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Fu, I-M., C. Shennan, and G.E. Welbaum. 1993. Evaluating Chinese cabbage cultivars for high temperature tolerance. p. 570-573. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Evaluating Chinese Cabbage Cultivars for High Temperature Tolerance

I-Mo Fu, Carol Shennan, and Gregory E. Welbaum

  1. METHODOLOGY
  2. RESULTS AND DISCUSSION
    1. California Trials
    2. Virginia Trials
  3. CONCLUSIONS
  4. REFERENCES
  5. Table 1
  6. Table 2
Chinese cabbage [Brassica campestris L., Pekinensis group (Lour), Brassicaceae] has been an important vegetable in eastern Asia for many centuries (Li 1981). Chinese cabbage is an annual with only a few characteristics in common with cabbage (B. oleracea L., Capitata group). There are both heading and nonheading types of Chinese cabbage. Plants of nonheading types have several thick, white petioles with smooth, dark green leaf blades arranged in a tight cluster. Heading types generally produce an elongated, compact head comprised of wrinkled leaves with broad veins. Chinese cabbage is becoming increasingly popular in the United States due to a growing Asian population and a greater appreciation of the crop in general. The strong market demand has many vegetable growers interested in Chinese cabbage production. However, Chinese cabbage, unlike common cultivars of cabbage, is intolerant of warm temperatures. This may limit the development of Chinese cabbage as an alternative crop in much of the United States. Loose head formation, tip burn, and soft rot are major problems often encountered when Chinese cabbage is grown at high temperatures (Kuo and Tsay 1981; Fritz and Honma 1987). Experiments were conducted in Virginia and California to determine whether cultivars differ with respect to their susceptibility to premature bolting and high temperatures, whether mulching treatments affect heat tolerance, and which planting dates are optimal for Chinese cabbage production.

METHODOLOGY

In Davis, California, five heat-tolerant cultivars of Chinese cabbage (ASVEG #1, Blues, B14, B40, and China Express) were evaluated. In April, June, August, and September of 1988, transplants at the six leaf stage were set in double rows 51 cm apart on 102 cm raised beds with an in-row spacing of 31 cm. Three mulch treatments were employed: control (bare ground), straw, and clear plastic. The experimental design was a randomized complete block with split plots, with mulch treatments assigned to blocks and replicated 3 times and cultivars assigned to plots. The frequency of irrigation was based on tensiometer and neutron probe measurements. The following parameters were recorded at harvest: average head weight; the percentage of harvestable heads, bolting heads, diseased heads, and loose heads; and head solidity (Opeña and Lo 1981).

In Virginia, the cultivars China Flash, China Express, Tropical Quick, Mei Qing Choi, Joi Choi, Springtime, Kasumi, China Pride, and Summertime were evaluated. Two replications of each cultivar were organized in a completely randomized design. Transplants were set in double rows 46 cm apart with an in-row spacing of 31 cm in 1990 (mid-April and late July) and 1991 (mid-June). Fertilizer (10N-4.3P-8.3K) was row-banded at the rate of 85 kg/ha before planting, and a drench consisting of 9N-19.4P-12.5K fertilizer (4 g/liter) and the insecticide, Diazinon (0.7 g/liter), was applied at a rate of 250 ml/plant after transplanting. A Bravo/Ridomil drench was applied during development to combat head rot. Plots were harvested 61 and 68 days after transplanting.

RESULTS AND DISCUSSION

California Trials

The mean daily temperature for the April transplanting was 16.0°C, while the mean maximum daily temperature was 24.5°C. Only 28% of all April transplants produced harvestable heads largely due to a disease rate of 45% and the fact that 12% of the plants bolted prematurely. The mean daily temperature for the June transplanting was 24.8°C. Only 20% of all June transplants produced harvestable heads due to soft rot and tipburn. In August, the mean daily temperature dropped to 21.7°C, and 66% of all plants produced harvestable heads. The mean daily temperature for the September transplanting was 15.5deg.C, and the harvestable yield was 93%. Heat-tolerant cultivars from the April and June transplanting dates could not be identified because all cultivars produced a relatively low percentage of harvestable heads. Conversely, temperatures following the September transplanting were nearly ideal for Chinese cabbage production, so heat-tolerant cultivars could not be detected. Temperatures after the August transplanting were intermediate between those following the June and September transplantings, revealing significant differences among cultivars for all characteristics except the percentage of bolting and diseased heads (Table 1A).

The cultivar 'ASVEG #1' produced a high percentage of disease resistant, solid heads (Table 1B). The cultivar 'Bl4' was similar to 'ASVEG #1'. The head quality of 'China Express' was very good, but a high percentage of plants failed to form heads (Table 1B). There was also a significant cultivar by mulch interaction that was probably caused by the inconsistent response of cultivars to mulch treatments, making it impossible to draw simple conclusions about differences among the percentages of loose and harvestable heads (Table 1A). There were also significant differences among mulch treatments for the percentage of diseased heads, but a highly significant cultivar by mulch interaction makes it impossible to draw simple conclusions about these differences. There were no significant differences among the mulch treatments for head weight, the percentage of bolting plants, or head solidity (Table 1C).

