Verticillium wilt (caused by V. dahliae) is an important soilborne disease that limits watermelon (C. lanatus) production in Washington State and worldwide (du Toit et al., 2005; Dung and Weiland, 2014; Johnson, 2012; Paplomatas et al., 2000; Paroussi et al., 2007; Sunseri and Johnson, 2001; Wimer et al., 2015). Once established in the field, V. dahliae is extremely difficult to manage because of its wide host range and long-lived survival structures (microsclerotia), which can persist in soil or plant debris for up to 14 years, and can remain viable up to 30 °C (Berlanger and Powelson, 2000; Klosterman et al., 2009; Tjamos, 1989). Losses from verticillium wilt have led at least one major Washington grower to discontinue watermelon production, and other growers have experienced yield reduction of 25% to 75% (J. Loos and M. Nelson, personal communication, 2015). Preplant soil fumigation with methyl bromide had been used for over 50 years to control V. dahliae (Carpenter et al., 2000; Klosterman et al., 2009); however, methyl bromide was eliminated from use in most countries under the Montreal Protocol and as part of the Clean Air Act in the United States (Carpenter et al., 2000; U.S. Environmental Protection Agency, 2015). Other available soil fumigants such as Telone (1,3-dichloropropene + chloropicrin) and Vapam HL (metam sodium) are not always reliable for controlling V. dahliae (Davis et al., 2008; Klosterman et al., 2009; Woodward et al., 2011). As there is no resistance in watermelon against V. dahliae, alternative strategies that are environmentally sustainable are critically needed to achieve successful management.
Commercial grafting of cucurbits originated in the 1920s in Japan with the primary intent of managing soilborne pathogens (Oda, 2007; Sakata et al., 2007). The practice of grafting was expanded as a means to improve management of abiotic stresses (e.g., high soil salinity, drought, high temperature) to reduce the reliance on chemical and fertilizer inputs, and enhance fruit quality (Colla et al., 2010; Proietti et al., 2008). Today, grafting cucurbitaceous crops is an important integrated pest management strategy used worldwide to control several soilborne pathogens, including V. dahliae (Buller et al., 2013; Cohen et al., 2007; Davis et al., 2008; Guan et al., 2012; Louws et al., 2010), but has not been widely adopted in the United States, primarily because it is perceived as expensive and growers have limited knowledge about grafting (Cushman, 2009; Davis et al., 2008; Leonardi and Romano, 2004). Yet, researchers have consistently demonstrated that grafting can reduce severity of V. dahliae in watermelon (Johnson, 2012; King et al., 2008; Louws et al., 2010; Wimer et al., 2015). Grafting watermelon onto disease-tolerant rootstocks can delay onset of verticillium wilt symptoms by up to 3 weeks, thus allowing sufficient time for crop maturation (Paplomatas et al., 2002; Wimer et al., 2015). Paroussi et al. (2007) observed that verticillium wilt incidence decreased on grafted watermelon plants grown in artificially inoculated soil, and Buller et al. (2013) and Wimer et al. (2015) both observed reduced verticillium wilt severity of grafted watermelon plants at a naturally infested field site in western Washington harboring a relatively high soil population of V. dahliae (18.0 cfu/g).
In addition to grafting, the use of plastic mulch is another alternative disease management practice. Although black polyethylene mulch is the standard mulch type used in vegetable production (Gordon et al., 2010), clear plastic mulch absorbs 5%, reflects 11%, and transmits 84% of radiation, thereby leading to higher soil temperature under the mulch (Gough, 2001; Tarara, 2000). Soil solarization can occur when temperature exceeds 30 °C and has been shown to be effective in controlling soilborne pathogens and nematodes, as well as weed seeds and seedlings (Elmore et al., 1997). Studies show that by using a clear plastic tarp on soil to achieve solarization, verticillium and fusarium wilts of several crops can be successfully controlled (Ashworth and Gaona 1982; Katan, 1984). Moreover, Rajablarijani and Aghaalikhani (2011) indicated that plants grown with clear plastic mulch had the highest early yields compared with plants grown with black and silver/black plastic mulch. In Washington, some watermelon growers sometimes use clear plastic mulch to increase plant growth rate, thereby decreasing days to maturity. The objective of this study was to investigate the efficacy of grafting onto disease-resistant rootstocks and using clear plastic mulch for controlling verticillium wilt in watermelon.
AgWeatherNet 2016 The Washington agricultural weather network. 15 Mar. 2015. <http://weather.wsu.edu/>.
