Monoecious cucumber (Cucumis sativus) plants generally produce enough pollen for fruit set. The amount of pollen required for fruit set depends on the number of pistillate flowers produced by the cultivar. ‘NC-Sunshine’ is a new monoecious slicing hybrid cucumber with a high percentage of pistillate nodes. Because of the high percentage of pistillate nodes, a pollenizer might be required to maximize pollination to get high total and early yield. Hence, an experiment was conducted at three locations to evaluate the effect of the pollenizer ‘Poinsett 76’ on yield of ‘NC-Sunshine’ compared with no pollenizer ‘Gray Zucchini’ squash (Cucurbita pepo). Differences (P ≥ 0.05) due to pollenizer, location, and the interaction of pollenizer and location on ‘NC-Sunshine’ yield traits were detected. Pollenizer influenced cucumber yield at two of three locations. Results indicated that the pollenizer ‘Poinsett 76’ significantly increased total, marketable, and early yield of ‘NC-Sunshine’. The percentage of early and marketable yield was also higher with the pollenizer ‘Poinsett 76’. In addition, the use of a pollenizer decreased cull yield. Therefore, a pollenizer is needed for monoecious hybrids having a high percentage of pistillate nodes.
Todd C. Wehner and Rakesh Kumar
Rakesh Kumar and Todd C. Wehner
There is a large genetic diversity for fruit size and yield in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus]. Current cultivars have high fruit quality but may not be the highest yielders. This study was designed to estimate variance components and heritability of fruit yield (Mg·ha−1), fruit count (th·ha−1), and fruit size (kg/fruit) in a cross involving high-yielding ‘Mountain Hoosier’ with low-yielding ‘Minilee’. Six generations (PaS1, PbS1, F1, F2, BC1Pa, and BC1Pb) were developed and tested in Summer 2008 at two locations in North Carolina. Discrete classes were not observed within the F2 segregating population. The actual distribution of the F2 population for fruit yield, fruit count, and fruit size deviated from the normal distribution. ‘Mountain Hoosier’ had higher parental and backcross variance than ‘Minilee’. High F2 variance for fruit yield indicated large phenotypic variance. There was a larger environmental variance than genetic variance associated with the yield traits. Estimates of broad- and narrow-sense heritability were low to medium. A large number of effective factors indicated polygenic inheritance for fruit yield and fruit size. Gain from selection for yield is amendable by selection. As a result of this complex inheritance, selection based on individual plant selection in pedigree method may not be useful for yield improvement in this population. Hence, a selection scheme based on progeny testing using replicated plots, perhaps at multiple locations, is recommended.
Rakesh Kumar, Mahendra Dia, and Todd C. Wehner
Understanding the natural mating behavior (self- or cross-pollination) in watermelon is important to the design of a suitable breeding strategy. The objective of this study was to measure the rate of self- and cross-pollination in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] using the dominant gene Sp (Spotted leaves and fruit) as a marker. The experiment consisted of two studies and was a split plot in a randomized complete block design with 3 years (2009 to 2011) and four locations (Clinton, Kinston, Oxford, Lewiston, NC). For the intercrossing study, whole plots were the two spacings (1.2 × 0.3 m and 1.2 × 0.6 m) with four replications in 2010. For the inbreeding study, whole plots were two equidistant spacings (3 × 3 m and 6 × 6 m) with four replications in 2009 to 2011. Cultivars Allsweet and Mickylee were subplots within each whole plot. In the inbreeding study, spacing and year had a significant effect on the rate of self-pollination, which was moderate (47% and 54%, respectively) when watermelon plants were trained in a spiral and spaced 3 × 3 m or 6 × 6 m apart. Spacing and cultivar did not have a significant effect on cross-pollination in the intercrossing study. Closely spaced watermelon plants (1.2 × 0.3 m and 1.2 × 0.6 m) had low natural outcrossing rate (31% and 35%, respectively) and was not adequate to intercross families. However, breeders should consider the amount of self-pollination in watermelon to calculate the estimates of component of genetic variances.