Propagation Of Horticultural Crops PDF

Fundamentals Of Horticulture Propagation of Horticultural Crops Introduction: Propagation of plants involves the formation and development of new individuals, which are used in establishment of new plantings. It is simply the reproduction or multiplication of a...

Fundamentals Of Horticulture Propagation of Horticultural Crops Introduction: Propagation of plants involves the formation and development of new individuals, which are used in establishment of new plantings. It is simply the reproduction or multiplication of a plant from a mother plant. Types of propagation: Depending upon the involvement of pollination and fertilization, plant propagation is divided into two types: 1. Sexual propagation 2. Asexual propagation Sexual method of propagation: Sexual propagation is propagation by seed. The flowers become fertilized by the union of the pollen (male) with the egg (female) and produce the seed that will grow into a new plant with both of the characteristics of the parent plants. In seed propagation, seeds can be germinated and planted in individual containers or starter plugs until they form seedlings. Once germinated, these seedlings can then be transferred to larger containers, or planted in beds or fields. In addition, seeds can be sown directly into the ground and allowed to grow. Example: Most of the vegetables (brinjal, tomato, okra, pumpkin, bottole gourd, bitter gourd, broccoli, cabbage, cauliflower, celery etc.) and flowers (marigolds, petunias etc.), also some fruits and plantation crops like papaya, phalsa, mangosteen, arecanut and coconut. Advantages of Propagating From Seed: Sexual method of propagation has several advantages, like Propagation by seeds is simple and easy. Seed propagation is only mean of diversity particularly in the selection of chance seedlings. Seedling plants are long lived, productive and have greater tolerance to adverse soil and climatic conditions and diseases. Seed propagation makes feasible to propagate plants like papaya, phalsa, mangosteen, arecanut and coconut in which asexual means of propagation is not common. Hybrids can only be developed by sexual means. Sexual propagation offers opportunities of polyembryony (citrus, mango or jamun) and apomixis (Malus sikkimensis, Malus hupehensis, Malus sargentii), which produces true- to - type plants. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture Seed is the source for production of rootstocks for asexual propagation Seeds, if stored properly can be kept for longer duration /period for future use. Disadvantages: Sexual method of propagation has some disadvantages, like Seedling plants are not true to type to the mother plants due to heterozygous nature of fruit plants. Seedling plants have long juvenile phase (6-10 years) and hence flowering and fruiting commences very late in them. Sexually raised plants are generally tall and spreading type and thus are cumbersome for carrying out various management practices like pruning, spraying, harvesting etc. Seeds of many fruits are to be sown immediately after extraction from the fruits as they lose their viability very soon e.g. cashew nut, jamun, jackfruit, citrus, mango and papaya. The beneficial influences of rootstocks on scion variety cannot be exploited in sexual propagation. Seedling plants usually produce fruits inferior quality. Different types of asexual propagation: Asexual Method of Propagation: Asexual propagation, also known as vegetative propagation, is a method of plant reproduction that doesn't use seeds and instead uses a part of the parent plant (stem, root, leaves, etc. instead of seeds) to grow new plants. Advantages  In some fruit plants like banana, which do not bear seeds, this is the only method of propagation.  The plants are generally true-to-type, uniform in growth, high yielding capacity and better fruit quality.  Have short juvenile phase, thus come into bearing earlier than seedling plants.  The advantages of rootstocks can be obtained by budding or grafting susceptible varieties on resistant/ tolerant rootstocks.  Plants have restricted growth, thus cultural practices and harvesting are easy. Disadvantages  New variety cannot be evolved by this method. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture  Plants are not as vigorous and long-lived as the seedling trees. Lack of tap root system results in poor anchorage in soil. Consequently, such plants are easily uprooted in storms or other such severe conditions.  Germplasm conservation requires lot of space and is expensive as compared to storage of seeds.  