhibited mild disease symptoms. The same gene or closely linked genes restricted virus accumulation and ameliorated symptom expression. No effect was observed on virus accumulation in inoculated leaves, which suggested that the initial phases of infection were not affected. The resistance was effective against a range of WMV isolates from Spanish melon production areas. Using aphid inoculations, resistant plants showed a lower propensity for infection by WMV and for serving as virus sources for secondary spread once infected. Resistance was determined to be under recessive genetic control.  相似文献   

7.
Occurrence of melon necrotic spot carmovirus in Italy   总被引：2，自引：0，他引：2  
Since 1995, a severe necrosis disease has been observed in winter melon ( Cucumis melo var. inodorus ) grown in the open in Sardegna region. At the stage of fruit ripening, infected plants show decline and premature death, a syndrome known as'collapse'. Fungal pathogens have never been detected. In 1998, melon necrotic spot carmovirus (MNSV) was isolated from diseased plants showing necrotic symptoms on leaves and branches. The virus was identified by biological and serological assays. MNSV may represent a limiting factor to winter melon production in Sardegna where the'inodorus'group is widely cultivated and appreciated for local consumption. This is the first occurrence of MNSV in Italy.  相似文献   

8.
新疆甜瓜对瓜类疫霉菌抗性的诱导   总被引：1，自引：0，他引：1  
用弱致病的和灭活的瓜类疫霉菌 (Phytophthoramelonis)培养物成功地诱导了新疆甜瓜对瓜类疫霉病的整体抗性 ,抗性持续可达 2 1d ,同时探讨了不同处理方法对甜瓜诱导抗性的影响  相似文献   

9.
Journal of Plant Diseases and Protection - Cucumis melo accession PI 313970 possesses numerous genes for race-specific resistance to powdery mildew incited by Podosphaera xanthii. It also exhibits...  相似文献   

10.
Pot experiments were carried out to characterize the response of two Cucumis metuliferus accessions (BGV11135 and BGV10762) against Mi1.2 gene (a)virulent Meloidogyne arenaria, M. incognita and M. javanica isolates and to determine the compatibility and the effect on physicochemical properties of fruit melons. In addition, histopathological studies were conducted. One week after transplanting, plants were inoculated with one J2 cm?3 of sterilized sand (200 cm3 pots) and maintained in a growth chamber at 25 °C for 40 days. The susceptible cucumber cv. Dasher II or melon cv. Paloma were included for comparison. The number of egg masses and number of eggs per plant were assessed, and the reproduction index (RI) was calculated as the percentage of eggs produced on the C. metuliferus accessions compared to those produced on the susceptible cultivars. The compatibility and fruit quality were assessed by grafting three scions, two of Charentais type and one of type piel de sapo, under commercial greenhouse conditions. The resistance level of both C. metuliferus accessions ranged from highly resistant (RI < 1%) to resistant (1% ≤ RI ≤ 10%) irrespective of Meloidogyne isolates. Melon plants grafted onto C. metuliferus accession BGV11135 grew as self‐grafted plants without negatively impacting fruit quality traits. Giant cells induced by Meloidogyne spp. on C. metuliferus were in general poorly developed compared to those on cucumber. Furthermore, necrotic areas surrounding the nematode were observed. Cucumis metuliferus accession BGV11135 could be a promising melon rootstock to manage Meloidogyne spp., irrespective of their Mi1.2 (a)virulence, without melon fruit quality reduction.  相似文献   

11.
Screening of genotypes of melon ( Cucumis melo ) for resistance to wilt caused by Fusarium oxysporum f.sp. melonis is often characterized by wide variability in their responses to inoculation, even under carefully controlled conditions. The variability at the seedling stage of 17 genotypes susceptible to race 1 was examined in growth-chamber experiments. Disease incidence varied from 0 to 100% in a genotype-dependent manner. Using four combinations of light (60 and 90  µ E m−2 s−1) and temperatures of (27 and 31°C), only light intensity showed a statistically significant effect. Marker-assisted selection for fusarium resistance breeding using cleaved amplified polymorphic sequence (CAPS) and sequence-characterized amplified region (SCAR) markers were compared using a single set of genotypes that included 24 melon accessions and breeding lines whose genotype regarding the Fom-2 gene was well characterized. The practical value of the markers for discriminating a range of genotypes and clarifying the scoring of phenotypes was also tested using a segregating breeding population which showed codominant SCAR markers to be useful in marker-assisted selection.  相似文献   