Virginia Trials

There were significant differe'nces among cultivars for the percentage of harvestable and bolting heads in June 1990 (Table 2). In some cases, the low percentage of harvestable heads was due to tipburn, soft rot, and bolting. The development of disease symptoms corresponded with an increase in the mean maximum daily temperature in April (21.2±0.7°C), May (21.4±0.8°C), and June (25.6±0.8°C). However, 'China Flash', 'China Express', and 'Kasumi' did not bolt and showed a lower frequency of head rot than other cultivars. Heads harvested in early October from the July transplanting did not bolt and had fewer incidences of head rot (not shown).

In 1991, Chinese cabbage was transplanted to the field in late June. Temperatures as high as 33°C were recorded on several occasions during head formation in July and August. The occurrence of head rot and tipburn were much greater than for the early June harvest from the previous year. The percentage of harvestable heads ranged from 25 to 72% in 1991 (not shown). In Virginia, soft rot may have been promoted by overhead irrigation and poor drainage, yet, in California where raised beds and furrow irrigation were used, soft rot was also a serious problem. Raised beds, in some instances, have been shown to be beneficial in reducing the incidence and spread of soft rot (Fritz and Honma 1987).

CONCLUSIONS

As reported by Palada et al. (1987), premature bolting is a problem with spring but not fall crops. In this study, several cultivars were found to be resistant to bolting (Table 1). There were also differences in heat tolerance among cultivars, although no cultivar was sufficiently resistant to be productive in mid-summer at either location. The highest incidence of diseased heads occurred in plantings that matured under high temperature conditions in mid-summer in both Virginia and California. In both locations, best results were obtained when Chinese cabbage was grown as a fall crop. This is in contrast to results showing that Chinese cabbage can be successfully grown as a spring crop (Palada et al. 1987). The cultivar 'ASVEG #1' performed well in California and has also performed well in other locations (Fritz and Honma 1987).

REFERENCES

Table 1. Performance of mulched and unmulched Chinese cabbage cultivars, Davis, California, August, 1988z.

Variable Head weight (g) Harvestable heads (%) Bolting heads (%) Diseased heads (%) Loose heads (%) Solidity (g/cm3)x
A. Analysis of cultivar and mulch treatments
Cultivar * ** NS NS ** **
Mulch NS * NS * * NS
Cult x mul NS * ns ** * NS
B. Variation in cultivar performancey
ASVEG 771ab 84 2 10 4 0.69a
Blues 961ab 27 0 19 54 0.49b
B14 782ab 75 0 23 3 0.55ab
B40 744b 51 0 16 22 0.41b
China Exp. 1002a 56 0 14 31 0.52b
C. Effect of mulch treatmenty
Control 894 66 1 10 16 0.49
Plastic 888 60 0 18 32 0.53
Straw 777 50 0 20 20 0.58
NS, *, ** Nonsignificant, significant at P = 0.05, and 0.01, respectively.
zN = 15, 9, 15, for Tables A, B, and C, respective.
ymean separation by Tukey's Studentized Range (HSD) Test.
xSolidity = mean head wt (g)/volume of head (cm3); volume (cm3) is estimated as (0.524)(head width)(head height).

Table 2. Performance of Chinese cabbage cultivars, June harvest, Blacksburg, Virginia, 1990.

Cultivar (Seed Co.) Head weight (kg±SE) Harvestable heads (%) Bolting heads (%) Plant height (cm±SE) Plant diameter (cm±SE) Comments
Mei Qing Choi (Sakata) 0.54±0.08 7 35 23.3±1.9 9.7±0.3 Light green petioles and foliage, a nonheading pak choi type. Soft rot affected about 65% of the plants, resulting in low harvestable yield.
Joi Choi (Sakata) 1.09±0.13 79 5 37.3±0.9 14.3±0.7 A nonheading pak choi type with dark green foliage and white petioles. Attractive large plants were less susceptible to soft rot compared to 'Mei Qing Choi'.
China Flash (Sakata) 1.85±0.17 80 0 28.9±0.6 17.0±0.5 Medium green napa type. Very compact plants produced medium sized heads. About 20% were affected by head rot. Recommended for further trial in Virginia.
Tropical Quick (Sakata) 0.44±0.97 0 100 39.2±2.2 10.4±0.6 Medium green tropical heading type. Plants bolted early in development. Does not appear to be adapted to Virginia.
China Express (Sakata) 1.56±0.10 85 0 30.2±0.6 16.5±0.8 Similar in appearance to 'China Flash'. Only a few plantswere affected by rot. Plants held well in the field without splitting. Recommended for further trial in Virginia.
Springtime (Stokes) 0.96±0.05 55 15 24.6±1.2 11.7±0.4 Light green napa type. Early maturing but susceptible to tipburn, soft rot, and splitting. May have some value as an early season cultivar.
Kasumi (Stokes) 2.14±0.13 90 0 26.9±0.6 19.2±0.7 Medium green napa type. Compact plants produced uniform extremely solid heads with little head rot. Recommended for further trial in Virginia.
China Pride (Stokes) 1.97±0.22 0 60 34.2±3.7 18.7±01.1 Large dark green napa type. Most plants bolted prematurely before head formation.
Summertime (Stokes) 1.39±0.08 50 0 32.6±0.8 15.1±0.3 Late maturing medium green napa type. Plants lacked uniformity and were susceptible to head rot.
LSD .05 0.45 24 29 3.1 2.8

Last update April 29, 1997 aw