The spread of aggressive fungal pathogens into previously non-endemic regions is a major threat to plant health and food security. Analyses of the spatial and genetic structure of plant pathogens offer valuable insights into their origin, dispersal mechanisms and evolution, and have been useful to develop successful disease management strategies. Here, we elucidated the genetic diversity, population structure and demographic history of worldwide invasion of the ascomycete Verticillium dahliae, a soil-borne pathogen, using a global collection of 1100 isolates from multiple plant hosts and countries. Seven well-differentiated genetic clusters were revealed through discriminant analysis of principal components (DAPC), but no strong associations between these clusters and host/geographic origin of isolates were found. Analyses of clonal evolutionary relationships among multilocus genotypes with the eBURST algorithm and analyses of genetic distances revealed that genetic clusters represented several ancient evolutionary lineages with broad geographic distribution and wide host range. Comparison of different scenarios of demographic history using approximate Bayesian computations revealed the branching order among the different genetic clusters and lineages. The different lineages may represent incipient species, and this raises questions with respect to their evolutionary origin and the factors allowing their maintenance in the same areas and same hosts without evidence of admixture between them. Based on the above findings and the biology of V. dahliae, we conclude that anthropogenic movement has played an important role in spreading V. dahliae lineages. Our findings have implications for the development of management strategies such as quarantine measures and crop resistance breeding.

Field experiments were conducted in the two cropping seasons between 2002 and 2004 to determine effects on soil-borne diseases, weeds and yield of strawberry of raised bed solarization (RBS), alone or with chicken manure (CM) amendment, methyl bromide (MB), TeloDrip (1,3-dichloropropene + chloropicrin), short RBS combined with reduced doses of metam sodium (MS) and TeloDrip. In both seasons, raised bed soil solarization (for 7 weeks) alone or with CM amendment (10 t/ha), MS (50 ml/m 2 ) after 2-week RBS, and MB (50 g/m 2 ) significantly reduced soil-borne diseases (caused by Rhizoctonia spp. and Phytophthora cactorum) while application of TeloDrip at a rate of 500 kg/ha and a half-dose after short solarization controlled the soil-borne diseases to a lesser extent in the 2003-2004 cropping season. All treatments provided effective control of four weed species; annual bluegrass (Poa annua), common purslane (Portulaca oleracea), redroot pigweed (Amaranthus retroflexus) and barnyardgrass (Echinochloa crus-galli) but not horseweed (Conyza canadensis). In the first year trial, total marketable yields from RBS with or without CM and 2-week solarization plus MS were equivalent to yields produced by MB treatment whereas only raised bed soil solarization and CM amendment led to the same increase of yield as MB in the second year.

This study was aimed to determine the causal agents of soil-borne fungal diseases that pose a threat to the strawberry production in Aydin, Turkey and to investigate the potential effects of solarization and three fumigants (metam sodium, dazomet and methyl bromide) on these diseases. As the agents of the diseases, Rhizoctonia solani Ku¨hn. Phytophthora cactorum (Lebert and Cohn) J. Schro¨t., Verticillium dahliae Kleb. were detected. Trials to determine the effects of solarization and the fumigants were conducted in two successive cropping seasons of strawberries. Soil temperatures at 0, 10 and 20 cm depth of solarized and unsolarized plots were measured. In 1998-99, soil solarization gave significantly better control of the diseases than fumigants and the highest yield of 59 tons/ha was obtained from the solarized plots. This is followed by dazomet (50 g/m 2 ) treated plots with the yield of 34.4 tons/ha, while non-treated control plots yielded 22.4 tons/ha. In 1999-2000, all treatments gave higher yields than non-treated control plots (26.1 tons/ha), but there were no difference (P < 0.05) among the treated plots where the yields varied between 33.3 and 36.1 tons/ha.

A weed survey conducted in 2004 and 2005 in Aydin province of Turkey showed that Solanum nigrum, Xanthium strumarium, Amaranthus retroflexus, Portulaca oleracea, Sonchus oleraceus and Datura stramonium were the most prevalent weeds in the cotton fields exhibiting Verticillium wilt. Verticillium dahliae Kleb. was recovered from A. retroflexus and X. strumarium in those cotton fields. This is the first report of V. dahliae occurring naturally in A. retroflexus in Turkey. Pathogenicity tests on cotton and weeds showed that the virulence of V. dahliae isolates from weeds was higher on cotton plants than on weeds, with the disease severity ranging from 31.7% to 98.0%. Disease severity of V. dahliae isolates was 54.7-93.9% on eggplant, 23.7-51.6% on cucumber and 11.0-16.4% on tomato, whereas it did not cause any disease symptoms, or only low levels, on pepper and bell pepper. Two vegetative compatibility groups (VCGs) were identified among seven tested weed isolates: VCG2A (two isolates) and VCG2B (three isolates) using international reference strains.

