, all other cucurbits, including bottlegourd [ Lagenaria siceraria (Mol.) Standl.], are vulnerable to ZYMV infection. Natural infection of bottlegourd by ZYMV has been reported in Hawaii ( Ullman et al., 1991 ), India ( Verma et al., 2004 ), and Serbia
Kai-Shu Ling and Amnon Levi
Jacob Mashilo, Hussein Shimelis, Alfred Odindo, and Beyene Amelework
Bottle gourd [ Lagenaria siceraria (Molina) Standl.] belongs to the Cucurbitaceae family. It is a diploid (2 n = 2 x = 22) vine crop widely grown in rural communities in South Africa ( Achigan-Dako et al., 2008 ; Beevy and Kuriachan, 1996 ). The
Jeung-Sul Han* and Chang Kil Kim
A procedure for producing transgenic bottle gourd plants by inoculating cotyledon explants with Agrobacterium tumefaciens strain AGL1 carrying a binary vector pCAMBIA3301, which contains glufosinate ammonium-resistant (bar) and the reporter (gus) genes, is describe. Infection was the most effective (highest infection frequency and index) when explants were co-cultivated with Agrobacterium for 6-8 days on co-cultivation medium supplemented with 0.001-0.1 mg/L L-a-(2-aminoethoxyvinyl) glycine (AVG). Transgenic plants were obtained with frequencies of about 0.2% when the explants were cultured on selection medium (MS medium supplemented with 3.0 mg/L BAP, 0.5 mg/L AgNO3, 500 mg/L cefotaxime, 2.0 mg/L DL-phosphinothricin, 0.3% sucrose and 0.8% Plant Agar. A histochemical gus assay, PCR and Southern blot analyses confirmed that transformation had occurred. Genetic analysis of T1 progenies showed that the transgenes were inherited in a Mendelian fashion. To our knowlege, this study represents the first report for Agrobacterium-mediated transformation in bottle gourd, rootstock for watermelon and other cucurbit crops in many countries.
Asma Mohammed Saeed Al-Kubati, Baoshan Kang, Liming Liu, Aqleem Abbas, and Qinsheng Gu
cropping ( Colla et al., 2010 ). For cucurbits, the bottle gourd ( Lagenaria siceraria ) is an essential rootstock used to improve the disease resistance of grafted plants (also known as a scion), especially watermelon or melon ( Gaion et al., 2017
Benjamín Moreno, Cristián Jacob, Marlene Rosales, Christian Krarup, and Samuel Contreras
. Lee, S. Ko, K. 2012 Development of fusarium wilt-resistant F1 hybrids of bottle gourd ( Lagenaria siceraria Standl.) for watermelon rootstocks. Cucurbitaceae 2012. Proc. Xth EUCARPIA Mtg. Genet. Breeding Cucurbitaceae, Antalya, Turkey, 15–18 Oct. 2012
Jesse Wimer, Debra Inglis, and Carol Miles
Grafting watermelon (Citrullus lanatus Thunb.) onto resistant rootstocks is used in many areas of the world to overcome soilborne disease losses including verticillium wilt caused by Verticillium dahliae Kleb. Currently, this disease poses a serious risk to watermelon growers in Washington State. To identify resistant rootstocks, the verticillium wilt reactions (chlorosis, necrosis, and wilting) of 14 nongrafted PI accessions including Benincasa hispida Thunb., Cucurbita moschata Duchesne ex Poir., and Lagenaria siceraria Molina Standl. from the U.S. Department of Agriculture National Plant Germplasm System (USDA NPGS); 11 nongrafted commercially available rootstocks; and, nongrafted ‘Sugar Baby’ watermelon (verticillium wilt–susceptible control) were visually assessed in a field naturally infested with V. dahliae at a rate of 17 colony-forming units (cfu) per gram of soil. Typical symptoms of verticillium wilt were observed on all entries. ‘Sugar Baby’ had the highest relative area under disease progress curve (RAUDPC) value (26.80), which was not significantly different from ‘64-19 RZ’, ‘Marvel’, PI 368638, PI 634982, and PI 642045 (average = 10.16). PI 419060 (1.46) had the lowest RAUDPC value, which was not significantly different from ‘Miniature Bottle Gourd’, PI 326320, PI 419016, PI 536494, PI 636137, ‘Strong Tosa’, ‘Strongtosa’, and ‘TZ 148’ (average = 3.36). The mean RAUDPC value of PI accessions (5.49) did not differ significantly from the mean value of the commercial rootstocks (5.68). Microsclerotia typical of Verticillium spp. were observed in the stems of all but one entry (PI 181913). In a greenhouse study, a subset of 12 entries were inoculated with V. dahliae, and by 22 days after inoculation (DAI), ‘Sugar Baby’ had a significantly higher disease rating than all entries except PI 419060, PI 438548, and ‘Titan’. A strong positive correlation was observed between the field and greenhouse studies. Results indicate that commercial rootstocks as well as PI accessions could be used to successfully manage verticillium wilt in Washington; however, grafting compatibility with watermelon must first be ascertained for the promising PI accessions. Although greenhouse-based verticillium wilt assays can be used to help predict rootstock performance in the field, accurate assessment may require manipulating environmental conditions (e.g., temperature and humidity) to approximate field conditions.
