Lagenaria siceraria (Mol.) Standl., a viny species of the Cucurbitaceae family, is thought to be among the first domesticated plant species (Cutler and Whitaker, 1967). Its dry, mature fruit is used by people throughout the world for making jars, utensils, tubes, and musical instruments, is used as a vegetable, and is commonly known as the bottle gourd (Decker-Walters et al., 2001, 2004; Erickson et al., 2005). It is also known as the white-flowered gourd or calabash (Jeffrey, 1967). Bottle gourd is indigenous to Africa (Morimoto et al., 2006; Richardson, 1972); however, remains found in archeological digs point to the possibility that it reached temperate and tropical areas in Asia and the Americas over 10,000 years ago. The increased geographical distribution of the bottle gourd plant is likely due to human migration (Erickson et al., 2005), though dispersion of bottle gourd could have occurred through movement across oceans. Bottle gourd fruits are known to have the capacity to float on seas for many months without losing seed viability (Decker-Walters et al., 2004). The crop thrives in a wide range of soil types and is more tolerant of a high water table (Yetisir et al., 2006) and to salt than watermelon Citrullus lanatus (Thunb) Matsum and Nakai (Colla et al., 2005). In addition to the aforementioned comparative advantages of bottle gourd, research should be conducted focusing on the response of bottle gourd to herbicides that are registered in watermelon. This research would provide knowledge for making selections of bottle gourd rootstocks for grafting with watermelon.
More than 105 million tons of watermelon are produced annually on a global scale (Food and Agricultural Organization; http://faostat.fao). The herbicide clomazone (Anonymous, 2005) is widely used in cucurbit crop production in the United States. Clomazone controls many important annual weeds such as barnyardgrass [Echinochloa crus-galli (L.) Beauv], velvetleaf (Abutilon theophrasti Medicus), and cocklebur (Xanthium strumarium L). The recommended use rates for watermelon are 0.17–0.28 kg·ha−1 depending on the soil type. Clomazone can cause moderate injury to young plants that is expressed as chlorosis of leaves and growing tips (Grey et al., 2000). A study performed at the University of Florida demonstrated that preemergence (PRE) applications of clomazone at 0.28 kg·ha−1 to transplanted watermelon grafted to bottle gourd resulted in ≈8% injury (Adkins, 2011).
Previously, differences were reported in clomazone tolerance among genotypes of watermelon and its relatives (Harrison et al., 2011). The most tolerant genotypes were accessions of the African watermelon Citrullus lanatus var. citroides obtained from the U.S. National Plant Germplasm collection; however, other accessions of C. lanatus var. citroides were highly susceptible. About 5-fold higher clomazone concentrations were required to cause equivalent injury and growth reduction in the most tolerant genotypes when compared with susceptible genotypes in a greenhouse concentration–response experiment. Hines and Wilson (1992) also reported that watermelon cultivars varied in clomazone injury in a greenhouse experiment. Staub et al. (1991) screened the U.S. National Plant Germplasm collection of cucumber for clomazone tolerance in the field and identified tolerant and susceptible accessions based on injury ratings. In a greenhouse evaluation of selected accessions, the relative differences in tolerance of the accessions did not range as much as those observed in the field. Al-Khatib et al. (1995) reported differences in clomazone tolerance among five cucumber cultivars in greenhouse and field experiments. Following the observation of differences in clomazone injury in a field trial, Harrison and Keinath (2003) evaluated 67 pumpkin (Cucurbita maxima Pang) cultivars for tolerance in the greenhouse. Differences in tolerance were greatest between the species marketed as pumpkins; however, differences in tolerance were also observed among cultivars within species. Thus, there is a precedent of clomazone tolerance being variable among varieties of cucurbit species. Watermelon was the most sensitive to clomazone when compared with honeydew (Cucumis melo L. var. inodorus Naud), zucchini (Cucurbita pepo L.), winter squash (C. maxima Duch, Ex. Poiret), cucumber (Cucumis sativus L.), and muskmelon (Cucumis melo L. var. reticulatus Naud) (Figueroa and Kogan, 2005) based on early season injury ratings and growth measurements. However, clomazone at up to 0.9 kg·ha−1 did not affect watermelon crop yields. Boyhan et al. (1995) reported that watermelon yields were reduced by clomazone applied PRE at 1.1 kg·ha−1 to direct seeded watermelon. Grey et al. (2000) reported that clomazone applied preplant incorporated at 0.84 kg·ha−1, preplant to the soil surface, and posttransplant to the soil surface caused minor foliar bleaching (14% injury or less), but did not reduce the yields of seeded or transplanted ‘Royal Sweet’ watermelon. Cohen et al. (2008) concluded from a greenhouse study that clomazone applied at 1.0 and 2.0 kg·ha−1 was too injurious to grafted and nongrafted watermelons. Variation among cultivars in clomazone tolerance has been reported in several non-cucurbit crops, including bean (Sikkema et al., 2006), cabbage (Hopen et al., 1992), corn (Keifer, 1989), rice (Mudge et al., 2005; Scherder et al., 2004; Zhang et al., 2004), and sweetpotato (Harrison and Jackson, 2011). The variable tolerance observed in other crops necessitates screening a large number of bottle gourd accessions for clomazone sensitivity to increase the probability of finding a line with high tolerance.
