Soil disinfestation options in Aydın province,Turkey, strawberry cultivation

Two field experiments were conducted in the two successive seasons of 2005/2006 and 2006/2007 in strawberry-growing areas of Aydin province of Turkey to (a) compare soil solarization and metam sodium (MS) combinations with low-density polyethylene (LDPE) and virtually impermeable film (VIF); and (b) evaluate strawberry fruit yield, soilborne disease and weed control efficacy. Disinfestation treatments were as follows: (i) raised bed solarization for about 6 weeks, (ii) raised bed solarization for 3 weeks, (iii) raised bed solarization for 2 weeks + MS (50 ml m^-2), (iv) MS (50 ml m^-2) with LPDE (v) MS (100 ml m^-2) with LDPE, (vi) MS (50 ml m^-2) with VIF, (vii) MS (100 ml m^-2) with VIF. Results indicated that Macrophomina phaseolina and Fusarium spp. were the major fungal pathogens isolated from the crown of dead or dying plants in both cropping seasons. MS treatment (100 ml m^-2) through the drip irrigation system under LDPE sheet or VIF reduced soilborne diseases significantly while reduced dosage of MS (50 ml m^-2) under LDPE or VIF and in combination with 2-week soil solarization controlled the soilborne diseases to a greater extent than soil solarization treatments. All treatments controlled the following weed species: Portulaca oleracea, Amaranthus spp., Poa annua, Alopecurus myosuroides, Matricaria chamomilla, Digitaria sanguinalis, Raphanus raphanistrum, Seteria verticillata, Chenopodium album, Stelleria media, Capsella bursa-pastoris, Echinochloa cruss-galli, Veronica hederifolia, Lamium amplexicaule and Silybum marianum. None of the treatments provided acceptable control of horseweed (Conyza canadensis). Metam sodium application (100 ml m^-2) significantly increased yields by 18.5% and 14.5% in the 2005/2006 and 21.6% and 18.5% in the 2006/2007 season under LDPE and VIF, respectively, while marketable fruit yield was not significantly increased by soil solarization treatments in either trial. There was no significant difference between MS applications under LDPE and VIF for the weed and disease control, and marketable fruit yield.     

Efficient in vitro multiplication in Ornithogalum ulophyllum Hand.-Mazz. from twin scale explants

Ornithogalum ulophyllum Hand.-Mazz. with beautiful white flowers is an important medicinal and ornamental plant of the Middle Eastern countries and need exploitation for commercial propagation. The study reports in vitro mass proliferation of bulblets achieved from twin scales and “in vitro regenerated bulblet” explants on MS medium supplemented with various concentrations of BAP–NAA. The best regeneration on twin scales and “in vitro regenerated bulblets” was obtained on MS medium containing 2 mg l⁻¹ BAP–0.5 mg l⁻¹ NAA and 2 mg l⁻¹BAP–1 mg l⁻¹ NAA, respectively. However, bulb scales seemed to be more potent for bulblet regeneration. A large number of the developing bulblets rooted on the regeneration medium. Remaining non-rooting bulblets were rooted on MS medium containing 1 mg l⁻¹ NAA. All plants were acclimatized in the environmental chamber for 4 weeks and were transferred to the greenhouse for flowering. Regenerated bulblets developed into morphologically normal plants.     

Use of different plastics for soil solarization in strawberry growth and time–temperature relationships for the control of <Emphasis Type="Italic">Macrophomina phaseolina</Emphasis> and weeds

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 sheet-covered plots, whereas it was 27,365 kg.ha⁻¹ for untreated control plots.     

Weed hosts of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> in cotton fields in Turkey and characterization of <Emphasis Type="Italic">V. dahliae</Emphasis> isolates from weeds

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.     

A laboratory bioassay for evaluating pathogenicity of Macrophomina phaseolina and Rhizoctonia solani isolates to strawberry stolons

Macrophomina phaseolina and Rhizoctonia spp. are the most important soilborne pathogens of the strawberry crop that cause seriously reduced yields. Various methods are being used to determine pathogenicity of these fungi isolated from strawberry; however, they take a long time to grow strawberry plants. They also encounter some problems to provide a large number of healthy plants for the pathogenicity tests. Therefore, the aim of this study was to develop a faster and more reliable pathogenicity test for soilborne fungal pathogens of strawberry by using the stolons of healthy strawberry plants. The stolon inoculation method was demonstrated to be easy and rapid for properly distinguishing soilborne fungal species of strawberry, whether pathogenic or non-pathogenic, and also for assessing the isolates for virulence.