Genomic Characters And Taxonomy
The following six Brassica species, plus Raphanus sativus, radish 2n 18, have been inter-crossed, with varying levels of difficulty requiring embryo culture or fusion to obtain hybrids Brassica nigra Koch, black mustard, 2n 16 Brassica carinata Braun, Ethiopian mustard, 2n 34 Brassica juncea L. Coss, brown mustard, 2n 36 Brassica napus, swede or rutabaga, rape or oilseed rape canola 2n 38 Brassica rapa, turnip and Chinese cabbage, 2n 20 and Brassica oleracea, cole crops, 2n 18. Table 2.1 shows...
Seed Purity
Control of seed purity is vital for all crops, but is of particular importance with vegetable brassicas where the uniformity of the plant stand is essential for the future profitability of the crop. The detection and elimination of siblings is of particular importance where F1 hybrids are predominantly used as cultivars as with most Brassica crops. The sibling problem arises because B. oleracea possesses a single locus, multiallelic, sporophytic incompatibility system. Plant breeders usually...
Albugo Candida white blister or white rust Fig
Control can be achieved by preventative and eradicant fungicidal sprays against foliar and systemic infections. Race-specific resistance governed by single dominant genes has been identified in several Brassica and Raphanus spp. quantitative inheritance of disease reaction type was demonstrated in B. rapa. Resistance to race 2 of A. candida is controlled by a single dominant gene, and resistance was associated with leaf pubescence, which is also governed by a single dominant allele Kole et al.,...
Effective Cultural Practices
Cultural weed control aims to optimize sowing or planting dates, seed rates or transplant densities, spacing layouts, soil fertility, irrigation practices and cultivar selection to achieve rapidity of crop growth which is able to outcompete weeds for resources. The aim should be to ensure either that the crop plants emerge first or that transplants can establish ahead of weed development and close their canopy over the weeds, thereby smothering them. Manipulating crop geometry can radically...
Rotation
The manipulation of husbandry systems to lessen the impact of pests and pathogens is the major avenue for the control that is directly placed in the hands of the grower. Such an approach is particularly appropriate with soil-inhabiting organisms. One of the first elements of husbandry control is the Table 7.2. Comparison of black rot disease severity ratings Xanthomonas campestris pv. campestris following the inoculation of seedling and mature plants. Table 7.2. Comparison of black rot disease...
Physical barriers
Crop covering involves laying transparent plastic sheets over drilled or transplanted crops. The growing plants support the cover as they develop underneath. Alternatively, opaque plastic sheets are placed on the soil surface and on the crop. Then the crop either grows through holes in the sheet or is transplanted through them. Both covers and mulches offer barriers between the developing crop and pests. For Brassica crops, covers have more universal value in the control of pests. The original...
Natural products
As an alternative to conventional synthetic pesticides, recently interest has focused on evaluating plant extracts as potential insecticides on the premise that these materials are less specific in their mode of action. Hence insects will require longer lasting resistance in order to circumvent them. In addition, plant extracts are mostly biodegradable, which suggests that their application would be more environmentally acceptable and compatible with IPM programmes. Numerous plant extracts or...
Seed Priming
Seeds require water, oxygen and a suitable temperature for germination. Water uptake follows a three-phase pattern with an initial rapid uptake or imbibition phase 1 , followed by a lag period phase 2 and then a second increase in water uptake associated with seedling growth phase 3 . Seeds are tolerant of desiccation during phases 1 and 2 but frequently intolerant of it in phase 3 Taylor et al., 1998 . Water uptake may be either uncontrolled or controlled. In the former, water is freely...
Chinese cabbage
The storage life of Chinese cabbage is relatively short, extending to only a few weeks at 0-1 C yellowing caused by tissue senescence is a major source of spoilage even under these conditions. Leaf spotting Alternaria spp. will develop in stores at 0-1 C and 95-97 relative humidity, and may be accelerated at higher temperatures. Soft rotting E. carotovora is a major source of postharvest damage during the transit and storage, and blackening of the leaf veins is caused by Xanthomonas campestris.
Tipburn
Internal tipburn is one of the most common physiological disorders affecting a wide range of vegetables and fruit. A necrotic breakdown of the marginal tissues of leaves is seen in cabbage heads both Chinese and European cabbage are afflicted. Tipburn is usually attributed to localized calcium deficiency and related in incidence to genotype and prevailing weather conditions, and the availability of nitrogen fertilizer. Large applications of easily available nitrogen at transplanting increase...
