Gerbera: Genetics and Modification | Flowers

After reading this article you will learn about:- 1. Genetics and Breeding of Gerbera 2. Varietal Wealth of Gerbera 3. Modification of Environmental Conditions 4. Propagation 5. Division 6. Micropropagation 7. Planting 8. Manuring and Fertilization 9. Irrigation 10. Weeding and Hoeing 11. Flower Regulation 12. Flowering Yield 13. Storage 14. Harvesting and Packing.

Gerbera ranks fifth amongst cut flowers after rose, carnation, chrysanthemum and tulip. On an average 241 million blooms are produced every year. The reason for its popularity is its floral beauty, attractive colour, good keeping quality and suitable for long distance travelling. It is an important flower grown throughout the world in a wide range of climatic conditions under open conditions or under heated or unheated glass house, plastic houses or tunnels.

Gerbera is commonly called as Transvaal Daisy or African daisy. Botanically, it is Gebera jamesonii and belongs to family compositae. This genus has been named after German botanist Traugott Gerber. This is native of South Africa (Natal G. jamesonii and cape—G. uirdifolia were crossed with each other to produce modern types) and Asia. In India gerbera is widely found in temperate Himalayas from Kashmir to Nepal at the altitudes of 1300 to 3200 mts.

It is herbaceous, stems less plant and makes a rosette growth. Leaves are petioled, lanceolate and deeply lobed and are arranged at the base. Flower heads are solitary, composite (many flowered) having conspicuous ray floret in 1 or 2 or more rows. Inner row is very short and tubular and 2 lipped. Flowers are like daisy in many clear or bi-colours e.g. White, Yellow, Pink, Orange, brick red, scarlet, salmon, terracotta, etc.

On the basis of double-ness, flowers are grouped into single, semi double and double cvs. The double cultivars are highly attractive due to contrast colour of disc i.e. yellow or black colour. The flower stem are long, thin and leafless. Seeds are beaked achene’s with pappus (hairs).

Genetics and Breeding of Gerbera:

There are about 40 species which are half hardy and perennial in nature. Important species are G. jamesonii, G. uirdifolia, G. asplenifolia, G. aurantiaca, G. kunzeana; G. aberdaria, G. abyssinica, G. ambigua, G. anadria, G. bojeri, G. bracteata, G. chiliensis, G. eineraria, G. elliptica, G. krausii, G. tuberosa, G. tomentosa, etc. Diploid and tetraploids forms exist. The basic no. of chromosome is 25. Increase in number of chromosomes has shown useful effects on plant and flower size.

Different level of sterility exists and plants could be divided into:

(i) Completely self-sterile plants,

(ii) Plants with distinct differences in seed set when pollination takes place within inflorescence, and when pollination takes place between neighbouring inflorescence on the same plant and

(iii) Plants in which these differences were less pronounced. For the production of hybrid seed first two types are suitable whereas third type was less favourable due to frequent selfing.

In gerbera, productivity is due to additive gene effects. High heritability in G. jamesonii for inflorescence diameter and number of ray florets and relatively low for disc diameter and stem length has been reported. The numerous cultivars of gerbera have been developed through mostly hybridization and through mutation.

The development of gerbera plants from seed till flowering takes 3-4 years. The seeds are to be sown immediately after harvest otherwise they lose viability. Seedling stage continues for about one month, the juvenile stage continues up to 4-5 months whereas the reproductive stage continuous 3-4 or more years.

Varietal Wealth of Gerbera:

Gerbera is very rich in its varietal wealth due to ease in hybridization and survival of seedlings. Thousands of cultivars have been developed which are highly suitable for commercial production of cut flowers under open as well as under green-house conditions. Several varieties suitable for pot culture which are characterized by their bushy nature, dwarf, bearing large number of flowers, may be, somewhat little smaller in size have also been developed.

According to flower size also cultivars are grouped into large and mini types.

Similarly according to flower stem length, varieties are grouped as follows:

Tall varieties—when flower stem length is more than 50 cm. e.g. Funda, Diablo, Sunanda, Dark Red ; medium—(40-50 cm)—Ornella, Sun set, Thalassa, Tavila, Kolika, Ruby Red, Pink Elegance, Rose bella; Dwarf—(30-40 cm)—J.S. Lai, Alemasa, V. Record, Janson Hybrid, Verasace, Indu Kumari, Yellow Queep, Gen Khaiser, Nebulusa, Red Monarch, Sangria. The performances of varieties greatly vary from region to region and flower quality differs area wise.