Ashworth, L.J. Jr & Gaona, S.A. 1982 Evaluation of clear polyethylene mulch for controlling Verticillium wilt in established pistachio nut groves Phytopathology 72 243 246
Berlanger, I. & Powelson, M.L. 2000 Verticillium wilt. The Plant Health Instructor. 16 Sept. 2013. <http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/VerticilliumWilt.aspx>.
Bruton, B.D., Fish, W.W., Roberts, W. & Popham, T.W. 2009 The influence of rootstock selection on fruit quality attributes of watermelon Open Food Sci. J. 3 15 34
Buller, S., Inglis, D. & Miles, C. 2013 Plant growth, fruit yield and quality, and tolerance to verticillium wilt of grafted watermelon and tomato in field production in the Pacific Northwest HortScience 48 1 7
Calderon, R., Lucena, C., Trapero-Casas, J.L., Zarco-Tejada, P.J. & Navas-Cortes, J.A. 2014 Soil temperature determines the reaction of olive cultivars to Verticillium dahliae pathotypes PLoS One 9 10e110664doi: 10.1371/journal.pone.0110664
Carpenter, J., Gianessi, L. & Lynch, L. 2000 The Economic impact of the scheduled U.S. phase-out of methyl bromide. Natl. Ctr. Food Agr. Policy. Bul. 756
Cohen, R., Burger, Y. & Horev, C. 2007 Introducing grafted cucurbits to modern agriculture: The Israeli experience Plant Dis. 91 8 916 923
Colla, G., Suarez, C.M.C., Cardarelli, M. & Rouphael, Y. 2010 Improving nitrogen use efficiency in melon by grafting HortScience 45 559 565
Cushman, K. 2009 Grafting techniques for watermelon. Univ. Fl. Coop. Ext. Serv. Gainesville, FL
Davis, A.R., Perkins-Veazie, P., Sakata, Y., Lopez-Galarza, S., Maroto, J.V., Lee, S., Huh, Y., Sun, Z., Miguel, A., King, S.R., Cohen, R. & Lee, J. 2008 Cucurbit grafting Crit. Rev. Plant Sci. 27 50 74
Dung, J.K.S. & Weiland, J. 2014 Verticillium wilt in the Pacific Northwest. PNW Plant disease management handbook. 25 Aug. 2015. <http://pnwhandbooks.org/plantdisease/pathogen-articles/common/fungi/verticillium-wilt-pacific-northwest>.
Elmore, C. L., Stapleton, J. J., Bell, C. E. & Devay, J. E. 1997 Soil solarization: A nonpesticidal method for controlling diseases, nematodes, and weeds. Univ. California Div. Agr. Natural Recourses Publ. 21377
Georgia Vegetable Team 2000 Commercial watermelon production. Univ. Ga. Coop. Ext. Serv. Bul. 996.V
Gordon, G.G., Foshee, G.W., Reed, S.T., Brown, J.E. & Vinson, E.L. 2010 The Effects of colored plastic mulches and row covers on the growth and yield of okra HortTechnology 20 224 233
Gough, R.E. 2001 Color of plastic mulch affects lateral root development but not root system architecture in pepper HortScience 36 66 68
Guan, W., Zhao, X., Hassell, R. & Thies, J. 2012 Defense mechanisms involved in disease resistance of grafted vegetable HortScience 47 164 170
Hemphill, D. 2010 Oregon vegetables. 13 Sept. 2016. <http://horticulture.oregonstate.edu/content/watermelon-0>.
Huitron-Ramirez, M.V., Ricardez-Salinas, M. & Camacho-Ferre, F. 2009 Influence of grafted watermelon plant density on yield and quality in soil infested with melon necrotic spot virus HortScience 44 1838 1841
Johnson, S.J. 2012 Grafting eggplant, tomato, and watermelon to manage Verticillium wilt caused by Verticillium dahliae. MS Thesis, Washington State Univ., Pullman, WA
Katan, J. 1984 Soil solarization. In: C. Van Assche (ed.). Second International Symposium on Soil Disinfestation. Acta Horticulturae. Intl. Soc. Hort. Sci., Leuven, Belgium
Klosterman, S.J., Atallah, Z.K., Vallad, G.E. & Subbarao, K.V. 2009 Diversity, pathogenicity, and management of Verticillium species Annu. Rev. Phytopathol. 47 39 62
Louws, F.J., Rivard, C.L. & Kubota, C. 2010 Grafting fruiting vegetables to manage soilborne pathogens, foliar pathogens, arthropods and weeds Sci. Hort. 127 127 146
Miles, C., Hesnault, L., Johnson, S., Kreider, P. & Dabirian, S. 2016 Vegetable grafting: Watermelon. Washington State Univ. Ext. Pub. FS100E. 15 Sept. 2016. <http://cru.cahe.wsu.edu/CEPublications/FS100E/FS100E.pdf>.
