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1.
Didymella bryoniae is an important pathogen of cucurbits worldwide. Virulence factors of D. bryoniae were investigated in regard to fungal growth and the production of the cell wall-degrading enzymes, polygalacturonase (PG), pectate lyase (PL), pectin lyase (PNL), β-galactosidase (β-Gal) and cellulase (Cx). Virulence levels of five D. bryoniae isolates were determined by the severity of inoculated cantaloupe fruit decay. The highly virulent isolates had more mycelial growth than the moderately virulent isolates in different media. PG activities produced by the highly virulent isolates in shake cultures and in decayed fruit were greater than those of the moderately virulent isolates. PNL, but not PL, in decayed fruit was higher with the highly virulent isolates compared to the moderately virulent ones. The highly virulent isolates showed higher Cx activity than the moderately virulent ones in decayed fruit and in fruit tissue shake culture. β-Gal activities of the highly virulent isolates in pectin shake culture and in decayed fruit were greater than those of the two moderately virulent isolates although fruit also produced β-Gal. Protein analysis showed two fungal β-Gal isozymes in decayed fruit compared to those of healthy fruit. Correlation analysis indicated that the activities of PG, PNL, β-Gal and Cx in cultures and in decayed fruit positively correlated with fungal growth and fruit decay severity. The results of this study suggest that PG, PNL, β-Gal, and Cx appear to be virulence factors of D. bryoniae in cantaloupe decay with PG and β-Gal as the most predominant fruit decay enzymes.  相似文献   

2.
Zhang J  Bruton BD  Biles CL 《Phytopathology》1997,87(10):1020-1025
ABSTRACT Production of polygalacturonase (PG), a cell wall-degrading enzyme, by Phomopsis cucurbitae (latent infection fungus) was studied in relation to different carbon sources and various stages of cantaloupe fruit development. P. cucurbitae produced multiple PG isozymes both in vitro and in vivo. The fungus produced the highest PG activity and the greatest number of isozymes on pectin compared with those produced on glucose, galactose, and sucrose. Eight P. cucurbitae PG isozymes (pIs 3.7, 4.2, 6.6, 7.0, 7.3, 7.5, 7.8, and 8.6) were detected in extract from inoculated mature fruit (40 days after anthesis) by isoelectric focusing. Isozyme bands with pIs of 4.2, 7.3, and 7.8 were the most prominent. A similar set of PG isozymes was produced by P. cucurbitae in autoclaved mature fruit tissue (mesocarp). When tissue discs taken from 20-, 30-, 40-, and 50-day postanthesis fruit were inoculated with P. cucurbitae, PG activity and the number of PG isozymes extracted from the macerated fruit tissue discs increased with the degree of fruit maturity and ripening. Increases in PG activity and PG isozymes were also correlated with reactivation of latent infections and the beginning of tissue maceration. An anionic PG isozyme (pI 4.2) was only visualized on decayed 50-day-old fruit exocarp, as well as 40- and 50-day-old fruit mesocarp. The experimental results support the hypotheses that P. cucurbitae PG isozymes play an important role in fruit decay once latent infection becomes active following harvest.  相似文献   

3.
Fresh rhizomes of Zingiber officinale (ginger), when subjected to steam distillation, yielded ginger oil in which curcumene was found to be the major constituent. The thermally labile zingiberene‐rich fraction was obtained from its diethyl ether extract. Column chromatography of ginger oleoresin furnished a fraction from which [6]‐gingerol was obtained by preparative TLC. Naturally occurring [6]‐dehydroshogaol was synthesised following condensation of dehydrozingerone with hexanal, whereas zingerone and 3‐hydroxy‐1‐(4‐hydroxy‐3‐methoxyphenyl)butane were obtained by hydrogenation of dehydrozingerone with 10% Pd/C. The structures of the compounds were established by 1H NMR, 13C NMR and mass (EI‐MS and ES‐MS) spectral analysis. The test compounds exhibited moderate insect growth regulatory (IGR) and antifeedant activity against Spilosoma obliqua, and significant antifungal activity against Rhizoctonia solani. Among the various compounds, [6]‐dehydroshogaol exhibited maximum IGR activity (EC50 3.55 mg ml ?1) while dehydrozingerone imparted maximum antifungal activity (EC50 86.49 mg litre?1). © 2001 Society of Chemical Industry  相似文献   

