Meaning of crop propagation
This is the process of production or development of new and identical crop plants either from the seeds, or through parts of the parent plant that can regenerate. This process ensures perpetuation of the crops from generation to generation.
Methods of Crop Propagation
Crops can be propagated either through sexual or asexual methods.
1. Sexual Propagation: In this method, seeds are used for propagation. Seeds normally germinate and grow into new plants, which have much of the character of their parents. However, due to cross-pollination, there may be variations as a result of genetic make-up of both parents.
Advantages of Propagation by Seed
i. Seeds are more convenient to carry, easy to store, handle and transported.
ii. They retain viability long after harvest, until needed for planting if well preserved.
iii. They are used easily to increase plant population because they are produced in large quantities.
iv. Seeds are used to achieve crop improvement because of assurance of disease free plants.
Disadvantages of Propagation by Seed
i. It reduces the quantity available for consumption by man and farm animals.
ii. Optimum conditions for seed germination may be lacking.
iii. Dept of sowing, evenness of spacing, time of planting, etc. may affect growth performance.
iv. Seeds mistakenly collected from unhealthy and less vigorous plants may become unviable.
2. Asexual Or Vegetative Propagation: This is propagation by means of plant vegetative organs/parts, E.g stems, roots, leaves, etc, other than the seeds. This is made possible because some plants are by nature capable of regenerating new root and shoot system from their parts.
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Vegetative propagation can be natural or artificial. In artificial method, stem cuttings, budding, grafting and layering methods are adopted. In natural vegetative propagation, corms, e.g., cocoyam, stem or root tubers (yams and sweet potatoes, rhizomes), onions, ginger, suckers, plantain and pineapples are used.
Advantages of Propagation by Vegetative/Asexual Organ
i. The plants are more resistant to diseases and pests when established.
ii. The problem of unavailability of seeds no longer arises.
iii. Many ornamental plants that do not produce seeds are obtained and multiplied easily.
iv. The plants mature earlier than those propagated through seeds.
v. They are more vigorous in growth.
vi. Offspring are identical with their parents.
vii. Purity of line can be maintained for a long time.
viii. Vegetative or asexually propagated plants withstand adverse soil and weather conditions better than seed-propagated plants.
Disadvantages of Propagation by Vegetative/Asexual Organ
i. There is no hybrid vigour produced because there is no genetic recombination.
ii. Disease transmission is easier especially if the sanitary condition of the farm is not properly maintained.
iii. The vegetative parts used are not easily stored.
iv. Disease of the parent is easily manifested in the offspring.
v. It cannot be easily used to achieve crop improvement through cross-breeding as it does not ensure change in the genetic constitution of the plant.