The objectives of these greenhouse experiments were to assess the variability of clomazone tolerance in an extensive bottle gourd germplasm collection and to identify lines with high levels of tolerance. The potential end application would be to select clomazone-tolerant bottle gourd lines that could be used as rootstock to graft to watermelon scions. In the past, bottle gourd rootstock had effectively improved salt tolerance to the watermelon scion (Colla et al., 2010). Certain bottle gourd lines are resistant to multiple viruses that would infect economically important watermelon lines (Ling et al., 2013). Crown rot (Phytophthora capsici Leonian) disease, root-knot nematodes, and whiteflies are reduced with certain bottle gourd varieties as well (Kousik et al., 2012; Levi et al., 2009). A dose–response experiment was conducted to quantify the difference in tolerance between the most and least tolerant accessions.
Adkins, J.I. 2011 Herbicide use in grafted triploid watermelon [Citrullus lanatus (thunb.) Matsumura and Nakai] (Order No. 3514926). Available from ProQuest Dissertations & Theses Global; SciTech Premium Collection (1018715311), Clemson Library loan. Jan. 2012. <http://libproxy.clemson.edu/login?url=http://search.proquest.com/docview/1018715311?accountid=6167>
Al-Khatib, K., Kadir, S. & Libbey, C. 1995 Broadleaf weed control with clomazone in pickling cucumber (Cucumis sativus) Weed Technol. 9 166 172
Anonymous 2005 Command 3ME herbicide label, EPA Reg. No. 279-3158. FMC Corp, Philadelphia, PA
Boyhan, S.P., Kovach, G.E., Norton, B.J., Abrahams, D.R., Hollingsworth, H.M. & Dangler, J.M. 1995 Preemergence herbicides for cantaloupe and watermelon J. Veg. Crop Prod. 1 79 92
Cohen, R., Eizenberg, H.M., Edelstien, M., Horev, C., Lande, T., Porat, A., Achdari, G. & Herschenhorn, J. 2008 Evaluation of herbicides for selective weed control in grafted watermelon Phytoparasitica 36 66 73
Colla, G., Fanasca, A., Cardarelli, M., Rouphael, Y., Saccardo, F., Graifenberg, A. & Curadi, M. 2005 Evaluation of salt tolerance in rootstocks of Cucurbitaceae Acta Hort. 697 469 474
Colla, G., Rouphael, Y., Leonardi, C. & Bie, Z. 2010 Role of grafting in vegetable crops grown under saline conditions Scientia Hort. 127 147 155
Cutler, H.C. & Whitaker, T.W. 1967 Cucurbits from the Techuacan Caves, p. 212–219. In: D.S. Byers (ed.). The prehistory of the Tehuacan valley: Environment and subsistence. University of Texas Press, Austin, TX
Decker-Walters, D., Staub, J.E. & Chung, S.M. 2001 Diversity in landraces and cultivars of bottle gourd (Lagenaria siceraria: Cucurbitaceae) as assessed by random amplified polymorphic DNA Genet. Resources Crop Evol. 48 369 380
Decker-Walters, D.S., Wilkins-Ellert, M., Chung, S.M. & Staub, J.E. 2004 Discovery and genetic assessment of wild bottle gourd (Lagenaria siceraria (Mol.) Standley; Cucurbitaceae) from Zimbabwe Econ. Bot. 58 501 508