It is a special job and requires special training and knowledge on the part of the plant propagator. Propagation through cutting: Cutting is a method of asexual propagation in which plant part such as stem, root or leaf is cut from the parent plant and placed under favourable condition to from roots and shoots thus producing a new independent plant. It is of three types: 1. Root cutting 2. Leaf cutting 3. Stem cutting Types of cutting: Root cutting: Root cuttings are generally made in early or late winter or early spring, when the roots are well supplied with ample reserve carbohydrates. The plants capable of producing sucker are good for root cutting. For example- bael, pointed gourd, spine gourd and guava. Propagation by means of root cutting is simple and can be practiced in species that are difficult to propagate by other methods of cutting. In root cuttings new shoots are developed from adventitious buds mostly at the proximal end. Leaf Cutting: It is successful in ornamental plants. Mostly succulent plants having thick and leathery leaves are propagated through leaf cutting. Bryophyllum, Begonia, sansavieria, jade plant, etc. are propagated through leaf cutting. The leaf is separated from mother plant and planted in suitable medium where it gives out roots and generates a complete plant. Stem Cutting: A portion of stem is cut from mother plant and planted in rooted media for easy rooting. After successful root formation rooted stem is planted as new plant. According to age and hardiness of stem used for propagation stem cutting are of four types. 1. Hard woodcutting Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture 2. Semi hardwood cutting 3. Soft wood cutting 4. Herbaceous cutting Hardwood cutting: This type of cutting is taken during November to February before commencement of sprouting. This type of cutting is suitable for Bougainville, Grape, fig, pomegranate, rose, etc. In this method one year old and mature shoots are selected for the purpose of propagation. The selected shoots should be healthy and should not be too vigorously growing. The length of cutting may vary to 10 to 45cm according to the need. The cutting must possess at least 2 to 3 buds. The lower cut is made round just below the node and the uppercut given about 1 to 2cm above the upper node in slanting manner. The base part of stem is quick dipped in IBA (Indole-3 butyric acid) solution @ 500- 1500 ppm or commercially available root powder for better rooting in rooting medium. Semi-hardwood cutting: This type of cutting is usually practiced during rainy season preventing drying of cutting. Mostly practiced in evergreen plants like ficus, lemon, aonla, etc. In this type 4 to 9 month old shoot of semi-hard nature is used for raising new plants. Shoots of 7 to 20cm length are used for propagation. Basal leaves from the shoots are removed. Terminal 2 to 4 leaves are left intact with root. Softwood cutting: Length of cutting is kept 10 to 15cm and age of shoot is 2 to 3 month. E.g. ornamental plants like Duranta, hibiscus, murrya, ixora etc. This type of cutting is not practiced for fruits. Humidity requirement is too high; it is not possible to practice in open condition. Herbaceous cutting: Mostly ornamental plants are planted through herbaceous cutting. Shoots of 1 to 2 month old are selected for cutting. Alternathera, Coleus, creeping jenny, chrysanthemum etc. are propagated by herbaceous cutting. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture Layering: Introduction: It is a technique of propagation in which plant is forced to produce adventitious root while it still remains attached to mother plant. In this process, a single portion of plant constitutes root and shoot system. After emergence of roots the shoot is detached from the mother plant and planted separately. Types of Layering: 1. Simple Layering: In this method one year old shoot is used for layering. The shoot is bent downward in the soil using peg or nail and tied with the help of rope to make it stayed in the position. The ground touching portion is wounded. In about 4 to 5 months, roots emerged out. E.g. Guava, bougainvillea, hibiscus, jasmine, Hazelnut,etc. 2. Serpentine or Compound Layering: Covering the branches of the plant at their nodes with soil throughout its length by alternate exposing of intermodal length of shoots is termed as compound layering. It is practiced in plants like Clematis, Smilax, Wisteria and Muscadine Grape. Girdling of intermodal spaces also gives better result. Rooting hormone may beapplied. 3. Mound Layering or Stooling: This type of layering is practiced in which the branches are very firm and bending is difficult. For mound layering the plant is pruned severely at 2.5cm above ground level before the start of new growth. As a result many shoots emerged out from the base of the plant. When the shoot become little sturdy, it is girdled at the base, rooting hormone is applied if needed and it is covered with soil to a height of about 15 to 20cm. Depending upon case of rooting, roots emerged out in about 3 to 4 month. After rooting the shoots are separated from mother plant and planted separately. It is practiced in Guava, Apple, Pear, Quince, Currant and Gooseberry for clonal propagation. 