Arava Research and Development

Arava, Israel

Arava Research and Development

Arava, Israel
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Cohen R.,Newe Ya'ar Research Center | Pivonia S.,Arava Research and Development | Crosby K.M.,Texas A&M University | Martyn R.D.,Purdue University
Horticultural Reviews | Year: 2012

Monosporascus root rot and vine decline (sudden wilt), caused by the soilborne fungus Monosporascus cannonballus, has become one of the most important diseases of melon and watermelon worldwide. The fungus infects the roots early in the growing season, causing severe necrosis and ultimately resulting in a sudden and severe collapse of the vines late in the season. Melon (Cucumis melo) and watermelon (Citrullus lanatus) are the most severely affected, but all cucurbits tested to date can be infected; severe disease, however, is rarely observed except on melon and watermelon. The extensive root systems of the Cucurbita spp. and Lagenaria spp. offer some tolerance to the disease, which makes them suitable to serve as rootstocks. Fruit load, heat, drought, and other stresses may exacerbate disease symptoms and cause a collapse of the vines. Monosporascus cannonballus is somewhat unique as an ascomycete as it produces only one large ascospore per ascus, while two other species in the genus produce more than one. All species of the genus are pseudothermophiles, growing optimally at 25o-30oC, and are presumably native to hot, semiarid climates. Monosporascus spp. have been isolated from roots of numerous plant species, including dicots and monocots, although disease symptoms in plants other than cucurbits are rare. Monosporascus was described as a new genus and species in 1974, but pathogenicity to cucurbits was not established until 1983. Disease development in the field requires warm soil temperatures above 25oC. Ascospores are the overseasoning propagule and germinate in the presence of host root exudates and soil microflora. Initial infection occurs in the fine feeder roots, causing severe necrosis. The stimulation of tyloses in the xylem tissue leads to reduced water uptake and translocation, causing the vines to wilt suddenly. Management of sudden wilt has relied predominantly on preplant soil fumigation with methyl bromide. While effective, this method is not sustainable, given the phase-out of methyl bromide. Sanitation techniques that remove infected roots from the soil immediately after harvest can reduce the inoculum buildup in the soil and disease the following cycle but could be cost prohibitive in some production areas. Timely application of fungicides through the drip irrigation system during the growing season offers a cost-effective alternative to fumigation. Grafting melon or watermelon onto tolerant Cucurbita spp. rootstocks is gaining acceptance; however, there may fruit quality issues in some instances. The development of host plant resistance utilizing exotic C. melo germplasm has been pursued with promising results, but it is a slow process and has focused on just a few commercial melon types. An integrated strategy continues to evolve for control of sudden wilt and includes enhancing plant root system development, timely fungicide application, irrigation and soil management practices, and adoption of improved rootstocks and resistant melon lines. © 2012 Wiley-Blackwell. Published 2012 by John Wiley and Sons, Inc.

Pivonia S.,Arava Research and Development | Gerstl Z.,Institute of Soil, Water and Environmental Sciences | Maduel A.,Arava Research and Development | Levita R.,Arava Research and Development | Cohen R.,Newe Ya'ar Research Center
European Journal of Plant Pathology | Year: 2010

Sudden wilt (vine decline) of melon caused by Monosporascus cannonballus is a problem in arid and semiarid regions worldwide. Preplanting soil disinfestation with methyl bromide, a common treatment for disease management, has been banned in many countries, raising the need for alternative disease-control measures. Soil fungicide application during the growing season is one possible treatment. Twelve fungicides were evaluated in vitro for M. cannonballus suppression, seven of those were evaluated under field conditions. The fungicides azoxistrobin, prochloraz and pyraclostrobin + boscalid exhibited high and similar efficacies in controlling sudden wilt disease under field conditions. Fludioxonil applied at high rates was also effective but was phytotoxic. Fluazinam, the first fungicide found capable of suppressing sudden wilt and one which has been used in Israel since 2000, was less effective. The results indicate that two applications of a fungicide during the short fall season should be sufficient for effective control of the disease. In the long spring season, at least three applications are needed to protect the melon crop. Melon fruits were examined for fungicide residues and only boscalid residues were found. This fungicide was therefore limited to the first application before fruit set. © 2010 KNPV.