Under Indian conditions, the popular gerbera varieties amongst commercial growers are: Jaffa, Sangria, Rosula, Oprat, Romona, Salina, Tecora, Starlight, Aida, Venturi, Ornella, Aalasmeer, Goliath, Pink Elegance, Rosa lina, etc.

Other important varieties of gerbera from Terra Nigra, Holland are being propagated and marketed by M/s Germini Agro Pvt. Ltd., Pune. These varities are Cariba (Red), Lamborshini (Red), Bliss (Red), Dino (Yellow), Gucci (Yellow), Flow Basic (Pink), Grizzly (Pink), Cauca (Orange), Virginia (White), White Grizzly (White), Aligator (Violet), Crossroad (Yellow with red center), Solemio (Yellow with orange center), etc.

The characteristics of different large and mini varieties as reported by nurserymen are given in following tables:

Climate:

Gerbera needs mild climate for its vegetative growth and flowering. Extreme of cold or hot temperatures are not desirable. Therefore, under tropical and sub-tropical climate gerbera is grown in open or in unheated plastic houses. In temperate climate, gerbera plants need protection from frost and are grown in green houses.

Gerbera plants require sunny situation. In temperate climate, poor light conditions during winter adversely affect the flower quality and hence, artificial lighting is done. Night temperature plays an important role in production and quality of flowers. It has been observed that a night temperature of 12°C has been found optimum. During entire growing and flowering period high humidity is to be maintained. If the air humidity drops below 50%, the young plants suffer. The humidity can be maintained more easily in closed structures.

Soil:

For growing gerbera successfully, soil should be porus and well drained. Thus light soils with good organic contents are more suitable than heavy soils. The pH of the soil becomes a limiting factor when it is not in desirable limit. By nature gerbera loves acidic media than alkaline soil.

The ideal pH for gerbera growing is 6.0-6.5 but it can tolerate little higher pH i.e. up to 7.2. Higher pH of soil needs its correction to the desirable limits. On the other hand, too acidic soil can be made sweeter by adding lime. Most of the problems associated with its growth and productivity can be solved by adjusting pH and drainage system.

Before starting a cultivation of gerbera, soil sterilization is absolutely necessary especially against fungus like phytophothera, cryptogera and nematodes which causes serious wilt disease and may destroy a crop partly or even completely. For this, formaldehyde or methyl bromide gas can be used and soil is covered with polythene for 48 hrs.

Gerbera also responds well to artificial media if it satisfies the conditions of porosity, drainage and pH Artificial media like coco peat, peaty soils, vermiculite, perlites, etc. do find favour for gerbera growing. Better grades of peat like mixes can be used. Gerbera will not grow happily in soil mixes with poor aeration.

Modification of Environmental Conditions for Gerbera:

Area suitable for gerbera production should have mild weather conditions and temperature ranging from 16-20°C which should be in day whereas 12°C should be during night. This is the temperature which should be maintained in green houses. As gerbera plants cannot tolerate extreme of weather conditions, there is a need to modify the environment and bringing it in limits so that optimum flower yield can be obtained.

Mild weather conditions are available in places like Bengaluru, Pune, Nasik, Hyderabad, Kodai Kanal, etc. In these places gerbera is cultivated with fewer efforts. On the contrary under north Indian conditions due to extreme of weather conditions during summer and winter, it is not possible to grow gerbera under open conditions with optimum yield.

During summer, lowering of temperature can be achieved by shading and having evaporative cooling system. Different materials like shading net (green or white), saran cloth, aluminium coated nets are available and can be selected judiciously.

In the winter raising the temperature by heating or mere by covering with single or double polythene layers can be achieved depending upon the local conditions. Adoption of such expensive technology will depend upon it economics and profitability.

Propagation of Gerbera:

Both sexual and asexual methods are employed in propagation of gerbera. Propagation through seed is used to breed new varieties by breeders. Gerbera seedlings exhibit variation when obtained from open pollinated seeds or in a planned programme useful variations are released as new varieties.