4. Trench Layering: It is useful for the propagation of apple, pear and cherry. In this method, the branch of the plant is bent downward in a horizontal position in a shallow trench. When the shoot develops the base is covered with 5 to 10 cm layer of soil. Covering the shoots with soil gives etiolation effect and helps in rooting. The rooted layers are separated from mother plants and planted in nursery. Trench layering is Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture successful in woody species which are not propagated through stooling. 5. Tip Layering: Tip layering is a natural method of reproduction of blackberries and raspberries. In these plants rooting takes place near the tip of current season growth. The shoot tip re-curve upward to produce bend in the stem from which roots develop. The top of the plant is layered by making a hole 2 to 5cm below the soil. The tip roots out produce shoot. The rooted tip is separated from plant along with old shoot. Old shoot act as handle also for handling new rootedtip. 6. Air Layering: It is also known as Chinese layering, Pot layering, Marcottage or Gootee. For the purpose of air layering, one year old or previous season shoot of pencil thickness is selected. About 5 to 7 cm away from the base of selected shoot, a girdle of 2.5 to 3.0 cm size, by removing the bark, is prepared. The girdled Portion of the shoot is scrapped using gunny bag or rear side of the blade. This process helps in removal of phloem and ultimately prevents the food supply and formation of bark at the girdled portion. The girdled portion is then covered using moist sphagnum moss grass. Covering with moss grass retains better moisture at the point of air layering. The girdled portion is now wrapped using transparent polyethylene tape (alkathene) and both the end tied air-tightly. Depending Upon ease of success, rooting appears in about 1.5-3 months. When root emergence is there and it becomes visible from the transparent wrapped tape, the layered shoot is separated from mother plant giving 2-3 cuts in instalments. The layered plants are planted in nursery under partial shade where frequent watering is provided and high humidity is maintained. Usually, air layering is practiced in the month of June-August (rainy season). Air layering is practiced in litchi, water apple, rose apple, lime, cashew nut, guava, etc. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture Grafting: Grafting is a technique of propagation in which scion stick and rootstock is connected in a manner such that they may unite and subsequently grow and develop as a successful plant. Thus, it is clear that grafting utilizes rootstock and scion which ultimately constitutes as plant. The rootstock of 1-2 year age having pencil thickness and desired attributes is selected for grafting. On rootstock, the scion of desirable variety is grafted. Generally, the scion shoot of matching thickness as of rootstock is selected. To get success in union of grafting, the cambium of both the rootstock and scion should unite properly. Types of grafting: 1. Veneer grafting. This method is used for propagating mango. In this method, a terminal shoot of 10-15 cm length having pencil thickness is used as a scion. The swollen shoot is used as scion. About 10 days before grafting, the scion-shoot is defoliated to facilitate swelling of bud. Shallow, downward and inward cut ensuring V-shape incision in lower portion of rootstock is prepared. Similar matching cut is given in slanting manner is prepared on lower portion of scion. Both rootstock and scion are fastened together using 300 gauge polyethylene tape of 0.5 cm width. During May and September this system is quite successful and good result is obtained. In about 3-4 weeks, union is completed. When scion sprouts completely, the upper portion of rootstock above graft union is removed in 2-3 instalments. 2. Whip grafting. This is very simple technique of grafting. Generally, rootstocks are used and scions of matching thickness are used. Both rootstock and scion are united and tied using polyethylene tape. When union is completed, the polyethylene tape is cut otherwise it restricts the growth at the point of union and such plants break due to wind. It is used for propagating walnut, apple and pear. 3. Cleft grafting- It is one of the oldest techniques of top working trees. It is also useful for propagating small trees. Mango, hazelnut, pecan nut, grape etc. are propagated through cleft grafting. In case of top working tree, the use of this technique should be limited to branches of about 2.5 to 10 cm diameter. The plant species which has straight grained wood and splits evenly, are