Brassica oleracea - cauliflower and broccoli (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Vegetable
Forage / feed
Food security

1, plant habit (cauliflower); 2, young inflorescence (cauliflower); 3, young inflorescence (broccoli). Source: PROSEA

cauliflower, product

cauliflower, plant habit

broccoli

Brassica oleracea L. (cauliflower and broccoli)

Protologue: Sp. pl. 2: 667 (1753).

Family: Brassicaceae (Cruciferae)

Chromosome number: 2n = 18

Vernacular names

• Cauliflower (En).
• Chou-fleur (Fr).
• Couve flor (Po).

• Broccoli, sprouting broccoli, calabrese (En).
• Brocoli, chou brocoli (Fr).
• Brócolos, couve brócolo (Po).

Origin and geographic distribution

Cauliflower and broccoli probably evolved in Roman times from wild or primitive cultivated forms of Brassica oleracea from the eastern Mediterranean region. A remarkable diversity of cauliflower and broccoli-like vegetables developed in Italy. During the last 400 years, white-headed cauliflower spread from Italy to central and northern Europe, which became secondary centres of diversity for annual and biennial types. Cauliflower adapted to hot and humid tropical climates has evolved in India during the last 200 years from biennial cauliflower of mainly British and central European origin. Broccoli with one main green ‘head’ (calabrese) was introduced into the United States by Italian immigrants during the early 20th century. From the United States it has spread throughout the world in the last 50 years. In tropical Africa cauliflower and broccoli are grown, usually on a small scale, in many countries with highland areas, in West Africa occasionally also in lowland areas during the cool harmattan season.

Uses

Cauliflower and broccoli are grown for their large, edible, very young inflorescence. Cauliflower heads (curds) and in broccoli the heads and the fleshy upper portion of the stem are mostly consumed as a cooked vegetable; sometimes they are cut into small pieces (florets) and used raw in mixed salads or in pickles. Broccoli, and to a lesser extent cauliflower, have become popular as quick-frozen vegetables, particularly in the United States and Europe. Both are also processed in mixtures of dried vegetables.

Production and international trade

Total world production of cauliflower in 2002 was estimated at 15.3 million t per year from 812,000 ha. Major cauliflower producing areas are China 303,000 ha, India 260,000 ha, Europe 120,000 ha, North America 37,000 ha, Middle East 20,000 ha, Japan 10,000 ha and North Africa 11,000 ha. World statistics on broccoli production are incomplete and often mixed with cauliflower data. Important broccoli producing areas are: North America 56,000 ha, Europe 45,000 ha, Latin America 8000 ha and Asia 17,000 ha. In tropical Africa cauliflower and broccoli are minor crops; statistical data are very incomplete.

Properties

Cauliflower contains per 100 g edible portion (florets only, 45% of product as purchased): water 88.4 g, energy 142 kJ (34 kcal), protein 3.6 g, fat 0.9 g, carbohydrate 3.0 g, dietary fibre 1.8 g, Ca 21 mg, Mg 17 mg, P 64 mg, Fe 0.7 mg, Zn 0.6 mg, carotene 50 μg, thiamin 0.17 mg, riboflavin 0.05 mg, niacin 0.6 mg, folate 66 μg, ascorbic acid 43 mg. Raw green broccoli contains per 100 g edible portion (tough stems removed, 61% of product as purchased): water 88.2 g, energy 138 kJ (33 kcal), protein 4.4 g, fat 0.9 g, carbohydrate 1.8 g, dietary fibre 2.6 g, Ca 56 mg, Mg 22 mg, P 87 mg, Fe 1.7 mg, Zn 0.6 mg, carotene 575 μg, thiamin 0.10 mg, riboflavin 0.06 mg, niacin 0.9 mg, folate 90 μg, ascorbic acid 87 mg (Holland, B., Unwin, I.D. & Buss, D.H., 1991). Both vegetables have a high nutritional value, but broccoli scores overall higher than cauliflower. Broccoli is rich in Se, containing 3 μg/100 g.

