Flowering Patterns of Pollenizer and Triploid Watermelon Cultivars

McGregor, Cecilia; Waters, Vickie

doi:10.21273/hortsci.49.6.714

Cited by 10 publications

(9 citation statements)

References 4 publications

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“…In comparison, 'SP-6' has high pollen release/quantity, thin branches, and small, deep lobed leaves to increase flower visibility to honeybees over an extended period of time (Brusca and Zhang, 2012). Although first bloom dates for male or female flowers were not recorded during the watermelon cultigen evaluations used for this study, male flowering usually begins at 10 to 14 d posttransplant, and female flowers appear at 21 d posttransplant (McGregor and Waters, 2014). Average day and night temperatures were similar during the three growing seasons (May-September), although cumulative rainfall was considerably higher in 2013 compared with 2012 and 2014 ( Table 1).…”

Section: Resultsmentioning

confidence: 96%

“…Pollinators need to visit a triploid flower 16 to 24 times to achieve adequate pollen grain transfer and fruit set (Fiacchino and Walters, 2003;Walters, 2005). Pollen amount and viability, pollinator activity, and pistillate flower receptivity are highly influenced by environmental factors such as rainfall and fluctuations in day and night temperatures, and they contribute to HH formation (Fiacchino and Walters, 2003;Freeman and Olson, 2007a;McGregor and Waters, 2014). High daytime temperatures (>30°C) and low morning temperatures (>15°C) or fluctuations in humidity soon after anthesis can decrease pollen viability (Lyu et al, 2019) and trigger the onset of HH (Stanghellini and Schultheis, 2005).…”

Section: Resultsmentioning

confidence: 99%

“…Inadequate pollination is thought to be one of the leading causes of HH in watermelon and is generally worse in triploid (seedless) watermelons because they require a diploid (seeded) pollenizer with viable pollen (Diezma-Iglesias et al, 2004). Inadequate pollination can come from an improper diploid pollenizer-triploid combination (McGregor and Waters, 2014), reduced bee visits, or unfavorable weather conditions (e.g., decrease in pollen viability and/or pollinator activity) (Pisanty et al, 2016). Additionally, cytokinins known to promote cell division can affect watermelon flesh firmness and cell density (Soteriou et al, 2017) and may contribute to inadequate pollination.…”

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confidence: 99%

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Predicting Hollow Heart Incidence in Triploid Watermelon (Citrullus lanatus)

Trandel¹,

Perkins‐Veazie²,

Schultheis³

2020

horts

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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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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Predicting Hollow Heart Incidence in Triploid Watermelon (Citrullus lanatus)

Trandel¹,

Perkins‐Veazie²,

Schultheis³

2020

horts

View full text Add to dashboard Cite

show abstract

“…Factors known to induce HH include heavy rainfall events, temperature fluctuations, pollen viability and pollinator activity during the time of pollination ( Fiacchino and Walters, 2003 ; McGregor and Waters, 2014 ). Hollow heart is most common in triploid watermelon, where blooms cannot produce viable pollen.…”

Section: Discussionmentioning

confidence: 99%

Cell Wall Polysaccharide Composition of Grafted ‘Liberty’ Watermelon With Reduced Incidence of Hollow Heart Defect