Heat tolerance
Cauliflower is heat susceptible, but not to the same extreme degree as broccoli. Some of the Indian cauliflowers such as 'Pusa Katki' have the greatest heat tolerance, but these are early and have relatively poor quality curds. If the temperature is high, then the curd may develop bracts green bracts corresponding to auxilary leaves are usually present in the curd, Fig. 2.6 which make it unmarketable. Bracting is recessive, and heritability was reported at 73 . The curd may also produce true...
Brussels Sprout B Oleracea Var Gemmifera
The imperative for improved understanding of growth and maturity in Brassica crops began with Brussels sprouts in the early 1960s as their production for quick-freeze processing took an increasing share of the market especially in the early and mid-season periods. The processing companies demanded regular and predicable supplies entering their factories so that the production lines operated at maximum efficiency as had previously been achieved for vining peas and green beans. Plant breeders...
Seed Size And Maturity
In Brassica spp., determination of seed maturity is complicated by the indeterminate growth and extended flowering periods of the parent plants Jett and Welbaum, 1996 . Overall inflorescence development continues for a considerable period of time within individual racemes and between different racemes. The processes of flower opening, pollination and fertilization each requires an extended period of time, causing the fruits and seeds to mature in rotation. Harvesting too early results in poor...
Seed Coating
Seeds vary greatly in size, shape and colour. Many seeds are small and irregular, making their separation and precision placement in the field difficult. Additionally, seeds require protection from pests and pathogens. Seed coating is used to allow mechanical sowing in precise patterns. This achieves uniformity of plant spacing and provides carriers for plant protection agents. Seeds may be both pelleted and film coated. Pelleting is defined as the deposition of a layer of inert material that...
TRANSFERRING HIGH QUALITY FROM FIELD TO PLATE Shelf life
Development, pre-maturation, maturation, ripening and senescence are the five phases that vegetables and fruit pass through during production, harvesting, storage and into the distribution chain to the ultimate retail consumer. Brassica crops are not required either to ripen or to senesce. These phases are mainly reserved for fruit crops. Indeed, senescent Brassica crops are generally unmarketable and worthless. Development in terms of product quality begins with the initiation and subsequent...
Temperature
Crop temperature is not normally controlled in open field crops. The advent of plastic film covers and mulching, however, permits some modest manipulation of temperature. Mulching in spring increases soil and air temperature. This advances the date of transplanting and accelerates growth, leading to earlier maturity. The timing of mulch removal becomes critical in late spring or early summer to sustain the quality in crops such as broccoli, leafy and hearted cabbage and some forms of early...
What Are Weeds
An ecologist defines weeds as 'plants growing entirely or predominantly in situations that are disturbed by man without being deliberately cultivated' G.R. Dixon 2007. Vegetable Brassicas and Related Crucifers G.R. Dixon Baker, 1965 . This definition includes all plant types, not solely the flower-forming angiosperms, although these comprise the great majority of weed taxa. The world weed flora mainly contains plants from relatively few, highly advanced families Table 6.1 Hill, 1977 which...
Floral Biology As Related To Controlled Pollination
The flower Fig. 2.1 differentiates by the successive development of four sepals, six stamens, two carpels and four petals. The carpels form a superior ovary with a 'false' septum and two rows of campylotropous ovules. The nucellar tissue is largely displaced by the embryo sac and, when the buds open, the ovules mainly consist of the two integuments and the ripe embryo sac. The buds open under pressure from the rapidly growing petals. Opening starts in the afternoon, and usually the flowers...
Internal browning
Internal browning of Brussels sprout buds was seen mainly as a problem for quick-freeze crops where even a small percentage of blemished buds would cause rejection since affected buds could not be identified and extracted from Table 8.4. Nutrient composition of field-grown cauliflower leaves showing normal and tipburn growth. Nutrient composition percent dry weight Table 8.4. Nutrient composition of field-grown cauliflower leaves showing normal and tipburn growth. Nutrient composition percent...
Wild hybrids
Wild Brassica and its close relatives hybridized naturally, forming polyploids. These amphidiploids together with their parental wild diploids were key building blocks from which our domesticated brassica crops have evolved. Three hybrid species are of particular interest as ancestors of the crop brassicas. Brassica carinata n 17 was formed from B. oleracea n 9 X B. nigra n 8 . This species is characterized by the slow steady growth of B. oleracea and the mustard oil content of B. nigra. Wild...
