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1.
The level of resistance of carnation ( Dianthus caryophyllus ) cultivars to wilt caused by Fusarium oxysporum f.sp. dianthi was compared in root-dip-inoculated plants grown in pots (filled with tuff or sandy soil) in a greenhouse and plants grown in a field where the soil was artificially infested with the fungus. In the field, wilt symptoms appeared first in susceptible and subsequently in resistant cultivars; none was immune. Variations in the level of resistance were expressed either by different percentages of wilted plants (i.e. disease incidence) or by delayed disease progress as compared to a susceptible cultivar. The range of disease severity in the field, ranked on a scale from 0 to 4, was highly and significantly correlated with the percentage of diseased plants. The greenhouse test was unreliable as a predictor of the degree of resistance observed in the field. Similar wilt levels in the greenhouse and the field were found only in susceptible cultivars.  相似文献   

2.
The severity of fusarium wilt is affected by inoculum density in soil, which is expected to decline during intervals when a non‐susceptible crop is grown. However, the anticipated benefits of crop rotation may not be realized if the pathogen can colonize and produce inoculum on a resistant cultivar or rotation crop. The present study documented colonization of roots of broccoli, cauliflower and spinach by Fusarium oxysporum f. sp. lactucae, the cause of fusarium wilt of lettuce. The frequency of infection was significantly lower on all three rotation crops than on a susceptible lettuce cultivar, and the pathogen was restricted to the cortex of roots of broccoli. However, F. oxysporum f. sp. lactucae was isolated from the root vascular stele of 7·4% of cauliflower plants and 50% of spinach plants that were sampled, indicating a greater potential for colonization and production of inoculum on these crops. The pathogen was also recovered from the root vascular stele of five fusarium wilt‐resistant lettuce cultivars. Thus, disease‐resistant plants may support growth of the pathogen and thereby contribute to an increase in soil inoculum density. Cultivars that were indistinguishable based on above‐ground symptoms, differed significantly in the extent to which they were colonized by F. oxysporum f. sp. lactucae. Less extensively colonized cultivars may prove to be superior sources of resistance to fusarium wilt for use in breeding programmes.  相似文献   

3.
Seventy isolates of Fusarium oxysporum (Schlechtend: Fr.) f. sp. melongenae Matuo and Ishigami (Fomg), the causal agent of eggplant Fusarium wilt, were tested for their interaction with different lines and cultivars to determine whether there was race-specific interaction. Also, a total of 13 cultivars were tested under greenhouse conditions to evaluate the presence of resistance to Fusarium wilt. The disease severity (%) and the area under disease progress curve (AUDPC) for each of the Fomg isolates were calculated by scale values. Results showed that neither of the resistant lines (LS1934 and LS2436) exhibited wilting symptoms, whereas susceptible local cultivars (cvs. ‘Kemer’ and ‘Hadrian’) displayed severe disease symptoms. There was no significant variation in the virulence, indicating the occurrence of a race or races among 70 Fomg isolates tested on resistant lines and susceptible cultivars. This may indicate a genetically homogeneous population structure of Fomg in Turkey. The eggplant cultivars Amadeo, Anatolia, Angela, Brigitte, Corsica, Hawk, Koksal, Nouma, Sharapova and Yula exhibited various degrees of susceptibility to three virulent Fomg isolates, but disease severity for AGR-703 was significantly different and lower among the tested eggplant cultivars, as well as rootstocks. Therefore, it is considered as the most appropriate for rootstock purposes in eggplant cultivations where Fusarium wilt is present in the soil.  相似文献   

