After reading this article you will learn about:- 1. Origin of Cauliflower 2. History of Cauliflower in India 3. Production 4. Botany 5. Major Types 6. Pollination Techniques 7. Characteristic Variability and Ideo-Type in Cauliflower 8. Qualitative Genetics 9. Breeding Objectives 10. Breeding Methods 11. Transgenic Cauliflower 12. Seed Production 13. Varieties.
Contents:
- Origin of Cauliflower
- History of Cauliflower in India
- Production of Cauliflower
- Botany of Cauliflower
- Major Types of Cauliflower
- Pollination Techniques of Cauliflower
- Characteristic Variability and Ideo-Type in Cauliflower
- Qualitative Genetics of Cauliflower
- Breeding Objectives of Cauliflower
- Breeding Methods of Cauliflower
- Transgenic Cauliflower
- Seed Production of Cauliflower
- Varieties of Cauliflower
1. Origin of Cauliflower:
Cauliflower is thought to have been domesticated in the Mediterranean region since the greatest range of variability in the wild types of B. oleracea is found there. It originated in the island of Cyprus from where it moved to other areas like Syria, Turkey, Egypt, Italy, Spain and northwestern Europe.
The cole crops, including cauliflower and cabbage have descended from a common kale like ancestor, the wild cabbage (B. oleracea L. var. sylvestris L.) still found in Western and Southern Europe and North Africa. Cabbage, cauliflower, broccoli, Brussels sprouts etc. have been separated morphologically on the basis of few gene differences.
The varieties B. oleracea have the same chromosome number (n = 9) and there are almost no differences in chromosome morphology. Pachytene chromosome studies have shown that the species B. oleracea is a triple tetrasomic with the genome formula A BB CC D EE F with 6 basic genomes and showing some secondary pairing.
2. History of Cauliflower in India:
Cauliflower has been in cultivation in India since last 150 years. It was introduced from England in 1822 by Dr. Jemson, In-charge of Company Bagh, Saharanpur, U.P. The imported seeds were tested in various parts of India. The growers raised the crop during May to July which corresponded with the growing period in England.
However, the climatic conditions of the same period in both the countries varied considerably and this resulted in the adaptation of some introduced varieties to early production during warmer and humid conditions in the country.
The growers made selection of such early adapted types and raised their seeds for their own use. The local strains, seeds of which were produced in the country were found to be better adapted and earlier in maturity being ready in November-December as compared to the crops raised from imported seeds.
This was the beginning of the development of an entirely new cauliflower now termed as Indian cauliflower. The first four Indian varieties listed by Sutton and Sons, India in 1929 were Early and Main Crop Patna and Early and Main Crop Benaras.
3. Production of Cauliflower:
Cauliflower (Brassica oleracea L. var. botrytis L. 2n – 2x = 18) follows cabbage in importance with regard to area and production in the world. However, in India cauliflower is more widely grown than cabbage. This crop grows at latitude 11°N to 60°N with average temperature ranging from 5-8°C to 25-28°C.
In its vegetative growth period, it may stand temperature as low as -10°C and as high as 40°C for a few days. Italy and India are the major countries growing cauliflower on large scale.
In India, cauliflower is grown both in hills and plains and from 11°N to 35°N. Important cauliflower-growing states in India are UP, Karnataka, West Bengal, Punjab, and Bihar. It is also commonly grown in northern Himalayas and in Nilgiri hills in south. Cauliflower is harvested from August or early September to late February or early March in north Indian plains and from March to November in the hills.
Cauliflower acreage in India is about 2.5 lakh hectares, in which the seed intake potential is 125 tons of OP cultivars and 45 tons of hybrid cultivars and market value of this seed comes at Rs. 85 crores. The current traded seed market of cauliflower seed in India is about Rs. 55 crores. The hybrid seed is imported from Japan, Taiwan, China and Korea.
4. Botany of Cauliflower:
Cauliflower, i.e. B. oleracea var. botrytis has diploid chromosome No. as 2n = 2x = 18. In meiosis, pairing of homologous chromosomes occurs. Sometimes bivalents show a secondary pairing. In B. oleracea, for example, three groups of two bivalents and three groups of one bivalent each have been found like this.
From this secondary pairing of mono-genomic Brassica species it has been concluded that they have a basic chromosome number of six i.e. B. oleracea can be indicated as AA BB CC DEF, B. campestris as AA BB CC DD EF and B. nigra as AB CD EE FF.
The stem of the vegetative cauliflower plant is rather short, and it thickens to about the same extent as that of cabbage. The leaves are large, generally oblong, the younger ones being nearly always sessile. In contrast to situation in other cole crops, buds do not usually arise in the leaf axils.