Trace Elements
Depending on soil type, soil pH and crop sensitivity, trace element deficiencies can develop and cause significant crop losses. Deficiencies of trace elements have substantial effects on the yield, quality and storability of Brassica crops. Cauliflower and swede are susceptible to boron deficiency, especially when grown on light soils with pH values gt 6.5. Boronated fertilizers should be used as a matter of routine, or applications made to the seedbed or prior to transplanting at 20 kg ha...
Defects
Crop defects may have genetic, physiological, pathological or mechanical origins, or alternatively result from the presence of extraneous organic or inorganic items. Defects inherent in the crop resulting from interactions between genotype, environment and microbial pathogens are dealt with later in this chapter. Surface blemishes, insect deposits, fungal growth, necrotic zones and virus-induced yellowing can all constitute defects of Brassica crops. Mechanical damage includes cuts, bruises and...
Field monitoring
Regular crop walking and inspection are essential for the successful prediction of pest and pathogen epidemic development. The crop is inspected at regular intervals to determine whether pest and pathogen problems are emerging. Quantitative evaluations of a developing pest or pathogen problem are gained visually through the manual use of pests and disease assessment keys that quantify developing signs and symptoms. Examples are shown in Figs 7.2 and 7.3 for powdery mildew E. cruciferarum on the...
Seed Increases
Hand pollination is best performed in the greenhouse or in a large screened cage to eliminate insects. If cross- or self-pollination is desired in the field, cheesecloth bags can be used to enclose the blossoms of one or two plants. It is preferable to enclose several plants in a screen cage 2 m high. The plants should be held away from the cage walls to avoid pollination through them by visiting bees and other insects. Bees are the best pollinators, but flies can also be used. If large-scale...
Weed Control In Brassica Seed Crops
Brassica seed crops suffer from weed competition in an analogous manner to ware or cash crops. Weed competition may reduce seed yield dramatically in cabbage by gt 50 Al-Khatib and Libbey, 1992 Al-Khatib et al., 1995 . The presence of weeds at seed harvest increases mechanical damage to cabbage seed and reduces harvest efficiency weeds also reduce seed quality by interfering with the processing operations. Weeds such as bedstraw or cleavers Galium aparine , charlock 5. arvensis and wild mustard...
Mamestra brassicae cabbage moth
Several wasps colonize the eggs Trichogramma evanescens , larvae Apanteles glomeratus and Hyposoter ebenius and pupae Ptetomalus puparum and Pimpla instigator additionally the flies Phryxe vulgaris and Compsilura concinnata are parasites of M. brassicae. Studies indicate that species of fungal and viral parasites offer potential biological control systems the larvae are not susceptible to current commercial strains of B. thuringiensis unlike other lepidopteran pests e.g. Pieris spp. ....
Cabbage head shape
The desirable cabbage head shape in commerce has changed from pointed, flat or round to almost exclusively round. Pointed head is dominant to round. Many genetic factors, however, influence head shape. Selection is best made by cutting the head vertically through the core this allows selection for head shape, core length, diameter and solidity, or leaf toughness, leaf configuration within the head and leaf or rib size. The cut core will heal and lateral buds develop from it so that selected...
Crop Monitoring Forecasting And Disease Management
The philosophy of 'forewarned is forearmed' whereby pest and pathogen invasion is anticipated and crops monitored for the first signs of their arrival is not new, but the application of new technologies makes it more efficient and effective. Monitoring Brassica crops helps to ensure that control measures, particularly where chemical methods remain available, are applied swiftly and effectively, and as part of the integrated strategy. This contrasts with the previous practices whereby chemical...
BREEDING PROCEDURES Male sterility
A considerable number of dominant male sterility genes have been found. Some have been used to a limited extent employing asexual propagation to multiply the sterile lines for hybrid seed production. The prime future method for hybrid production, however, is likely to be via cytoplasmic male sterility This is rapidly moving to the forefront of methods for production of new hybrids in the vegetable brassicas. Older established hybrids will continue to use self-incompatibility. The first B....
Overwintered cauliflower Roscoff and Walcheren types
The overwintered crop is transplanted into the field in mid to late summer, forming a large framework of leaves in the juvenile phase. Only very limited and, in some cases, rudimentary information is available concerning curd initiation by winter cauliflower. Information available for these crops in general compares poorly with summer and autumn types where recent research has made significant advances in defining the parameters controlling plant juvenility and maturation, and the subsequent...