4.
Glucosinolate degradation products (GLDPs), mainly isothiocyanates, obtained by myrosinase‐catalysed hydrolysis of glucosinolates (GLs), are an important group of natural bioactive substances. The fungitoxic activity of four GLDPs, chosen on the basis of their side‐chain structures, was assayed against Pythium irregulare and Rhizoctonia solani. The effectiveness of the degradation products (DPs) of sinigrin (alkenyl GL), epi‐progoitrin (hydroxy‐alkenyl GL), glucoiberin and glucoerucin (thiofunctionalised GLs) in inhibiting P irregulare oospore germination and R solani soil colonisation were tested in a closed system, using an artificially infected soil. The fungitoxic activity of these GLDPs varied according to their side‐chain structure. As in previous in vitro studies, the thiofunctionalised GLDPs were found the most effective, producing complete inhibition of P irregulare oospore germination (0.01 µmole g−1 soil) and R solani soil colonisation (0.5 µmole g−1 soil), but even sinigrin DP showed a fungitoxic activity higher than that of epi‐progoitrin DP. © 2000 Society of Chemical Industry  相似文献   

5.
Gene S31pg1, which encodes a polygalacturonase (PG), was previously isolated from citrus race S31 of Geotrichum candidum, the causal agent of citrus sour rot. We have now isolated and sequenced an additional PG gene, S31pg2, with 95% identity to S31pg1 in the mature proteins. To evaluate the contribution of the two PG genes in the development of citrus sour rot, each gene was expressed in the fission yeast Schizosaccharomyces pombe. Both genes conferred PG activity to the yeast. Crude enzyme solutions containing S31PG1 severely degraded the albedo tissue of lemon peel, but those containing S31PG2 did not. Concentrated crude S31PG1 solutions also caused soft rot on lemon fruit, indicating that not S31PG2 but S31PG1 is an important pathogenicity factor in citrus sour rot. Next, the protopectinase (PP) activity of each PG was measured. Although S31PG1 and S31PG2 are highly homologous, S31PG1 had high PP activity, whereas S31PG2 had much lower activity. PG from G. candidum noncitrus race S63 (nonpathogenic to citrus fruits) was also assayed but did not have any PP activity at all. These results suggest that the different PP activities of the PGs are a key to the pathogenicity of G. candidum to lemon fruit.  相似文献   

6.
Methods are described for the extraction and analysis by gas-liquid and high-pressure liquid chromatography of the fungicide imazalil, 1-(β-allyloxy-2, 4-dishlorophenethyl) imidazole, on potatoes. Before storage, over 80% was recovered from potatoes treated with 0.01–3.0 mg imazalil kg?1, with a detection limit of 2 μg kg?1. Imazalil applied to potatoes at 10 g t?1 before storage decreased the incidence of gangrene (Phoma exigua), silver scurf (Helminthosporium solani), skin spot (Polyscytalum pustulans) and black scurf (Rhizoctonia solani), and was at least as effective as thiabendazole applied at 40 g t?1. At 1 g t?1 it also decreased skin spot and silver scurf. Incidence of black dot (Colletotrichum coccodes) was unaffected by these fungicide treatments.  相似文献   

7.
Netted cantaloupe (Cucumis melo var. cantalupensis cv. Magnum 45) were harvested from 5 to 35 days postanthesis. The fruit of each age group were divided into exocarp, outer mesocarp, mid mesocarp, inner mesocarp, placenta, and seed. Each tissue was extracted and assayed for polygalacturonase-inhibiting protein (PGIP) activity against polygalacturonases (PGs) from three fungal pathogens of cantaloupe fruit. The PGIP activity of all tissues except placenta was high from the flower stage through the first week of fruit development but decreased markedly between 5 and 10 days postanthesis. PGIP activity against Phomopsis cucurbitae PG remained high and nearly constant in placental tissue throughout fruit development. However in this same tissue, PGIP activity against Fusarium solani PG decreased during fruit development to about 25% of its level in the 5-day-old fruit. This differential change in PGIP activity toward the two PGs suggests that different forms of the inhibitor are expressed between early and late stages of cantaloupe fruit development. The results also illustrate the importance of using multiple pathogen enzyme systems that can provide an opportunity for more accurate elucidation of mechanisms involved in the host–pathogen interaction. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. All programs and services of the US Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. The article cited was prepared by a USDA employee as part of his/her official duties. Copyright protection under US copyright law is not available for such works. Accordingly, there is no copyright to transfer. The fact that the private publication in which the article appears is itself copyrighted does not affect the material of the US Government, which can be freely reproduced by the public.  相似文献   