considered ideal for cleft grafting. On the stub to beg rafted, a downward vertical split of 5 to 8 cm length is prepared. The vertical incision is made on two sides of stock. The scion shoot of 8 to 10 cm length and pencil thickness is used. Matching incision is prepared on Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture lower portion of scion. The scion is inserted in vertical slits of rootstock. The completed graft is thoroughly waxed. In case of grafting small plants, rootstock of one year old and pencil thickness is selected. It is cut back in terminal region. Vertical slits of 2.5 to 3.0 cm length is prepared on rootstock. Scion shoot matching to thickness of rootstock is selected. On lower portion of scion matching incision is given. The scion is inserted in incision made on rootstock. It is wrapped using polythene tape. The sprouting starts after 3-4 weeks. After that the wrapping is removed. 4. Wedge grafting- This method is also used for top working old tree. V-wedge shape incision of about 5 cm length is prepared on the stub of the plant. Shallow and downward matching incision is prepared on lower portion of scion. The scion is inserted in rootstock firmly. The incised portion of rootstock is waxed property. 5. Bridge grafting- This method is practiced in plants in which scion is healthy and some portion of rootstock near collar region is damaged. In this technique, the damaged portion of rootstock is scratched. In healthy portion of rootstock incision is made on top and bottom portion of the stock. The scion portion of suitable length is inserted into incision. It is fixed using nail and then sealed using wax. The sprouted bud from inserted stick should be removed time to time. Slowly and slowly, it grows in diameter and cover the damaged portion. This method is useful in repairing damaged wood in apple, pear, cherry, walnut etc. 6. Epicotyl grafting- It is also known as stone grafting. In this method, the seeds of Mango are sown in nursery bed and covered with 5 cm to 7 cm thick layer of farm yard manure. While sowing seed, preference is given to sand bed which provides ease in uprooting of seedlings required at the time of grafting. In about 15 to 20 days, seeds start germination. The germinated seedlings of 10 to 15 days age when its leaves remain coppery in colour, is used for grafting. The seedling is beheaded at a height of 10 cm from ground level. A vertical slit of 2.5 to 4 cm length is given on beheaded portion of rootstock. Scion shoot of 2 to 3 months age having pencil thickness is used. The leaves of scion are defoliated 10 days before grafting to facilitate sprouting. After uniting rootstock and scion, it is wrapped using polyethylene tape of 300 gauge. The grafted plants are then maintained in other beds or pots in nursery. This method of grafting is practiced during June-July during which the environment remains sufficiently moist. 7. Soft wood grafting- This is very successful technique of grafting. It is commonly practiced in mango. In this method, the seeds of mango are sown at desired distance in the field during rainy season. To ensure germination, 2 to 3 seeds are sown in each pit. When the plant Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture becomes one year old and attains pencil thickness, it is used for grafting. The grafting is done at permanent site of planting in the field itself. The process of grafting is done during rainy season when new growth appears on rootstock. When new growth leaves start turning yellow from coppery colour grafting is performed. Scion shoot of 10 to 15 cm length, 3 to 5 months of age and pencil thickness girth is selected. At 15 to 20 cm height from ground level, the rootstock is beheaded. A vertical slit of 2.5 to 4.0 cm length is given on rootstock. On scion shoot, similar matching cut is prepared in slanting manner on both the surfaces in lower portion. It is inserted in incision on rootstock and wrapped using polyethylene tape. In about 3 to 4 weeks, sprouting starts and graft starts growing. The grafted plant develops at its own root system and shows better survival in the field. 