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1.
Verticillium wilt (VW) in olive is best managed by an integrated disease management strategy, of which use of host resistance is a key element. The widespread occurrence of a highly virulent defoliating (D) Verticillium dahliae pathotype has jeopardized the use of commercial olive cultivars lacking sufficient resistance to this pathogen. However, the combined use of resistant wild olive rootstocks and Trichoderma spp. effective in the biocontrol of VW can improve the management of VW in olive. In vivo interactions between D V. dahliae and Trichoderma harzianum were studied in olive and wild olive plants displaying different degrees of resistance against this pathogen using confocal microscopy. This multitrophic system included wild olive clones Ac‐4 and Ac‐15, olive cv. Picual, and the fungal fluorescent transformants T. harzianum GFP22 and V. dahliae V138I‐YFP, the latter being obtained in this study. In planta observations indicated that V138I‐YFP colonizes the roots and stems of the olive and wild olive genotypes, and that GFP22 grows endophytically within the roots of them all. YFP fluorescence signal quantifications showed that: (i) the degree of root and stem colonization by the pathogen varied depending upon the susceptibility of the tested wild olive genotype, being higher in Ac‐15 than in Ac‐4 plants; and (ii) treatment with T. harzianum GFP22 reduced the extent of pathogen growth in both clones. Moreover, root colonization by strain GFP22 reduced the percentage of pathogen colonies recovered from stems of olive and wild olive plants.  相似文献   

2.
Verticillium wilt caused by Verticillium dahliae is one of the most threatening diseases of olive worldwide. For pre‐planting and post‐planting control of verticillium wilt in olive trees, availability of a rapid, reliable and non‐destructive method for detection of V. dahliae is essential. For such a method, suitable and easily performed sampling and efficient processing of samples for extraction of DNA are necessary. In this study, the suitability of young twig and leaf samples of olive trees, which are easy to collect and extract DNA from, were assessed for the detection of V. dahliae in routine procedures. The lower (about 50 cm from the tip) and top parts (about 5 cm from the tip) of twigs, as well as leaves from infected olive trees were screened for V. dahliae infection and distribution using real‐time PCR. The biomass of V. dahliae detected in individual twigs was highly variable, but there was no significant difference between mean quantities of V. dahliae DNA detected in top and lower parts of twigs. Furthermore, it was demonstrated that analysis of combined samples containing DNA extracted from five twigs of an infected tree accurately detected the presence of the pathogen. Similarly, testing combined samples of 5–10 leaves enabled reliable detection of the pathogen in an infected tree. The development of this assay enables reliable detection of V. dahliae in infected olive trees that can aid in management decisions for the implementation of integrated disease management.  相似文献   

3.
Biological control of plant diseases using soil amendments such as animal manure and composted materials can minimize organic waste and has been proposed as an effective strategy in crop protection. In this study, 35 organic amendments (OAs) and 16 compost mixtures were evaluated against Verticillium dahliae by assessing both the antagonistic effect on the mycelial growth of two representative isolates of V. dahliae and the effect on the reduction of microsclerotia viability of the pathogen in naturally infested soil. Eleven OAs and five compost mixtures showed a consistent inhibition effect in in vitro sensitivity tests, with solid olive‐oil waste compost one of the most effective. Therefore, a bioassay with olive plants was conducted to evaluate the suppressive effect against V. dahliae of these selected OAs and compost mixtures. Significant reduction in the severity of the symptoms of V. dahliae indicates the potential use of grape marc compost (100% disease severity reduction) and solid olive‐oil waste, combined with other OAs. Microorganism mixtures and dairy waste OAs had a potential suppressive effect when they were combined with compost, showing a 73% and 63% disease severity reduction, respectively. A mixture of agro‐industrial waste with other biological control agents is a promising strategy against verticillium wilt of olive. To the authors' knowledge, this is the first report on the effectiveness of compost extracts (compost teas) on the inhibition of natural microsclerotia of V. dahliae, and also on verticillium wilt suppression in olive with solid olive‐oil waste.  相似文献   