8.
Decay caused by fungal pathogens is responsible for significant economic loss of muskmelon fruit (Cucumis melo L.) in China. However, postharvest treatment is not effective in controlling all of these pathogens, owing to the ability of some of them for latent infection. Therefore, preharvest treatment has been considered as a promising method to control postharvest decay in muskmelon fruit. The effect of multiple preharvest treatments with harpin on postharvest disease and quality of cv. ‘Huanghemi’ muskmelon fruit was investigated in this study. Results showed that harpin treatment significantly decreased the incidence of latent infection caused by Alternaria alternata and Fusarium spp. in harvested fruit. Meanwhile, the postharvest pink rot in treated fruit inoculated with Trichothecium roseum was suppressed noticeably. Moreover, preharvest treatment increased the activities of peroxidase, phenylalanine ammonia lyase, 4-Coumarate:CoA ligase and β-1,3-glucanase compared with control fruit. Harpin treatment also contributed to the accumulation of total phenolic compounds and lignin. In addition, harpin treatments were able to maintain the quality of harvested fruit. These results suggest that multiple treatments with harpin before harvest may be a promising technology to control postharvest disease and delay quality losses in Huanghemi muskmelon fruits.  相似文献   

9.
Studies were conducted to explain the relative success of ‘Dickeya solani’, a genetic clade of Dickeya biovar 3 and a blackleg‐causing organism that, after recent introduction, has spread rapidly in seed potato production in Europe to the extent that it is now more frequently detected than D. dianthicola. In vitro experiments showed that both species were motile, had comparable siderophore production and pectinolytic activity, and that there was no antagonism between them when growing. Both ‘D. solani’ and biovar 1 and biovar 7 of D. dianthicola rotted tuber tissue when inoculated at a low density of 103 CFU mL?1. In an agar overlay assay, D. dianthicola was susceptible to 80% of saprophytic bacteria isolated from tuber extracts, whereas ‘D. solani’ was susceptible to only 31%, suggesting that ‘D. solani’ could be a stronger competitor in the potato ecosystem. In greenhouse experiments at high temperatures (28°C), roots were more rapidly colonized by ‘D. solani’ than by biovar 1 or 7 of D. dianthicola and at 30 days after inoculation higher densities of ‘D. solani’ were found in stolons and progeny tubers. In co‐inoculated plants, fluorescent protein (GFP or DsRed)‐tagged ‘D. solani’ outcompeted D. dianthicola in plants grown from vacuum‐infiltrated tubers. In 3 years of field studies in the Netherlands with D. dianthicola and ‘D. solani’, disease incidence varied greatly annually and with strain. In summary, ‘D. solani’ possesses features which allow more efficient plant colonization than D. dianthicola at high temperatures. In temperate climates, however, tuber infections with ‘D. solani’ will not necessarily result in a higher disease incidence than infections with D. dianthicola, but latent seed infection could be more prevalent.  相似文献   

10.
Previously, we established an expression system of polygalacturonase (PG) S31PG1 and S31PG2 from Geotrichum candidum pathogenic isolate S31 using the fission yeast Shizosaccharomyces pombe and clarified the importance of S31PG1 in the pathogenicity of G. candidum S31 on lemon fruit. In the present study, we established an expression system for S63PG1 from the nonpathogenic isolate S63. When S63PG1 was expressed, only PG activity was detected, whereas both PG and protopectinase (PP) were active when S31PG1 was expressed. Furthermore, S63PG1 had no ability to cause soft rot, while S31PG1 did. These results indicate that the PP activity of PG is a key to the pathogenicity of the fungus.  相似文献   