It is a long processes and it takes 3-4 years to bloom a seedling. Care should be taken that seeds should be sown immediately after harvest otherwise they lose viability quickly. Vegetative methods like division of clump, cuttings, and micro propagation are very commonly used.

Division of Gerbera:

Large clumps are divided into seedling plants and are set in the field. Before planting, roots and leaves are trimmed keeping central axis intact. While setting the suckers care should be taken that soil does not cover up the central axis. Suitable time of separation will depend upon local conditions. At the time of separation environmental weather conditions should be mild and much ahead of winter so that winter crop is in the time.

Gerbera is also propagated through cuttings. Healthy plants are kept without water for 3-4 weeks, roots are pruned, planting in the peat are kept at 25-30°C with 80% humidity. The buds in the axil of leaves are detached and rooted in rooting medium. Plants become ready for transplanting in 2-3 months. Young stem cuttings produce roots and shoots much easily and quickly under misty conditions.

Micropropagation of Gerbera:

Normally, gerbera is propagated through seeds and division, but with the availability of modern techniques of tissue culture of plants which allows the production of disease free planting material in unlimited number from single explant. It offers a very good opportunity for large scale multiplication of gerbera. It involves rapid multiplication of explants by repeated sub-culturing and preparation of divisions for transfer to the soil.

Various explants in gerbera like, shoot tips, inflorescence buds, capitulum, and mid ribs have been employed. Various culture media for different explants have been found effective in obtaining the highest number of plantlets. Overall, Murashige and Skoog’s medium with certain modification have been found successful in gerbera.

Planting of Gerbera:

In green houses or in open field conditions, two rows or four rows planting system are generally followed. Hence, accordingly bed width is kept. For large flowering gerberas 8-10 plants/m² are planted. Close planting is followed for small flower cultivars.

The spacing in rows ranges from 30-40 cms. Plants are planted at 30-37.5 cms apart. While planting, care should be taken that crowns should be well above the soil surface. Planting time varies with place of growing, its climatic conditions and method of growing.

Planting can be done round the year under Pune, Bengaluru, Hyderabad, conditions but under North Indian conditions optimum time for planting is September and October. The plants should be left in the field undisturbed for two years for flower production.

Manuring and Fertilization of Gerbera:

Gerbera prefers organically rich medium for proper growth and flowering. Therefore, addition of organic matter in medium results in healthy plants and excellent flower production of better quality of flowers. It is advised before addition of fertilizers, leaf blade analysis should be done.

Leaf blade analysis has been found better than petioles as it is better index of nutrient contents. It has been observed that good flowering yield was recorded when the leaves contained 2.7-3.13% N, 0.19-0.35% P 3.06-3.64% K, 1.66-2.18% Ca and 0.3-0.4% Mg.

Soil analysis will decide the quantity of organic matter and other fertilizers to be added. Generally in fairly sandy soil, addition of 7.5 kg/m² well rotten farm yard manure gives desirable results. Gerbera responds well to the applications of NPK which improves the numbers of leaves, suckers and large number of blooms of big size.

Excess of N reduces of flower quality and flower production. Generally, N @ 15 g/m² was found to be optimum for better flower production of quality bloom. N, P & K in the ratio of 3:1:1 produced highest flower yield.

Gerbera being sensitive to pH of the soil, if pH is not in ideal range, plants can exhibit the deficiency of micro nutrients. Under high pH of conditions, deficiency of Fe or Mn or both is very common. Hence, it is recommended that gerbera plants should be sprayed with micro nutrients time to time even if plants do not exhibit micro nutrient deficiencies to avoid development of deficiency symptoms of these micro nutrients and harm to occur to the plants.

Irrigation of Gerbera:

Gerbera is a moisture loving plant and hence, it needs thorough irrigation at regular interval. However, wet feet are not desirable so avoid water logging conditions. Water requirement vary with the varying environmental conditions.

It has been observed that there was an increase in flower number when the water regime was higher in summer and low in winter when it was compared with constant water supply. Hence, watering should be adjusted according to crop requirement.

Water quality is also important and different varieties responds to various levels of salts. Irrigation water should be of good quality and low in total soluble salts. Watering methods like flood irrigation, sprinkler and drip irrigation can be employed according to the facilities and finances available.

