Predicting Hollow Heart Incidence in Triploid Watermelon (Citrullus lanatus)

In triploid (seedless) watermelon [Citrullus lanatus var. lanatus (Thunb. Matsum. and Nakai)], hollow heart (HH) is a disorder that is expressed as a crack in the center of the fruit that expands to an open cavity. Although HH incidence and severity is part of a screening process for marketable watermelon fruit during cultigen evaluations, HH incidence is highly variable with growing season, even when the best cultural practices are used. Placental tissue firmness is also measured because firmness is related to the marketability of watermelon and may be related to HH. Genetic and environmental factors can influence watermelon HH development, including plant genetics, pollen amount and viability, pollinator activity, and temperature and rainfall fluctuations. We used seedless watermelon cultigen evaluation data collected over 3 years (2012–14) to determine the relationship between germplasm HH and tissue firmness. Transplanted watermelon representing 30 to 44 cultigens per year were grown at the Central Crops Research Station, Clayton, NC, and interplanted with pollenizers ‘Ace’ and/or ‘SP-6’. Harvested fruit were cut length-wise and rated for HH incidence and severity. Flesh firmness was determined by a handheld penetrometer at five locations in the flesh (stem end, top side, ground spot, blossom end, and heart). A common cultigen subset, consisting of 13 cultigens that were grown in all three experiments, was used for analysis of HH severity and incidence, and placental firmness. The presence of HH was negatively correlated with tissue firmness in both the large multiyear cultigen set (R2 = −0.32; P = 0.0001) and the common cultigen set (R2 = −0.78; P = 0.0001). Cultigens with lower watermelon tissue firmness values had higher HH incidence and severity. By using multiyear cultigen studies and logistic regression, we were able to detect trends for cultigen susceptibility to this highly variable disorder. Using logistic regression, the probability of HH development was highest for ‘Bold Ruler’, ‘Liberty’, and ‘Affirmed’, and lowest for ‘Maxima’ and ‘Captivation’. The identification of cultigens with a tendency for higher or lower rates of HH will be useful for further research of the causes of HH. Measurements of placental flesh firmness may be useful indicators of susceptible cultigens.

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Influence of Diploid Pollinizer Frequencies on Triploid Watermelon Quality and Yields

HortTechnology ◽

10.21273/horttech.13.1.0058 ◽

2003 ◽

Vol 13 (1) ◽

pp. 58-61 ◽

Cited By ~ 3

Author(s):

Dena C. Fiacchino ◽

S. Alan Walters

Keyword(s):

Significant Interaction ◽

Citrullus Lanatus ◽

Hollow Heart ◽

Heart Disorder ◽

Soluble Solids ◽

Growing Seasons ◽

Frequency Interaction ◽

Quadratic Response ◽

Seedless Watermelon ◽

Triploid Watermelon

During the 1999 and 2000 growing seasons in Illinois, studies were conducted to determine the influence of two pollinizers (`Crimson Sweet' and `Fiesta') and three pollinizer frequencies (11%, 20%, and 33%) on `Millionaire' seedless watermelon (Citrullus lanatus) quality and yields. More large-sized [>16 lb (7.2 kg)] `Millionaire' watermelons were produced when `Crimson Sweet' was used as the pollinizer compared to `Fiesta', which resulted in `Crimson Sweet' leading to greater marketable and total `Millionaire' yields. Pollinizers responded similarly over the pollinizer frequencies for `Millionaire' watermelon yields as no pollinizer by pollinizer frequency interaction was observed. The 20% and 33% pollinizer frequencies produced similar `Millionaire' yields per acre and both resulted in greater yields compared to the 11% pollinizer frequency. Soluble solids in `Millionaire' fruits were not influenced by pollinizer or pollinizer frequency. However, hollow heart disorder followed a quadratic response with respect to pollinizer frequency with the lowest amount of hollow heart observed at the 33% pollinizer frequency and greatest at the 11% pollinizer frequency. No significant interaction (P ≤ 0.05) was observed for pollinizer by pollinizer frequency for hollow heart disorder in `Millionaire'; although, more hollow heart disorder in `Millionaire' was observed when `Fiesta' was used as the pollinizer.