Health And Welfare Benefits
The hidden attributes of Brassica crops lie in their abilities to reduce the incidence of human cancer and coronary diseases when consumed over periods of years as part of a balanced diet. Medical evidence for these attributes has accumulated substantially in the past decade, and these properties are coming into prominence with the general public Mazza, 2004 see Table 8.1 . In this respect, the Brassica crops, such as broccoli calabrese , have especial interest because of their sulphorathane...
EXAMPLES OF GERMINATION AND VIGOUR TESTS Standard germination tests
These are performed according to internationally accepted rules established by the International Seed Testing Association ISTA using prescribed temperature regimes. Example regimes could be either continuous 20 C or alternating 20 30 C during dark and illuminated periods. Lighting regimes are also standardized. Radicle emergence is recorded daily for the first 5 days of incubation, and counts of normal and abnormal seedlings are made after 10 days by suitably qualified seed analysts.
BROCCOLI BREEDING Heat tolerance
Susceptibility to high temperature damage is one of the major problems in broccoli. This makes the crop agronomically more suitable for cultivation in cool, moist climates. Heat at harvest time is not critical, except for the fact that high temperatures will reduce the period over which the crop is marketable. About 3-4 weeks prior to the head being marketable is the critical period when the growing point is differentiating to become reproductive Chapter 4 . Bjorkman and Pearson 199 7 studied...
Callus Culture Fusion And Transformation
Tissue culture techniques have been applied to several B. oleracea vegetables, either for clonal propagation or for development of novel and sometimes improved plant types. Plants have been regenerated from diverse multicellular explants, including immature embryos seedling parts such as hypocotyls or cotyledons stem pieces leaves roots and floral tissues such as flowering stalks or caulilfower curds. Plants can be recovered from single wall-free protoplasts, usually isolated from leaves or...
CAULIFLOWER B OLERACEA VAR BOTRYTIS Summer early and late and autumn maturing
The cauliflower is a short caulescent plant with shoot tips composed of young leaves and leaf primordia situated around an apical dome and separated by expanding internodes. In comparison with most Brassicas, the shoot tip components of the cauliflower are large, and easy to detach, measure and analyse following environmental changes. The grower's cauliflower consists of a large immature inflorescence the curd , formed at the stem tip after a period of vegetative growth. The growth phases of...
Bud pollination
Bud pollination to overcome self-incompatibility is accomplished by opening the bud and transferring pollen from an open flower of the same plant. Fertilization will not occur where this is done when the bud is very small. At this stage, the style is not receptive, but about 3-4 days before the flower has opened the style and stigma are fully receptive and the self-incompatibility factor has not yet developed, therefore self-fertilization is possible and self-incompatibility can be bypassed....
Brassica rapa group n the Oriental group
The International Code of Botanical Nomenclature Gilmour et al., 1969 Greuter et al., 2000 rules that the author who first combines taxa of similar rank bearing epithets of the same date chooses one of them for the combined taxon. Metzger 1833 first united B. rapa L. and B. campestris L. of 1753 under B. rapa L. as used in this text. Brassica rapa L. n 10, A and the amphiodiploids B. carinata Braun n 17, BC , B. juncea Coss n 18, AB , B. napus L. n 19, AC and R. sativus n 9, R are grown...
Seedling Propagation
The plant breeding and seed industry has refined Brassica seed into a defined and reliable resource. This makes it a major item of cost in the crop balance sheet. As a result, its initial propagation into seedlings has also become refined and diverged as the separate and specialized industry of plant propagation. Frequently this is quite distinct from the production industry that produces the finished item that is sold to retail consumers. The separation of propagation and production enables...
Soil Ph And Calcium Content
Brassica crops are most productive when grown on land with an approximately neutral pH. The ideal is pH 6.5 for mineral soils and pH 5.8 for organic soils. This rule should be altered where soil-borne pathogens are present, especially Plasmodiophora brassicae, the causal agent of clubroot disease. Land where even very low levels of infection are present should be raised to pH values in excess of 7.0. Brassica crops vary in their sensitivity to acidic pH and the point at which crop productivity...
Crop density
Stand density and crop plant architecture will affect the risk of disease infection and its subsequent impact. Stand density affects air movement, shading and moisture retention within the crop. Root 1973 proposed the 'resource concentration hypothesis' whereby 'any herbivores, especially those with a narrow host range are more likely to find hosts that are concentrated'. This hypothesis predicts that the density of herbivores per host plant is higher in dense stands of their host plants. The...