Like all Brassica crops, cauliflower and broccoli contain various bioactive compounds such as flavonoids and hydroxycinnamoyl derivatives. They also contain glucosinolates, which are responsible for the characteristic flavour and taste, and some of them have strong anticarcinogenic properties. In cauliflower the main glucosinolate is sinigrin, in broccoli glucoraphanin. Sulforaphane, a breakdown product of glucoraphanin, has shown anticancer activity in rats and humans against several forms of cancer. It is a potent inducer of enzymes that protect cells against electrophile toxins including carcinogens; it also upregulates the synthesis of hepatic detoxification enzymes. The glucosinolate content is influenced by ecological factors (e.g. soil S content) and cultivar. ‘Brigadier’, ‘Majestic’ and ‘Wintergarden’ are particularly rich in glucoraphanin. Although the concentration of glucoraphanin is highest in the seed, the total amount accumulated is highest at the green head stage.

Description

• Erect, glabrous, annual or biennial herb up to 80 cm tall at the mature vegetative stage, up to 150 cm when flowering, with unbranched stem thickening upwards; root system strongly branched.
• Leaves alternate but closely arranged and more or less erect, forming a rosette surrounding the young inflorescence especially in cauliflower, usually simple; stipules absent; leaves almost sessile, but often shortly petiolate in broccoli; blade ovate to oblong, up to 80 cm × 40 cm, undulate or irregularly incised to almost entire, coated with a layer of wax, blue-green with whitish veins.
• Inflorescence a terminal paniculate raceme up to 70 cm long, when young (curd or head) composed of more or less densely arranged branching partial inflorescences and fleshy peduncles, in cauliflower up to 30 cm in diameter, very solid and globular to rather loose and flat, white to green, in broccoli less densely arranged with longer peduncles, green to purple.
• Flowers bisexual, regular, 4-merous; pedicel up to 2 cm long, ascending; sepals oblong, c. 1 cm long, erect; petals obovate, 1.5–2.5 cm long, clawed, pale to bright yellow or whitish; stamens 6; ovary superior, cylindrical, 2-celled, stigma globose.
• Fruit a linear silique 5–10 cm × c. 5 mm, with a tapering beak 5–15 mm long, dehiscent, up to 30-seeded.
• Seeds globose, 2–4 mm in diameter, finely reticulate, brown.
• Seedling with epigeal germination, with a taproot and lateral roots; hypocotyl 3–5 cm long, epicotyl absent; cotyledons with petiole 1–2 cm long, blade cordate, 1–1.5 cm long, cuneate at base, notched at apex.

Other botanical information

Cauliflower and broccoli have been classified in convar. botrytis (L.) Alef., as var. botrytis L. and var. italica Plenck, respectively. They can best be considered as cultivar-groups and as such have been called Cauliflower Group and Broccoli Group. Both groups are sometimes subdivided into several smaller ones, but such classifications are of no relevance in tropical Africa. Modern cauliflower cultivars can also be grouped according to their horticultural characteristics: temperate biennial winter cultivars (frost resistant or not frost resistant), temperate annual cultivars (spring, summer and autumn cultivars) and tropical cultivars. Temperate summer cultivars and increasingly tropical cultivars are grown in tropical Africa, but the last group of cultivars, adapted to hot and humid climates, is most suitable. Popular cultivars like ‘Patna’, ‘Agahani’ and ‘Kartika’ were developed in India from landraces. These selections are of rather poor quality. Modern F₁ hybrids developed in Japan, China and India, combining good quality with heat tolerance, are rapidly replacing the old landraces.

In broccoli the single headed ‘calabrese’ type with a compact dome-shaped head with small beads (flower buds) is grown worldwide, under conditions comparable to the summer types of temperate cauliflower. The buds are preferably dark green.

Growth and development

Cauliflower and broccoli seed (6% moisture content) will remain viable for at least 4–6 years when stored dry at temperatures below 18°C. Seeds germinate within 3–6 days and seedlings have 7–9 true leaves within 30–40 days at > 20°C average daily temperatures.

Differentiation of floral primordia in cauliflower can only start at the end of the juvenile phase, when plants have 12–15 leaves for early types to more than 30 leaves for late biennial types. Good curd induction requires a subsequent period of 20–30 days at relatively low night temperatures of 10–15°C for temperate and 18–22°C for tropical cultivars. Higher than optimum temperatures during this period will cause delayed curd formation and defects such as fuzziness and bracting (development of bracts, which may grow through the curd surface). Premature flower bud formation causing a rough granular appearance can occur when the temperature is below optimum. Curd induction requirements of most broccoli cultivars are similar to those of temperate summer cauliflower. Heads of annual cauliflower and broccoli are ready for harvesting 75–150 days after sowing, depending on cultivar and climate.