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In-row Spacing Influences Triploid Watermelon Yield and Crop Value

HortTechnology ◽

10.21273/horttech.12.3.437 ◽

2002 ◽

Vol 12 (3) ◽

pp. 437-440 ◽

Cited By ~ 5

Author(s):

Carl E. Motsenbocker ◽

Ramon A. Arancibia

Keyword(s):

Cultural Practices ◽

Citrullus Lanatus ◽

Fruit Weight ◽

Row Spacing ◽

Plastic Mulch ◽

Marketable Yield ◽

Farmers Market ◽

Subsequent Decrease ◽

Small Fruit ◽

Triploid Watermelon

Triploid watermelon (Citrullus lanatus), commonly called seedless watermelon, is increasing in popularity and market share. The optimum in-row spacing of triploid watermelon has not been studied previously. Triploid watermelon `Crimson Jewel' and `Honeyheart' were grown with drip-irrigation and black plastic mulch at 1-, 2-, 4-, 6-, and 8-ft (0.3-, 0.6-, 1.2-, 1.8-, and 2.4-m) in-row spacings in 1996 and 2-, 3-, 4-, 5-, 6-, 7-, and 8-ft. (0.6-, 0.9-, 1.2-, 1.5-, 1.8-, 2.1-, and 2.4-m) spacings in 1997 to determine the effect of in-row plant spacing on fruit yield. Marketable yield of `Crimson Jewel' was not affected by in-row spacing while narrower in-row spacing resulted in greater `Honeyheart' yield both years. For both cultivars, narrower spacing resulted in the highest number of fruit per acre, but primarily more extrasmall and small fruit. Fruit number per plant, fruit weight per plant, and individual fruit weight were higher at wider spacings, and yield per acre was lower. The data suggest that triploid watermelon yield, fruit weight and number can be adjusted by in-row spacing. Narrower in-row spacing can maximize yields, depending on the specific grower's cultural practices. In wider in-row spacings, the yield of medium and large fruit is maintained with a subsequent decrease in extra small and small fruit. Gross returns per acre were only different for farmers' market prices, not wholesale, and net returns were not significantly influenced by in-row spacing.

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Seedless Watermelon Production: Extension's Role in Supporting a New Crop Enterprise

HortScience ◽

10.21273/hortsci.35.5.830d ◽

2000 ◽

Vol 35 (5) ◽

pp. 830D-831

Author(s):

Tracy Wootten ◽

Ed Kee

Keyword(s):

Management Practices ◽

Cultural Practices ◽

Supply And Demand ◽

Intensive Management ◽

Extension Programs ◽

Poor Seed ◽

Seedless Watermelon ◽

Triploid Watermelon ◽

On Farm ◽

New Crop

In response to a national increase in the consumption of triploid (seedless) watermelons, seedless watermelon production in Delaware has increased to 43% of the total watermelon acreage. Cultural practices for triploid watermelon production are similar to seeded (diploid) types. However, poor seed germination, high seed costs, erratic performance, and inadequate varieties limited their adoption until the early 1990s in Delaware. Univ. of Delaware Cooperative Extension has worked with Delaware growers to develop a “recipe” for successful triploid production. Extension programs, such as on-farm demonstrations, research trials, educational seminars, and one-on-one consultations, have enabled producers to provide high-quality fruit and yields. Intensive management and marketing are the keys tosuccess as Delaware producers have become leaders of triploid production in the Northeast region. As demand for triploid watermelon continues to increase, extension will remain a vital part of the $4.5 million industry. Growers continually deal with marketing issues in a supply and demand-driven market. As more seedless are on the market and profits lessen, growers will have to be diligent in their marketing and management practices.

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Influence of Honey Bee Pollination on Triploid Watermelon Fruit Set and Quality

HortScience ◽

10.21273/hortsci.40.4.1118c ◽

2005 ◽

Vol 40 (4) ◽

pp. 1118C-1118

Author(s):

S. Alan Walters

Keyword(s):

