Propagation from Seed

Propagation from Seed

Propagation from Seed While propagation by seed appears to be an extremely cheap and simple method of producing new plants, it is not without drawbacks. Parentage and whether or not a seed is a true offspring of its parent is a critical matter. The grower of early commercial tomatoes purchases a certain variety of seed because of its special qualities in early fruiting, along with fruit size and quality, and the economic consequences of any performance variation are enormous, and this is true of many other plants at all centres of production.

The exhibitor of a flower or vegetable, while not involved in economic results, stands to lose much if the seed he sows does not produce plants true to form. Indeed, the ordinary gardener seeking a special colour of flower or shape of turnip would be bitterly disappointed by considerable variation from inherent form. Conversely of course there is always the possibility of finding a form better than the parent. Fortunately there are many plants which produce seed that can, in most cases, be accepted as true to type because of many years of careful re-selection and controlled seed production. The whole secret of a seed house acquiring a good reputation lies in ensuring careful and rigorous selection.

 

Hybridization

Matters are much more complicated today than in past years, due to the considerable degree of hybridization which has taken place in an effort to produce better form, colour, size, shape, and indeed improve on every characteristic imaginable. The seeds of true species of plants such as common broom Cytisus scoparius and many others do however breed true to type from seed with little noticeable variation.

In recent years much use has been made of F1 (and F2) hybrid seed. In the case of F1 seed this is the result of controlled fertilization between the two parents annually selected from those plants which are either annuals or treated as such. Mendel’s Law refers to the true exhibition of the parental characteristics of both male and female parents in the first generation of seed produced, when thereafter segregation occurs in fixed proportions into respective male or female parent characteristics. The important issue with F1 seed is the true and vigorous exhibition of the parents’ qualities in ‘blended’ form, called hybrid vigour. This has very special significance also as far as the inbred resistance to disease is concerned, such resistances which are bestowed manifesting themselves strongly.

The success which has been achieved with flowers and vegetables in F1 seed form allows the seeds-man to predict with certainty that certain qualities will be present in the offspring, whereas with ordinary seed there can be variations, loss of disease resistance, loss of vigour and many other deficiencies, particularly over a period of time unless vigorous re-selection is practised. It follows also that the same re-selection is required to maintain the qualities of the selected male or susceptibility of an F1 hybrid. This perhaps serves to explain why seeds can give variable results, and the popularity of F1 hybrids, but it must be emphasized once more that the careful selection and re-selection of ‘ordinary’ seed over a great many years will still, in many cases, give results of a high order.

It was said earlier that seed was cheap, and while this is true to a certain extent, the obviously high cost of producing F1 seed, involving a re-cross annually, has raised the price of many seeds considerably. Examples of this are the Fi geraniums, whose seeds are sufficiently expensive to cause gardeners some thought as to whether vegetative or seed propagation is cheaper, an issue still further complicated by the rather slower speed at which the F1 geranium seed produces a flowering plant. F, seed is generally cheaper.

 

Speed of propagation

Where a plant can be propagated either from seed or vegetatively by cuttings or from other parts of the plant’s anatomy, vegetative prodiincapablehe quicker way of producing a mature plant. But the F1 seedling may in turn overtake the vegetatively propagated plant and become bigger, more floriferous and productive.

The advantage of seed is that it is an easily stored embryonic plant. An interesting technique is primed seed, the seed being germinated and then held in suspense pending immediate growth.

 

Transmission of disease

In the more technical aspects of disease transmission, it is obvious that seed offers a method of plant production much less prone to disease transmission than vegetative propagation. Virus and fungal diseases usually exist in the vegetative tissue of the plant, and it is not thought that the seminal reproductive section of the plant is affected, which means that the seed produced even by virus infected parents should be free from virus. One cannot, however, be too emphatic on this matter, as research is still probing into the facts surrounding the introduction of disease, but for all practical purposes non-transmission of disease by seminal means is a fact, although the importance of inheritance and disease susceptibility cannot be overlooked. It is also possible that the embryo itself may well be free of disease but the tissue surrounding it is not, which in practical terms gives rise to immense problems.

13. April 2011 by Dave Pinkney
Categories: Greenhouse Gardening, Propagating | Tags: , , | Comments Off on Propagation from Seed

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