4.
E. C. TJAMOS 《EPPO Bulletin》1993,23(3):505-512
Control of verticillium wilt of olive currently depends on preventive measures. Since systemic fungicides are unable to prevent or control the disease, its control should primarily be based on cultural methods, including irrigation systems which restrict dissemination of Verticillium dahliae propagules by irrigation water and avoidance of intercropping with hosts susceptible to V. dahliae. Since leaves from affected olive trees contribute, through formation of microsclerotia, to the inoculum in the soil, pruning should be practised prior to branch defoliation. As for resistant olive rootstocks or cultivars, promising verticillium-wilt resistance has been found in two rootstocks selected in California (US). However, these have to be tested under local conditions before they can be released to Mediterranean growers, while further search for other resistant rootstocks is needed. Soil solarization applied to individual diseased trees in established olive groves could substantially contribute to recovery or long-lasting symptom remission in the treated trees. This effect is mainly attributed to the decrease or eradication of V. dahliae microsclerotia in the treated soil but also to heat-tolerant fungal antagonists of the pathogen. Using herbicides to control weeds, and limiting soil rotovation, can restrict symptom development. Biological control can also be considered as a promising trend in controlling the disease by searching, testing and exploiting potential fungal or bacterial antagonists.  相似文献   

5.
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   

6.
Spread of Verticillium wilt into newly established olive orchards in Andalucía, southern Spain, has caused concern in the olive industry in the region. This spread may result from use of Verticillium dahliae-infected planting material, which can extend distribution of the highly virulent, defoliating (D) pathotype of V. dahliae to new areas. In this study, a molecular diagnostic method for the early in planta detection of D V. dahliae was developed, aimed especially at nursery-produced olive plants. For this purpose, new primers for nested PCR were designed by sequencing a 992-bp RAPD marker of the D pathotype. The use of the specific primers and different nested-PCR protocols allowed the detection of V. dahliae pathotype D DNA in infected root and stem tissues of young olive plants. Detection of the pathogen was effective from the very earliest moments following inoculation of olive plants with a V. dahliae pathotype D conidia suspension as well as in inoculated, though symptomless, plants.  相似文献   

7.
Understanding pathogenic variation in plant pathogen populations is key for the development and use of host resistance for managing verticillium wilt diseases. A highly virulent defoliating (D) pathotype in Verticillium dahliae has previously been shown to occur only in one clonal lineage (lineage 1A). By contrast, no clear association has yet been shown for race 1 with clonal lineages. Race 1 carries the effector gene Ave1 and is avirulent on hosts that carry resistance gene Ve1 or its homologues. The hypothesis tested was that race 1 arose once in a single clonal lineage, which might be expected if V. dahliae acquired Ave1 by horizontal gene transfer from plants, as hypothesized previously. In a diverse sample of 195 V. dahliae isolates from nine clonal lineages, all race 1 isolates were present only in lineage 2A. Conversely, all lineage 2A isolates displayed the race 1 phenotype. Moreover, 900‐bp nucleotide sequences from Ave1 were identical among 27 lineage 2A isolates and identical to sequences from other V. dahliae race 1 isolates in GenBank. The finding of race 1 in a single clonal lineage, with identical Ave1 sequences, is consistent with the hypothesis that race 1 arose once in V. dahliae. Molecular markers and virulence assays also confirmed the well‐established finding that the D pathotype is found only in lineage 1A. Pathogenicity assays indicated that cotton and olive isolates of the D pathotype (lineage 1A) were highly virulent on cotton and olive, but had low virulence on tomato.  相似文献   

