Plant Growth, Fruit Yield and Quality, and Tolerance to Verticillium Wilt of Grafted Watermelon and Tomato in Field Production in the Pacific Northwest

Abstract

<jats:p>Growth, fruit yield and quality, and potential tolerance to verticillium wilt (<jats:italic>Verticillium dahliae</jats:italic>) were compared among non-grafted, self-grafted, and grafted triploid watermelon (<jats:italic>Citrullus lanatus</jats:italic> Thunb., ‘Crisp’n Sweet’) and heirloom tomato (<jats:italic>Solanum lycopersicum</jats:italic>, ‘Cherokee Purple’). Rootstocks for watermelon were ‘Emphasis’ bottle gourd (<jats:italic>Lagenaria sicerarea</jats:italic>) and ‘Strong Tosa’ interspecific squash hybrid (<jats:italic>Cucurbita maxima</jats:italic> × <jats:italic>Cucurbita moschata</jats:italic>), and rootstocks for tomato were ‘Beaufort’ and ‘Maxifort’ interspecific tomato (<jats:italic>Solanum lycopersicum</jats:italic> × <jats:italic>Solanum habrochaites</jats:italic>). Field trials were carried out in 2010 and 2011 at Hermiston and Eltopia (eastern Oregon and Washington, respectively) and Mount Vernon (western Washington). Grafted watermelon had significantly larger stem diameter than non-grafted and self-grafted plants both years at Mount Vernon, whereas there were no differences at Hermiston or Eltopia. Grafted tomato in 2011 had significantly larger stem diameter than non-grafted and self-grafted plants at Eltopia and Mount Vernon, and ‘Beaufort’-grafted plants were significantly taller than other treatments at Mount Vernon. Grafting did not impact watermelon or tomato fruit yield or quality at any location either year. Foliar symptoms of verticillium were not observed on ‘Crisp’n Sweet’ watermelon at the eastern locations either year; however, at Mount Vernon, ‘Emphasis’ and ‘Strong Tosa’-grafted plants had significantly lower verticillium wilt severity than non-grafted and self-grafted plants both years. Microsclerotia were observed in all recovered watermelon stems sampled at Eltopia and Mount Vernon. <jats:italic>V. dahliae</jats:italic> was isolated from non-grafted and ‘Emphasis’-grafted ‘Crisp’n Sweet’ stems at Eltopia and non-grafted, self-grafted, and ‘Strong Tosa’-grafted stems at Mount Vernon. Foliar symptoms of verticillium wilt and microsclerotia in stems were not observed on ‘Cherokee Purple’ plants at either location both years despite site histories of the disease. Grafting with ‘Emphasis’ and ‘Strong Tosa’ rootstocks may be an effective strategy for managing verticillium wilt on watermelon in western Washington; however, grafting ‘Cherokee Purple’ onto ‘Beaufort’ and ‘Maxifort’ did not provide any advantages for tomato under the field conditions of this study.</jats:p>

Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

“…Our work found a decrease in SSC in fruit from grafted plants, which contradicts the work of Buller et al (2013), who found no effect of grafting on SSC in 'Cherokee Purple'. The key difference here being the rootstock types, 'RST-04-106-T' in our study and 'Beaufort' and 'Maxifort' used by Buller et al (2013). Their study found no increase in fruit firmness or lycopene content due to the use of grafting, which is consistent with our findings.…”

“…Alternative rootstocks have been shown to increase plant vigor in environments in which soil pathogens are present. For example, Buller et al (2013) found that stem diameter of 'Cherokee Purple' was larger for plants grafted to the rootstock 'Maxifort' in a soil infested with verticillium wilt, although the disease itself did not affect the plants. Plant height of 'Cherokee Purple' was larger for plants grafted to the rootstock 'Beaufort'.…”

“…Perhaps the most impactful result of grafting tomatoes is greater resistance to soil-borne pests, such as root-knot nematode (Barrett et al, 2012a), verticillium wilt (Buller et al, 2013;Liu et al, 2009), fusarium crown and root rot (Vitale et al, 2014), and bacterial wilt (McAvoy et al, 2012). Specific rootstocks need to be developed, researched, and used for these and other biotic pressures (Guan et al, 2012;Louws et al, 2010).…”

Cucurbitaceae Germplasm Resistance to Verticillium Wilt and Grafting Compatibility with Watermelon

“…Recent studies in Washington have shown that grafting watermelon onto resistant rootstocks is a suitable management option for verticillium wilt (Buller et al, 2013;Dabirian et al, 2017;Wimer et al, 2015a). On a commercial scale, growers in Asia have been using grafting for several decades as a management strategy for biotic stresses such as fusarium wilt and verticillium wilt, and abiotic stresses such as soil salinity and cold stress in watermelon.…”

Field and Greenhouse Evaluations of Cucurbit Rootstocks to Improve Verticillium Resistance for Grafted Watermelon

“…Although Paplomatas et al (2002), Paroussi et al (2007), Buller et al (2013), andWimer et al (2015) have demonstrated that grafting can significantly reduce verticillium wilt of watermelon, no commercial growers in Washington are currently using grafted plants to manage this disease. Adoption of this practice is hindered by the increased costs of grafted seedling production attributed to the extra (and often expensive) seed needed to grow the rootstock, the labor needed to perform the grafting and care for the grafted seedlings, and the special facilities that are required for proper graft union formation (Boughalleb et al, 2007;King et al, 2010;Lee et al, 2010).…”