4.
ABSTRACT A precise real-time polymerase chain reaction (PCR) assay was developed for quantifying Verticillium albo-atrum DNA. The assay was used in a repeated experiment to examine the relationship between the quantity of pathogen DNA detected in infected leaves and shoots and the severity of Verticillium wilt symptoms in several alfalfa cultivars expressing a range of disease symptoms. Plants were visually inspected for symptoms and rated using a disease severity index ranging from 1 to 5, and the quantity of pathogen DNA present in leaves and stems was determined with real-time PCR. No significant differences in pathogen DNA quantity or disease severity index were observed for experiments or for cultivar-experiment interactions. Significant differences were observed between cultivars for the quantity of pathogen DNA detected with real-time PCR and also for disease severity index ratings. In both experiments, the highly resistant check cultivar Oneida VR had significantly less pathogen DNA, and significantly lower disease severity index ratings than the resistant cultivar Samauri, the moderately resistant cultivar Vernema, and the susceptible check cultivar Saranac. In both experiments, the Spearman rank correlation between the amount of V. albo-atrum DNA detected in leaves and stems with real-time PCR and disease severity index ratings based on visual examination of symptoms was positive (>0.52) and significant (P < 0.0001). These results suggest that resistance to Verticillium wilt in alfalfa is characterized by a reduced colonization of resistant genotypes by the fungus.  相似文献   

5.
 尖孢镰刀菌黄瓜专化型(Fusarium oxysporum f. sp. cucumerinum, Foc)是引起黄瓜枯萎病的病原真菌,为了明确不同抗性黄瓜品种连作对枯萎病菌遗传分化的影响,本研究采用TEF1-α、H3基因片段对不同抗性黄瓜品种连作及对轮作后分离的枯萎病菌群体进行遗传分化分析。结果表明,感病品种连作及轮作后菌群分化程度较低( 0.007< FST <0.045 );与种植抗病品种一茬后的菌群相比,连作三、五茬后的菌群均发生显著分化(FST > 0.050),其中连作三茬后的菌群遗传分化程度最高(FST > 0.300)。单倍型分析发现,抗、感病品种连作后部分菌株形成新的单倍型,且分离自抗病品种的病原菌群体分化产生的单倍型数量多于感病品种。主成分分析结果进一步证明,与感病品种连作及轮作相比,抗病品种连作后病原菌菌群呈现出更显著的菌群分化。综上所述,抗病品种连作能够加剧黄瓜枯萎病菌群体的遗传分化。  相似文献   

6.
Two susceptible barley cultivars and two moderately resistant advanced breeding lines were grown as pure stands and as the 11 possible equi-proportional mixtures over three field seasons, in the presence of scald and net blotch. Plots were either inoculated with infested straw, or non-inoculated and sprayed with fungicide. On average, the variety mixtures restricted leaf disease development by 12%. However, mixtures of either or both susceptible cultivar/s with the moderately resistant line 1861018 restricted disease severity by 20-32%. Generally, the mixtures did not increase yield relative to the mean of the pure stands. However, in the year of highest disease severity, yield was increased by 7% owing to mixing in the inoculated plots. In addition, one mixture consistently increased yield (mean of 4%) and one mixture had consistently lower yields (mean of 6%)) over years and inoculation treatments. Thus, careful evaluation is required in this environment and with these genotypes in order to identify mixtures with positive effects on disease control and yield.  相似文献   

7.
Sugarcane cultivars with a high (susceptible cultivars) and low (resistant cultivars) virus titer of Sugarcane yellow leaf virus were grown in the field. The carbohydrate composition in green leaf tops and in stems was determined. In RT-PCR of leaf extracts, susceptible cultivars had a high SCYLV-titer, whereas resistant cultivars had a very low titer. The cultivars differed in biomass yield, but these differences were not correlated with susceptibility. However, carbohydrate composition did have susceptibility-specific differences. Hexose levels were lower in green leaf tops and stalks of susceptible (strongly infected) cultivars than in those of resistant (weakly infected) cultivars. The stalks of susceptible cultivars also had less starch than those of resistant cultivars. Thus, the viral susceptibility (and infection) affected sugar metabolism. In addition, a positive correlation between hexose and starch in stems and between hexose and sucrose in green leaf tops was observed. The results from susceptible versus resistant cultivars were the opposite of those in the comparison between infected versus virus-free lines of the same cultivar. The breeding process apparently had unintentionally selected clones with modulated carbohydrate metabolism to avoid or compensate for the adverse effects of SCYLV infection.  相似文献   