Nagata, M. & Yamashita, I. 1992 Simple method for simultaneous determination of chlorophyll and carotenoids in tomato fruit J. Jpn. Soc. Food Sci. Tech. 39 925 928
Oda, M. 2007 Vegetable grafting in Japan. In: J. Janick (ed.). Proc. XXVII IHC on Global Hort.: Diversity and Harmony. Acta Hort 759:175–180
Oms-Oliu, G., Odriozola-Serrano, I., Soliva-Fortuny, R. & Martin-Belloso, O. 2009 Effects of high-intensity pulsed electric field processing conditions Food Chem. 115 1312 1319
Paplomatas, E.J., Elena, K. & Tsagkarakou, A. 2000 Screening tomato and cucurbit rootstocks for resistance to Verticillium dahliae EPPO Bul. 30 2 239 242
Paplomatas, E.J., Elena, K., Tsagkarakou, A. & Perdikaris, A. 2002 Control of Verticillium wilt of tomato and cucurbits through grafting of commercial varieties on resistant rootstocks Acta Hort. (ISHS) 579 445 449
Paroussi, G., Bletsos, F., Bardas, G.A., Kouvelos, J.A. & Klonari, A. 2007 Control of Fusarium and Verticillium wilt of watermelon by grafting and its effect on fruit yield and quality. Proc. IIIrd Balkan Symp. Veg. and Potatoes Acta Hort. (ISHS) 729 281 285
Perkins-Veazie, P., Collins, J.K., Pair, S.D. & Roberts, W. 2001 Lycopene content differs among red-fleshed watermelon cultivars J. Sci. Food Agr. 81 983 987
Proietti, S., Rouphael, Y., Colla, G., Cardarelli, M., De Agazio, M., Zacchini, M., Rea, E., Moscatello, S. & Battistelli, A. 2008 Fruit quality of mini-watermelon as affected by grafting and irrigation regimens J. Sci. Food Agr. 88 1107 1114
Qi, H.Y., Li, T.L., Liu, Y.F. & Li, D. 2006 Effects of grafting on photosynthesis characteristics, yield, and sugar content in melon J. Shenyang Agr. Univ. 37 155 158
Rajablarijani, H.R. & Aghaalikhani, M. 2011 Non-chemical weed control in winter canola (Brassica napus L.). In: Proc. 2nd Intl. Conf. Agr. Animal Sci., IPCBEE 22:30–34
Sakata, Y., Ohara, T. & Sugiyama, M. 2007 The history and present state of the grafting of cucurbitaceous vegetables in Japan Acta Hort. 731 159 170
Sunseri, M. & Johnson, D.A. 2001 Verticillium wilt. Wash. State Univ. Coop. Ext. Bul. EB1908, Pullman, WA
Tjamos, E.C. 1989 Problems and prospects in controlling Verticillium wilt. NATO ASI Series 28:441–446
University of California 2010 SoilWeb: Online soil survey browser. California Soil Resource Lab, Davis, CA. 12 Jan. 2016. <http://casoilresource.lawr.ucdavis.edu/>.
U.S. Environmental Protection Agency 2015 The phase out of methyl bromide. Ozone layer protection: Regulatory Program. 6 Oct. 2015. <http://www.epa.gov/ozone/mbr/>.
Wimer, J.A., Miles, C.A. & Inglis, D.A. 2015 Evaluating grafted watermelon for verticillium wilt severity, yield, and fruit quality in Washington State HortScience 50 1332 1337
Woodward, J.E., Wheeler, T.A., Cattaneo, M.G., Russell, S.A. & Baughman, T.A. 2011 Evaluation of soil fumigants for management of Verticillium wilt of peanut in Texas Plant Health Prog. doi: 10.1094/PHP-2011-0323-02-RS
Wu, Y.F., Chen, Y. & Zhao, Y.J. 2006 Effect of pumpkin stocks on growth, development, yield, and quality of grafted muskmelon Fujian J. Agr. Sci. 21 354 359
Xu, C.Q., Li, T.L. & Qi, H.Y. 2005 Effects of grafting on the photosynthetic characteristics, growth situation, and yield of netted muskmelon China Watermelon and Melon 2 1 3