12.
European Journal of Plant Pathology - Macrophomina phaseolina is a soil-borne fungal pathogen that incites charcoal rot in more than 500 plant species including melon, Cucumis melo. Disease...  相似文献   

13.
Glasshouse evaluations of rootstocks of melon for resistance to Didymella bryoniae were conducted on different cucurbits previously selected as resistant or partially resistant to race 1,2 of Fusarium oxysporum f. sp. melonis. Cucumis anguria, C. ficifolius, C. figarei, C. metuliferus, C. zeyheri and Benincasa hispida showed a very high degree of resistance to D. bryoniae both on leaves and stems. Among the commercial rootstocks, Cucurbita hybrids ELSI, ES 99-13, RS 841, displayed a similar level of resistance. Stem inoculation of three cucurbit species grafted with susceptible melon cv. Proteo determined the occurrence of limited symptoms, but the lesions remained confined in the rootstock not affecting the grafted plant. Cultivation of susceptible melon cultivars grafted on resistant rootstocks may represent an efficient method for controlling Didymella crown rot and Fusarium wilt.  相似文献   

14.
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15.
Oligonychus ilicis (McGregor) (Acari: Tetranychidae), is one of the most important mite pests found in coffee plants. One way to reduce intensive pest attacks is management via resistant plants. The purpose of this study was to evaluate the resistance of 14 C. canephora genotypes to O. ilicis by antixenosis and antibiosis mechanisms and to determine the preimaginal conditioning effect on resistant genotypes using O. ilicis reared on C. canephora. Resistance by antixenosis was not found; however, nine genotypes showed resistance to O. ilicis via an antibiosis mechanism. Two of these resistant genotypes showed a more persistent resistance than the O. ilicis reared on C. canephora, which indicated that a previous host can affect the selection of a genotype by O. ilicis. The study may provide a model to evaluate the preimaginal conditioning effect on plant resistance, which can be useful for plant breeders.  相似文献   

16.
Monosporascus cannonballus, a host-specific root-infecting ascomycete, is the causal agent of a destructive disease of melon (Cucumis melo L.) known as vine decline. Ascospores germinate only in the rhizosphere of melon plants growing in field soil. However, no germination occurs in the rhizosphere of melon plants if the field soil is heated to temperatures >50°C prior to infestation with ascospores. This observation suggested that germination is mediated by one or more heat-sensitive members of the soil microflora. Although bacteria or actinomycetes were heretofore suspected as the germination-inducing microbes, our data demonstrate that Olpidium bornovanus, an obligate, host-specific, root-infecting zoosporic fungus, is responsible. In four experiments conducted in autoclaved field soil amended with various population densities of culturally produced ascospores, significant ascospore germination was recorded only in the rhizosphere of cantaloupe seedlings colonized by O. bornovanus.  相似文献   

17.
以3个果实大小不同的品种为材料,研究光照强度对甜瓜果实糖分积累的影响。结果表明:果实定个前(玉金香花后14 d,银帝和黄河蜜花后28 d),果实中糖分积累以葡萄糖和果糖为主,蔗糖次之,可溶性总糖含量较低。果实定个后,蔗糖开始快速积累,并持续至果实成熟。果实成熟时,三品种含糖量为玉金香(136.63 mg/g)>银帝(119.9 mg/g)>黄河蜜(108.14 mg/g),果实3个部位的含糖量为脐部>中部>蒂部。遮阴对甜瓜果实糖分积累模式影响不显著,但使蔗糖开始大量积累的时间推迟、果实最终糖分积累量显著下降,表明甜瓜果实糖分积累量依赖于同化产物供应水平。果实生育期糖分积累动态表明:玉金香耐弱光性较强,银帝能够逐渐适应弱光,黄河蜜对弱光最敏感。遮阴后甜瓜果实糖分积累量降幅具有品种依赖性:大果型品种黄河蜜>中果型品种银帝>小果型品种玉金香。  相似文献   