Honey Bee ◽

Fruit Set ◽

Citrullus Lanatus ◽

Hollow Heart ◽

Pistillate Flower ◽

Soluble Solids ◽

Vegetable Crops ◽

Bee Pollination ◽

Male Flowers ◽

Triploid Watermelon

Cucurbit vegetable crops, such as watermelon (Citrullus lanatus), require insect pollination for fruit set, which is usually achieved by placing honey bee (Apismellifera) colonies in a field or relying upon natural bee populations. Pistillate (or female) watermelon flowers require multiple honey bee (or other bee) visitations after visiting staminate (or male) flowers for fruit set, and pollination is even more of a concern in triploid watermelon production since staminate flowers contain mostly nonviable pollen. Six honey bee visitation treatments, 1) no visitation control, 2) two visits, 3) four visits, 4) eight visits, 5) 16 visits, and 6) open-pollinated control, were evaluated to determine the effect of honey bee pollination on `Millionaire' triploid watermelon fruit set, yield, and quality utilizing `Crimson Sweet' at a 33% pollinizer frequency. No differences (P> 0.05) between honey bee pollination treatments were observed for `Millionaire' quality characters (hollow heart disorder or percent soluble solids). The lowest pistillate flower abortion rate (20%) and subsequently the greatest triploid watermelon yields (fruit numbers and weights per hectare) occurred with the openpollinated control compared to all other honey bee visitation treatments. Fruit abortion rates decreased linearly, while fruit numbers and weights per hectare increased linearly as number of honey bee visits to pistillate flowers increased from 0 (no visit control) to the open-pollinated control (≈24 visits). This study indicated that >16 honey bee visits are required to achieve maximum triploid watermelon fruit set and yields, which is twice the number of honey bee visits required by diploid watermelons to achieve similar results.

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Effect on Production and Quality of Intensifying Triploid Watermelon Crops Using ‘Temporary Trellises’ and CPPU for Fruit Development

HortScience ◽

10.21273/hortsci.43.1.149 ◽

2008 ◽

Vol 43 (1) ◽

pp. 149-152

Author(s):

Francisco Javier Núñez ◽

Maria Victoria Huitrón ◽

Manuel Díaz ◽

Fernando Diánez ◽

Francisco Camacho-Ferre

Keyword(s):

Plant Density ◽

Citrullus Lanatus ◽

Quality Parameters ◽

Traditional System ◽

Crop Intensification ◽

Production Techniques ◽

Seedless Watermelon ◽

Triploid Watermelon ◽

Improve Cost

In Spain, the adoption of the triploide ‘Queen of Hearts’ (Citrullus lanatus Thunb.) watermelon cultivar has brought important changes in the production of seedless watermelon thanks to its magnificent acceptance by the market. The experiments on triploid watermelon presented here examined innovative production techniques that would guarantee the productivity and quality of this cultivar in plastic greenhouses and improve cost-effectiveness, serving growers. Crop intensification was tested under a “temporary trellis” management system, increasing plant density from 2500 plants/ha in the traditional or creeping crop system to 10,000 plants/ha. The “temporary trellis” system was combined with fruit set through the localized application of a 150- to 200-mg·L−1 solution of 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU). The increase of grafted watermelon plant density to 1 plant/m2 gave rise to an increase in early harvest measured as the number of fruits per surface area compared with the traditional system with a density of 0.25 plant/m2. In addition, a process of temporary trellising facilitates choosing female flowers for applying CPPU. The °Brix and pulp firmness quality parameters did not show significant differences between “temporary trellised” and creeping crops.

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Use of Commercially Available Pollenizers for Optimizing Triploid Watermelon Production

HortScience ◽

10.21273/hortsci.45.4.541 ◽

2010 ◽

Vol 45 (4) ◽

pp. 541-545 ◽

Cited By ~ 7

Author(s):

Peter J. Dittmar ◽

David W. Monks ◽

Jonathan R. Schultheis

Keyword(s):

Citrullus Lanatus ◽

Hollow Heart ◽

Fruit Yield ◽

The Other ◽

Yield And Quality ◽

Triploid Watermelon ◽

Marketable Fruit ◽

The Hill ◽

Pollen Movement ◽

Selection Of

An experiment was conducted during 2005 and 2006 in Kinston, NC, with the objective of maximizing triploid watermelon [Citrullus lanatus (Thunb.) Matsum. and Nak.] fruit yield and quality by optimizing the choice and use of pollenizers. Treatments were pollenizer cultivars planted singly [‘Companion’, ‘Super Pollenizer 1’ (‘SP1’), ‘Summer Flavor 800’ (‘SF800’), and ‘Mickylee’] or in pairs (‘Companion’ + ‘SP1’, ‘Companion’ + ‘SF800’, and ‘SP1’ + ‘SF800’). All pollenizers from these seven treatments were interplanted with the triploid cultivar Tri-X-313. Planting arrangement was compared by establishing ‘SF800’ in a hill versus an interplanted field arrangement. Effect of pollenizer establishment timing on triploid fruit yields and quality was evaluated by establishing ‘SP1’ 3 weeks after planting and comparing it with the establishment of ‘SP1’ at the time of triploid plant establishment. Finally, a triploid planting with no pollenizer (control) was included to determine pollen movement. Fruit yield from the control was 22% or less of yield of the other treatments containing a pollenizer and less than 10% in the initial or early harvests. Pollen movement was minimal among plots and differences in yield and fruit quality could be attributed to pollenizer treatment. In 2005, the use of ‘Companion’, ‘SP1’, or ‘Mickylee’ as pollenizers produced similar total yields, whereas ‘SF800’ produced the lowest yield. In 2005, ‘Companion’ produced more large fruit than the other individual pollenizer treatments. Combining the pollenizers generally did not enhance triploid yields or quality. Interplanting of pollenizers consistently resulted in greater yield compared with the hill system. Late planting of ‘SP1’ increased the incidence of hollow heart in the marketable fruit and decreased yield compared with simultaneously planting ‘SP1’ and triploid plants. Thus, selection of pollenizer, planting arrangement, and time of pollenizer establishment are all important considerations to optimizing triploid yield and quality.