Weeding and Hoeing of Gerbera:

Depending upon season and method of growing, and weeds types will appear in gerbera field. Gerbera being perennial crop and remains in the field for 2-3 years and its rosette nature of growth, weed appears only in the early stages of crop. Later on gerbera plants cover most of the field except irrigation channels or furrows. Two to three manual weeding’s are required. Efforts should be done to keep the soil loose and friable by regular hoeing and free from weeds.

Flower Regulation of Gerbera:

After planting, normally it takes 2-3 months to produce flower by the plants. If plants take longer period for flower production. Plants can be sprayed with 100 ppm of GA₃. This will result in early flowering with longer stems.

Flowering Yield of Gerbera:

Once the gerbera plants enter into a reproductive stage, continuously plants keep on producing flowers. Under green-house modern varieties are very heavy yielder and produces about 250-300 flowers/m² from 8-10 plants. Under open conditions different varieties show variation in yield depending on types of media, pH, climatic conditions and seasonal changes.

Storage of Gerbera Flowers:

Optimum storage temp, (wet) for gerbera is 4°C. The flowers can be stored efficiently up to 4 weeks. The cut flowers should be kept in clean water containing preservative and bactericide without delay after harvesting. Removal of heel of stem improves water uptake, Addition of HQS or chrysal is generally used.

Harvesting and Packing of Gerbera Flowers:

The harvesting of gerbera flowers should be done at optimum stage. This stage can be identified very easily by observing outer two whirls of disc florets which should be per­pendicular to the stem and show pollen grains otherwise flowers will wilt and close at night.

After harvesting individual flower head is provided with thin layer of plastic cup which protects it during transport and keeps fresh and do not allow any damage to occur to flower head. The gerbera cups of following three sizes are available.

All the flowers are packed in insulated boxes individually for safe transport. Good quality gerbera should have at-least 40 cm stem length and should be firm and straight. Stems showing bending are not desirable in the trade. The flower should be uniform in size and should not be less than 7 cm in diameter. Flowers of gerbera are packed in flat boxes having paper shreds and holes for individual flowers.

Main problems observed in field or green house:

(i) If flower stems are too long or foliage is too large, increase light intensity or use B-9.

(ii) If flowers are too short or hidden in foliage, this condition could result from excessive fertilizer (nitrogen or ammonia).

(iii) If plants are dying out too frequently, too much growth regulator or average growing temperature is too low.

(iv) If flowers are distorted, it is caused by mites or thrips.

(v) If plants fail to grow, usually caused by poor drainage, packing soil too tightly or low soil temp.

(vi) If plant wilts or dies, it might be planted too deep and eventually was killed by crown rot.

Important Diseases, Insects and Pests:

Diseases:

1. Alternaria:

It is a common disease caused by Alterneria sp. Phyllostica gerbera and other fungus. It can be easily controlled by spraying 0.2% captan, or Benomyl (0.1%) on mancozeb (0.2%).

2. Root Rot and Foot Rot:

It is soil borne disease caused by Pythium irregularae and Rhizoctonia solani. Soil sterilization is through formaline is good solution. Drenching of soil with copper oxy-chloride (0.4%) or Dithane M-45 (0.2%) gives the good control of disease.

3. Powdery Mildew:

It is caused by fungus Oidium erysiphoides sp. gerbera and produces a white coating on the foliage. Good control can be achieved by spraying Karathane 40 EC @ 0.5% (50 ml in 100 L of water).

Insects and Pests:

(i) Leaf miners:

Gerbera is often attacked by leaf miners (Liriomyza trifolii). Adults of the insect lay eggs on the leaves. The larvae bore into the leaf and make irregular shaped tunnels which are easily identified by the presence of yellowish tan coloured marking on the leaves. On maturity, larvae fold leaves on inner surface. It can be controlled by spraying 0.1% 30 EC Rogor.

(ii) Mites:

It is commonly found in green house. The development of leaves and buds was adversely affected and flowers became malformed and un-saleable. These can be controlled by spraying Pentac W.P or Aqua flow on a preventive basis.

(iii) Thrips:

These are small insects and suck the cell sap from leaves and flower stalk. It can be controlled by 125 ml of Dimecron 85 SL (phosphamidon) or 400 ml of Rogor 30 EC (dimithoate) in 80-100 L of water.