Most often tree crops are propagated first by seed, then other techniques like grafting may follow.

Sourcing the seed:

 Seeds can be collected from several alternative sources:-

1. harvested from trees locally – from farms
2. from public land or forest (as long as one collects from at least more the 30 trees)

• from market places

1. can be bought from specialized suppliers, example National Tree Seed Center

For tree crops seeds may be collected in dry and grain form, some are collected in form of fruits. Specialized information must be sought for each species of tree crop dealt with. Important tropical landscape tree plants could include Ficus spp; Delonix regia, Polyalthia longifolia (extensively known as ashok or ashoka tree, which is incorrect), Terminalia spp (T. catapa, T. mantaly or tropical almond, etc), Azadirachta indica, various types of palms, timber species like mkangazi (Khaya nyasica; African mahogany); Cederea etc.

When getting seed from a supplier, it is important to look at the seed and check that it appears to be of good quality. Good quality seed means:-

– it is clean from dirt, debris and chaff

– it must be free from pests and pathogens

– it must have a high percentage of germination

– it must be accompanied by a note, carrying the scientific name of the species, place of collection, date of collection, number of seeds/unit weight and whether any treatment has been applied

Before planting a lot of seed, it is a good idea first to check it’s viability by seeing if it germinates well. Once you have an idea about viability, then it will be possible to estimate how many seed need to be planted to get a certain number of trees.

To ensure good seed quality when a nursery collects seeds on its own , fruit collection must be made from trees having the desirable characters. Such trees are labelled and their locality recorded on a map.

Phonology of these trees should be observed as to when they flower, set fruit, and have mature fruits. Does fruiting take place every year, every two years? Are there any factors influecing fruit production? e.g. drought, defoliation by insects, etc.

Nature of fruit: dehiscent or intact. Does it remain on the tree or fall to the ground?

Hazards to the fruits: insects, pathogens ?

Collection time and method: well developed and mature fruits contain good seeds. So the collection time is when fruits are fully matured.

Fruits are either collected from the tree by beating the tree with a stick, or shaking the crown with a long hook, or by climbing.

Some fruits fall to the ground and they are collected. In such a case, the place of collection must be cleaned beforehand.

Treatment of fruits: Collected fruits are cleaned, sprayed against insects and spread on a clean sheet to dry.

Seed extraction                                                                                                                                            This is the process of separating the seeds from the fruit. Therefore, the method of extraction varies with the type of fruit. For example, some spp such as leguminous trees dehisce once they are completely dry and a gentle shaking is sufficient to extract the seeds. In some spp. seeds are difficult to extract. The fruit may first need pounding to remove the pulpy material, may even additionally need treating with acid for example dilute hot hydrochloric acid; then washed and dried.

Some seeds may be extracted very easily. For example, in species with such fruits as those of Eucalyptus,  seeds are extracted very easily when fruits become brown on top; they are collected and put in clean open tins to dry, once dried the fruits open, shedding the seeds and chaff.

Some seeds may be extracted with a lot of difficulty. For example, Hyphaene thebaica seeds are extracted by sawing-off the shell.

Seed drying                                                                                                                                                Once seeds are extracted, they are cleaned of chaff and dirt and dried in the sun or in an oven. If seeds are stored wet, moulds and pathogens may spoil them.

Seed storage                                                                                                                                             Seeds, whether bought or collected, must be stored in a proper way until needed. Dry seeds can be safely stored in air-tight polythene bags at room temperature.

When seeds are stored they are normally labelled, given a number and placed in an air-tight bag inside a closed tin. A single tin may contain several bags and a card register system is used to indicate in which tin seeds are stored and how much is left after using a given quantity.

Viability testing                                                                                                                                         Some seeds lose their viability in a short period, e.g. Azadirachta indica seeds lose viability in about 6 months. Therefore it is important to test seeds which are stored to determine their germination percentage and it is useless to store any seeds that fall below 40% germination unless they are very rare or very expensive. The viability can be tested by:

Germination test: Filter paper method – where seeds are small, about 100 seeds are germinated in a petri-dish over a filter paper. Silt test – 100 seeds are sown in a container with silt soil.

Tetrazonium chloride test: This is a chemical that imparts colour to living tissue. The seed is cut and the liquid is smeared onto the cut surface to find whether the embryo is alive

Fruit crops                                                                                                                                               Seeds of most of fruit species are usually within the fresh (or dry) fruit and need to be extracted from the fruit. Each species may need some specific consideration.

Mango                                                                                                                                                    Mango fruits are collected at the ripe stage, ideally from uniform trees and best from polyembryonic varieties (bse plts from polyembryonic seeds become more uniform). It is much better to use seeds extracted from ripe fruit rather than overripe or unripe fruits. Freshly collected mango seeds from ripe fruits germinate with higher frequencies (76 – 91 %) than those from overripe, firm or green fruits.