During transition to the generative phase, which, in contrast to the situation in most other cole crops, is accomplished in many types of cauliflower in the first year, the peduncles in the axils of the bracts formed by the main growing point branch repeatedly, so that branches even of the fifth order can arise?
At first the numerous peduncles do not grow lengthwise but become thick and fleshy. Thus, a colourless, roughly spherical, terminal compact head arises, of which, the upper surface consists of vast numbers of naked apical meristems. The peduncles are composed of thin walled parenchyma and vascular bundles which do not become woody.
The young ‘curd’ is at first entirely covered by the foliage, on becoming visible it already has a diameter of over 5 cm. After sometime the flower stems elongate, and a number of the apices develop into normal flowers.
According to Sadik (1962) soon after floral primordia appear some of the 2nd order branches bearing them elongate leaving other non-elongated 2nd order branches behind. These later bear lateral floral primordia which abort.
Later, several 3rd order branches with floral primordia around their apex elongate leaving behind rest of the 3rd order branches with abortive floral primordia. These processes of elongation and abortion may be repeated till floral primordia develop into normal flowers (Fig. 18.1).
There are 4 sepals, 4 petals, 6 stamens, and two carpels. The carpels form a superior ovary with false septum and two rows of campylotropous ovules. The androecium is tetradynamous, i.e. there are two short and four long stamens. The pollen grains are 30-40 µ in diameter and have three germination pores. The bright yellow petals become 15-25 mm long and about 10 mm wide. The sepals are erect.
The buds open under the pressure of the rapidly growing petals. This process starts in the afternoon, and usually the flowers become fully expanded during the following morning. The anthers open a few hours later, the flowers being slightly protogynous. The flowers are pollinated by insects, particularly bees, which collect pollen and nectar.
The nectar is secreted by two nectaries situated between the basis of the short stamens and the ovary. Situated outside the basis of the pairs of long stamens are also two nectaries, but these are not active. Flowers are borne in racemes on the main stem and its branches.
The inflorescence may attain a length of 1-2 m, but the slender pedicels are only 1.5-2 cm long. The fruits are glabrous siliques, 4-5 mm wide and sometimes over 10 cm long, with two rows of seeds lying along the edges of the replum (false septum, an outgrowth of the placentae).
A silique contains from 10-30 seeds. Three to four weeks after the opening of the flower from which it is formed, the silique reaches its maximum length. When it is ripe, dehiscence takes place through the two valves breaking away from below upwards, leaving the seeds attached to the placentas.
5. Major Types of Cauliflower:
1. European Cauliflowers:
Systematic and extensive cultivation of cauliflower was first started in Italy where the ‘originals’ were developed. These original Italian types were taken to France, England, Germany and Netherlands where some important local types were developed from them e.g.,
The ‘Northerns’ in Yorkshire and Durbyshire,
the ‘Cornish’ in Cornwall,
the ‘Angers’ & ‘Roscoff in Brittany and the ‘Erfurt’ or its allied ‘Snowball’ in Germany and Netherlands.
These types were mainly for winter cultivation except ‘Erfurt’ which was suitable for growing in summer. The chief characteristics of these important types are presented in Table 18.1.
It should be emphasised that these different types of cauliflower adapted to cold winter as well as summer conditions were developed by man through simple selection from the original material from Italy, a region of mild Mediterranean climate.
2. Indian Cauliflowers:
Indian cauliflowers are characteristically different from the types grown in Europe, as they are tolerant to high temperature and humid condition and are perhaps the earliest maturing types known. Indian cauliflowers are dwarf selections of Erfurt or Snowball types.
This view is also supported by Nieuwhof (1969) who stated that selections from Erfurt types have yielded early varieties that performed better in warmer regions producing good curds at temperature above 20°C (some of these varieties were Early Patna, Early Benaras, Early Market). However, Swarup and Chaterjee (1972) questioned this. According to them, Indian hot weather types have not originated from Erfurt or Snowball types as suggested by Giles or Nieuwhof.
Their argument is based on following evidences:
(i) Typical Indian cauliflowers belong to maturity group I and II (September, early November, mid-November, early December). In contrast, group III (mid-December-mid-January) compares favourably with late Snowball or Erfurt types in regard to climatic requirements.
From these observations it appears that parental varieties contributing most to the Indian types tolerant to high temperature and rainfall conditions are the Cornish which are predominant types in Group I and II but almost absent in group III.
(ii) Morphological and other characteristics of long stalk, open habit, exposed, yellow, uneven curds which loosen up easily and strong flavour are some attributes common to both Cornish and Indian cauliflower particularly early types maturing in September to November.
(iii) The observations on self-incompatibility also support the view that Indian types are genetically different from Erfurt because in former self-incompatibility is predominant, while, in latter self-compatibility is more common.