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Intercropping Seedless Watermelon and Cotton

HortScience ◽

10.21273/hortsci13428-18 ◽

2018 ◽

Vol 53 (12) ◽

pp. 1799-1803

Author(s):

Gilbert Miller ◽

Jeremy Greene

Keyword(s):

South Carolina ◽

Crop Production ◽

Citrullus Lanatus ◽

Geographical Area ◽

Hollow Heart ◽

Crop Management ◽

Net Income ◽

Cotton Production ◽

Management Procedures ◽

Seedless Watermelon

Intercropping of seedless watermelon [Citrullus lanatus (Thumb.) Matsum. & Nak.] and cotton [Gossypium hirsutum (L.)] in the eastern geographical area of South Carolina requires changes in normal crop-management programs but has the potential to improve grower profits compared with typical production of each crop separately. The alteration and timing of several normal crop-production practices for both crops can present challenges and must be well-defined for successful intercropping of watermelon and cotton in the region. Notable adjustments in production for watermelon are delayed planting date, reduced row spacing and bed width, and modification of herbicide applications. Significant changes in normal cotton production also include modification of herbicide applications, but additional considerations, such as temporal limits on side-dressed fertilizer and insecticide applications, are needed because of the raised beds and plasticulture used for watermelons and also because of labeling restrictions for pesticides across crops. Research was conducted to 1) identify modifications in standard crop-management procedures for watermelon and cotton intercropping; and 2) determine the feasibility and profitability of intercropping the crops. Although there was a slight numerical reduction in intercropped watermelon yield each year, there were no significant differences in total watermelon yield between intercropping and watermelon monoculture in any of the years. There were also no significant differences in watermelon fruit quality parameters (size, brix, hard seed, hollow heart) in any of the years. Intercropped cotton yield was significantly less than monoculture cotton yields in each of the three years. The net income from intercropping in each year was slightly less than the net income from watermelon monoculture.

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Flowering Patterns of Pollenizer and Triploid Watermelon Cultivars

HortScience ◽

10.21273/hortsci.49.6.714 ◽

2014 ◽

Vol 49 (6) ◽

pp. 714-721 ◽

Cited By ~ 2

Author(s):

Cecilia E. McGregor ◽

Vickie Waters

Keyword(s):

United States ◽

Fruit Set ◽

Citrullus Lanatus ◽

Staminate Flower ◽

The United States ◽

Specific Production ◽

The Past ◽

Seedless Watermelon ◽

Triploid Watermelon ◽

Fundamental Requirement

The past 10 years has seen a steep increase in production of seedless watermelon (Citrullus lanatus) in the United States. Seedless fruit is produced on triploid plants that require pollination from diploid pollenizers for fruit set. Synchronization of the staminate flowers on the pollenizers with the appearance of pistillate flowers on the triploids is a fundamental requirement for this production system. Previous research suggested that pistillate flowers reach peak production early in the season, but data are only available for a small number of triploid cultivars. We compared the flowering patterns of 29 triploid cultivars and 20 pollenizers, including 10 harvested pollenizers, during the first 6 weeks after transplanting over 2 years. The average number of days from transplanting (DAT) to the first staminate flower was between 5.3 days and 19.1 days in 2012 and 9.7 days and 24.4 days in 2013 for the pollenizers and between 18.7 days and 27.6 days and 22.1 days and 32.7 days for the pistillate triploid flowers in the 2 years, respectively. K-means clustering of the weekly percentage of plants with staminate and pistillate flowers for the different cultivars shows that different triploid and pollenizer cultivars have different flowering patterns and that some combinations have better synchronized flowering than others. Growers should take particular care when choosing pollenizers for early-flowering triploid cultivars. Harvested pollenizers are better suited to late-flowering triploids and growers should choose triploid and pollenizer cultivar combinations with flowering patterns that best satisfy their specific production goals.