et al. 2021

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Grafting watermelon scions to interspecific squash hybrids has been found to increase fruit firmness. Triploid (seedless) watermelon are prone to hollow heart (HH), an internal fruit disorder characterized by a crack in the placental tissue expanding to a cavity. Although watermelon with lower tissue firmness tend to have a higher HH incidence, associated differences in cell wall polysaccharide composition are unknown. Grafting “Liberty” watermelon to “Carnivor” (interspecific hybrid rootstock, C. moschata × C. maxima) reduced HH 39% and increased tissue firmness by 3 N. Fruit with and without severe HH from both grafted and non-grafted plants were analyzed to determine differences in cell wall polysaccharides associated with grafting and HH. Alcohol insoluble residues (AIR) were sequentially extracted from placental tissue to yield water soluble (WSF), carbonate soluble (CSF), alkali soluble (ASF), or unextractable (UNX) pectic fractions. The CSF was lower in fruit with HH (24.5%) compared to those without HH (27.1%). AIRs were also reduced, hydrolyzed, and acetylated for GC-MS analysis of monosaccharide composition, and a portion of each AIR was methylated prior to hydrolysis and acetylation to produce partially methylated alditol acetates for polysaccharide linkage assembly. No differences in degree of methylation or galacturonic and glucuronic acid concentrations were found. Glucose and galactose were in highest abundance at 75.9 and 82.4 μg⋅mg–1 AIR, respectively, followed by xylose and arabinose (29.3 and 22.0 μg⋅mg–1). Mannose was higher in fruit with HH (p < 0.05) and xylose was highest in fruit from grafted plants (p < 0.05). Mannose is primarily found in heteromannan and rhamnogalacturonan I side chains, while xylose is found in xylogalacturonan or heteroxylan. In watermelon, 34 carbohydrate linkages were identified with galactose, glucose, and arabinose linkages in highest abundance. This represents the most comprehensive polysaccharide linkage analysis to date for watermelon, including the identification of several new linkages. However, total pectin and cell wall composition data could not explain the increased tissue firmness observed in fruit from grafted plants. Nonetheless, grafting onto the interspecific hybrid rootstock decreased the incidence of HH and can be a useful method for growers using HH susceptible cultivars.

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“…less seed watermelon fruits have become more popular and desirable throughout the world due to easy consumption, gustatory advantages, consumer preference, and greater economic value to growers over traditional seeded cultivars 7 , 40 , 41 . For example, in the United States, the popularity of less seed watermelon has steadily increased over the past decade 42 , 43 . Less seed watermelon accounts for over 80% of watermelon production (AgMRC, 2018).…”

Section: Discussionmentioning

confidence: 99%

A 2.09 Mb fragment translocation on chromosome 6 causes abnormalities during meiosis and leads to less seed watermelon

Tian¹,

Ge²,

Ai³

et al. 2021

Hortic Res

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Seedlessness is a valuable agronomic trait in watermelon (Citrullus lanatus) breeding. Conventional less seed watermelons are mainly triploid, which has many disadvantages due to unbalanced genome content. Less seed watermelon can be achieved at the diploid level when certain reproductive genes are mutated or by chromosome translocation, which leads to defects during meiosis. However, the formation mechanism of diploid less seed watermelons remains largely unknown. Here, we identified a spontaneous mutant line, watermelon line “148”, which can set seeds normally when self-pollinated. A total of 148 × JM F1 hybrid plants exhibited seed number reductions to 50.3% and 47.3% of those of the two parental lines, respectively, which are considered to be less seed. Examination of pollen viability and hybridization experiments revealed that F1 hybrids produce semisterile pollen and ovules. Further cytological observations indicated that semisterility was a result of a reciprocal translocation of chromosomes, which exhibited one quadrivalent ring of four chromosomes at prometaphase I during meiosis. RT-qPCR analysis indirectly confirmed that the semisterile phenotype is caused by chromosome translocation rather than disruption of specific meiotic gene expression. F2 population genetic analysis indicated that the “148” watermelon line is a homozygous translocation and that the less seed phenotype of the F1 hybrid is prompted by one chromosome fragment translocation. The translocated fragment was further fine mapped to a 2.09 Mb region on chromosome 6 by whole-genome resequencing and genetic map cloning procedures. Our work revealed that a 2.09 Mb chromosome fragment translocation on chromosome 6, causing meiotic defects at metaphase I during meiosis, leads to diploid less seed watermelon. Our findings provide a new promising method for less seed watermelon breeding at the diploid level, as well as a fragment size reference for breeding less seed watermelon through artificially induced chromosome translocation.

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Flowering Patterns of Pollenizer and Triploid Watermelon Cultivars

Cited by 10 publications

References 4 publications

Predicting Hollow Heart Incidence in Triploid Watermelon (Citrullus lanatus)

Predicting Hollow Heart Incidence in Triploid Watermelon (Citrullus lanatus)

Cell Wall Polysaccharide Composition of Grafted ‘Liberty’ Watermelon With Reduced Incidence of Hollow Heart Defect

A 2.09 Mb fragment translocation on chromosome 6 causes abnormalities during meiosis and leads to less seed watermelon

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