However, in maturity group III, some self-compatibility has been recorded. This indicates that Indian types particularly Group I & II have been developed from winter types and not from summer types (Snowball). Cornish, Roscoff and Northerns are classified as winter types and have been reported to be highly self-incompatible.
(iv) Genes for resistance to black rot are present only in Group I (except one inbred line in group II) while all the varieties tested in Snowball groups are susceptible to black rot. Finally, it is interesting to note that cauliflower after its origin in Cyprus, became established around Mediterranean, particularly in Italy.
Its further development and improvement were achieved in northern and northwestern Europe and its cultivation was extended to 60°N. Selection and development of Indian cauliflower types made it possible to extend the growing areas to the tropics and subtropics.
Besides, certain favourable genes such as tolerance to high temperature and rainfall which were unknown in European types, have been successfully utilised in other tropical and sub-tropical regions for developing improved varieties such as Pua Kea in Hawaii, Campinus in Brazil, Improved Japanese and D 96 in Israel and Extra Early in Taiwan.
Thus, the crop is presently cultivated from 11°N to 60°N. Such flexibility in adaptability is attributed to inherent characters of ancestral parent B. oleracea L. var sylvestris which is found growing well in various regions varying from temperate to tropical conditions. The difference between Indian and European type of cauliflower is summarised in Table 18.2.
6. Pollination Technique of Cauliflower:
Selfing:
The self-compatible varieties of cauliflower can be selfed by simply bagging the flowering stalk. Selfing is also done by caging some plants with flies in cages or by isolation planting of lines having decreased level of self-incompatibility. With self-incompatible plants, bud pollination gives better results. In this system, the pollination is carried out in buds before 2-4 days of opening, with emasculation or without emasculation.
Crossing:
The flowers may be emasculated by removing 6 stamens using a pair of forceps. In self- compatible cauliflowers (European types), the stamens are removed before the opening of the buds as the flowers are already fertile in the bud stage, crossing can be done at the same time.
In self-incompatible types, emasculation may be omitted. When pollination cages are available, crosses between self-incompatible types can be made by insects such as honey bees, bumble bees and flies.
7. Characteristic Variability and Ideo-Type in Cauliflower:
Plant type:
There are 4 distinct plant types viz.
Plant type 3 is considered the best as it has long erect leaves with or without self-blanching habit and has medium size curds. A lower plant type is generally dominant over the higher one.
Stem Pigmentation:
Generally, the stem of Indian cauliflower seedlings is green unlike the Snowball which is pigmented. However, in some Indian cauliflowers, stem pigmentation is quite pronounced, almost like Snowball. Stem pigmentation is a dominant character and useful as a marker gene.
Stem Length:
Short – 15 cm
Medium – 16-20 cm
Long – > 20 cm
Predominant stem length in Group I and II is medium while in group, III it is short. Short stem length is dominant over long. Generally, shorter stem length is preferred for selection.
Leaves:
Leaves may be long and narrow, long and broad and short and broad. The margins are straight, broadly wavy or sinuate. The colour varies from bluish green to waxy green or glossy green.
Curd:
The weight may vary from 200 g to 1 kg or more. In earliest group curd size is smaller than later group. Shape of curd may be flat with even surface or hemispherical with uneven surface. In some cases curds are slightly conical. Hemispherical and conical curds are compact and may be 35-40% of total plant weight.
Many authors describe it as being composed of compressed hypertrophied flower stalks which produce only rudiments of abortive flowers. It has also been described as being excessively branched brought about by suppression of apex of main axis and growth of lateral branches whose apices were again suppressed.
It has also been stated that flowers are represented by ‘grains or papillae’ that make up surface of curd and these are modified thickened flowers which are not functional. The functional flowers arise on branches from below the curd such as they do from cabbage after the head is removed.
Curd Quality:
It is primarily determined by compactness and colour. It should be compact and retentive white. The curd colour of Indian cauliflower is yellowish to creamish white while the Snowball is bright white. A major defect of curd is riceyness.
It is perhaps caused by precocious and frequently uneven development of flower bud initials over the curd surface. Ricey curds are regarded as undesirable for market, in nature the precocious formation of flower buds is advantageous because it assists the ultimate expansion and development to flowering so that plants with ricey curds set seed more easily than those with perfect curd.
Grade 1 – Perfect:
Grade 2 – A few projections on each whorl but perfect when held at arms length
Grade 3 – Clear patches but many elongated buds, furry all over
Grade 4 – Well-formed buds over whole surface
Although this phenomenon has no effect on the taste, it is nevertheless looked upon as a serious fault. Little is known about the influence of the environment on the incidence of riceyness, though its occurrence is sometimes related to high temperature.
Disease Resistance:
The most important disease of cauliflower is black rot caused by Xanthomonas campestris. It causes heavy losses in seed yield of Snowball varieties which are produced in the hills. On screening the germplasm of Indian and exotic cauliflower some Indian inbreds (MGS, Pua Kea and S. No. 445) were found to be resistant.