The aim of this study was to determine the effect of soil solarization on soilborne diseases, weeds and plant yields by using polyethylene film (30-μm-thick) containing different additives [ultraviolet (UV), ultraviolet + infrared (UV + IR), ultraviolet + infrared + anti-fog + anti-dust (UV + IR + AF + AD)], and used polyethylene film (260-μm-thick). Trials were conducted in commercial strawberry (Fragaria ananassa cv. 'Camarosa') fields in the town of Sultanhisar in Aydin province, Turkey, between 2007 and 2009. The highest soil temperatures at the depth of 10 cm under a polyethylene sheet containing UV + IR + AF + AD were 54°C in 2007 and 50.7°C in 2008. During the 2007 growing season, collapse and death of strawberry plants were not detected. At the end of the 2008 season (May-June), collapsed and dying strawberry plants were observed. Pure cultures of Macrophomina phaseolina and Rhizoctonia solani were isolated from affected roots and crowns of plants. Viability studies of M.phaseolina were conducted under various field conditions and temperatures and M. phaseolina sclerotia survived more than 18 days at 45°C. There was a sharp decline in M. phaseolina at 50°C, where it survived for 19 h but was completely killed at 20 h. It first lost viability after 17 h at 50°C and after 60 min at 55°C. In the field, solarization did not reduce the viability of M. phaseolina at a soil depth of 10 or 20 cm; however, a significant reduction (66%) in survival was determined at a soil depth of 5 cm. All treatments controlled Portulaca oleracea, Amaranthus spp., Digitaria sanguinalis, Echinochloa crus-galli, Veronica hederifolia, Raphanus raphanistrum, Setaria verticillata and Mercurialis annua at a rate of 100%, but no treatment was effective on Cyperus rotundus. The marketable fruit yield was 38,004 kg.ha −1 for UV + IR, 35,834 kg.ha −1 for UV-added polyethylene film and 35,368 kg.ha −1 for used polyethylene sheetcovered plots, whereas it was 27,365 kg.ha −1 for untreated control plots.

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Samples of strawberry transplants were randomly collected from 47 growers in Aydın province of Turkey. A total of 26 Fusarium oxysporum isolates were identified by morphological characterization, sequence analysis of factor-1 alpha gene, and pathogenicity tests on strawberry, cucumber and tomato seedlings. To our knowledge, this is the first report of the presence of F. oxysporum in strawberry transplants in Turkey.Keywords Fragaria ananassa . Fusarium wilt . Fusarium oxysporum f. sp. fragariae Turkey is the fourth largest strawberry producer in the world, with an annual production of 372 thousand tones (FAOSTAT 2015). Recent studies indicated that Macrophomina phaseolina and Fusarium spp. were the major fungal pathogens isolated from the crown of dead or dying strawberry plants in Aydın province where 13 % of Turkey's strawberry production takes place (Benlioglu et al. 2014). During two cropping seasons 2009/10 and 2010/11, samples of strawberry transplants from 47 growers were randomly collected and examined for the presence of Fusarium oxysporum. After observation of longitudinal sections of transplants, fungal isolations were made aseptically on Potato Dextrose Agar (PDA) plates from internal vascular and cortical tissues of the crowns exhibiting a brown-to-orange-brown discoloration.Fusarium-like colonies with light purple mycelia and orange reverse colony colours (Fig. 1) were sub-cultured on carnation leaf agar, and observed for microscopic conidial characteristics after obtaining single-spore cultures (Leslie and Summerell 2006). Twenty-six out of 73 Fusarium oxysporum-like strains exhibiting identical morphological characteristics were selected randomly for further identification tests. Macroconidia were 3 to 5 septate, straight to slightly curved, gently tapered and curved at the apical end (15.7 to 35.4 × 2.9 to 4.3 μm). Microconidia were oval elipsoid, 0-septate and formed abundantly on short monophialides (6.1 to 12.5 × 2.1 to 3.6 μm) (Fig. 2). Pathogenicity tests were conducted in a growth chamber on 4-week-old strawberry transplants propagated from runners (cv. Camarosa), 4-week-old tomato (cv. Supermarmande) and cucumber (cv. Çengelköy) plants. Spore suspensions (10 5 conidia per ml) for each of 26 isolates were prepared and the roots of 5 plants each were dipped in each spore suspension for 15 min and each plant was transplanted into plastic pot containing sterilized peat. Plants were maintained at 24 ± 2°C with a daily 16-h photoperiod of fluorescent light. Control plants were soaked in water prior to planting. Within 8 weeks, all inoculated strawberry plants exhibited wilting and decline symptoms (Fig. 3) including root rot and vascular discoloration of the crown. All treated tomato and cucumber plants, including control plants did not show any disease symptoms, and vascular discoloration was not observed when longitudinal or transverse cuts were made on the main stems or crown. The pathogenicity test was conducted twice. The fungus was successfully reisolated from the crown of inocul...