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Effect of 2,4-D and CPPU on Triploid Watermelon Production and Quality

HortScience ◽

10.21273/hortsci.42.3.559 ◽

2007 ◽

Vol 42 (3) ◽

pp. 559-564 ◽

Cited By ~ 12

Author(s):

Maria Victoria Huitrón ◽

Manuel Diaz ◽

Fernando Diánez ◽

Francisco Camacho ◽

Antonio Valverde

Keyword(s):

Citrullus Lanatus ◽

Soluble Solids ◽

Dichlorophenoxyacetic Acid ◽

Cucurbita Moschata ◽

Average Production ◽

Pollinating Insects ◽

Seedless Watermelon ◽

Triploid Watermelon ◽

2,4 Dichlorophenoxyacetic Acid

Pollination is one problem with intensive seedless watermelon (Citrullus lanatus Thunb.) production under unfavorable environmental conditions (low solar radiation and temperature) due to the lowered activity of pollinating insects, such as the bee (Apis mellifera L.). An alternative to overcome these problems is the use of plant growth regulators. For this reason, experiments were conducted for 2 years in plastic greenhouses in the fields of Almeria, southwestern Spain, to evaluate the production and quality of ‘Reina de corazones’ triploid watermelon grafted onto RS841 rootstock (Cucurbita maxima × Cucurbita moschata). Two phytoregulators were used for the development of the ovary: 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) and 2,4-dichlorophenoxyacetic acid (2,4-D). Concentrations of CPPU evaluated were 50, 100, 150, and 200 mg·L−1. An application of 0.6 mL was applied to each ovary in addition to 4, 6, 8, or 12 mg·L−1 of 2,4-D to the foliar mass at a proportion of 1000 L·ha−1. Results showed that the production and number of fruit obtained with CPPU treatments were similar to what is obtained by using bees for fruit pollination. Maximum production was reached at concentrations of 100–200 mg·L−1. Average production was 32% to 83% higher than results from 2,4-D at 8 mg·L−1. The number of fruit per plant was 33% to 35% higher as well. In the first assay, a positive correlation was also observed between production and CPPU concentration. CPPU treatments had a lower accumulation of sugars than those with 2,4-D; nevertheless, both treatments showed values of commercially acceptable soluble solids.

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Seedcoat Structure and Oxygen-enhanced Environments Affect Germination of Triploid Watermelon

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.128.2.0253 ◽

2003 ◽

Vol 128 (2) ◽

pp. 253-259 ◽

Cited By ~ 11

Author(s):

Stacie Grange ◽

Daniel I. Leskovar ◽

Leonard M. Pike ◽

B. Gregory Cobb

Keyword(s):

Citrullus Lanatus ◽

High Moisture ◽

Excess Water ◽

Original Weight ◽

Air Space ◽

Structural Differences ◽

Morphological Defects ◽

Seedless Watermelon ◽

Triploid Watermelon ◽

Submerged Conditions

Triploid or seedless watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] cultivars often have erratic germination and low seedling vigor. The morphology of the seedcoat on two triploid cultivars—Tri X 313 and Tri X Sunrise—was examined by scanning electron microscopy (SEM) to identify structural differences compared to diploid seeds. Triploid seeds incubated with oxygen-enhanced treatments that included nicking, 1% hydrogen peroxide (H2O2), and 40% oxygen were investigated at low and high medium moisture levels. Triploid seed has a thicker seedcoat with a dense endotesta layer and a larger and highly variable air space surrounding the embryonic axis as compared with diploid seed. All cultivars rapidly imbibed water (≈50% of the original weight) during the first hour of imbibition, with a faster increase for triploids than for diploids. High moisture affected germination to a lesser extent in diploid than triploid seeds. Triploid germination under low medium moisture ranged from 96% to 76%, but was severely reduced to <27% under high medium moisture. Triploid seed germination was significantly improved at high moisture by H2O2 and by 40% oxygen. Triploid watermelon seed is very sensitive to submerged conditions, possibly due to a combination of physiological and morphological defects. The rapid imbibition and excess water collected in the seedcoat and air space surrounding the embryo, could reduce oxygen diffusion and impair metabolic pathways leading to normal germination and seedling development.

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