Abstract
Combining ability and heterosis for yield, maturity, and plant traits in bush muskmelon (Cucumis melo L.) were estimated through the use of a 6-parent diallel evaluated in 1981 at Excelsior, Minn. and at Santa Paula, Calif. The variance of GCA was greater than that of SCA for all traits. Minnesota 266 was the best general combiner for yield weight characteristics. Minnesota 101 was exceptional for GCA in those traits associated with earliness, and U.C. Perlita Bush and U.F. G508 combined well for main crop yield. Correlations between the performance of parental lines and the average of their hybrids were consistently positive and often significant. Favorable heterosis over the midparent was found for all traits but days to first fruit. Favorable heterosis over the superior parent was found for plant health and all yield traits except total number of fruit per plant. In a 3 × 10 design II at Excelsior, estimates of additive variance exceeded those of dominance variance in general, providing for moderately high heritability estimates (40–70%) for most traits.
Abstract
Individual leaves of Cucumis melo L. acropetal to a developing fruit were treated with a pulse of 14CO2. The level of 14C in the leaves, internodes, and fruits was determined after various periods of time when the leaf at the 3rd node acropetal to the fruit was treated. Leaves at the same node as the fruit, the 2nd, the 3rd, the 6th, and the 18th node acropetal to the fruit were treated and the level of 14C in the leaf, internodes, and fruit was determined after 2 hours. The percent of the incorporated 14C which was exported from the leaf was strongly affected both by time and leaf position relative to the fruit. Leaves which were 3 nodes acropetal to the fruit exported 65% of the label in 6 hours, while those further from the fruit retained the label longer. The influence of the fruit on the movement of 14C label is limited to a few internode lengths along the branch.
Abstract
A mutant seedling with retarded growth and interveinal chlorosis of leaves characteristic of iron deficiency was discovered in a group of ‘Edisto’ muskmelon transplants. The seedling responded to supplemental Fe, suggesting that the mutant affects Fe uptake or use. The F1 phenotypes from crosses of the mutant with ‘Edisto’ and ‘Mainstream’ were normal. F2, F3, and testcross data indicate that the chlorotic phenotype is controlled by a single recessive gene, which is not allelic or linked to virescent.
The southern root-knot nematode, Meloidogyne incognita [(Kofoid & White) Chitwood], causes serious economic losses to melon (Cucumis melo L.) production in the United States. The present study was conducted to determine if separable differences in nematode resistance of Cucumis melo could be found at some inoculum level. Five C. melo lines were compared with Cucumis metuliferus Naud. (C701A), a highly resistant species, for root necrosis, galling, egg mass production, and reproduction when inoculated at 0, 500, 1000, 2000, or 5000 nematode eggs per plant. Using these criteria, melon line C880 inoculated with 1000 eggs per plant was highly susceptible, while PI140471, PI 183311, and the cultivars Chilton, Georgia 47, Gulf Coast, Planters Jumbo, and Southland were less susceptible. In greenhouse tests with an inoculum level of 1000 eggs per plant, low levels of resistance were evident. A thorough screening of the available germplasm against M. incognita may identify higher levels of root-knot nematode resistance for incorporation into improved melon cultivars.
Combinations of mulch/rowcover systems were tested using 'Earligold' melon (Cucumis melo L.) transplanted between 7 and 9 May during each of 3 years. The mulches used were black (B), wavelength-selective green (G), or clear (C). In 1993 and 1994, these three mulches were combined with two rowcover systems, either a clear perforated polyethylene (PO; 500 holes/m2) or a clear nonperforated polyethylene with a water-filled tube (UT, thermal tube). Controls consisted of mulch-alone treatments. In 1995, only the green wavelength-selective mulch was tested. A clear mulch combined with an infrared-blocking polyethylene with a thermal tube (IT) and a spunbonded polypropylene agrotextile (AO) were also tested. The highest air temperatures, sometimes >40 °C, were recorded under the CIT and BUT treatments. Perforated tunnels were less efficient in increasing daytime air temperatures, particularly during windy conditions, than the nonperforated tunnels. When combined with all tunnel types, the wavelength-selective mulch produced effects intermediate between those of the clear and black mulches for air and soil temperatures, chilling injury, and days to flowering of perfect flowers. In 1994, only those plants grown with a clear mulch combined with an infrared-blocking or standard nonperforated tunnel with a thermal tube (CIT and CUT) survived seven sequential nights with temperatures between 1.6 and 5.8 °C. Plants in the nonperforated tunnels flowered first, had the heaviest biomass at anthesis, and gave the highest early yields, both in terms of fruit number and mass. However, total yields did not differ significantly between perforated and nonperforated tunnels. Plants produced smaller fruits in treatments that resulted in earlier flowering, i.e., nonperforated tunnels.
