Sexual Propagation and Asexual Propagation

Usually Vegetables and flower crops are commercially propagated by seeds, but fruit crops are mainly propagated by vegetative means of propagation. Normally, field crops, most of the vegetables, and flower crops are highly self-pollinated in nature, which are considered as homozygous. Hence, when they undergo sexual reproduction, the resultant offsprings will be homozygous in nature, similar to the mother plant. But in the case of fruit crops, they are highly cross-pollinated in nature, meaning highly heterozygous.
Hence, on sexual process, they will produce offspring not true to the type of the mother plant. Therefore, in fruit crops, in general, vegetative means of propagation is more desirable to get true to the type of mother plant than the sexual method of propagation.

Table of Contents

Sexual Propagation

Sexual propagation is method of propagation by seed. Raising of plants by means of seeds.

Advantages of Sexual propagation

Seed is relatively a cheaper and simple way of obtaining a large number of plants as compared to vegetative propagation.
Seedlings have usually long life as compared to vegetatively propagated plants.
Seedling plants have better root systems and therefore provide better anchorage than vegetatively propagated plants.
It is the only practical method of propagation for most of the vegetables, annual flowers, and fruit plants like papaya, phalsa, and mangosteen, which cannot be propagated by vegetative means.
Hybrids are first raised through seeds.
Rootstocks for budding and grafting purposes are raised through seeds only.
Sexual propagation may sometimes lead to the production of chance seedlings, which may be superior to the mother plant.
Seedling plants are comparatively more resistant to insect pests and diseases than vegetatively propagated plants.
Seeds can be stored for a longer time and can be easily transported to distant markets.
Seedlings are usually hardy and can tolerate adverse climatic conditions better than vegetatively propagated plants.
No special technical skill is required for raising plants through seeds.
The majority of viruses are not transferred through seeds. Thus, seed propagation is useful in producing virus-free plants.
Nucellar seedlings can be utilized to raise uniform plants.
In polyembryonic crops like mango and citrus, seeds on sowing give rise to more than one seedling. Thus, seed is the desirable means of propagation in such crops.
Mangosteen fruit is developed through parthenogenesis. Seedlings obtained from seeds of such fruits are similar to their mother plants and thus propagated commercially through seeds.

Disadvantages of Sexual propagation

Seedling plants are highly heterozygous in nature. Owing to segregation, the seedling trees are not uniform in growth, yield, and fruit quality parameters.
Seedling plants are usually tall and spreading types; thus, the management cost involved in operations like harvesting, pruning, and plant protection, etc., is comparatively higher.
Seedling plants usually have a long juvenile phase and take more time to come into bearing.
In the case of recalcitrant crops, seeds lose viability very soon after extraction and thus have a very low germination rate.
The beneficial effect of rootstock on scion variety cannot be taken in sexual propagation.
Some fruit plants like pineapple and banana do not produce viable seeds, and propagation through seeds is not possible in them.
It is not possible to perpetuate the exact characters of any superior selection through seeds.

Vegetative propagation or Asexual Propagation

Many plants are propagated commercially through asexual means in which vegetative parts of the plant are used. It is possible because all the living cells of a plant have the capacity to regenerate into a full plant under favorable environmental conditions. This tendency of plant cells is called totipotency, a term given by Haberlandt in 1902. The plants produced by vegetative means are therefore genetically identical and similar to the mother plant.

Advantages of Vegetative propagation

True to the type and uniform in growth, yield, and fruit quality.
Ideal method of propagation for plants prone to seed dormancy (all the temperate fruits).
Vegetatively propagated plants are less vigorous and can easily be maintained compared to seedling plants.
Some fruit crops like banana, pineapple, fig, and varieties of grapes, guava, and lemon produce seedless fruit and have no viable seeds. Thus, they can only be perpetuated through vegetative means.
Plants come into bearing earlier than seedling plants.
It is possible to regulate tree size, fruit quality, and precocity in bearing by exploiting the desirable effects of different rootstocks.
It is possible to exploit the desirable abiotic effect of rootstocks on scion cultivars by budding and grafting.
Helpful to overcome the problem of self-incompatibility of different fruit crops by top working the desirable pollinizers on scattered trees throughout the orchards.
Detection of viruses in the plant system by using indicator plants is only possible through budding or grafting. For example, Kagzi lime can be used as a rootstock (indicator plant) for detecting the presence of tristeza virus in citrus.
Helps in shortening the breeding cycle by grafting the scion of a new cultivar onto a large established tree or on certain dwarfing rootstocks for early assessment.
A clone can only be perpetuated by vegetative means.
The benefit of certain interstocks can only be obtained through vegetative means.
Damaged parts of the tree trunk or root can only be repaired by bridge grafting or inarching

Disadvantages of Vegetative propagation

Parthenium, raspberry, apple, onion, Poa, etc. In some species, this phenomenon occurs without the stimulus of pollination, whereas in others, pollination appears to be necessary for the development of a viable embryo.

Example of Vegetative Propagation:

1-Cuttings

Hardwood cuttings
Semi-hardwood cutting
Softwood cutting

2-Budding

Shield or T budding
Patch budding
Ring budding
Flute budding
Chip budding

3- Grafting

Tongue grafting
Whip grafting
Wedge grafting