8.
Forty five descendants from a crossing between olive cultivar Picholine de Languedoc and the local cultivar Meski were evaluated for their susceptibility to olive leaf spot (Fusicladium oleagineum) in field and laboratory studies. Disease incidence varied greatly among the descendants and was correlated with the severity of leaf symptoms. Based on field observations and laboratory tests, the hybrids were classified into five groups: 1) very susceptible to the disease: Meski and 17H, 2) susceptible to the disease : 20J, 8I, 11I, 21I, 14H, 16H, 23H, 6J, 8J and 23J, 3) moderately resistant to the disease : 15I, 16I, 22I, 23I, 8K, 13H, 18H, 22H, 9J, 10J, 11J, 12J, 14J, 16J, 18J, 4) resistant to the disease: 21J, 12I, 13I, 18I, 19I, 9K, 10K, 12H, 15H, 19H, 15J and 22J, and completely resistant to the disease : cultivar Picholine and hybrids 6I and 19I. The analysis of anatomical parameters showed that the polyphenol content and composition were not correlated with disease incidence. However, the cuticle thickness and the trichome density are very important physical parameters that can determine the degree of susceptibility of hybrids to the disease. The assessment method may be useful to screen olive cultivars and hybrids for Fusicladium resistance.  相似文献   

9.
Twelve wild Solanum accessions were tested in a glasshouse at the seedling stage for resistance to Fusarium oxysporum f. sp. melongenae, the causal agent of fusarium wilt of aubergine. Four isolates of the fungus (three Turkish and one Italian) were used. Solanum incanum and S. linneanum were highly susceptible, whereas S. sisymbrifolium, S. torvum and S. aethiopicum Gilo group (one accession) were resistant. In Solanum aethiopicum Aculeatum (two accessions), S. aethiopicum Gilo, S. viarum and S. macrocarpon there were both resistant and susceptible individuals. The sources of resistance found in these wild Solanum spp. could be conveniently used to breed aubergine cultivars resistant to fusarium wilt.  相似文献   

10.
The effects of chlamydosporesandconidia of Fusarium oxysporum f sp. tracheiphilum at different initial spore concentrations were compared in the wilt-susceptible cowpea cultivar California Blackeye No. 5 (CB5). In glasshouse experiments with one inoculum density of either Meloidogyne incognita or M javanica, chlamydospores resulted in greater incidence and severity of Fusarium wilt than conidia at the same inoculum densities. Wilt symptoms also increased on wilt-resistant cultivar CB3 as inoculum densities of M. javanica were increased. When three cultivars were infested with moderate or high densities of both F. o. tracheiphilum and M. javanica. only CB5 developed sere wilt at either inoculum density. The wilt-tolerant cultivar Grant had mild wilt symptoms in most plants at moderate inoculum densities, and a tenfold increase in inoculum did not increase wilt ratings. CB3. however, had higher incidence and severity of Fusarium wilt symptoms at high inoculum densities, although 60% of the plants survived for 9 weeks.  相似文献   

11.
Tomato plants are severely infested with Aphis gossypii in all over the world. The present investigation aims at evaluating effects of tomato leaf biochemical components as well as leaflet surface physical features on the susceptibility of five tomato cultivars (Alissa, GS, Logan, Super Strain B and Andos). Results clearly indicated significant differences among the five tested tomato cultivars according to their susceptibility to A. gossypii infestation. In addition, the cultivars Logan and Andos are the most susceptible, while Super Strain B and Alissa cultivars showed moderate resistance. The GS cultivar, finally, was the most resistant one. Photosynthetic pigments, biochemical components and antioxidant defense enzymes activity were negatively affected by infestation. Moreover, the density and length of leaflet non-glandular trichomes negatively effect on the population density of A. gossypii, while this was not the case with glandular trichomes. From these results, the susceptibility of tomato cultivars on the basis of these results in the integrated aphids management programs.  相似文献   