Very soon after the optimum harvesting date, curds of cauliflower plants start to enlarge, become loose, the peduncles lengthen and turn green and the floral meristems develop into inflorescences. Particularly in modern cauliflower cultivars with very firm and dense curds, only the outer rim of the curd develops flowers, with the rest aborting and becoming a substrate for pathogenic fungi under humid conditions. In broccoli the head is a mass of fully developed flower buds and normally very little abortion takes place.

Flowering starts at the base of the inflorescences and continues for about one month in cauliflower and for 20–25 days in broccoli plants. Insects, especially bees, effect pollination. Seeds are mature 45–50 days after anthesis.

Ecology

Temperate summer cultivars of cauliflower and broccoli can be grown in the tropics when maximum temperatures do not exceed 30°C and night temperatures drop below 18°C for about four weeks about one month after planting to ensure good curd induction. In subtropical areas these conditions often occur in the dry winter season. In the equatorial areas these conditions can be found at elevations above 1000 m, at higher latitudes in the tropics during the dry winter season. In tropical lowland conditions only adapted tropical types can be grown, but their weight and quality are in general inferior to temperate types. For successful seed production a fairly cool and dry climate is a prerequisite.

Soils should be well drained and fertile, with good moisture retaining capacity and a high organic matter content; the optimum pH is 6.5–7.5.

Propagation and planting

Seed of cauliflower and broccoli is mostly sown on seedbeds, sometimes in soil blocks or modules. The 1000-seed weight is 2.5–4 g, the seed requirement 100–200 g/ha. Dormancy of freshly harvested seed can be reduced by overnight soaking and rinsing in water; it also disappears after 3–4 months storage, so seed from seed companies is not dormant. Young seedlings may have to be shaded to prevent sun scorching. Transplanting to the field should be done when seedlings have 7–9 true leaves, 30–40 days after sowing. Plant densities for cauliflower are 15,000–35,000 plants/ha; for broccoli similar or somewhat higher densities are applied. Vegetative propagation of broccoli plants is possible by rooting and transplanting of lateral shoots. In cauliflower lateral shoots are not available, but propagation through tissue culture from young floral meristems is easy to realize. This is only practised in breeding programmes to maintain selected plants.

Management

Soil preparation includes deep digging, mixing with compost or stable manure (20 t/ha), followed by fine tillage. NPK fertilizers – type and rates depending on soil type, mineral reserves in the soil and expected yields – are applied before planting; another two or three N fertilizer dressings are applied later to stimulate good head formation. A high-yielding crop needs about 220 kg N, 25–40 kg P and 200–300 kg K per ha. Nitrogen deficiency at the early growth stage will cause ‘buttoning’: stunted plants with reduced leaf and head development. Cauliflower and broccoli have a high demand for Mg, Bo and Mo. Applications of dolomite limestone, borax and ammonium molybdate may be necessary to prevent physiological disorders, such as browning of the head and plants without a heart. Deficiencies occur more commonly on acid soils.

A regular water supply is required throughout the growing season, but the heads of cauliflower and broccoli are easily affected by fungal rots when continuously exposed to wet conditions. Therefore, the mature plant stage and harvesting should be planned as much as possible outside the rainy season and overhead irrigation should be avoided.

The young crop should be kept free of weeds. Mulching, e.g. with rice straw, is beneficial to growth as it retains moisture, keeps soil temperatures down and suppresses weeds. Growth of the plant should be regular and undisturbed. Sudden increases in temperature or water stress may cause the formation of bracts, fuzziness or splitting of cauliflower curds and irregular head formation and premature flowering in broccoli. Maturing cauliflower curds must be protected from direct sunlight by covering with broken-off leaves to prevent them from turning yellow and/or pink. Many modern cultivars are self-protecting, i.e. inner leaves wrap tightly around the curd.

Diseases and pests

Diseases and pests are similar to those of cabbage in tropical regions. For important diseases such as Fusarium yellows (Fusarium oxysporum f.sp. conglutinans), downy mildew on leaves and heads (Peronospora parasitica), black rot (Xanthomonas campestris pv. campestris) and clubroot (Plasmodiophora brassicae), resistance or field tolerance have been found in cauliflower and broccoli accessions, but the majority of present-day cultivars are still susceptible. A pH of 7 is recommended to prevent clubroot damage. Other diseases causing problems are the seedborne diseases black leg (Leptosphaeria maculans; asexual form: Phoma lingam) and Alternaria blight (Alternaria brassicae), and the not seedborne diseases powdery mildew (Erysiphe polygoni), damping off (Pythium ultimum), stem rot (Rhizoctonia solani), bacterial soft rot (Erwinia carotovora) as storage disease, cauliflower mosaic virus (CaMV) and turnip mosaic virus (TuMV). Root-knot nematodes (Meloidogyne spp.) can be a serious problem and should be avoided by proper crop rotation.