Plant to plant variability observed in non-segregating generations of all the crosses studied led to a strong belief that resistance to black rot is inherited in a quantitative manner. Further, resistance was found to be dominant in expression.
Ideo-type:
On the basis of genetic stocks available in Indian cauliflower it has been possible to determine the most desirable ideo-type in cauliflower.
This is as follows:
Maturity – Specific group (75 to 80 percent uniformity)
Stalk length – 12 to 15 cm
Plant type – No. 3
Frame – 35-15 cm
Leaf number – 18-22
Leaf length – 50-55 cm
Curd shape – Hemispherical
Curd size (diameter) – 15-18 cm
Curd weight – 750 g-1 kg
Curd colour – Retentive white
Resistance to – Black rot, stump rot
8. Qualitative Genetics of Cauliflower:
As per reports of Ahluwalia (1977) the qualitative genetic information using Indian cauliflowers is as follows:
Leaf Colour:
It is controlled by two dominant genes I and G of which the former suppresses the biosynthesis of wax and thus inhibits the expression of gene G that is for the normal bluish-green leaf colour. Thus,
iiGG = Normal
IIGG, Ilgg etc. = Glossy
Stalk Length:
Long stalk, St; short stalk, st
Leaf Apex:
Round, Ro; pointed, ro
Plant Type:
Erect, E; flat, e
Curd Colour:
Yellow, Y; white, y
Length of the Flowering Stalk:
Long, F; short, f
Colour of Flowering Stalk:
Variegated, V; green, v
Siliqua Size:
Long, SI; short, sl
Green Curd Colour:
A genetic model was fitted by Crisp and Angel (1985) who observed curd colours in a segregating population derived from crosses between white and green curded types. The model was of a gene (Wiwi) giving white dominant over yellow, and an independent co-dominant gene (gr1 gr2) for greenness.
The genetic model proposed by them for cauliflower curd colour is as follows:
The pale green phenotypes could be divided further into very pale (Wi-gr1 gr2) and darker (Wi-gr2 gr2) in a ratio of 2: 1. Similarly, yellow phenotypes could also be divided into those without any green tint and those with, corresponding to the expected ratio of 1: 2 for the genotypes wiwi gr1 gr1 and wiwi gr1 gr2.
9. Breeding Objectives of Cauliflower:
1. High yield
2. Non-ricey, compact, bract free protected curds with retentive cream/white colour
3. Heat tolerance for producing curds in August/September
4. Suitable varieties for curd formation in summer and rainy seasons in the hills
5. Better seeding ability
6. Self-incompatible but cross-compatible inbreds to produce hybrids of tropical type
7. Resistance to diseases (black rot, sclerotinia rot, alternaria blight, erwinia rot)
10. Breeding Methods of Cauliflower:
Population Improvement Methods:
These methods (mass selection, family selection, etc.), are applicable to open-pollinated heterogeneous stocks having sufficient variability due to self-incompatibility.
Development of Inbreds as Cultivars:
This is applicable to European types which have self-compatibility. In this approach two self-compatible lines are crossed and the hybrid progeny is subjected to simple pedigree/bulk/ backcross method of breeding.
Hybrid Breeding:
This is based on the principle of developing inbreds through bud stage selfing and production of F1 seed by crossing/interplanting two self-incompatible but cross-compatible inbreds. With the exception of some Japanese varieties, initially none was commercially successful, and it is only since 1985 that F1 hybrid cauliflowers have become important. The lack of development of F1 cultivars of cauliflower is in marked contrast to other Brassica vegetable crops and has been due to following factors.
(i) Selfing of parental plants or sib-mating within the parental lines giving rise to ‘off types after planting of commercial hybrid seed.
(ii) Less effective self-incompatibility in cauliflower than in other brassicas.
(iii) Nonsynchronous flowering of male and female parents leading to increased proportion of sibs.
(iv) The inflorescence of cauliflower tends to be cymose than racemose as in other brassicas, which results in a flush of flower production over a shorter length of time, leading to greater tendency for non-synchrony of flowering of the parents of a cauliflower hybrid.
(v) Minor heterosis for curd size in contrast to substantial heterosis in other brassicas (cabbage, Chinese cabbage, Brussels sprouts, etc.), which are grown, primarily for their vegetative leafy tissues.
Breeding for Curd Quality:
Selection against Bracing Defect:
The cauliflower curd consists of a mass of compressed, branched peduncles bearing many thousands of pre-floral meristems. White bracts corresponding to the axillary leaves are usually present inside the curd. Often these bracts grow through the surface of the curd and give it a papillate appearance which reduces its commercial value. Its value is further reduced if the bracts develop green or purple colouration.
