Spacing and Genotype Affect Fruit Sugar Concentration, Yield, and Fruit Size of Muskmelon
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HORTSCIENCE 36(2):274–278. 2001. Short internode (SI) muskmelons are inde- terminate, but have fewer nodes, shorter inter- nodes, and less leaf area per plant than the Spacing and Genotype Affect Fruit vining muskmelons (Knavel, 1991). They may have potential for culture at higher densities Sugar Concentration, Yield, and Fruit (Mohr and Knavel, 1966). Birdsnest melons are unique because of Size of Muskmelon their compact growth habit and ability to ger- minate rapidly at cool temperatures (Nerson et F. Kultur1, H.C. Harrison2, and J.E. Staub3 al., 1982, 1983; Paris et al., 1981, 1982). These melons possess a uniform, highly branched Department of Horticulture, University of Wisconsin, Madison, WI 53706-1590 plant habit with shorter internodes than vining Additional index words. Cucumis melo, plant density, sucrose, birdsnest, vining types (Paris et al., 1982), and have a relatively concentrated fruit setting period in compari- Abstract. Muskmelon (Cucumis melo L.) genotypes, Birdsnest 1 [‘Qalya’ (BN1)], Birdsnest son with short internode and vining types 2 (BN2), and ‘Mission’ (V) were used to determine the effects of differing plant architec- (Nerson et al., 1983). They also set fruit near ture and spacing on fruit sugar concentration and yield. The BN1 and BN2 genotypes the center of the plant, causing uniform fruit possessed a highly branched growth habit specific to birdsnest melon types, but not development and maturity (Paris et al., 1981). characteristic of standard indeterminate vining types (e.g., ‘Mission’). Experiments were If high-yielding birdsnest type melons could conducted at both the Hancock and Arlington Experimental Farms in Wisconsin, where produce early, uniformly mature, high-quality plant response to two within-row spacings [35 cm (72,600 plants/ha) and 70 cm (36,300 fruit, they might offer a financially viable plants/ha)] in rows on 210-cm centers was examined. Genotypes were grown in a alternative to muskmelon growers for once- randomized complete-block design with four replications at each location and evaluated over harvesting. for primary lateral branch number, fruit number per plant and per hectare, average fruit As within-row spacing increases, yield per weight, yield per plant (g), yield per hectare (t), and fruit sugar concentration. Yield, fruit plant, number of fruits per plant, weight per number, and sugar concentration were higher for all genotypes at Arlington than at fruit, and percentage of soluble solids increase Hancock. The main effect of genotype was significant for all traits examined. Genotypes (Bhella, 1985; Davis and Meinert, 1965; BN1 and V had higher mean fruit weight, yield per plant and per hectare, and fruit quality Maynard and Scott, 1998; Mendlinger, 1994; (fruit sugar concentration) than did BN2. Spacing affected all traits, except primary Zahara, 1972). Although Bhella (1985) branch number and fruit sugar concentration. Fruit number and yield per plant and reported that plant density did not affect average fruit weight were higher with wider spacing, but yield (t·ha–1) and fruit number per yield/ha of ‘Classic’ and ‘Burpee hybrid’ hectare were lower. vining-type muskmelons, Knavel (1988) showed that as within-row spacing of short internode muskmelon decreased from 90 cm Muskmelon is an important horticultural the hard-ripe or early-slip maturity stage, but (8140 plants/ha) to 45 cm (16,268 plants/ha), crop in the Cucurbitaceae family. Worldwide fruits picked at full slip usually have closer to fruit number and yield per plant decreased. muskmelon production is ≈18 million t [Food 15% soluble solids. The soluble solids con- Fruit quality (sugar concentration of and Agriculture Association (FAO) 1997], centration is an important quality determinant birdsnest melon types) as influenced by spacing with China, Turkey, Iran, the United States, that has long been used as an indicator of and soil type has not been investigated. Thus, an and Spain being the major producers. Arizona, muskmelon sweetness, flavor, maturity, and experiment was designed to determine the ef- California, and Texas are the primary musk- acceptability (Rosa, 1928). As the percentage fect of plant architecture on yield and fruit melon production areas in the United States of soluble solids increases, fruit quality also quality for several plant populations. Birdsnest [National Agricultural Statistics Service increases (Nonnecke, 1989). According to melon types were compared with a vining type (NASS), 1995]. Bianco and Pratt (1977), soluble sugars ac- for their ability to produce early, uniform ripen- According to U.S. Dept. of Agriculture count for >97% of the total soluble solids in ing, high-quality fruit for commerce. (USDA) standards, a high-quality muskmelon maturing muskmelon fruits, with sucrose ac- fruit has between 9% and 11% soluble solids counting for ≈50% of all sugars. Glucose and Materials and Methods (Pratt et al., 1977; Rubatzky