8.
Verticillium wilt is the most serious olive disease in the Mediterranean countries and worldwide. The most effective control strategy is the use of resistant cultivars. However, limited information is available about the level and source of resistance in most of the olive cultivars and there are no published data using microsclerotia, the resting structures of Verticillium dahliae, as the infective inoculum. In the present study, we correlated symptomatology and the presence of the fungus along with the DNA relative amount (molecules μl−1) of a defoliating (D) and a non-defoliating (ND) V. dahliae strain in the susceptible cv. Amfissis and the tolerant cvs Kalamon and Koroneiki, as quantified by the Real-Time QPCR technology. The viability of the pathogen in the plant tissues was confirmed by isolating the fungus on PDA plates, while symptom assessment proved the correlation between the DNA relative amount of V. dahliae in plant tissues and cultivar susceptibility. It was further demonstrated that the D and ND strains were present at a significantly higher level in cv. Amfissis than in cvs Kalamon and Koroneiki. It was finally observed that the relative amount of the pathogen in roots was lower than in stems and shoots and declined in plant tissues over time. These data constitute a valuable contribution in evaluating resistance of olive cultivars or olive root-stocks to V. dahliae pathotypes.  相似文献   

9.
Since 2006, verticillium wilt of olive induced by Verticillium dahliae has caused considerable economic losses in olive orchards in Tunisia. The genetic structure of V. dahliae isolates collected from different olive growing regions was investigated using virulence tests, vegetative compatibility grouping (VCG) and amplified fragment length polymorphism (AFLP) analyses. In total, 42 isolates of V. dahliae from diseased olive trees were tested. Cluster analysis and principal coordinate analysis revealed that geographic origin was the main factor determining the genetic structure of V. dahliae populations and both methods indicated a genetic separation between the central and coastal isolates. Isolates were divided into two major groups: the AFLP‐I group included all isolates from Sidi Bouzid, Kairouan, Kasserine and Sfax (centre of the country) and the AFLP‐II group included isolates from Monastir, Zaghouane, Sousse, Mahdia (coastal region), and two isolates from Sfax. Analysis of the molecular variance (amova ) indicated a significant level of genetic differentiation among (76%) and within (23%) the two populations. Analyses of both the defoliating (D) and non‐defoliating (ND) pathotypes and VCG markers indicated that most of the isolates belong to VCG 2A and 4B/ND pathotype. The disease severity was highly variable among the isolates tested (P < 0·05) with no evidence of association between aggressiveness and geographical origin of the isolates. Overall, results of this study revealed a clear association between the genetic diversity of the isolates and their geographic origin, but not between genetic diversity and virulence patterns.  相似文献   

10.
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   

11.
Developing verticillium wilt resistant genotypes is currently a major objective in olive breeding. In this study, 6017 genotypes derived from 48 crosses obtained by open pollination and crosses between olive cultivars, wild olive genotypes and other Olea species and Olea europaea subspecies were individually evaluated for verticillium wilt resistance. More than 800 genotypes were identified as resistant to the disease based on the absence of symptoms. High genetic variability and wide segregation in resistance were observed. The inheritance of resistance was studied, and the best parents and crosses to breed resistant genotypes were identified. According to the results, verticillium wilt resistance in olive appears to be a quantitative trait. The results obtained by comparing the level of resistance between different crosses as well as by estimating heritability suggest that it is possible to breed for verticillium wilt resistance in olive.  相似文献   

12.
Verticillium dahliae causes severe yield reductions in a variety of important annual crops worldwide. Control of verticillium wilt has relied on soil fumigation; however, the use of the main soil fumigant, methyl bromide, has been banned in the European Union since 2010, creating a demand for novel crop protectants. As such, the use of biocontrol agents (BCAs) is an appealing management strategy. Prerequisites for the development of a successful BCA are an understanding of the modes of action of the antagonist, its ecological fitness and an efficient and economically feasible delivery system. Therefore, two BCAs (Paenibacillus alvei K165 or the nonpathogenic Fusarium oxysporum F2) and two release strategies (seed coating or amendment of the transplant soil plug) were assessed against verticillium wilt of aubergine (eggplant). Mixing the transplant soil plug with K165 or F2, at a rate of 10 and 20% (v/v), respectively, reduced verticillium wilt symptom development. Furthermore, a positive correlation was revealed between the release strategy and the BCA rhizosphere population. Correlation analysis also showed that disease severity was negatively correlated to the rhizosphere size of the BCA population. In addition, qPCR analysis showed that both BCAs induced the expression of the pathogenesis‐related (PR) proteins PR1 and PR4 in the stem of aubergines before and after inoculation with V. dahliae in a manner that suggests a link with the rhizosphere size of the BCA population.  相似文献   