8. Inarching. This is called as attached method of grafting. In contrast to other method, in this method the scion is detached after completion of union. This method is practiced in mango, jackfruit, sapota, loquat and custard apple. In this method, the rootstock is grown in pot or container. The rootstock is brought close to the scion. The rootstock and scion shoots of pencil thickness are selected. Shallow cut of 2.5 to 4.0 cm length is prepared on scion. Similar matching cut is also given on rootstock. Both rootstock and scion are brought close to each other and wrapped using polyethylene tape. When union takes place, the upper portion of rootstock is cut. The scion shoot is detached from mother plant. The united portion is kept in nursery and cared till next planting season. The process of marching is practiced during July-August during which high humidity favours better union. Budding: 1. Shield or T-budding: As the name indicates shield is the shape of the bud and ‘T’ is the shape of cut given on the rootstock. It is the most common method of budding used by nurserymen worldwide. For shield budding one year old rootstock seedlings of 25-35 cm height and 2-2.5 cm thickness is selected. The bark of seedlings should slip easily. The selected bud of desired cultivar is inserted 15-20cm above the ground level and is tied with a polythene strip. For performing budding operation, a “T” shaped cut is made on the selected portion of the stock with the help of a sharp budding knife. The incision should be given through the bark not the wood. The two flaps of bark are loosened with the help of budding knife. The healthy bud is removed from the bud wood by cutting shallowly Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture about 5-6 mm below and 2-3cm above the bud. This shield piece containing a bud is inserted in the “T” cut made on the rootstock. The shield should be covered by two flaps of the bark, but bud should be exposed. The buds are pressed firmly, fitted into the “T” cut and finally tied with polythene strip. When bud healing process is over, the bud may attain height of 15-20cm, the remaining portion of the stock is cut to about 10-15cm above the bud. Plants with thin bark, with sufficient flow of the sap like apple, pear, peach, plum and apricot, cherry, rose and citrus are propagated by this method. 2. Patch budding: In case of patch budding a rectangular patch of bark is removed completely from the rootstock and replaced with a patch of bark of the same size containing a bud of the cultivar to be propagated. It is slower and difficult to perform than T-budding. It is widely used in thick-barked species, such as walnuts and pecans and rubber tree, where T-budding gives poor results due to poor fit around the margins of the bud-particularly the top and bottom. It is usually done in late summer or early fall, but can be done in spring also. In patch budding, the stock and scion should preferably of same thickness (20-25mm). First a rectangular piece of bark (25mm long and 10-15cm wide) is removed from the stock and a similar patch, containing a bud is removed from the scion by making two horizontal cuts above and below the bud and then two vertical cuts connecting the horizontal cut. After removing the patch, the bud should fit tightly at the top and bottom. It is then wrapped with polythene strip, keeping the bud uncovered. The wrapping material should hold the bark tightly and cover all the cut surfaces to prevent free entry of air or water. After the bud starts sprouting, the stock above the bud union may be cut off step by step. In addition to pecan nut and walnut, mango, rubber plant, aonla, jackfruit and jamun are also propagated by this method. 3. Ring or annular budding: In this type of budding, a complete ring of bark is removed from the stock and it is completely girdled. A similar ring of bark containing a bud is removed from the bud stick and is inserted on to the rootstock. The thickness of stock and scion should be same size. It has been utilized in ber, peach and mulberry because the newly emerged shoots from the heavily pruned plants are capable of giving such buds for budding, which can be easily separated. In this method since the stock is completely girdled and if the bud fails to heal in, the stock above the ring may eventually die. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture 4. Forkert budding: In forkert budding, the stock is prepared by giving two vertical cuts and a transverse cut above the vertical cuts to join them. The bark is removed carefully along the cuts, so the flap of bark hangs down. The scion is prepared in a fashion similar to patch budding, having the size similar to cuts made on the stock. The scion is then slipped into the exposed portion of the stock and the flap is drawn over the inserted bud patch. It is then tied with a suitable wrapping material. After successful growth of bud, the portion of stock above union is removed carefully. Precautions:  The bud to be used as scion should be mature.  Wrapping of bud union should be performed carefully to avoid air entry at the point of union.  Budded stock should be irrigated at regular intervals  De-shooting of sprouts below bud union should be done as the sprouts appear  The wrapping material should be removed when it gets tightened.  In case of chip budding in fall season the bud grafts should be protected from chilly winter in cold arid conditions. Class Notes. 2 Dr. Shuvadeep Halder.  Fundamentals Of Horticulture Class Notes. 2 Dr. Shuvadeep Halder.