and Yamaguchi, fructose account for >90% of the total soluble 1997). The soluble solids concentration varies sugars during the first 24 d after antithesis Plant material. One vining (V) ‘Mission’ with fruit maturity (Peirce, 1987); fruits have (Lester et al., 1985; McCollum et al., 1988; and two birdsnest muskmelon types were used. 8% to 12% soluble solids when harvested at Ofusu-Anim and Yamaki, 1994; Schafer et al., Birdsnest 1 (BN1) ‘Qalya’ was obtained from 1992). Thereafter, sucrose begins to accumu- the Agricultural Research Organization, Newe Received for publication 24 Aug. 1998. Accepted late and predominates in the ripe fruit. Fruits Ya’ar Experiment Station, Hafia, Israel, and for publication 10 Feb. 1999. This research was should be harvested when fully ripe to obtain Birdsnest 2 (BN2) was an experimental line supported by the Graduate Research Committee the highest quality because sucrose accumula- (F5) obtained from the USDA, Agricultural and the College of Agricultural and Life Science of tion takes place solely in fruit attached to the Research Service (ARS), Vegetable Crops the Univ. of Wisconsin, Madison, and the govern- plant (Bianco et al., 1977; Schafer et al., 1992; Research Unit, Madison, Wis. This line origi- ment of Turkey. We appreciate the assistance of Wang et al., 1996; Wyllie et al., 1995). x Eric V. Nordheim with the statistical analyses and nated from a cross between ‘PMR 45’ Persia of Jiwan P. Palta with the sugar analyses. Mention Muskmelon cultivars exhibit three major 201. The BN2 genotype was developed to of a trade name, proprietary product, or specific growth habits: vining, short internode, and obtain U.S. Western shipping market class equipment does not imply approval to exclusion of birdsnest (multiple branching), but only pros- melon genotypes with high, early yield for other products that may be suitable. The cost of trate vining melons are grown commercially once-over harvest. publishing this paper was defrayed in part by the in the United States. Vining types typically set Experimental design. Experiments were payment of page charges. Under postal regula- fruit distal to the center of the plant. The fruits conducted at the Hancock and Arlington Ex- tions, this paper therefore must be hereby marked do not mature uniformly, and hence are har- perimental Farms in Wisconsin utilizing a advertisement solely to indicate this fact. 1 vested individually when mature. Since vines randomized complete-block design with four Former Graduate Student. spread between rows, cultivation and weed 2Professor. To whom requests for reprints should replications at each location. Replications con- be addressed. E-mail address: hcharris@facstaff. management are difficult and require 30 to 60 sisted of 25 plants (i.e., five rows of five plants wisc.edu. cm within-row spacing on 200-cm centers each) with the interior nine plants being 3Professor and U.S. Dept. of Agriculture Research (15,000 and 20,000 plants/ha) (Rubatzky and sampled, and the remaining 16 plants being Horticulturist. Yamaguchi, 1997). used as guards. Plant culture. In Hancock, which has 95% ethyl alcohol for 1 min. Twenty µL of the equate room to produce the optimum numbers Plainfield sandy soil (Typic updisamment, homogenate was combined with 50 µL phenol, and weight of fruit at both spacings used. mixed mesic), 130 kg·ha–1 0N–0P–50K was 5000 µL sulfuric acid, and 1980 µL of distilled Although genotypes differed in number of applied preplant, while a total of 652 kg·ha–1 of water. Absorbance at 490 nm was recorded primary lateral branches, neither location nor 20N–8.7P–16.6K was applied five times dur- using a Beckman DU 50 spectrophotometer spacing influenced this trait. Sugar concentra- ing the growing season to allow for nutrient (Beckman Instruments, Fullerton, Calif.). Sugar tion was higher at Arlington than at Hancock leaching. On the plano silt loam (Typic concentration in the homogenate (x) was (Table 1), yet the ranking among genotypes argiudol; fine-silty, mixed mesic) soil at Ar- determined by reference to a linear standard remained the same at each location (Table 2). lington, 305 kg 34N–0P–0K, 55 kg 0N–20.1P– curve [y = m x + b, where y = absorbency Although spacing was significant for average 0K, and 305 kg 0N–0P–50K were preplant value and x = concentration of solution plant yield (g), it had surprisingly little effect incorporated per hectare according to soil test (µg·mL–1)]. This method was used to calcu- on sugar concentration (Tables 1 and 2). recommendations (Binning et al., 1998). late total mg sugar/g fruit tissue. The percent- Fruit number. All genotypes set more fruit Muskmelon seeds were sown into 48-cell age of soluble solids in the juice of the fruit at Arlington than at Hancock. Although fruit packs (T.O. Plastic, Minneapolis) containing was determined using a hand refractometer number per plant was higher for BN2 than Faward Ag Mix No. 2 media (Faward, (Currence and Larson, 1941). BN1 or V at Arlington, data for all genotypes Agawam, Me.) on 15 and 23 May 1997 at Statistical analysis.