The seeds are immediately extracted from the fruits (de-pulped) then dried. De-pulped seeds are washed to free the seed which if it is to be dried it is within a usually tough husk. The fresh seeds (or stones) may also be collected from a canning unit. Such seeds have higher germination if collected and planted. Prior to sowing actual seeds usually have to be extracted again (or peeled) from the husk.

De-husking involves make a small cut at the distal or both ends of the seed and pull the husk away to get the seed inside without any damage to it. When the cut is made at the distal end of the seed with husk, even if it cuts the seed inside, it does not damage the embryo.

Drying husked or de-husked seeds both trigger germination and vigour deterioration of the seed

Seeds extracted from husks may have mango weevils inside. When such seeds are planted, whole seed may be destroyed. Therefore, dip the seeds in an insecticide solution such as ‘Dimethoate’ before planting for a few minutes. Use of fungicides such as ‘Captan’ at this time is helpful to protect the seeds from fungal infections at the nursery.
Mango seeds are recalcitrant, and lose viability within 30 days. Seeds should be collected and sown within 1 week after collection. About 80% germinn occurs if seeds are sown within 1 month after extraction. Seeds that are free of pulp can be stored for up to 84 days at 15^oC on sterile cotton with deionized water.

Storage of mango seeds in polyethylene bag or in polyethylene bag with charcoal powder has been found to retain viability of the order of 40 – 53% germination for about 3 months (90 – 103 dys), with the charcoal powder improving storability (103 dys

If the stones are treated with r-hydroxyauinolene sulphate and stored in polyethylene bags of 100 guage at 1⁰ C temperature, viability of mango seeds can be preserved for one year without decline in vigour.

Ideally mango seeds are sown after de-husking. Some nurserymen however sow the seeds flat in husks. It is very time-consuming to remove the seed from the husks and some nurserymen find de-husking un-economical.

De-husked seeds are best sown with their concave side down, in raised  beds at least 10 – 15 cm above ground level, within rows spaced 15 – 20 cm, roughly 1 – 2 cm beneath soil level, touching each other or in a spacing of approximately 2 – 3 cm between seeds in a row.     Sowing the seeds flat may cause crooked stems and roots. Likewise sowing the seeds with concave side up will cause unnatural growth of the roots

After seeding, keep the nursery bed moist at all times. Mango seeds germinate and seedlings emerge 10-14 days after planting, with about 80% germination on the 25th day. About three weeks after emergence, seedlings are suitable for transplanting (pricking out) in polyethylene pots or any other secondary nursery

Mango seed (concave side down)                              Curved stem and roots (right hand)

Avocado                                                                                                                                                     Best practice for collection of avocado seeds is to harvest from selected tree (not picked from the ground). Ripe fruits are opened then the seed removed from the pulp. Extracted seed should be planted as soon as possible in order to avoid drying out.

It is common to encounter infection of Phytophthora cinnamoni (avocado root rot) and to eliminate this fungus seeds should be sunk in hot water at 50^oC for 30 minutes before planting.

Germination of the seed is hastened by removing the brown seed coats and cutting a thin

slice from the apical and basal end of each seed before planting.The seed coat can be removed by wetting the seeds and allowing them to dry slightly in the sun.

Avocado seed should be placed in the soil with the large basal end down, just deep enough to cover the tips. Seedling should be ready for grafting after 5 -6 months

Citrus

Citrus seeds are collected from fresh mature or ripe fruits picked from the tree and not from the ground. Picking from the ground predisposes Phytophthora infection.

Seeds are extracted by cutting the fruit then squeezing the pulp in a sieve. Extracted seeds

are washed and may be sown immediately. The seed should not be dry out or germination will be reduced.

After extraction it is advised to soak the seed in hot water at 47^oC for 10 minutes to kill any fungus which adhere to the coat. Seeds should be planted in the nursery bed, 3-5cm deep and covered with sand or other light material which will not compact. The soil should be kept permanently moist to for best germination. After emergence when the seedlings are 10cm high the frequency of watering should diminish but the quantity increased

SELECTION AND COLLECTION OF SCION WOOD FOR GRAFTING

Selection of Elite Mother Trees

The In-charge of the Fruit Nursery will ensure to give top priority for the selection of mother plant, as it decides the fate of the production efficiency in fruit crops. The performance will depend on the source of scion wood material which should be taken from the trees fulfilling all the scientific criteria for the best performance. These are:

• The mother plant must have been tested for its performance over a number of years so well known. In other words, it should be of known identity
• It must be healthy and free from any transmittable disease
• The fruit shape, size and quality must conform to the typical specification of the variety. In other words, the elite mother trees must be of commercial acceptance
• Must have production potential

Selection of Scion Wood

• The scion should be from mature shoot i.e. at least one year old
• A scion wood of diameter 0.6-1.2 cm is satisfactory for better bud wood
• The scion shoot should have healthy, well-developed round and plump buds
• Scion should be selected from elite trees known for quality production of fruits
• Scion wood should be free from any bacterial, fungal and viral diseases
• The scion should be dormant, while selected for grafting on rootstock
• The best scion wood can be obtained from the central portion or from the basal portion of shoot.