11.
Ageratum conyzoides L. is an annual herb in the tropics and subtropics whose extracts are known to possess pharmacological and biocidal activity. We report on the bioactivity of a secondary metabolite (a chromene) isolated from the shoots ofA. conyzoides against some plant pathogenic fungi. Organic solvent extracts from the shoots were tested for antifungal activity against the plant pathogenic fungiRhizoctonia solani, Sclerotium rolfsii, Botryodiplodia theobromae, Phomopsis theae andFusarium species growingin vitro on potato dextrose agar medium. The cruden-hexane extract completely inhibited the growth ofR. solani andS. rolfsii. Then-hexane extract was chromatographed over a column of silica gel followed by activity-guided fractionation to give an antifungal principle. Structure elucidation by detailed analysis of1H,13C NMR and mass spectroscopy identified the active compound as precocene II. The growth ofR. solani andS. rolfsii was completely inhibited by precocene II at a concentration of 80–100 ppm. The sclerotia ofR. solani andS. rolfsii were also completely suppressed by 150 ppm of precocene II. Sub-culture of these inhibited fungi onto precocene II-free medium restored growth of the fungus, indicating that precocene II is fungistatic. Crude or refined extracts fromA. conyzoides offer the possibility of biocontrol of plant pathogenic fungi. http://www.phytoparasitica.org posting Feb. 11, 2004.  相似文献   

12.
Tomato root rot caused by Rhizoctonia solani is a major soilborne disease resulting in significant yield loss. The culture filtrates of six isolates of Trichoderma/Hypocrea species were evaluated for in vitro production of hydrolytic enzymes. Results demonstrated that all the six isolates were able to produce chitinase, β-1, 3 glucanase and protease in the range of 76–235 μmol GlcNAc min-1 mg-1 protein, 31.90–37.72 nmol glucose min-1 mg-1 proteins and 63.05–86.22 μmol min-1 mg-1 proteins, respectively. Trichoderma/Hypocrea-based formulation(s) were prepared with chitin (1% v:v) and CMC (0.5% w:v) for root rot management in a greenhouse. Root dip application with bioformulation(s) resulted in a significant reduction of the root rot index. In addition, bioformulations increased plant growth attributing traits significantly relative to untreated control. Accumulation of total phenols, peroxidase, polyphenoloxidase and phenylalanine ammonia lyase increased in chitin-supplemented Trichoderma/Hypocrea formulation-treated plants challenged with R. solani. The results suggest that chitin-fortified bioformulation(s) could be an effective system to control root rot of tomato in an eco-compatible manner.  相似文献   

13.
为探索马铃薯糖苷生物碱诱导采后枸杞鲜果抗病性的效应,采用菌丝生长速率法测定了离体条件下马铃薯糖苷生物碱对枸杞鲜果采后主要致腐病原菌镰孢菌Fusarium sp.的抑菌活性;采用浸泡处理法测定了马铃薯糖苷生物碱对采后枸杞鲜果发病病情指数及对果实多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)和超氧化物歧化酶(SOD)等相关防御酶活性的影响。结果表明:不同浓度马铃薯糖苷生物碱对镰孢菌均具有一定的抑制作用,EC50为0.11 g/mL;0.05～0.25 g/mL(提取原料)的马铃薯糖苷生物碱能显著降低采后枸杞鲜果病情指数,较对照降低了10.18%～38.51%;以0.15 g/mL(提取原料)的马铃薯糖苷生物碱处理后对枸杞鲜果抗果腐病的诱导效果最好,达45.81%;马铃薯糖苷生物碱处理枸杞鲜果后,果实中4种防御酶PPO、POD、PAL、SOD的活性均较对照有不同程度提高,分别于处理后第4、5、2、2天与对照差异达到最大,较对照提高了30.76%、21.34%、31.35%和21.91%。表明马铃薯糖苷生物碱能够诱导枸杞鲜果对采后病害的抗性效应,且采后抗病性可能与枸杞相关防御酶活性的增加有关。  相似文献   

14.
为了探索新型异齅唑啉类化合物作为杀菌剂候选化合物开发的潜力,本研究以廉价易得的芳香醛类化合物为原料制备了32个氯代肟类化合物,通过其与天然产物丁香酚的1,3-偶极环加成反应和后期官能团化反应,制备了35个异齅唑啉类化合物 ( D1 ~ D32 , E1 ~ E3 ),其中34个为新化合物。所有化合物的结构均经过液相色谱-电喷雾质谱 (LC-ESI-MS)、核磁共振氢谱 (1H NMR) 及元素分析确认。初步抑菌活性测试结果表明:多数目标化合物对油菜菌核病菌、水稻纹枯病菌、番茄早疫病菌和辣椒疫霉病菌具有较好的抑菌活性,其中化合物 D26 对油菜菌核病菌的活性最高,有效抑制中浓度 (EC50) 为14.3 mg/L,具有进一步研究的价值。  相似文献   

