EXERCISE 2

EXERCISE 2: Propagation of temperate fruits

Materials required: Seed. Wooden box, moss grass, bavistin, sand,referigrator
  • Temperate fruits are commercially propagated through asexual method of propagation, however, sexual method is generally employed for raising seedlings rootstocks.
  • The propagation is classified in two broad categories.
(1)Propagation of rootstocks
(2) Propagation of scion cultivars
  • The rootstock propagation is accomplished through seed in case of seedlings rootstock and through layering, cutting and tissue culture in case of clonal rootstock .
  • The scion cultivar is propagated through grafting and budding.
1.Propagation of rootstock
(i) Seedling rootstocks: -
  • Seedling rootstocks are commercially used on which scion variety is grafted or budded. I
  • In apple, seeds of crab apple (Malus baccata) or self pollinizing varieties like Golden Delicious and Granny Smith are used for raising seedling rootstocks.
  • Seedlings of Kainth (Pyrus pashia) and Zarainth (Pyrus serotina) are used as a rootstock for pear.
  • For peach, wild peach, for plum and apricot wild apricot called chulli and for almond bitter almond and behmi seeds are used for raising seedling rootstocks.
  • Cherry plants are raised either on Paja (Prunus cerasoides) seedling or on clonal rootstocks. Seeds of wild persimmon called khau for persimmon are used
  • Seeds of katha walnut for walnut, Burkett variety of pecan for pecan nut and Bruno variety of kiwifruit for kiwifruit are used for raising seedling rootstocks.
  • Seeds should be collected from fully ripened fruits, extracted by hand or machine should not contain flesh on the skin and dried under shade.
  • Seed are treated with Bavistin (3g /Kg seed) to be stored for some time before sowing.
Seed stratification
  • Seeds of deciduous fruit trees generally do not germinate until they get chilling treatment. Exposing the seeds to low temperature (0 to 5oC) for a considerable period helps in breaking the dormancy thus resulting in stimulation of germination..
  • Seeds are placed in alternate layers of moist sand either in wooden box for small seed like apple, pear and kiwifruit and in pits for bold seed like peach, apricot, walnut and almond.
  • This box is kept at low temperature a little above the freezing point for specific period depending upon the type of seed (Table 1).

2.1

Plate.1 Seed stratification in wooden box

2.1t

  • In addition to low temperature treatment there are other methods to improve germination like soaking seeds in water, scarification mechanical as well as acid treatment and by chemical treatments such as GA 200-400 ppm, thiourea 0.25 to 5% or KNO3 0.2%.
Seed sowing
  • Pre-stratified seeds are sown in nursery beds during March at a spacing of 8-10 cm from seed to seed and 15-20 cm from line to line at a depth of 3-5 cm.
  • After sowing, the nursery beds are mulched with 10 cm thick dry grass and light irrigation is given to avoid desiccation of stratified seeds.
  • As the seeds start germinating, mulch material is removed. Cultural operations like weeding, hoeing, irrigation and spray of insecticide and fungicides are done at regular intervals.
  • The seedling rootstock attain graftable size in a year.

2.3

  • In high hills areas experiencing sufficient snowfall in winter, seeds are sown directly in the field during December, however, some times poor germination occurs due to heavy rainfall.
(ii) Clonal rootstocks :-
  • Clonal rootstock of temperate fruits are propagated through layering, cutting and tissue culture, however, through layering (mound and trench layering) is the most common method.
(A) Mound and trench layering:-
(i) Establishment of stool beds:-
(a) Selection of site:-
  • The site for the establishment of mother stool beds of clonal rootstocks should be selected at an isolated place where the soil are fertile and well drained.
  • The land should be prepared by deep ploughing and soil is made labeled, free of stones and weeds.
(b) Selection of mother plants:-
  • The main consideration in the selection of mother stock for the establishment of stool beds are (i) Quality (ii) Trueness to type (iii) Disease, insect and virus free.
  • The mother plant should be elite material taken from a single indexed mother plant and should be free from diseases, insects and viruses.
  • The mother plant material selected for the establishing stool beds should be 8-10 mm in diameter, 60-70 cms in length and have well-developed root system.
Mound Layering:-
  • Mound layering is a method of propagation where the plants are established vertically and plant shoots are stimulated to develop roots at their bases as a result of etiolation caused by mounding of the soil or rooting medium around the base of such growing shoots.
  • For the establishment of mother stool beds for mound layering, the planting of mother stock is done at a distance of 40 to 45 cm plant to plant and 1.5 meters from rootstock to rootstock during the month of December - January.
  • At planting, the plants are headed back 45 to 60 cm and allowed to grow for one year. The mother beds are irrigated after planting and proper aftercare like weeding, irrigation, fertilization, pest and disease control is followed during establishment phase of mother stool.
  • In the second year, stooling cycle starts and in the month of Jan-Feb before new growth start in the spring the plants are cut back to about 2.5 inches above the ground level.
  • In the spring two to five shoots will develop from the stub in the first year and more in later years. As these shoots attain 10-15 cms height, first earthing up with a media containing soil: FYM/ Vermicompost: Sand : Coco peat (1:1:1:1) is done to cover the half of height of shoots.
  • In difficult to root clonal rootstocks like M-9 and Merton –793 of apple and Gisela and F 12/1 of cherry, 5000 ppm IBA as linolin paste is applied at the base of shoot by removing some bark before earthing up of shoots.
  • When the shoots attain 25-30 cm height, second hilling operation, followed by third hilling is done in the mid summer when the shoots have grown 45 cm.
  • In the month of December, the soil around the stool beds are removed and rooted layers are cut close to the their base from the mother plants and transplanted in the nursery beds for grafting and budding.
  • After the harvest of the rooted layers, the mother stool beds are kept exposed until the new shoots have grown.