13.
Vegetable grafting for disease management was first used successfully when watermelon grafted onto a Cucurbita moschata rootstock overcame Fusarium wilt. Interspecific grafting has since been used effectively to mitigate several soilborne pathogens in a variety of solanaceous and cucurbitaceous cropping systems. Verticillium wilt caused by Verticillium dahliae is a significant disease in watermelon crops and is difficult to manage. Current management practices, including crop rotation, soil fumigation, and host resistance, are insufficient due to the ability of microsclerotia to persist in absence of a host, lack of efficacy of soil fumigants, and limited availability of resistant cultivars. Watermelon grafted onto commercial cucurbit rootstocks have increased tolerance to Verticillium wilt, although no cucurbit rootstocks are known to be completely resistant. Verticillium wilt incidence decreased on grafted plants grown in artificially and naturally infested soils, while scion health and growth as well as rootstock root mass and vigour increased. Commonly used rootstocks are Lagenaria siceraria, C. moschata, and C. maxima × C. moschata; of these, only C. maxima × C. moschata ‘Tetsukabuto’ reduced severity of Verticillium wilt across several scion cultivars, locations, years, and soil densities of V. dahliae. Although studies on Verticillium wilt resistance of grafted watermelon are few, their combined results suggest the threshold of V. dahliae soil density for watermelon may be around 5–12 cfu/g. This review summarizes available information on Verticillium wilt of watermelon and effects of different rootstock × scion combinations, assisting growers and breeding programmes in decisions to adopt watermelon grafting for management of Verticillium wilt.  相似文献   

14.
In the present study, we evaluated the susceptibility of different commercial olive cultivars to verticillium wilt. Two Verticillium dahliae isolates, obtained from olive and artichoke, were used in pathogenicity tests. Two-year-old rooted cuttings were inoculated using either the root-dip or the stem-wounding method. The results were similar with both inoculation methods. Cvs Carolea and Cipressino proved to be moderately susceptible whereas Cassanese, Nocellara del Belice, Nocellara Etnea, Tonda Iblea and Uovo di Piccione were very susceptible. The response of cv. Coratina varied from susceptibility to moderate susceptibility.  相似文献   

15.
Talaromyces flavus, a fungal antagonist of Verticillium dahliae, naturally occurring in clay loam artichoke fields or sandy loam olive groves, is able to survive following application of soil solarization. Survival was almost always linked to an increase in T. flavus populations detected in the rhizosphere of artichoke plants or olive trees with a verticillium wilt history as compared with the untreated control soils. It was evident that soil solarization resulted in the control of the disease in artichoke fields and the recovery of olive trees from V. dahliae infection. It was furthermore proved that solarization had a beneficial long-term effect in controlling V. dahliae for a period of 2 or 3 consecutive years. This could at least partially be attributed to the activity of T. flavus in inhibiting the germination of microsclerotia or causing their death. Aspergillus terreus, another potential V. dahliae antagonist, was also found to survive and occasionally increase following the application of the technique.  相似文献   