15.
Early blight of tomato (Lycopersicon esculentum) caused by Alternaria solani has the potential to become one of the most serious diseases throughout the tomato‐producing regions of Greece. Controlled environment experiments were conducted to study the virulence of A. solani isolates and the susceptibility of commercial tomato cultivars and hybrids to early blight. The isolates used, derived from naturally infected tomato plants during the period 1997/1998, differed significantly (P>0.05) in the rate of mycelial growth as well as in their ability to sporulate in vitro. No correlation (R2= 0.33) was found between mycelial growth and conidia production. Isolates of A. solani were virulent to young tomato plants (cv. Ace 55VF), although they differed significantly (P>0.05) in the intensity of symptoms produced on leaves, stems, petioles and flowers. Defoliation was linearly related (R2= 0.87) to the percentage of leaf area with symptoms. Twenty‐three tomato cvs. or F1 hybrids were evaluated for their susceptibility to early blight. The cultivars or hybrids were arbitrarily categorized as immune, highly tolerant, tolerant, moderately tolerant, susceptible and highly susceptible based on a percent disease index range: 0%, 1‐9%, 10‐24%, 25‐49%, 50‐74% and 75% or more respectively. None of the cultivars or hybrids tested was immune or tolerant to A. solani infection.  相似文献   

16.
氯苯醚酰胺[N-(2-(2,4-二氯苯氧基)苯基)-3-(二氟甲基)-1-甲基-1H-吡唑-4-酰胺,Y13149]是由华中师范大学基于药效团连接碎片虚拟筛选策略(PFVS)快速发现的新型琥珀酸脱氢酶抑制剂类(SDHIs)化合物。采用菌丝生长速率法,测定了该创制化合物的农药生物活性。结果表明:氯苯醚酰胺对真菌具有较广的抗菌谱,对供试10种植物病原真菌均具有较好的抑制活性,EC50值在0.008~15.25 mg/L之间,其对立枯丝核菌的抑制活性最强,但对辣椒疫霉和链状腐霉活性较弱。田间试验表明,氯苯醚酰胺对水稻纹枯病具有较好的防治效果,有效剂量75 g/hm2时的平均防效为79.6%,其防效总体略好于噻呋酰胺(75 g/hm2的平均防效为77.3%)。此外,氯苯醚酰胺对采自浙江和江苏两省的125株水稻纹枯病菌的EC50值分布在0.002~0.259 mg/L之间,且呈近似正态单峰曲线,平均EC50值为(0.021 ±0.008) mg/L,因此可将其作为水稻纹枯病菌对氯苯醚酰胺的敏感性基线,用于田间抗药性监测。  相似文献   

17.
The in vitro production of extracellular polygalacturonase, pectin lyase, and cellulase by hop isolates of Verticillium albo-atrum was studied. A total of 24 isolates belonging to the two pathotypes commonly described as fluctuating or progressive, according to the symptoms produced in certain susceptible hop cultivars, were grown in liquid shake cultures. The media used contained glucose, pectin or acetone-extracted hop tissue as a carbon source. The production of all three enzymes was significantly correlated with pathotype when the medium contained hop tissue. Pectin lyase production was also correlated with pathotype when pectin was used as the carbon source. The influence of carbon source on enzyme output and possible reasons for some exceptions to the correlations observed are discussed.  相似文献   