Breeding against this defect could be effective, but the expression of this character is influenced by the environment. In the same cultivar, bracting may be virtually absent in one environment and may be a serious problem in another environment. Normally, assessment of bracting is made macroscopically in the field and efficiency of selection is correlated with the stringency of this assessment.
Detection of bracts could be made more effective by:
(i) Microscopic examination:
This involves examination with a scanning electron microscope and is thus impracticable in a large scale breeding programme.
(ii) Defining a field environment suitable for selection against bracting. The difficulty with this method is that it may not be suitable for selection work involving characters other than bracting. It is, therefore, necessary to develop techniques which maximise the expression of this character without affecting the assessment of other characters.
Crisp (1975) reported that when curds were taken from field grown plants and aseptically cultured, bracts had usually stopped growing after about 20 days in culture and their relative sizes were recorded at this stage as small (score 1) to very large (score 4). The bracts were characteristically different from the leaves which developed from the apical meristems (Fig. 18.2).
Typically, bracts had parallel to palmate venation, no petiole, entire margins, and a thick leathery appearance. Regenerated true leaves had a midrib and often distinct petiole and markedly serrate margins. Based on this, Crisp (1975) advocated a two-tier system of selection. Firstly in the field, and then in culture and suggested that it would increase the likelihood of breeding bract free cauliflowers.
Breeding Against Riceyness:
Precocious flower bud formation, i.e. riceyness is appearance of outgrowth of about 1 mm diameter from curd surface. These structures are immature flower buds. This character is relatively consistent and is induced by cold temperatures.
That is why cauliflower varieties bred in tropics produce ricey curds if grown under cool conditions, however, the reverse is not true. This defect has been shown to be highly heritable, mono-factorial and hence, highly responsive to selection.
Breeding for Optimum Leaf Geometry:
Variation exists among cauliflower germplasm in the geometric configuration of leaves. Most of cauliflower produced in USA is hand-tied to prevent head discolouration due to sunlight exposure. Discoloured or yellow heads of cauliflower fetch less price.
Therefore, cauliflower varieties should be developed, in which, the leaves assume a more upright position around the developing head, rather than a horizontal position. The upright leaves provide partial covering around the head and protect it from sunlight and thus eliminate the need for tying.
Chaterjee and Swarup (1972) have described four plant types as given earlier and recommended Plant Type No. 3 which corresponds to plant type of Snowball. Plant Type 3 is considered the best as it has long erect leaves with or without the self-blanching habit and has medium sized curds.
Plant Type 1 has completely horizontal leaves and Plant Type 4 has erect leaves, whereas Plant Type 2 and 3 are intermediate ones, Type 2 being closer to Type 1 and Type 3 being closer to Type 4.
The inheritance of leaf geometry was studied by Werner and Honma (1980) who evaluated P1, P2, F1, F2, BC1 and BC2 of MSU 839 (upright) X MSU 831 (horizontal). A relative measure of leaf geometry for an individual leaf was determined in the manner as given in Fig. 18.3.
A point 35 cm from the base of the leaf petiole (B) measured along the midrib of the leaf is marked. A metal rod is inserted in the vertical axis of the plant and the distance from vertical axis (A) to the B point is determined (ab). An upright leaf will show a smaller value than horizontal leaf.
The mean geometric value of the first, fifth, and ninth fully expanded leaves subtending the head is used as a measure of individual plant performance. They found following number of upright and horizontal leaf geometry plants in the F2, BC1 and BC2 generations in the cross of MSU 831 x MSU 839 in fall season experiment (Table 18.3).
The genetic ratios giving good fit in the F2, BC1 and BC2 and as proposed by Werner and Honma were as follows:
F2 – 54 : 10
BC1 – 1:1
BC2 – 1:0
In order to explain the above ratios a genetic model was proposed. Three major loci designated a, b and c make up the parents MSU 831 (P1) and MSU 839 (P2). The proposed genotype of MSU 839 is AABBCC (upright) and that of MSU 831 is aabbcc (horizontal). The genotype A-B-conditions upright expression regardless of the state of the c locus. Recessive homozygosity at either the a or b locus in combination with cc (aaB-cc or A-bb cc) conditions horizontal leaf expression.
The genotype C is epistatic to the expression of aa and bb and conditions upright expression when combined with either gene A or gene B. The dominance of genes A, B and C is incomplete, allowing for intermediate levels of leaf geometry. On this basis the proposed genotypes of F2 and backcross generation individuals for leaf geometry are as given in Table 18.4.
For illustration purpose, the BC2 ratio is shown as follows:
The ratio of upright and horizontal leaf progenies in BC2 is 4: 4 = 1: 1. Further, Werner and Honma (1980) made the following observations regarding their results: Both the parents used in this study, MSU 831 (P1) and MSU 839 (P2) were derived from the cross (Pua Kea X Snowball M) x Self-Blanche.