Important pests are diamondback moth (Plutella xylostella), cut worm (Agrotis spp. and Spodoptera littoralis), cabbage root fly (Delia radicum), cabbage moth (Crocidolomia binotalis), cabbage butterfly (Pieris spp.) and aphids (Aphis spp. and Brevicoryne brassicae), the vectors of CaMV and TuMV. Diamondback moth is extremely noxious because it quickly develops resistance to many insecticides, and because of the small size of the larvae and pupae, which makes removal virtually impossible. Methods of integrated pest management applied to cabbage (using parasitoids, sex pheromones, trap plants and very restricted chemical control) can also be effective in cauliflower and broccoli.

Harvesting

Annual cauliflower and broccoli are ready for harvesting 60–150 days after transplanting; some early heat-tolerant cultivars, mainly F₁ hybrids, are even ready within 40–55 days in tropical regions. Harvesting takes place over a period of 1–2 weeks. Modern F₁ hybrids can be harvested in 2–3 cuttings.

Cauliflower heads are cut with sufficient trimmed leaves still attached to protect the curds during packing and transport. Broccoli heads are harvested with 10–15 cm of stem, without leaves.

Yield

Cauliflower yields can attain 12–30 t/ha and broccoli yields 10–15 t/ha; in the tropics the highest yields are obtained above 1000 m altitude. Seed yields are 200–600 kg/ha in temperate climates.

Handling after harvest

Cauliflower and broccoli heads will deteriorate quickly unless cooled soon after harvesting. Cauliflower curds can be stored for about 3 weeks at 1°C and 95% relative humidity, but storage life for broccoli is much shorter and heads are usually wrapped in polythene film to prevent rapid desiccation and yellowing.

Genetic resources

In temperate regions F₁ hybrids have completely replaced the landraces as well as the open-pollinated improved cultivars of both cauliflower and broccoli. This process is also taking place in tropical regions, hence the need to collect tropical landraces. Germplasm collections of cauliflower and broccoli are available in several genebanks, particularly in Europe, the United States, India, China and Japan. In Europe a Brassica genebank has been established in co-operation with private companies. A central electronic catalogue of the collections is available at the Centre for Genetic Resources (CGN), Wageningen, Netherlands. While genetic erosion reduces the existing variability, interspecific crosses within the Brassicaceae family widens the genepool available to breeders.

Breeding

F₁ hybrids based on a single cross between two inbred lines are the only goal of the breeding programmes of seed companies and most government institutes. Until recently commercial hybrid seed production was based on sporophytic self-incompatibility (SI), a 1-locus system with multiple alleles that precludes self-fertilization in most cauliflower and broccoli. Exceptions are the annual cauliflower types developed in northern Europe, which are selected for self-fertility (absence of S-alleles). Bud pollination or treatment with CO₂ (4–7%) after bee pollination prevent the self recognition reaction. These methods are used in breeding programmes to develop and maintain inbred lines. Since about 1995 F₁ hybrids based on the SI system are gradually being replaced by hybrids based on cytoplasmic male sterility (CMS).

Inbred lines are increasingly developed from plants regenerated from anther and microspore cultures. DNA-markers are used for precise screening for resistance to diseases and other important traits. The main breeding objectives include: curd quality, yield, earliness, stress tolerance and resistance to diseases. Some breeding companies in Western countries focus on increasing the content of anticarcinogenic glucosinolates in broccoli.

Prospects

Breeding companies and institutes in India, China and Japan are developing heat-tolerant cultivars, which will result in a more reliable production with better quality in tropical conditions. Considerable progress is being made with effective methods of integrated pest management, as in cabbage, and this will reduce pesticide use. Cultivars resistant to fusarium yellows, downy mildew and clubroot will become available within five years. Resistance to black rot will take another five years. Consequently, cauliflower and broccoli are expected to become more important in tropical Africa. Information on cauliflower and broccoli production in tropical Africa is scarce, but valuable data can be found in the literature from tropical Asia.