18.
The use of soil fumigants and fungicides to control soilborne pathogens is reduced due to awareness of their negative drawbacks. Long-term application of such agrochemicals negatively affects soil microbiota and reduces natural soil suppressiveness. We investigated long-term impacts of biochar and not-pyrogenic organic amendment (OAs: manure, alfalfa straw and glucose), on disease suppression compared with conventional management in three pathosystems: Fusarium oxysporum f. sp. lactucae (FOL)–lettuce, Rhizoctonia solani–tomato and Sclerotinia sclerotiorum–lettuce, by conditioning soil for 2 years. Soil analyses included pH, electrical conductivity, organic carbon, total nitrogen, C:N ratio, N-NO3−, N-NH4+, cation exchange capacity, available phosphorus, Ca2+, Mg2+, K+, Na+, fluorescein diacetate (FDA), and total and active limestone. Soil microbiota was characterized by combining BIOLOG EcoPlates with next-generation sequencing of 16S and 18S rRNA genes. Soil amended with OAs generally suppressed disease by S. sclerotiorum and FOL compared to fumigants and synthetic fertilizers. However, the incidence of R. solani infection was lower in soil treated with synthetic fertilizers than soil amended with OAs. EC, pH, C:N, N-NO3−, N-NH4+, FDA and BIOLOG were significantly correlated with disease, depending on pathosystem. Bacterial richness and diversity, presence of some genera like Acidobacteria, Chloracidobacteria, Solibacteres, Anaerolineae, Nitrospira and Deltaproteobacteria were negatively related to disease incidence of FOL and S. sclerotiorum, whereas damping-off caused by R. solani was negatively affected by the presence of Flavobacterium and Chitinofagha. Therefore, we concluded that long-term application of OAs can effectively improve soil suppressiveness and reduce disease incidence against root pathogens, although the effects vary considerably depending upon pathosystem.  相似文献   

19.
Trichoderma harzianum is an effective biocontrol agent against the devastating plant pathogen Rhizoctonia solani. Despite its wide application in agriculture, the mechanisms of biocontrol are not yet fully understood. Mycoparasitism and antibiosis are suggested, but may not be sole cause of disease reduction. In the present study, we investigated the role of oxidant-antioxidant metabolites in the root apoplast of sunflower challenged by R. solani in the presence/absence of T. harzianum NBRI-1055. Analysis of oxidative stress response revealed a reduction in hydroxyl radical concentration (•OH; 3.6 times) at 9 days after pathogen inoculation (dapi), superoxide anion radical concentration (O2•−; 4.1 times) at 8 dapi and hydrogen peroxide concentration (H2O2; 2.7 times) levels at 7 dapi in plants treated with spent maize-cob formulation of T. harzianum NBRI-1055 (MCFT), as compared to pathogen-inoculated plants. The protection afforded by the biocontrol agent was associated with the accumulation of the ROS gene network: the catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and ascorbate peroxidase (APx), maximum activity of CAT (11.0 times) was observed at 8 dapi, SOD (7.0 times) at 7 dapi, GPx (5.4 times) and APx (8.1 times) at 7 dapi in MCFT-treated plants challenged with the pathogen. This was further supported by the inhibition of lipid and protein oxidation in Trichoderma-inoculated plants. MCFT stimulated the accumulation of secondary metabolites of phenolic nature that increased up to five-fold and also exhibited strong antioxidant activity at 8 dapi, eventually leading to the systemic accumulation of phytoalexins. These results suggest that T. harzianum–mediated biocontrol may be related to alleviating R. solani-induced oxidative stress.  相似文献   

20.
Seventy three isolates of Pythium aphanidermatum obtained from cucumber from four different regions of Oman and 16 isolates of muskmelon from the Batinah region in Oman were characterized for aggressiveness, sensitivity to metalaxyl and genetic diversity using AFLP fingerprinting. Twenty isolates of P. aphanidermatum from diverse hosts from different countries were also included in the study. Most isolates from Oman were found to be aggressive on cucumber seedlings and all were highly sensitive to metalaxyl (EC50 < 0·80 µg mL?1). Isolates from cucumber and muskmelon were as aggressive as each other on both hosts (P > 0·05), which implies a lack of host specialization in P. aphanidermatum on these two hosts in Oman. AFLP analysis of all isolates using four primer–pair combinations resolved 152 bands, of which 61 (~40%) were polymorphic. Isolates of P. aphanidermatum from Oman and other countries exhibited high genetic similarity (mean = 94·1%) and produced 59 different AFLP profiles. Analysis of molecular variance indicated that most AFLP variation among populations of P. aphanidermatum in Oman was associated with geographical regions (FST = 0·118; P < 0·0001), not hosts (FST = –0·004; P = 0·4323). These data were supported by the high rate of recovery (24%) of identical phenotypes between cucumber and muskmelon fields in the same region as compared to the low recovery (10%) across regions in Oman, which suggests more frequent movement of Pythium inoculum among muskmelon and cucumber fields in the same region compared to movement across geographically separated regions. However, recovering clones among regions and different countries may imply circulation of Pythium inoculum via common sources in Oman and also intercontinental spread of isolates.  相似文献   

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