Erickson, D.L., Smith, B.D., Clarke, A.C., Sandweiss, D.H. & Tuross, N. 2005 An Asian origin for a 10,000-year-old domesticated plant in the Americas Proc. Natl. Acad. Sci. USA 102 18315 18320
Grey, T.L., Bridges, D.C. & NeSmith, D.S. 2000 Tolerance of cucurbits to the herbicides clomazone, ethanlfluralin, and pendimethalin. II. Watermelon HortScience 35 639 641
Harrison, H.F. Jr & Jackson, D.M. 2011 Greenhouse assessment of differences in clomazone tolerance among sweetpotato cultivars Weed Technol. 25 501 505
Harrison, H.F. Jr, Kousik, K.S. & Levi, A. 2011 Identification of Citrullus lanatus germplasm lines tolerant to clomazone herbicide HortScience 46 684 687
Huang, Y., Thomson, S.J., Molin, W.T. & Reddy, K.N. 2012 Early detection of soybean plant injury from glyphosate by measuring chlorophyll reflectance and fluorescence J. Agr. Sci. 4 117 124
Jeffrey, C. 1967 Cucubitaceae, p. 47–53. In: E. Milne-Redlead and R.M. Polhill (eds.). Flora of tropical east Africa. Crown Agents, London, UK
Kousik, C.S., Donahoo, R.S. & Hassell, R. 2012 Resistance in watermelon rootstocks to crown rot caused by Phytophthora capsici Crop Prot. 39 18 25
Kousik, C.S., Levi, A., Ling, K-S. & Wechter, W.P. 2008 Potential sources of resistance to cucurbit powdery mildew (Podosphaera xanthii) in US plant introductions (PI) of Lagenaria siceraria (bottle gourd) HortScience 43 1359 1364
Levi, A., Thies, J.A., Ling, K., Simmons, A.M., Kousik, C.S. & Hassell, R. 2009 Genetic diversity of Lagenaria siceraria and identification of accessions useful for the development of disease and pest resistant rootstocks Plant Genet. Resources 7 216 226
Ling, K., Levi, A., Adkins, S., Kousik, C.S., Miller, G., Hassell, R. & Keinath, A.P. 2013 Development and field evaluation of multiple virus-resistant bottle gourd (Lagenaria siceraria) Plant Dis. 97 1057 1062
Morimoto, Y., Maundu, P., Kawase, M., Fujimaki, H. & Morishima, H. 2006 RAPD polymorphism of the white-flowered gourd Lagenaria siceraria (Molina) Standl. landraces and its wild relatives in Kenya Genet. Resources Crop Evol. 53 963 974
Mudge, C.R., Webster, E.P., Leon, C.T. & Zhang, W. 2005 Rice (Oryza sativa) cultivar tolerance to clomazone in water seeded production Weed Technol. 19 907 911
Richardson, J.B. III 1972 The pre-Columbian distribution of the bottle gourd (Lagenaria siceraria): A re-evaluation Econ. Bot. 26 265 273
Staub, J., Crubaugh, L., Baumgartner, H. & Hopen, H. 1991 Screening of the cucumber germplasm collection for tolerance to clomazone herbicide Cucurbit Crop Genet. Rep. 14 22 24
Yetisir, H., Çaliskan, M.E., Soylu, S. & Sakar, M. 2006 Some physiological and growth responses of watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai) grafted onto Lagenaria siceraria to flooding Environ. Expt. Bot. 58 1 8
Zhang, W., Webster, E.P., Blouin, D.C. & Linscombe, S.D. 2004 Differential tolerance of rice (Oryza sativa) varieties to clomazone Weed Technol. 18 73 76