Yield and Relationships among Head Traits in Cabbage as Influenced by Planting Date and Cultivar. I. Fresh Market

Yield and relationships among head traits were recorded in order to better understand the effects of planting date and cultivar selection on crop quality characteristics and to help increase the efficiency of cultivar development, evaluation, and selection. A total of seven cultivars of fresh market-type cabbage (Brassica oleracea L., Capitata Group) were planted in May and June of 1999 and 2000 at the OARDC Vegetable Crops Research Branch in Fremont, Ohio. Total and marketable yield, head traits (e.g., size, weight, density), and core dimensions were recorded at harvest. Main effects of year (Y), planting date (PD), and cultivar (C) and the Y × C interaction significantly affected seven to 10 of 10 head and core traits. However, the PD × C interaction was significant for head density, the ratio of head polar and equatorial diameter, and core base width. The Y × PD interaction was significant for six of 10 head and core traits. May planting tended to result in greater yield and larger, heavier heads with greater polar/equatorial diameter values relative to June planting. However, head density was unaffected by planting date. The number of head and core traits affected by planting date differed among cultivars. For example, six of 10 head and core traits were significantly affected by planting date in ‘Cheers and ‘DPSX315 while one trait was affected by planting date in ‘SuperElite Hybrid . The weight of numerous, individual, market-ready, trimmed heads showed a strong (avg. R value = 0.92) quadratic relationship to average head diameter. These data suggest that large-scale germplasm evaluations may benefit by including multiple plantings, as head weight, volume, diameter, and shape were affected by planting date, possibly due to variation in temperature and rainfall patterns. The data also suggest that routine measurement of numerous head traits in the same evaluations may be unnecessary, as selected traits (e.g., diameter and weight, head volume, and core volume) were strongly related. Studies in Florida, Puerto Rico, and the Netherlands have helped describe the influence of genetic and abiotic factors on yield and important traits of cabbage. Genotype, season, or planting date affected total and marketable yield, head weight, shape, and firmness, and core dimensions (de Moel and Everaarts, 1990; Fornaris-Rullan et al., 1989; Howe and Waters, 1994; Strandberg and White, 1979). de Moel and Everaarts (1990) found smaller, lighter heads and lower marketable yield in Juneand July-planted crops vs. May-planted crops but increases in core length with later planting in the Netherlands. Fornaris-Rullan et al. (1989) reported that head weight ranged from 0.63 to 1.73 kg, diameter from 12.4 to 18.6 cm, and length from 13.8 to 16.3 cm among 10 cabbage cultivars planted in Puerto Rico. ‘Bravo , ‘Big Cropper , ‘Market Prize , ‘Rio Verde , and ‘Titanic had the best overall acceptability in taste panel tests in the same study. Howe and Waters (1994) reported significant year × cultivar interactions in marketable yield, head weight and size, and other characteristics among 16 cabbage cultivars planted in two seasons in Florida. Differences among cultivars in major traits were also found in Louisiana, North Dakota, and Pennsylvania (Greenland et al., 2000; Orzolek et al., 2000; Sundstrom and Story, 1984). These reports notwithstanding, relatively less is known about the influence of abiotic factors on yield and important traits of cabbage compared to other major vegetable crops. Potential influences of climatic and genetic factors on relationships among key head traits are also not well understood, although head diameter, weight, and firmness are thought to increase, while moisture content may decrease during head formation and maturation (Isenberg et al., 1975; Strandberg, 1979). Therefore, additional study of cabbage growth is needed, especially under contrasting climatic conditions. The objectives of this study were to document planting date and cultivar effects on fresh market cabbage yield and head traits and to examine relationships among important head traits. Outcomes of this work are expected to include a greater understanding of planting date and cultivar effects on indicators of cabbage quality in Ohio and more efficient cultivar development, evaluation, and selection. Materials and Methods Plot establishment. Transplants of seven commercially important cultivars of fresh market cabbage (‘Blue Dynasty , ‘Bronco , ‘Cheers , ‘DPSX315 , ‘Emblem , ‘Red Dynasty , ‘SuperElite Hybrid ) having two to four true leaves were planted in the field using a two-row Holland Finger transplanter (Holland Transplant Co., Holland, Mich.) on 11 May 1999, 18 June 1999, 12 May 2000, and 30 June 2000 at the Ohio Agricultural Research and Development Center (OARDC) Vegetable Crops Research Branch in Fremont. Two-row plots were arranged in a randomized complete-block design with four (2000) or five (1999) replications per year; each replication contained both planting dates and all cultivars within each planting date. Plots measured 4.6 m long with 76 cm between rows and 28 cm between transplants. Soil type in each year was a Kibbie Fine-Sandy Loam (fine-loamy, mixed, mesic Hapludalfs). Preplant fertilizer applications included 72 kg·ha P2O5 via 0–46–0 and 291 kg·ha K2O via 0–0–60 in Sept.