Posmanik R.,Ben - Gurion University of the Negev | Sinay B.B.,Mevoot HaNegev Agricultural High School | Golan R.,Arava Research and Development | Nejidat A.,Ben - Gurion University of the Negev | Gross A.,Ben - Gurion University of the Negev
Water, Air, and Soil Pollution | Year: 2011

A major input in intensive organic agriculture is nutrient-rich liquid fertilizers. Guano and other fowl manure are frequently digested in water extracts, and the supernatant is supplied as fertilizer. The resultant manure biowaste (MBW) is commonly disposed of to the environment, posing potential pollution and health risks. The study aims were to determine two types of fowl MBWs for their chemical properties before and after lime treatment and to test their reuse potential as soil amendment. Guano and layer manure were digested, and the residues' chemical properties were analyzed before and after lime treatment. MBWs were then air-dried and used as a soil amendment in a parsley-growing experiment. The lime-treated MBW composition met the European standards for high-quality biowaste compost. Both digested and lime-treated MBWs had residual nitrogen, 3% and 1% in guano and layer manure, respectively. Parsley grown in soil amended with layer MBW had 100% survival, high yield, and good crop quality compared with controls. Plants grown with soil amended with guano biowaste exhibited lower yield and only 50% survival. These findings indicate that the current practice of disposing guano biowaste to the environment may pollute soil and water bodies, while the land spread of lime-treated layer MBW is safe and may improve soil fertility. © 2010 Springer Science+Business Media B.V.

Edelstein M.,Israel Agricultural Research Organization | Cohen R.,Israel Agricultural Research Organization | Elkabetz M.,Israel Agricultural Research Organization | Pivonia S.,Arava Research and Development | And 3 more authors.
HortScience | Year: 2016

Melon plants grafted on Cucurbita rootstock may suffer from nutritional deficiencies due to reduced absorption and translocation of minerals to the foliage. Melon (Cucumis melo L.) cv. 6023 was grafted onto two interspecific Cucurbita rootstocks (Cucurbita maxima 3 Cucurbita moschata) ‘TZ-148’ and ‘Gad’. Nongrafted melons were used as controls. Two fertilization field experiments were conducted in walk-in tunnels in the northern Arava valley of southern Israel. Two fertigation regimes were used: 1) standard and 2) enriched for magnesium (Mg; 150 mg·LL-1), manganese (Mn; 7.5 mg·LL-1), and zinc (Zn; 0.75 mg·LL-1) to increase the concentrations of the lacking elements. The enriched fertigation significantly increased Mn, Zn, and Mg contents in the leaf tissue. Concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), chloride (Cl), iron (Fe), and boron (B) were unaffected by the enriched fertilizer. There were no deficiency symptoms in grafted plants supplied with the enriched fertilizer. © 2016, American Society for Horticultural Science. All rights reserved.

Lugassi-Ben-Hamo M.,Ben - Gurion University of the Negev | Kitron M.,Arava Research and Development | Bustan A.,Ben - Gurion University of the Negev | Zaccai M.,Ben - Gurion University of the Negev
Scientia Horticulturae | Year: 2010

The effects of shading on lisianthus (Eustoma grandiflorum) floral transition, plant development, flower yield and quality, and content of starch and soluble sugars were assessed in three cultivars, over two consecutive years. Shading nets affording 67% or 88% reduction in light intensity, were fitted at planting in the greenhouse for periods ranging from 3 to 8 weeks. Meristem morphology at floral transition was characterized by apical meristem widening and the appearance of two bract primordia. Floral transition time was affected by cultivars, but in general, longer and heavier shade treatments delayed floral transition; the longest delay (6 weeks) being recorded in Mariachi White under 88% shade for 7 weeks or under a combined shade treatment of 88% for 3 weeks followed by 67% for 5 weeks. Despite interactions between cultivar and shade treatment, consistent trends were discerned: the heaviest and most prolonged shading reduced yield (up to 40%), cut stem length (up to 15%), and number of flower buds/stem (up to 26%), within cultivar. Total carbohydrates levels were very low, and it is questionable whether changes observed in carbohydrate quantity following shade treatments had any effect on plant growth or flower yield. Rather, it appears that lisianthus is very dependent on current photosynthesis, so that even a brief shading interlude could reduce branching and flower quality. It may be concluded that the intensive shading usually applied is detrimental for lisianthus. © 2009 Elsevier B.V. All rights reserved.

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