Major references

• Gray, A.R., 1982. Taxonomy and evolution of broccoli (Brassica oleracea var. italica). Economic Botany 36: 397–410.
• Gray, A.R. & Crisp, P., 1977. Breeding systems, taxonomy and breeding strategy in cauliflower (Brassica oleracea var. botrytis). Euphytica 26: 369–375.
• Holland, B., Unwin, I.D. & Buss, D.H., 1991. Vegetables, herbs and spices. The fifth supplement to McCance & Widdowson’s The Composition of Foods. 4th Edition. Royal Society of Chemistry, Cambridge, United Kingdom. 163 pp.
• Nieuwhof, M., 1969. Cole crops: botany, cultivation, and utilization. Leonard Hill, London, United Kingdom. 353 pp.
• Park, E.J. & Pezzuto, J.M., 2002. Botanicals in cancer chemoprevention. Cancer and Metastasis Review 21: 23–255.
• Salunkhe, D.K. & Kadam, S.S. (Editors), 1998. Handbook of vegetable science and technology: Production, composition, storage, and processing. Marcel Dekker, New York, United States. 721 pp.
• Shinohara, S. (Editor), 1984. Vegetable seed production technology of Japan. Volume 1. Shinohara's Authorized Agricultural Consulting Engineer Office, Tokyo, Japan. 432 pp.
• Swarup, V. & Chatterjee, S.S., 1972. Origin and genetic improvement of Indian cauliflower. Economic Botany 26: 381–392.
• van der Vossen, H.A.M., 1993. Brassica oleracea L. cv. groups Cauliflower & Broccoli. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 111–115.
• Whitwell, J.D., Jones, G.L. & Williams, J.B., 1982. Cauliflowers. ADAS/MAFF Reference Book 131, Growers Books, London, United Kingdom. 87 pp.

Other references

• Crisp, P., 1982. The use of an evolutionary scheme for cauliflower in the screening of genetic resources. Euphytica 31: 725–734.
• Crisp, P., Crute, I.R., Sutherland, R.A., Angell, S.M., Bloor, K., Burgess, H. & Gordon, P.L., 1989. The exploitation of genetic resources of Brassica oleracea in breeding for resistance to clubroot (Plasmodiophora brassicae). Euphytica 42: 215–226.
• FAO, 2003. FAOSTAT Agriculture Data. [Internet] http://apps.fao.org/page/collections?subset=agriculture. Accessed 2003.
• Jackson, S.J. & Singletary, K.W., 2004. Sulforaphane: a naturally occurring mammary carcinoma mitotic inhibitor, which disrupts tubulin polymerization. Carcinogenesis 25(2): 219–227.
• Jackson, S.J. & Singletary, K.W., 2004. Sulforaphane: a naturally occurring mammary carcinoma mitotic inhibitor, which disrupts tubulin polymerization. Carcinogenesis 25(2): 219–227.
• Nuchanart Rangkadilok, N., Nicolas, M.E., Bennett, R.N., Premier, R.R., Eagling, D.R. & Taylor, P.W.J., 2002. Developmental changes of sinigrin and glucoraphanin in three Brassica species (Brassica nigra, Brassica juncea and Brassica oleracea var. italica). Scientia Horticulturae 96: 11–26.
• Pelletier, G., 1993. Somatic hybridization. In: Hayward, M.D., Bosemark, N.O. & Romagosa, I. (Editors). Plant breeding: principles and prospects. Plant Breeding Series 1. Chapman and Hall, London, United Kingdom. pp. 93–106.
• Taylor, J.P., 1982. Carbon dioxide treatment as an effective aid to the production of selfed seed in kale and brussels sprouts. Euphytica 31: 957–964.
• USDA, 2002. USDA nutrient database for standard reference, release 15. [Internet] U.S. Department of Agriculture, Beltsville Human Nutrition Research Center, Beltsville Md, United States. http://www.nal.usda.gov/fnic/foodcomp. Accessed June 2003.
• Verkerk, R., 2002. Evaluation of glucosinolate levels throughout the production chain of Brassica vegetables, toward a novel predictive modelling approach. Thesis Wageningen University, Wageningen, Netherlands. 136 pp.

Sources of illustration

• van der Vossen, H.A.M., 1993. Brassica oleracea L. cv. groups Cauliflower & Broccoli. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 111–115.

Author(s)

• P. Tjeertes, Kweekwal 21, 1602 ED Enkhuizen, Netherlands

Based on PROSEA 8: ‘Vegetables’.

Correct citation of this article

Tjeertes, P., 2004. Brassica oleracea L. (cauliflower and broccoli) [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands.

Accessed 18 December 2024.