Contrasting the physiology and morphology of wild and cultivated brassicas
It will be evident by now that many of the wild Brassica spp. and their close allies inhabit dry coastal, arid rocky or desert habitats. These wild plants have very thick leaves containing less chlorophyll and many more cell wall components compared with cultivated plants. Typically, they have well-developed xylem vessels and small leaf areas these characteristics increase the efficiency of water conservation in plants. The foliage of wild xerophyllous the group including Brassica and other...
Physiological Disorders
Storage losses of Brassica vegetables such as winter white cabbage and Chinese cabbage are regularly reported at 10 and frequently exceed this figure. The Brassica crops suffer from a range of physiological disorders that are major causes of these losses after harvesting. Physiological disorders have been attributed to a range of nutrient deficiencies interacting with environmental or climatic conditions and, more recently, the effects of virus pathogens. It appears that under specific...
Fertilizer Applications
General fertilizer requirements for a range of Brassica vegetables are given in Table 5.6. These bear out the more specific requirements cited in the other tables indicating that these crops benefit from substantial applications of major nutrients. To avoid damage to the root systems by increasing soil conductivity to dangerous concentrations, it is advisable to apply nitrogen in particular as split dressings, with half applied to the seedbed or at transplanting and the residue about 2 weeks...
Cigar burn
Cigar burn is one of the major internal disorders of cabbage B. oleracea var. capitata . It is seen as sunken necrotic spots 5-10 mm diameter on internal tissues. Walsh et al. 2004 added evidence that virus pathogens may also be implicated in these syndromes Table 8.6 . They proposed that cigar burn is caused by turnip mosiac virus TuMV on cvs Polinius and Impala. The condition reached its most severe level at 4 months in store and did not progress after that date. The presence of cauliflower...
Advantages Of Arabidopsis Thaliana
The main objective is to clone genes that have been identified by mutational analysis. The combined efforts of many laboratories have resulted in a completed outline map of the A. thaliana genome. Detailed maps of morphological and biochemical markers such as RFLPs and RAPDs are available for much of the genome. Approximately 90 of the total A. thaliana genome lies within 0.8 Mbp of an RFLP marker and 50 is within 0.27 Mbp of an RAPD marker. The genome of A. thaliana lacks much of the...
Sclerotinia sclerotiorum white rot white mold in the USA
Control of this pathogen is extremely difficult because of its wide host range and formation of persistent sclerotial resting bodies. Resistance is recessive and quantitative. The introduction line PI206942, a non-heading cabbage from Turkey, has shown superior levels of resistance Dickson and Petzoldt, 1996 . Resistance was transferred to cabbage, broccoli and cauliflower. Sharma et al. 1995 reported that cauliflower cv. Early Winter Adam's White Head and EC 162587 were highly resistant, and...
Rapid Cycling Brassica Types
Rapidly reproducing forms of Brassica named 'Fast PlantsTM' have been bred for use in association with inexpensive growing systems developed from recycled plastic containers. This combination offers an effective and efficient set of tools for biological studies at all levels of complexity from the research bench to school students. Depending on the genotype used, Fast PlantsTM will germinate in 1 day, grow and flower in 2 weeks and produce viable seed in little more than 28 days. Changes in the...
Diversity within the amphidiploids
Considerable genetic diversity is present within the three amphidiploid species Song et al., 1996 . Based upon studies of genetic diversity, B. napus may be considered as the most ancient amphidiploid, succeeded by B. juncea and B. carinata. Two major factors are responsible for general diversity within amphidiploids multiple hybridizations with different diploid parents and genome modifications following polyploidization. A good example of multiple hybridizations was found in B. napus. Four...
Effects Of Weed Type
The morphological habit of a weed will substantially affect its impact on the growth and yield of the crop. For tall-growing weeds such as C. album fat hen , there is a linear relationship between the extent of yield reduction and weed Fig. 6.1. The rectangular hyperbolic model for relating yield loss to weed density, illustrating its parameters A and I. YL percentage of yield lost because of weed competition d weed density I percentage of yield loss per unit weed density as d 0 A percentage of...
STRATEGIES FOR PEST AND PATHOGEN CONTROL Host resistance
Genetic resistance to pests and pathogens is the principal means of control that is both economically and environmentally acceptable. Plant resistance to insects can result from i antixenosis or the dislike of the plant or non-preference Kogan and Ortman, 19 78 ii antibiosis or antagonistic reaction resulting from the presence of harmful compounds or iii tolerance and combinations of these attributes. Fig. 7.4. Food consumption by cabbage white butterfly Pieris rapae larvae of the fourth instar...