None of these cultivars exhibits upright leaf geometry. No upright progenies were recovered from segregating generations derived from the cross Pua Kea X Snowball M, and upright phenotypes were recovered in segregating generations derived from the cross (Pua Kea X Snowball M) x Self-Blanche. Based on the proposed genetic model, the above observations suggest the presence of an activator gene (D) controlling the expression of leaf geometry. It is proposed that gene D is an activator of gene C.
On that assumption, the following genotypes are proposed for various cultivars:
Crosses between Pua Key x Snowball M will not yield upright progeny due to the presence of dd and aa in both the parents. In progeny derived from this cross, the epistatic expression of Cover a will not be manifested, since the proposed genotype of the activator locus is dd. A cross of (Pua Kea X Snowball M) X Self-Blanche will yield upright progeny since self-Blanche carries both AA and DD.
Both MSU 831 (P1) and MSU 839 (P2) were selected from this cross. The data suggest that both parents are homozygous DD. Therefore, crosses between cauliflower types with horizontal leaf geometry could result in recombination of the proposed genes and ultimately result in the upright phenotypes.
Breeding for Resistance to Black Rot:
An important work on this aspect was carried out by Sharma (1972) in India. They evaluated parental lines, BC1, BC2 and F2 generations from five crosses involving MGS (highly resistant), Pua Kea and S. No. 445 (resistant) and S. No. 246, S. No. 15, EC 12013 and EC 12012 (susceptible-highly susceptible).
Seeds were soaked for 24 hrs. in the liquid inoculum. Inoculation by spray method was done thrice at about 8 day-intervals, at the seedling stage. Later the adult plants were inoculated twice by spraying and cutting the leaf tip inside the inoculum. Resistance to black rot was found to be dominant over susceptibility and governed by polygenes.
The dominance component of variation was greater than the additive in almost all the crosses. It has been suggested to adopt back-cross method or to attempt selection in the progeny of cross made between two resistant parents for evolving highly resistant lines. Heterosis breeding using two resistant parental lines in single crosses may also prove useful in obtaining F1 hybrids having a high degree of resistance.
Breeding System and Breeding Strategy:
A series of S alleles sporophytically control incompatibility in Brassica oleracea L. The expression of incompatibility is affected by environment and genetic background, and by dominance relationships between the S alleles. Thus, in general Brassica oleracea is outcrossing, but certain alleles under some conditions, may result in substantial levels of self-pollination.
The distribution of different S alleles within varieties of Brussels sprouts, B. olercea var. gemmifera L. has led to believe that a dynamic balance between cross-and self-pollination is maintained as a result of selection for agronomic vigour and uniformity. However, in cauliflower a range of incompatibilities appears to exist such that some annual types are essentially self- compatible.
Nevertheless, there is in the Indian sub-continent a wide range of annual cauliflowers, which are substantially, self-incompatible. These are believed to be the product of selection for annual habit from European autumn maturing stocks of the Italian types.
It has been suggested that annual Indian cauliflowers which include substantially, self-incompatible types, have been derived from European autumn/winter types by selection for early maturity.
However, it is also stated that European summer cauliflowers, which are self compatible, gave rise to types (such as Suttons Early Patna) specifically, adapted to hot climate, and these persist in India as local races.
An alternative explanation, therefore, is that hybridization between European self-compatible annuals and self-incompatible biennials in the Indian subcontinent have given rise to segregants combining self-incompatibility with the annual habit. This is substantiated by the fact that various morphological types of recognizable European origin exist within different maturity groups of Indian cauliflowers.
A parallel appears to exist in Australia, where various immigrant Europeans took their local vegetables and late maturing self-compatible cauliflowers of widely diverse morphological types were selected. These self-compatible types now form the basis for seed exported from Australia for growing in Europe as autumn and early winter maturing varieties.
Exploitation of the breeding system depends on the expression of heterosis and on gene additivity for the relevant characters. Several research workers in India have noted heterosis for yield. However, workers in Europe have noted overall, very slight although significant increases in curd weight and diameter in the F1 European summer cauliflowers.
There are reports of additive genetic control for curd solidity, but no heterosis in summer cauliflowers. Some workers have reported inbreeding depression in curd weight and diameter in self-incompatible Italian lines but not in self-compatible Australian lines. In general self-incompatible types display heterosis and self- compatible types do not show heterosis.
However, the question remains open as to whether these heterotic effects are best exploited by fixation by inbreeding, by the production of F1 or other hybrids, or by a less committed course such as by recurrent selection for agronomic characters, together with selection for self-compatible or self-incompatible types. The available evidences suggest that self-compatible individuals can be found in all groups of cauliflowers.