18.
The oomycete Pseudoperonospora cubensis is a leaf pathogen causing severe damage to members of the Cucurbitaceae, especially cucumber and melon. It propagates clonally by sporangia. Oospores of P. cubensis were previously observed in nature but their formation in the laboratory was never reported nor their germination or infection. Here we report on the sexual reproduction of P. cubensis under controlled conditions in the laboratory. When field isolates were inoculated singly onto detached leaves of cucurbits in growth chambers no oospores were produced. However, when pairs of selected isolates were mixed and inoculated onto detached leaves, oospores were formed in the mesophyll within 6–11 days, suggesting that P. cubensis is heterothallic, having two opposite mating types, A1 and A2. Isolates belonging to pathotype 3 were all A1 whereas isolates belonging to the new pathotype 6 were either A1 or A2. Oospores were spherical, ~40 μm in diameter, hyaline to red-brown in color. Oospores were produced regularly, in large numbers, in Cucumis sativum and Cucumis melo, very seldom and in very small numbers in Cucurbita pepo, Cucurbita maxima and Citrullus lanatus, and not in Cucurbita moschata. Oospores were formed at 12.5–21°C but not at 25°C. Under moisture-saturated atmosphere oospores were also produced in leaves of intact plants. Oospores inoculated onto detached leaves in growth chambers produced F1 downy mildew lesions at 6–21 days after inoculation, many in Cucumis sativum, Cucumis melo and Cucurbita moschata, very few in Cucurbita pepo or Citrullus lanatus, and none in Cucurbita maxima. This report shows that P. cubensis is heterothallic, having A1 and A2 mating types which can cross and enable sexual reproduction in cucurbits. A preliminary report on part of the results has been published earlier.  相似文献   

19.
Brown fruit spot symptoms were observed on yellow Spanish melons ( Cucumis melo var. inodorus ) grown in greenhouses at Almeria in Spain. Nonsporing, motile, rod-shaped bacteria were isolated from diseased fruits, which on nutrient agar produced small yellow colonies. Two bacterial isolates, used for further investigations, were pathogenic on fruits but not on cotyledons of Spanish melon plants. They provoked disease symptoms similar to those observed in the greenhouse. Both isolates were Gram-negative, catalase-positive, weakly oxidase-positive and phenylalanine deaminase-negative. They hydrolysed esculin but not gelatin and they utilized glucose oxidatively. Fatty acid analysis revealed that both isolates belong to the genus Sphingomonas . In addition, 16S rDNA sequence analysis, performed on one isolate, demonstrated that it had a significant sequence similarity (more than 98%) with Sphingomonas pruni and Sphingomonas mali , nonphytopathogenic bacteria isolated from plants. Although enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic PCR seem to indicate that the Sphingomonas isolates from Spanish melon fruits may belong to a new species, DNA–DNA hydridization analysis is necessary to verify this hypothesis.  相似文献   

20.
ABSTRACT Different levels of thrips resistance were found in seven Capsicum accessions. Based on the level of feeding damage, host preference, and host suitability for reproduction, a thrips susceptible and a resistant accession were selected to study their performance as Tomato spotted wilt virus (TSWV) sources and targets during thrips-mediated virus transmission. Vector resistance did not affect the virus acquisition efficiency in a broad range of acquisition access periods. Inoculation efficiency was also not affected in short inoculation periods, but was significantly lower on plants of the thrips resistant accession during longer inoculation access periods. Under the experimental conditions used, the results obtained show that transmission of TSWV is little affected by vector resistance. However, due to a lower reproduction rate on resistant plants and a lower preference of thrips for these plants, beneficial effects of vector resistance might be expected under field conditions.  相似文献   

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