–Oct. 1998 and 1999 and 78 kg·ha N via 45–0–0 spread and incorporated 2 weeks before planting in 1999 and 2000. Each transplant was provided with 150 mL of a dilute nutrient starter solution containing N and P at planting. Standard pest management strategies, based on scouting, thresholds, and application of labeled pesticides, were employed. Plots were irrigated (3.0 mm, 1 July; 12.7 mm 16 July) in 1999 only. Harvest and data collection. Plots were examined 2–3 times per week beginning 55 d after transplanting to assess harvest readiness. Specific harvest dates were selected based on estimated days to maturity from the seed source and visual examination of heads. At maturity (80–124 d after planting), all heads were collected from the center 3 m of both rows in each plot. Heads were scored as marketable or unmarketable (small, split, rotten, or containing evidence of damage due to physiological disorders, disease, or insect feeding) and weighed as a group. Five marketable heads were then selected at random from the harvested group for further evaluation. Five outer leaves were removed from each head before they were re-weighed individually using an electronic scale (FV-60KWP, A and D Co., Tokyo, or CW11-2EO, Ohaus, Pine Brook, N.J.). Heads were then cut in half longitudinally and the core length and base width and head polar and HORTSCIENCE 38(7):1349–1354. 2003. Received for publication 1 Oct. 2002. Accepted for publication 9 Mar. 2003. Manuscript number HCS03-10. Salaries and research support provided in part by State and Federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State Univ. Work also supported in part by grants from the Ohio Vegetable and Small Fruit Research and Development Program. The many important contributions of Brenda Schult and staff of the OARDC Vegetable Crops Research Branch in Fremont, Ohio, are gratefully acknowledged. We thank Ted Radovich for his technical assistance and critical reading of the manuscript. Use of trade names does not imply endorsement of the products named nor criticism of similar ones not named. Assistant Professor; to whom reprint requests should be addressed. E-mail: [email protected] Postdoctoral Research Associate. 7-7475, p1349-1354 1349 12/15/03, 12:44:16 PM HORTSCIENCE, VOL. 38(7), DECEMBER 2003 1350 CROP PRODUCTION equatorial diameters were recorded. The ratio between head polar and equatorial diameter for the 550 heads examined rarely deviated significantly from 1 (Fig. 1A). Overall, 50% of the ratio values were in the range 0.93 to 1.08 with a mean value of 1.01 (Fig. 1A). Therefore, heads were treated as spheres in calculating head volume using average head diameter values and a standard geometric formula: Table 1. Analysis of variance for the influence of year, planting date, and cultivar on head traits of seven cultivars of fresh market cabbage planted in May and June of 1999 and 2000 at the OARDC Vegetable Crops Research Branch in Fremont. Trimmed head Core Marketable Diameter Base % Head Source df yield Wt Vol Density Polar (P) Equatorial (E) Avg P/E Length width vol Year (Y) 1 * *** *** *** *** *** *** *** *** * NS Planting date (PD) 1 *** *** *** NS *** *** *** *** NS *** NS Cultivar (C) 6 *** *** *** *** *** *** *** *** *** *** ** Y × PD 1 ** * NS *** * * NS *** * NS NS Y × C 6 * ** * *** * * * *** * *** NS PD × C 6 NS NS NS * NS NS NS * NS *** NS NS, *, **, Nonsignificant or significant at P = 0.05, 0.01, or 0.001, respectively. V = 1.33 · 3.1415927 · r where r = average head radius. Head density (g·cm) was then calculated using weight values taken at harvest and estimated head volume. The core was treated as a cone with core volume calculated as: V = 0.33 · 3.1415927 · r · h with r = 0.5 · base width and h = core length. The percent of the head volume contained in the core was calculated as the ratio of head to core volume. Thus, for each cultivar, direct measures of head weight, head polar and equatorial diameter, core length and base width were collected on 25 and 20 individual heads per planting date in 1999 and 2000, respectively (a total of at least 280 heads in each year). Statistical analysis. Data were subjected to analysis of variance (ANOVA) to test main effects and interactions of year (Y), planting date (PD), and cultivar (C) using Statistical Analysis System version 7 for Windows (SAS Institute, Cary, N.C.). Fisher s least significant difference test ( = 0.05) was used to compare treatment (year, planting date) means.