Matthew B. Bertucci, David H. Suchoff, Katherine M. Jennings, David W. Monks, Christopher C. Gunter, Jonathan R. Schultheis, and Frank J. Louws
Grafting of watermelon (Citrullus lanatus) is an established production practice that provides resistance to soilborne diseases or tolerance to abiotic stresses. Watermelon may be grafted on several cucurbit species (interspecific grafting); however, little research exists to describe root systems of these diverse rootstocks. A greenhouse study was conducted to compare root system morphology of nine commercially available cucurbit rootstocks, representing four species: pumpkin (Cucurbita maxima), squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and an interspecific hybrid squash (C. maxima × C. moschata). Rootstocks were grafted with a triploid watermelon scion (‘Exclamation’), and root systems were compared with nongrafted (NG) and self-grafted (SG) ‘Exclamation’. Plants were harvested destructively at 1, 2, and 3 weeks after transplant (WAT), and data were collected on scion dry weight, total root length (TRL), average root diameter, root surface area, root:shoot dry-weight ratio, root diameter class proportions, and specific root length. For all response variables, the main effect of rootstock and rootstock species was significant (P < 0.05). The main effect of harvest was significant (P < 0.05) for all response variables, with the exception of TRL proportion in diameter class 2. ‘Ferro’ rootstock produced the largest TRL and root surface area, with observed values 122% and 120% greater than the smallest root system (‘Exclamation’ SG), respectively. Among rootstock species, pumpkin produced the largest TRL and root surface area, with observed values 100% and 82% greater than those of watermelon, respectively. These results demonstrate that substantial differences exist during the initial 3 WAT in root system morphology of rootstocks and rootstock species available for watermelon grafting and that morphologic differences of root systems can be characterized using image analysis.
Matthew B. Bertucci, Katherine M. Jennings, David W. Monks, Jonathan R. Schultheis, Penelope Perkins-Veazie, Frank J. Louws, and David L. Jordan
Grafting watermelon (Citrullus lanatus) is a common practice in many parts of the world and has recently received increased interest in the United States. The present study was designed to evaluate early season growth, yield, and fruit quality of watermelon in response to grafting and in the absence of known disease pressure in a fumigated system. Field experiments were conducted using standard and mini watermelons (cv. Exclamation and Extazy, respectively) grafted onto 20 commercially available cucurbit rootstocks representing four species: giant pumpkin (Cucurbita maxima), summer squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and interspecific hybrid squash [ISH (C. maxima × Cucurbita moschata)]. Nongrafted ‘Exclamation’ and ‘Extazy’ were included as controls. To determine early season growth, leaf area was measured at 1, 2, and 3 weeks after transplant (WAT). At 1 WAT, nongrafted ‘Exclamation’ produced the smallest leaf area; however, at 3 WAT, nongrafted ‘Exclamation’ produced the largest leaf area in 2015, and no differences were observed in 2016. Leaf area was very similar among rootstocks in the ‘Extazy’ study, with minimal differences observed. Marketable yield included fruit weighing ≥9 and ≥3 lb for ‘Exclamation’ and ‘Extazy’, respectively. In the ‘Exclamation’ study, highest marketable yields were observed in nongrafted ‘Exclamation’, and ‘Exclamation’ grafted to ‘Pelops’, ‘TZ148’, and ‘Coloso’, and lowest marketable yields were observed when using ‘Marvel’ and ‘Kazako’ rootstocks, which produced 47% and 32% of nongrafted ‘Exclamation’ yield, respectively. In the ‘Extazy’ study, the highest marketable