In this background, Gray and Crisp (1977) have argued that despite evidence of heterosis within many groups of cauliflowers, radical advances are probably best made by selecting self-compatible material from annual x biennial hybrid populations.
11. Transgenic Cauliflower:
A number of factors that are known to influence genetic transformation have been evaluated in India to optimise Agrobacterium-mediated transformation of hypocotyl explants of cauliflower variety Pusa Snowball K-1. The binary vector p35GUSINT mobilised into Agrobacterium strain GV2260 was used for transformation.
Explant age, pre-culture period, bacterial strain and density were found to be critical determinants of transformation efficiency.
Using the optimised protocol, the synthetic cry IA (b) gene was mobilized into cauliflower. Molecular analyses of transgenics established the integration and expression of the transgene. Insect bioassays indicated the effectiveness of the transgene against infestation by diamondback moth (Plutella xylostella) larvae. This work has been reported by Chakraborty (2002) at Centre on Plant Biotechnology. Indian Agricultural Research Institute, New Delhi.
12. Seed Production of Cauliflower:
Isolation Distance:
1. Breeder/foundation seed-1600 m
2. Certified seed-1000 m
Descriptors for Varieties:
This is based on George (1999).
1. Type of location and specific season for growing the market crop
2. Seedling: anthocyanin, absent or present
3. Plant height: at time of harvest for fresh market
4. Outer stem: length (up to insertion of first leaf): short, medium or long
5. Leaf:
Attitude: erect, semi-erect or horizontal
Length: very short, short, medium, long or very long
Width: very narrow, narrow, medium, broad or very broad
Shape: narrow elliptic, elliptic or broad
Lobing : absent or present
Colour (with wax if present): green, grey-green or blue-green
Intensity of colour : light, medium or dark
Cross-section of midrib at lower third : strongly flattened, weakly flattened or rounded
Torsion of tip : absent or very weak, weak, medium, strong or very strong
Shape in cross-section : concave, flat or convex
Blistering : absent or very weak, weak, medium, strong or very strong
Distribution of blisters : at tip only or on whole leaf
Crimping near main vein : absent or very weak, weak, medium, strong or very strong
Undulation of margin : absent or very weak, weak, medium, strong or very strong
6. Curd:
Covering by inner leaves: not covered, partly covered or covered
Height: short, medium or tall
Diameter: small, medium or large
Shape in longitudinal section: circular, broad transverse elliptic, transverse elliptic, narrow transverse elliptic or triangular
Doming (excluding cultivars with triangular curds): weak, medium or strong
Colour: whitish, yellow, orange or green
Knobbling: very fine, fine, medium, coarse or very coarse
Texture: fine medium or coarse
Anthocyanin coloration after harvest maturity : absent or present
7. Flower:
Colour: white or yellow
8. Earliness in specific growing season (50% at harvest maturity) : very early, early, medium, late or very late
Seed Yield:
1. 400 kg/ha
2. 1000 seed weight – 2.8 g
13. Varieties of Cauliflower:
Several varieties of cauliflower, namely, Early Kunwari, Pusa Deepali, Pusa Synthetic, Improved Japanese, Pusa Shubhra, Pusa Hybrid-2, Pusa Snowball-1, Pusa Snowball-2, Snowball-16, Pusa Snowball K-1, Pant Shubhra, Pant Gobhi-2, Pant Gobhi-3, Pant Gobhi-4, Punjab Giant-26, Hisar-1, have been developed.
A few important ones are described as follows:
Pant Shubhra:
This is a December-January maturity group cauliflower developed through simple recurrent selection in PI 272775 at Pantnagar. This was identified for release by 1981-all India coordinated vegetable improvement project and has been released by the U.P. state variety release committee in 1983 and central variety release committee in 1984. This is suitable for cultivation throughout the country.
The outer leaves are semi-erect and the inner leaves partially cover the curds. The curds are compact, slightly conical, non-ricey and have retentive creamish white colour. It takes about 120 days from nursery sowing to produce marketable curds. Net curd yield potential is about 200 q/ha.
Pant Gobhi-4:
This is a November maturity group cauliflower developed through simple recurrent selection in a local material known as ‘Agahani’ at Pantnagar. It has been released by both U.P. and central variety release committees in 1995. It has medium long stem, sparse, semi-erect leaves, hemispherical creamish-white, medium compact, non-ricey curds.
It takes 115-120 days for marketable curds after nursery sowing and is about 15 days earlier in maturity than Improved Japanese, the standard check cultivar. It yields about 140 q/ha net marketable curds as compared to about 120 q/he net marketable curds of Improved Japanese.