2.4

Trench Layering:
  • In trench layering, the mother plants are established in a horizontal position in the trenches.
  • Trench width should be 70 cms, depth 14 cms, distance between branches 150 cms and effective distance between stool bed 80 cms, distance between plant to plant 40-45 cms. and angle between plant and trench 45o.
  • The healthy, diseased free and elite mother plants are planted in dormant season at an angle of 45o in the trenches. The ideal length of mother stock for plantation in the trench beds is 50-60 cm. Each mother plant should be planted as to overlap the previously planted mother stock by approximately 20 cms.
  • After planting, the stool beds are well irrigated and further irrigation is given as an when required during the entire growing season.
  • The mother stock is allowed to establish for one years. The proper management practices like weeding, irrigation plant protection measures are followed at a regular intervals.
  • In the next dormant season, training and bending of mother stock is done. The main mother plant is bend horizontally along the bottom of the trench putting iron hooks and wooden pegs. Two to three suitable side shoots on either sides of main mother stock plant are selected while remaining unwanted side shoots are pruned off.
  • In the first season, the buds from the pinned down main stem as well as from shoots will break. As these shoot attain 10-15 cm height, the first earthing up is done with a medium containing sand:soil:FYM:cocopeat and saw dust.
  • The earthling up operations are done 3 times in a season.
  • In the dormant season, the medium is removed and stool shoots are cut from the parent plants and planted in the nursery beds for grafting and bud.

2.5

Propagation through cuttings:
  • Clonal rootstocks can also be propagated through hard wood and semi hard wood cuttings. The ability of cuttings to regenerate through cuttings varies with the rootstocks.
  • Use of special techniques like pre-planting and post-planting treatments of cuttings have helped in rooting of cuttings in difficult to root clonal rootstocks.
  • Hard wood cuttings of 15-20 cm long and 0.8 to 1.0 cm in diameter are taken during dormant season (January).
  • Cuttings are dipped in 2500 ppm IBA solution for 15-20 second and then transplanted in mist propagation chamber or in open field conditions in rooting medium of sand: cocopeat: vermicompost :soil (1:1:1:1).
  • The semi hard cuttings along with leaves are taken during July, dipped with 2500 ppm IBA solution and planted in mist propagation chamber for rooting.
  • In the month of December and January, the rooted cuttings are transplanted in nursery beds for further grafting and budding.

2.6

Propagation through tissue culture:
  • Clonal rootstocks of apple can be multiplied on large scale through tissue culture. The commercial micropropagation is achieved following a series of steps.
(I)Explant source :
Collection and preparation:
  • Explant used for initiating shoot culture of clonal rootstocks of apple can be obtained either from actively growing shoots or dormant shoots.
  • The shoot tip is better explant source but axillary buds can also be used.
  • About 5-8 cm long shoots from actively growing branches are collected and stored in polythene bags to prevent wilting until they can be processed in the laboratory.
  • The best time of collection of explant is March-April, because it shows less contamination and initiate growth in vitro quickly.
  • The leaves along with stipules are removed from the collected shoots ensuring that no damage is done to axillary buds. Axillary buds are excised from shoots with sharp blade in a beaker containing water.
  • One drop of liquid detergent is added to it and stirred gently to wash out the debris. The beaker with explant is covered with muslin cloth and kept under running water for about a hour.
  • In case of the dormant shoot, they are cut into pieces of 2-4 cm long with bud near the distal end. These sections are kept under running tap water.
2.Surface sterilization:
  • Surface steralization is carried out in laminar air-flow cabinet. First the buds are dipped in 70% ethanol for 40 second and washed 3-4 times with sterile distil water, last rinse is for 5-10 minutes.
  • Once the sterile distil water completely rinsed from the explant, they are inoculated as such or 2-3 outer leaflets are dissected away in 25 mm diameter test tubes.
3.Excision of meristem as explant:
  • After sterilization of axillary and terminal buds, they are dissected by removing bud scale, leaf primordia carefully to expose the growing point.
  • The growing point together with 2-4 leaf primordia is excised and explant with the base resting on the surface of the medium.

2.7

4.Establishment of explants:
  • Smaller explant can be used to initiate culture because they are relatively free from contamination .
  • The best sprouted explant should be selected for transfer to fresh medium.
  • Growth of buds usually begins 10-15 days after cutting. By 3-4 weeks, leaf primordia developed into long leaves .
  • The sprouted explant are transferred to fresh medium for growth of stem and axillary buds.
5.Shoot multiplication :
  • Once culture are established ,shoots will proliferated in MS medium. The presence of leaves on explant is followed by growth of shoot and stem formation, then axillary bud develop from primary shoot give rise to secondary shoots.
6.Rooting: -
  • Vigorously growing 2-3cm long shoots from proliferating cultures are selected for rooting.
  • These cuttings are then rooted in MS medium containing Auxin (IBA 1.5um) but no cytokinin and GA3. The concentration of auxin varies depending upon the rootstock.
7. Acclimatization:-
  • About 4-6 weeks old rooted cuttings are carefully removed from the culture tubes to avoid any damage to delicate root system.
  • After dipping the plants in 0.05% bavistin, they are planted in pots containing presterilized potting mixture (soil:sand:compost,1:!:1).
  • The pots are kept in green house having 100% humidity. After 3-4 weeks, plants are transferred to soil mixture and exposed to ambient conditions.
Last modified: Thursday, 5 April 2012, 10:36 AM