12.
Resistance of 23 important olive cultivars to Verticillium dahliae has been evaluated in four experiments under controlled conditions. Nine-month-old nursery olive plants were inoculated with a cotton non-defoliating (ND) (V4) or a cotton defoliating (D) (V117) isolate of V. dahliae. Resistance was evaluated by assessing symptom severity using a 0–4 rating scale and estimating the area under disease progress curves. The percentage of plants killed and of those which recovered from the disease were used as additional parameters for including a particular cultivar into a defined category. Most of the evaluated cultivars were susceptible, although at different levels, to both isolates of V. dahliae. All cultivars were more susceptible to the D pathotype than to the ND one. A group of 11 cultivars, including several important Spanish cultivars, were susceptible or extremely susceptible to both pathotypes of V. dahliae. A second group showed differences of resistance depending on the pathotype used. They were susceptible or extremely susceptible to the D pathotype but resistant or moderately susceptible to the ND one. Finally, 'Frantoio', 'Oblonga' and 'Empeltre' were moderately susceptible to the D isolate of V. dahliae and resistant to the ND one. The resistance of 'Empeltre' was evident by the plant ability to recover from infection with either isolates. 'Empeltre' is considered to be a valuable cultivar for inclusion in breeding programmes for resistance to Verticillium wilt.  相似文献   

13.
Verticillium wilt of olive (VWO) is probably the most devastating fungal disease for olive trees worldwide, and currently the main cultivars are susceptible or moderately susceptible to this disease. The evaluation of resistant cultivars as rootstocks to control the disease has scarcely been explored, and mainly in short-term studies under controlled conditions, which usually do not correspond with field evaluations. The main objective of this study was to assess the responses to VWO of different scion × rootstock combinations of the olive cultivars Picual, Arbequina, Changlot Real, and Frantoio in a long-term field experiment with a soil highly infested with the defoliating pathotype of Verticillium dahliae. The results showed that grafting the susceptible cultivar Picual onto resistant rootstocks delayed the onset of the disease symptoms; however, after 4 years, it was observed that all combinations that contain Picual (a) were extensively colonized by V. dahliae; (b) developed severe symptoms of the disease; and (c) had plant mortality similar to Picual growing on its own roots. This result highlights the importance of long-term field experiments to evaluate VWO and shows that grafting susceptible olive cultivars onto resistant ones does not provide a durable control of VWO under high inoculum potential, as V. dahliae is able to progress through the resistant rootstock and then extensively colonize and kill the susceptible scion. However, the high inoculum potential observed in this study does not allow us to consider the evaluated resistant cultivars as completely ineffective under lower inoculum densities.  相似文献   

14.
Fukui R  Fukui H  Alvarez AM 《Phytopathology》1999,89(11):1007-1014
ABSTRACT Effect of temperature on leaf colonization in anthurium blight was studied using a bioluminescent strain of Xanthomonas campestris pv. dieffenbachiae. In a susceptible cultivar, colonization of leaf tissues (monitored by detection of bioluminescence) and symptom development (assessed visually) advanced rapidly at higher temperatures. For a susceptible cultivar, there was a linear relationship between degree-days and percent leaf area colonized by the pathogen, indicating that leaf colonization in a susceptible cultivar was a direct function of the cumulative effect of temperature. The degree-day intercept of the regression line represented the time from inoculation to detection of bioluminescence, and the slope indicated the increase of leaf colonization per degree-day. There also was a linear relationship between the logarithm of degree-days and the logarithm of percent leaf area showing visible symptoms in a susceptible cultivar. The degree-day intercept of this relationship represented the incubation period (about 500 degree-days). The degree-days required to detect bioluminescence was not considerably different between susceptible and resistant cultivars. However, the subsequent rates of leaf colonization were significantly lower for a resistant cultivar than for a susceptible cultivar in all temperature regimes. The results suggest that multiplication of the pathogen in the leaf tissues is optimized in the susceptible cultivar. In contrast, in the resistant cultivar, the defense mechanisms overshadow the temperature effect. The differential response to temperatures may be an additional indicator of cultivar susceptibility.  相似文献   