Pusa Synthetic:
This was developed at IARI, New Delhi and identified in 1975 for greater yield potential in Indo-Gangetic plains. Plants are erect with 24-28 leaves. Plant frame is narrow. Curds are compact and creamy-white to white. It is suitable for planting from mid-September to late September in north India. Maturity duration for curds is 130 days. The yield potential is 225 q/ha.
Pusa Deepali:
This variety was developed at IARI, New Delhi. It has been identified for zone IV (sub- humid Sutlej-Ganga alluvial plains) and zone VI (arid western plains). It is early season variety, has erect tall plants with short, green waxy leaves.
Curds are compact and self-blanching type, medium in size and white in colour. Curds are well covered by leaves and riceyness is almost absent. Appropriate sowing time is end of May to early June. Curds are ready by late October.
Pusa Shubhra:
This is a selection from a triple cross of MGS-2-3, 15-1-1 and D- 96, developed at IARI, New Delhi. It has been identified for all the zones in 1985. Plants are erect with somewhat long stalk and light bluish green leaves. Curds are compact and white. Average curd weight is 700-800 g. Curds are non-ricey. It takes 125-130 days for 50% harvest. The best temperature for curding is 12-16°C. It is resistant to black rot.
Pusa Shard:
Developed at IARI, Nov. maturity, compact-white curds.
Pusa Hybrid-2:
In cauliflower F1 hybrids have been found advantageous for earliness, high yield, bigger curd size, better curd quality, uniform maturity and disease resistance. Heterosis breeding has been underway at the Division of Vegetable Crops, Indian Agricultural Research Institute, New Delhi with main emphasis on the exploitation and development of self-incompatible lines. This programme is being pursued at Pantnagar also.
At IARI, a large number of test crosses were made using a self-incompatible line as female parent. On the basis of their performance for two years in 1985-86 and 1986-87, the best cross combination cc X Sel. 1-3- 18-19 was put in all India coordinated trial under November maturity group.
On the basis of its performance, Pusa Hybrid-2 was identified by the 1992 vegetable workshop held at Hyderabad. It was later on released by the central sub-committee on Crop Standards, Notification and Release of Varieties in 1993 for cultivation in zones II and IV of the country comprising humid Bengal-Assam basin and sub-humid Sutlej-Ganga alluvial plains.
Pusa Hybrid-2 is the first F1 hybrid in cauliflower developed in India using self-incompatible lines in November maturity group. Plants of this variety are semi-erect with bluish green upright leaves.
Curds are creamy white and compact. Average curd weight is 900 g. Curd to plant ratio is 10% higher in this hybrid because of its very compact curd and less area of leaves. Average curd yield is 150 q/ha. This could never reach the market due to non-availibity of hybrid seed.
Snowball Type Cultivars:
This is an important group of cauliflowers well known for snow-white and solid curds. Seeds of this group used to be imported from European countries till 1958. However, due to persistent efforts made at Katrain, in standardizing the time of sowing and transplanting, seed production of this group became feasible in India.
To start with a strain of cauliflower Snowball-16 an introduction from Holland was released as such. Later on, hybridisation work was undertaken at Katrain and 3 varieties were developed and released.
These are:
Pusa Snowball-1:
EC 12013 and EC 12012 were crossed to combine the earliness of the former and the superior curd qualities like solidness and better staying power of the latter. Selections made in subsequent generations resulted in Sel. I. It possessed most of the desirable characters of the two parents.
This was released by the central variety release committee of the ICAR under the name Pusa Snowball-1 in 1977. It has straight upright leaves covering the head very tightly, very solid, medium sized white curds with good staying power. It takes 120 days from sowing to curd formation. It gives about 25% higher yield than EC 12013.
Pusa Snowball-2:
After 3 years of inbreeding in EC 12012, the best inbred line was entered in the all India coordinated trials. With the release of this variety (1977) the cauliflower availability time could be extended in the plains. It has upright leaves covering head tightly and slightly puckered at the margins.
The curds are solid, white with very good staying power and slightly raised in the centre. It takes 110-135 days from sowing to curd harvesting. It yields 150-200 q/ha in hills and 400-500 q/ha in plains. This variety could not become popular due to its poor seeding ability.
Pusa Snowball K-1:
This is a recent addition to Snowball group of cauliflower. It has snow-white curds which are very solid and have retentive white colour. The foliage is light green. The leaves are slightly puckered and wavy. This variety is becoming very popular due to its high yield and curd quality.
However, it is late by about 10 days from Pusa Snowball-1. This is the only variety of this group which has shown field resistance to black rot caused by Xanthomonas campestris. This is most popular variety of this group.
Hybrids:
Private Sector seed companies in India are importing several cauliflower hybrids seed in bulk (10-20 tons/year) from Japan, Taiwan, Korea, China. These hybrids are tropical to temperate types and consequently, cauliflowers are available round the year. Mostly these hybrids are based on CMS and some are extent SI based.