Extending the production season of melons (Cucumis melo L.) by using very early and late planting dates outside the range that is commercially recommended will increase the likelihood of developing a stronger melon industry in South Carolina. The objective of this study was to determine if early (February) transplanted melons or later (June through July) planting dates are effective in extending the production season of acceptable yields with good internal quality of the melon cultivars: Athena, Eclipse, and Sugar Bowl and Tesoro Dulce (a honeydew melon). Melons were transplanted in Charleston, S.C., in 1998, 1999, and 2000 on 12 and 26 Feb., 12 and 26 Mar., 9 and 23 Apr., 7 and 21 May, 4 and 18 June, and 2 July and required 130, 113, 105, 88, 79, 70, 64, 60, 60, 59, and 56 days from field transplanting to reach mean melon harvest date, respectively. Stands were reduced 67%, 41%, and 22% in the 12 and 26 Feb. and 12 Mar. planting dates, respectively, in contrast to the 26 Mar. planting date but ≤15% in all other planting dates. Planting in February had no earliness advantage because the 12 and 26 Feb. and 12 and 26 Mar. planting dates, all reached mean melon harvest from 19 to 23 June. Comparing the marketable number of melons produced per plot (averaged over cultivar) of the standard planting dates of 12 and 26 Mar. indicated decreases of 21%, 32%, 36%, 36%, 57%, 57%, and 54%, respectively with the planting dates of 9 and 23 Apr., 7 and 21 May, 4 and 18 June, and 2 July. The most productive cultivar of all was `Eclipse', which yielded significantly more melons per plot in all 11 planting dates followed by `Athena' (in 8 of 11 planting dates), `Tesoro Dulce' (7 of 11 planting dates), and `Sugar Bowl' (2 of 11 planting dates). In our study, any planting date with melon quality less than the USDA standard of “good internal quality” or better (Brix ≥9.0) was considered unacceptable because of potential market rejection. Therefore, the earliest recommended planting date with acceptable yield and “good internal quality” was 12 Mar. for all cultivars; the latest planting dates for `Athena', `Eclipse', `Tesoro Dulce', and `Sugar Bowl' were 4 June, 18 June, 7 May, and 9 Apr., respectively. With these recommendations, the harvest season of melons lasted 40 days from 24 June to 3 Aug. for these four cultivars, which extended the production season an additional 2 weeks longer than the harvest date of last recommended 21 May planting date.
Field experiments were conducted over 4 years to evaluate the effects of antitranspirant (Folicote, Aquatrol Inc., Paulsboro, N.J.) and polyacrylamide gel (SuperSorb, Aquatrol Inc., Paulsboro, N.J.) on early growth of transplanted muskmelon grown either protected by tree windbreaks or exposed to seasonal winds. A randomized complete block design (RCBD) with split plot arrangement was used with wind protection (sheltered and exposed) areas as the main treatment and use of an antitranspirant spray or gel dip as subtreatments. Based on destructive harvests in the field, treatments and subtreatments did not affect dry weight or leaf area index in the first 2 years. Specific contrasts, however, showed that gel application significantly increased fresh weight, dry weight, and leaf area index over that of the untreated transplants whereas the spray application tended to reduce these factors during the first 3 weeks after transplanting. Significant differences between gel and spray subtreatments disappeared by 5 weeks after transplanting. Shelterbelts ameliorated crop microclimate thereby enhancing plant growth. Significantly, wind velocity at canopy height was reduced 40% on average and soil temperatures were about 4% warmer in the sheltered plots compared to the exposed plots during the first 5 weeks post-transplant. Muskmelon plants in the sheltered areas grew significantly faster than the plants in the exposed areas in 2 of the 3 years reported, with the 3-year average fresh weight increased by 168% due to wind protection. Overall transplanting success and early growth were enhanced the most by wind protection, followed by the polyacrylamide gel root dip, and least by the antitranspirant foliar spray. We conclude that microclimate modification by wind speed reduction can increase early muskmelon plant growth more consistently than the use of polyacrylamide gel as a root dip at transplanting or the use of an antitranspirant spray. A polyacrylamide gel root dip generally will provide more benefit during early muskmelon growth than the use of an antitranspirant spray.
Muskmelon [Cucumis melo L. (Reticulatus Group)] fruit sugar content is directly related to potassium (K)-mediated phloem transport of sucrose into the fruit. However, during fruit growth and maturation, soil fertilization alone is often inadequate (due to poor root uptake and competitive uptake inhibition from calcium and magnesium) to satisfy the numerous K-dependent processes, such as photosynthesis, phloem transport, and fruit growth. Experiments were conducted during Spring 2003 and 2004 to determine if supplemental foliar K applications during the fruit growth and maturation period would alleviate this apparent inadequate K availability in orange-flesh muskmelon `Cruiser'. Plants were grown in a greenhouse and fertilized throughout the study with a soil-applied N-P-K fertilizer. Flowers were hand pollinated and only one fruit per plant was allowed to develop. Starting at 3 to 5 days after fruit set, and up to 3 to 5 days prior to fruit maturity (full slip), entire plants, including the fruit, were sprayed with a glycine amino acid-complexed potassium (potassium metalosate, 24% K) solution, diluted to 4.0 mL·L-1. Three sets of plants were sprayed either weekly (once per week), biweekly (once every 2 weeks) or not sprayed (control). Fruit from plants receiving supplemental foliar K matured on average 2 days earlier than those from control plants. In general, there were no differences in fruit maturity or quality aspects between the weekly and biweekly treatments except for fruit sugar and beta-carotene concentrations, which were significantly higher in the weekly compared to the biweekly or control treatments. Supplemental foliar K applications also resulted in significantly firmer fruit with higher K, soluble solids, total sugars, ascorbic acid (vitamin C) and beta-carotene concentrations than fruit from control plants. These results demonstrate that carefully timed foliar K nutrition can alleviate the developmentally induced K deficiency effects on fruit quality and marketability.