The terminal sections, which are generally succulent, pithy and low in store of carbohydrate (CHO), should be discarded

Collection and Storage of Bud Wood:

The best quality scion wood usually comes from shoots grown in the previous season. Scions should be severed with sharp, clean shears or knives and placed immediately in moistened plastic bags. It is good practice during the harvesting of scions and the making of grafts to clean the cutting tools regularly. Flaming or immersing them in a sterilizing solution may do this. Isopropyl alcohol also works well as a sterilant, although it evaporates quite readily. An alternative sterilizing solution may be prepared by mixing one part household bleach with nine parts water (by volume). However, this bleach solution can be highly corrosive to certain metals. For best results, harvest only as much scion wood as can be used for grafting during the same day. If large quantities of scion wood must to be harvested at one time, follow these steps:

• Cut all scions to a uniform length, keep their basal ends together, and tie them in bundles of known quantity (for example, 50 scions per bundle).
• Label them, recording the cultivar, date of harvest, and location of stock plant.
• Wrap the base of the bundles in moistened burlap or sphagnum, place them in polyethylene or waterproof paper bags, and seal the bags.
• Store the bundles for short periods, if necessary, either iced down in insulated coolers or in a commercial storage unit at 32° to 34°F.
• Never store scions in refrigerated units where fruits or vegetables are currently kept or have been stored recently.
• Keep the scions free from freezing during storage.

SELECTION OF ROOTSTOCK AND ROOTSTOCK SEEDLINGS

1. Rootstock should have a proper vigour and growth habits
2. Rootstock should be resistant to soil borne diseases and other pests
3. Rootstock should be tolerant/ resistant to toxic salts like Na, Mg, and Ca etc
4. It should have wide range of edaphic adaptability (all soil and climatic factors)
5. Should have wide range of graft compatibility
6. Should be easy to propagate
7. Seedlings should not have undergone or show signs of any mutation
8. Age of seedlings should be one to one and half years and not more than 2years
9. Diameter of seedlings should be greater than 1 cm (pencil thickness)

SCION AND ROOTSTOCK SOURCE MAINTENANCE

Fruit crops, mostly being perennial in nature, call for utmost care in selection of varieties, quality planting material and adoption of right technology for mass multiplication of planting material. Mistakes committed during the initial establishment of orchards cannot be corrected and will cause serious damage to production and productivity. The progeny trees are the basic component for the multiplication of fruit plants and ultimately deciding the quality and productivity of the fruit crops. Hence, it is necessary to stock the true to type and best quality progeny trees in the progeny or source orchard.

Establishment of Progeny Trees

If large scale and permanent grafted seedling production is exercised it may be crucially necessary to establish progeny orchards isolated from general production orchards. The detailed recommendations as given in the package of practices for the establishment of orchards shall be adopted for the plantation of progeny trees in the Progeny orchard:-

• The progeny trees should be planted by proper lay out, keeping in view the geographical conditions of the area.
• The high yielding clones of recommended varieties should be selected for developing new mother block of the progeny trees
• The selected plants should be planted in a closer spacing in separate block in order to get continuous supply of scions
• These plants should be severely pruned to keep them in vegetative phase and to produce enough shoots for propagation purposes
• The marked trees of outstanding merit for taking bud wood should be kept for bud wood only and no fruit crop be taken from these trees
• A map of the orchard should be maintained indicating the layout of the promising varieties planted
• The plants to be procured or raised for progeny trees should be of proven pedigree and free from any type of disease of visible or invisible symptoms.
• The fruit plants to be used for progeny trees should be of standard size and girth.
• The plants should have well developed root system.
• The grafting point should be at the appropriate level or height.
• The appropriate doses of FYM should be used while planting of progeny trees.

Maintenance of Progeny Orchards:

The maintenance of mother plants should be done rigorously, so that plants are healthy and free of diseases and insect pests. The orchard management practices for fruit crops are to be followed for the maintenance of progeny trees as per details below:

• The maintenance of mother plants, right from the time of planting to the stage of bearing and subsequent years involving the following management practices:
• Application of manures and fertilizers
• Weeding
• Irrigation and other intercultural operations
• Training and pruning
• Effective plant protection measures
• Labeling and proper record keeping

The trees may be indexed for the possible presence of virus by sending the twigs along with 10-15 leaves to a plant pathology laboratory competent in such tests. Report can be obtained within a week. This may even be implemented alongside certification of the propagules

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