15.
Mechanisms of resistance to fusarium wilt (Fusarium udum) were investigated in pigeon pea cultivars from Malawi. Wilt-susceptible (Malawi local) and wilt resistant (ICP 9145) plants were stem-inoculated with a spore suspension containing 2·106 conidia/ml of the pathogen. Occlusion of a small proportion of infected vessels was observed, but the resistant reaction appeared to depend mainly on rapid phytoalexin synthesis. Four fungitoxic isoflavonoid phytoalexins—hydroxygenistein, genistein, cajanin and cajanol-were isolated from plants 15 days after inoculation. Cajanol was identified as the main antifungal compound. The concentration of cajanol was 329·4 μg/g in the resistant cultivar as against 88·6 μg/g in the susceptible cultivar 15 days after inoculation. Crude extract from the resistant plants sampled at 24 h after inoculation contained 34·8 μg ml of cajanol. The LD50 value of cajanol for spore germination was determined as 35μg/ml. The cajanol content of fungus-infected ICP 9145 10 days after inoculation totally inhibited conidial germination of F. udum.  相似文献   

16.
分别提取黄瓜枯萎病感病品种津研4号和抗病品种中农10号的根分泌物,感病品种根分泌物甲醇提取液能够刺激枯萎病菌的菌丝生长,而抗病品种根分泌物甲醇提取液则抑制病原菌生长。利用LC-MS/MS技术分别对感病品种和抗病品种根分泌物中的差异物质进行分析鉴定。与感病品种津研4号相比,抗病品种中农10号根分泌物中含有7,8-苯并黄酮(7,8-BF),含量为0.02μg/株。50μg/mL的7,8-BF能够显著抑制黄瓜枯萎病菌菌丝生长和孢子萌发,而100μg/mL的7,8-BF能显著抑制抗感品种侧根形成,但是抗病品种的耐受力高于感病品种。用7,8-BF处理黄瓜种子,枯萎病侵染程度显著降低。当7,8-苯并黄酮浓度为50μg/mL时,感病品种病情指数从71.7降为30.8,达到中抗水平。  相似文献   

17.
Verticillium wilt of cotton (Gossypium hirsutum) is a widespread and destructive disease caused by the soil-borne fungal pathogen Verticillium dahliae. In this study, a green fluorescent protein (GFP) labelled V. dahliae strain (TV7) was obtained by transforming gfp into defoliating strain V991. Strain TV7 was used to study infection and colonization of wilt resistant cotton cultivar Zhongzhimian KV1 and susceptible cultivar 861 with the aid of confocal laser scanning microscopy. The results showed that initial infection and colonization of V. dahliae in Zhongzhimian KV1 and 861 were similar. Conidia and hyphal colonies formed and penetrated in the root meristematic and elongation zones and in the conjunction of the lateral and main roots. The invaded conidia started to germinate by 2 hpi (hours post-inoculation), penetrated into the root cortex and vascular bundles, eventually colonized in the stem xylem vessels and grew restrictedly in the individual tracheae of both resistant and susceptible cultivars. Moreover, pathogen DNA could be detected by qPCR in roots and stems of both cultivars, but its content in the wilt susceptible cultivar 861 was much higher than that in the wilt resistant cultivar Zhongzhimian KV1. The results indicated that the resistant cultivar has ability to suppress V. dahliae reproduction.  相似文献   