16.
Survival, germination, olive colonization, and water-use efficiency (WUE) impairments by Verticillium dahliae could be influenced by cultivar susceptibility or irrigation, and this could modify the irrigation–pathogen–disease relationship. In this study, the combined effects of irrigation and cultivar susceptibility on Verticillium wilt (VW) development were modelled by the temporary assessment of V. dahliae propagules (total inoculum density, density of micropropagules, and sclerotia in wet and air-dried soil; ID, MpD, SwD, and SdD, respectively), root (RCI) and shoot (SCI) colonization indexes, and WUE. The relationship of disease severity to the measured parameters was then explored. Under controlled conditions, plants of cultivars ‘Picual’ and ‘Frantoio’ were irrigated to a high and low rate by varying drip-irrigation frequencies: daily, twice weekly, and a combination of daily for 11 days and then twice weekly. Disease severity and colonization parameters were higher in ‘Picual’, while WUE was higher in ‘Frantoio’. However, high rate and twice weekly and combination treatments significantly increased disease incidence and reduced time-to-symptoms-onset only in ‘Picual’, while high rate reduced WUE and increased relative ID, MpD, and SwD in both cultivars. Irrigation did not affect SCI, but a higher RCI was found at high rate during the development of symptoms in ‘Picual’. By using classification trees to examine parameters—disease severity relationships, it was possible to determine the degree to which VW was affected by irrigation and/or cultivar susceptibility. MpD was the best indicator for VW detection at any time, WUE was best before symptoms developed, and RCI, total ID, and SdD after symptoms developed.  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.
For efficient integrated management of verticillium wilt in olive (VWO), it is important to establish whether irrigation treatments (with Verticillium dahliae‐free water) that mitigate the disease in V. dahliae‐infested soil, also reduce the levels of more and less persistent propagules of the pathogen in the soil. Effects of irrigation on VWO and V. dahliae propagules were evaluated under natural environmental conditions. Potted plants were irrigated (pathogen‐free water) to two ranges of soil water content (RWC; high and low) at three surface drip‐irrigation frequencies (daily, weekly, and daily during some periods and otherwise weekly). VWO and total inoculum density (ID), density of less persistent micropropagules (MpD) and more persistent sclerotia in wet soil (SwD), and sclerotia density for air‐dried soil (SdD) were monitored. A logistic model (multiple sigmoid) of disease incidence revealed the lowest parameter values in treatments irrigated daily. Daily frequency of irrigation showed significantly lower disease incidence (39.2%) and disease intensity index (43.9%) and MpD (88.0%) values as areas compared with other frequencies, regardless of the RWC. High RWC significantly reduced (70.8–84.9%) ID, SwD and SdD as areas, but significantly increased (18.0%) the incidence of infected plants (IIP), regardless of the irrigation frequency. The disease incidence was not correlated with temperature. Daily irrigation to low RWC mitigated the VWO and the IIP, kept soil to the lowest MpD and resulted in the lowest SdD level at the end of the trial. Results suggested that less persistent propagules could have played a part in the disease development.  相似文献   

19.
Verticillium wilt of olive was first recorded in Syria in mid-1978 and confirmed as due to Verticillium dahliae. This article reports observations made in a comprehensive survey of the disease in nine provinces over 7 years. Percent infection varied from 0.85 to 4.5 in different provinces. Newly planted groves in lowland areas showed more infection than older groves in hilly areas. Isolation of V. dahliae was possible at all times of year. Young trees were more susceptible to wilt than older ones. The performance of 13 local cultivars against wilt was studied under natural field conditions and found to vary greatly from susceptible to resistant. Agricultural practices greatly affect spread of the disease. High disease incidence was observed in irrigated groves compared with non-irrigated, and correlated positively with number of ploughings. Verticillium wilt causes a loss between 1 and 2.3% of total olive production annually.  相似文献   

20.
Olive groves have been established during the last decade in the coastal area of Halkidiki and in the northern part of the Kassandra peninsula (GR). Visual symptoms of verticillium wilt were observed recently all over this area, particularly in young trees of cv. Hondrolia Halkidikis but not in the occasional old trees already in the orchards. The symptoms appeared regardless of the previous crop (cotton or not), so the nurseries supplying the farmers with young trees were assumed to be the primary source of infection. A survey of olive nurseries in the area was conducted during 1991. Eleven out of the total 18 nurseries in the area were located in the Verticillium dahliae-infested zone and 9 of these were sampled. Three-year-old olive seedlings were selected and isolations were made from the xylem onto PDA acidified with 0.25% lactic acid. V. dahliae-infected seedlings were detected in 4 out of the 9 nurseries examined. The presence of infected young trees in nurseries covering 15.6% of the total nursery area provided strong evidence that nurseries may be responsible for the recent expansion of verticillium wilt in the area.  相似文献   

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