yield was observed in nongrafted ‘Extazy’, and ‘Kazako’ produced the lowest yields (48% of nongrafted ‘Extazy’). Fruit quality was determined by measuring fruit acidity (pH), soluble solids concentration (SSC), lycopene content, and flesh firmness from a sample of two fruit from each plot from the initial two harvests of each year. Across both studies, rootstock had no effect on SSC or lycopene content. As reported in previous studies, flesh firmness was increased as a result of grafting, and nongrafted ‘Exclamation’ and ‘Extazy’ had the lowest flesh firmness among standard and mini watermelons, respectively. The present study evaluated two scions with a selection of 20 cucurbit rootstocks and observed no benefits in early season growth, yield, or phytonutrient content. Only three of 20 rootstocks in each study produced marketable yields similar to the nongrafted treatments, and no grafted treatment produced higher yields than nongrafted ‘Exclamation’ or ‘Extazy’. Because grafted seedlings have an associated increase in cost and do not produce increased yields, grafting in these optimized farming systems and using fumigated soils does not offer an advantage in the absence of soilborne pathogens or other stressors that interfere with watermelon production.
Hans Spalholz and Chieri Kubota
Low-temperature storage is a technique to hold seedlings for a short period of time to adjust the production schedule of young seedlings. Labor-intensive grafting propagation can potentially benefit from the effective use of this technique to minimize peak labor inputs. Watermelon (Citrullus lanatus) seedlings are generally chilling sensitive and therefore difficult to store at low temperatures. However, the rootstocks used for watermelon grafting, interspecific squash (Cucurbita maxima × Cucurbita moschata) and bottle gourd (Lagenaria siceraria) are known to be chilling tolerant. To examine the influence of rootstocks on storability of watermelon seedlings, young seedlings of ‘Tri-X-313’ seedless watermelon grafted onto ‘Strong Tosa’ interspecific squash, ‘Emphasis’ bottle gourd, and ‘Tri-X-313’ watermelon as rootstock were placed for 2 or 4 weeks under 12 °C air temperature and 12 μmol·m−2·s−1 photosynthetic photon flux (PPF). Nongrafted watermelon seedlings were also treated in these same conditions. In addition, nonstored (grafted and nongrafted) seedlings were prepared for comparison. Regardless of seedling type (nongrafted or grafted with different rootstocks), all seedlings stored for 2 weeks had lower dry weight, comparable or greater number of leaves and stem length, when compared with their respective nonstored control groups after 2 weeks in the greenhouse. Seedlings stored for 4 weeks had lower number of leaves and stem length after 2 weeks in the greenhouse, except for those grafted onto the interspecific squash rootstock. Nongrafted and grafted watermelon seedlings with the same watermelon cultivar as rootstock showed significantly lower leaf net photosynthetic rates after 2 weeks in the greenhouse after the 2-week storage than those of nonstored control groups. In contrast, when grafted onto interspecific squash and bottle gourd rootstocks, seedlings showed comparable net photosynthetic rate to the control group. For all seedling types, 20% to 35% of seedlings died during 4-week storage or poststorage in the greenhouse, whereas all seedlings survived for the 2-week storage, except when grafted onto watermelon as rootstock. Therefore, chilling-tolerant rootstocks ‘Strong Tosa’ interspecific squash and ‘Emphasis’ bottle gourd improved storability of grafted ‘Tri-X-313’ watermelon seedlings but could not extend the storability beyond 2 weeks.
Matthew A. Cutulle, Howard F. Harrison Jr., Chandresakar S. Kousik, Phillip A. Wadl, and Amnon Levi
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