18.
Barley spot blotch (SB), caused by Cochliobolus sativus, is an important barley disease which causes extensive grain yield losses. These losses may not always correlate directly with the amount of diseased leaf area. Two barley cultivars, Quebracho (susceptible to SB) and Carumbé (with intermediate susceptibility to SB), were compared in field experiments in 2003, 2004 and 2006. Plots of each cultivar were either inoculated with C. sativus or protected with fungicide under field conditions to generate contrasting treatments: i) diseased, and ii) free of disease, respectively. SB severity over the growing season, photosynthetic rate on leaves with no visible symptoms and grain yield were assessed for each treatment and year. There was no treatment effect on cv. Carumbé, while cv. Quebracho showed a significant yield reduction, even though SB severity during the grain filling period was <10 %. This yield reduction was associated with a reduced photosynthetic rate at the beginning of the grain filling period in cv. Quebracho. A similar experiment was conducted under greenhouse conditions, adding a treatment without inoculum or fungicide. There were no differences in photosynthetic rate or grain yield per plant among treatments. These results suggest a distinct physiological response to SB infection among cultivars affecting leaf photosynthetic rate, and SB severity may not be the best estimator of yield losses caused by SB.  相似文献   

19.
To improve the breeding of chickpea varieties with resistance to Fusarium wilt, an attempt was made to analyse the biochemical basis of disease resistance by measuring levels of chitinase, β-1,3-glucanase, protease and proteinase inhibitor activities in dry and soaked seeds and in root and shoot tissues of wilt-resistant and wilt-susceptible cultivars. Marginal variation was observed in the levels of the candidate proteins in dry or soaked seeds. Chitinase activity was higher in roots than in shoots or cotyledons. No proteinase inhibitor activity was detected in root and shoot tissue of any of the cultivars. When the levels of these proteins were analysed in resistant (Vijay) and susceptible (JG-62) cultivars during development of wilt by growing plants in soil infested with F. oxysporum f.sp. ciceri , race 1, both cultivars showed induction of chitinase activity in the roots. However, the induced activity in JG-62 (3.82 U g−1) was equivalent to the constitutive level in Vijay (3.90 U g−1) and much lower than that induced in Vijay (5.18 U g−1). Induction of protease activity was observed only in root extracts of Vijay when challenged by the pathogen. The root extract of Vijay showed in vitro antifungal activity in a plate assay. Simultaneous induction of proteolytic and chitinolytic activities specifically in the resistant cultivar was correlated with antifungal properties of root extracts effective in conferring resistance.  相似文献   

20.
The interface between Erysiphe pisi and pea cv. JI 1049 was studied at the ultrastructural and cytochemical levels and compared with those in two susceptible cultivars. Haustorial efficiencies, as indexed by the length of mycelium associated with each haustorium, and growth rates on the resistant and one susceptible cultivar were also compared.The interaction in the resistant cultivar differed from those in the susceptible cultivars in the following ways: (i) there was no contact between the host plasmalemma and the A neckband region; (ii) papillae were contiguous with the surface of the neck and thus were probably formed before haustoria and (iii) there appeared to be less polysaccharide in the extrahaustorial membrane. The extrahaustorial membrane in the resistant cultivar lacked ATPase activity, whereas the rest of the host plasmamembrane had normal activity.Each haustorium supported a significantly greater total hyphal length in the resistant than in the susceptible cultivars. Growth rates of superficial hyphae were very similar on the susceptible and resistant cultivars but there was a delay in the onset on hyphal growth on the resistant cultivar which correlated with the previously reported delay in formation of the first haustorium. In contrast to hyphal growth rates, the rate of haustorium production was significantly less in the resistant cultivar. It is proposed that resistance in cv. JI 1049 operates at the stages prior to haustorium formation, similarly to that in some non-host and partial resistance systems. Once formed, however, the function of the haustorium seems to be unimpaired, despite the observed interfacial differences.  相似文献   

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