The processes of crop improvement include:
- Breeding or Hybridization.
a) Introduction: This involves the importation of introduction or some varieties of crops with desirable characteristics into areas where they have not existed before. In other words, it involves the movement of crop from its origin or supposed centre of evolution to another region or area where it can adapt. Crops with desired qualities are identified in their centres of origin and then procured. Such crops are then introduced into the breeder’s country for testing and multiplication. Such imported crops are usually quarantined by the nation’s plant quarantine service before introduction into the country importing it. Introduction is usually carried out to upgrade the qualities of the local varieties of crops.
Advantages of Introduction
- It helps in bringing new varieties of crops to a new area.
- It may enhance greater productivity.
- It may perform better if there is better climatic condition in the new location.
- It may also perform better if there is better soil condition in the new area.
- Absence of pests and diseases.
- It helps to upgrade the quality of the local varieties of crops.
Disadvantages of Introduction
- There is the possibility of introducing new crop diseases.
- The new crop may not be able to adapt to climatic conditions of the new environment.
- It may also introduce new pests to the new environment.
- The introduced crop may not be able to adapt to soil conditions of the new environment.
b) Selection: This involves the artificial picking of crops with desirable characteristics which are most favoured by the environment.
In other words, selection is the ability to choose certain crops which possess specific artificial or external characteristics which are easily recognised by merely seeing them.
Methods of selection include
- Mass selection: Crop plants are selected or rejected on the basis of their own performance or merit. Crop plants with the desired characteristics are chosen in preference to those not possessing them from a large group of crops.
- Pure line selection: This is the type of selection in which only one crop plant with good characteristics is selected. It leads to the concentration of that character which is uniform and pure.
- Pedigree selection: Crop plants are selected on the basis of the performance of their ancestors. It is based on the belief that the crop plant selected is likely to perform equally or even better than the ancestors.
- Progeny selection: Crop plants are selected on the basis of the performance of their offspring or progeny.
Advantages of Selection
- It ensures that only the best naturally available crop is grown.
- Crops with desired qualities are selected.
- Seeds from best stands are multiplied for distribution.
- Crops with undesirable characters are detected and rejected.
- It reduces the spread of diseases and pests.
Disadvantages of Selection
- Selection is tedious and time consuming.
- It is very expensive in terms of time and money.
- It requires expertise which may not be available.
- It brings about the elimination of some desirable traits of the parent stock.
c) Breeding or Hybridization: Hybridization is a method by which an offspring is produced through the crossing of two different plant varieties of the same species. In other words, it refers to the development of plants by combining inherited qualities of one plant with that of another through the fertilization of female with male gametes.
Types of Breeding
- In-breeding: This is the pollination and fertilization of closely related crop plants in order to retain certain desirable characteristics. This can lead to pure breed or pure line.
- Pure line: A plant which has been self fertilised or crossed continuously with closely related species (inbred) for many generations, so that the desirable qualities it possesses do not change from generation to generation, is called a pure line. Pure line will always reproduce itself with great precision.
- Cross breeding: This is the pollination and fertilization of unrelated crop plants belonging to different breeds. This results in the production of an offspring which is superior to the average performance of the parents. This is called hybrid vigour “heterosis”.
Advantages of Breeding
- It can produce a superior offspring resulting in hybrid vigour or heterosis (cross breeding).
- Progeny grows more rapidly (cross breeding).
- Production of pure line (inbreeding).
- Offsprings can withstand variations of environment (cross breeding).
Disadvantages of Breeding
- It could lead to “inbreeding depression”, which is the depression or loss in vigour and performance of offspring (in-breeding).
- There is a drop in production or yield of crops in terms of quantity and quality (in-breeding).
- It may lead to poor or low resistance to disease attack (in-breeding).
METHODS OF IMPROVING CROP PRODUCTIVITY
Productivity of crops can be achieved through a combination of methods which include:
- Crop Improvement Methods: As discussed earlier, crops can be improved through introduction, selection and hybridization.
- Proper Timing of Planting: Crops should be grown at the right time to avoid high temperature, inadequate rainfall or abundance of pests and diseases during growth.
- Adoption of Better Cultivation Methods: The adoption of better methods of cultivation like crop rotation which adds nutrients to soil, prevents erosion, pests and diseases outbreak and helps to increase yield.
- Use of Manures and Fertilizers: The use of manure like farm yard compost and green manure in combination with the use of fertilizers helps to add nutrients to soil and promotes good growth of crops.
- Control of Pests of Crops: The control of pests of crops which cause reduction in yield and growth can help in the improvement of crops.
- Control of Diseases of Crops: Diseases also cause a reduction in growth and productivity of crops. Where they are adequately prevented, it will lead to improvement of such crops.
- Use of Resistant Varieties: Some varieties of crops are capable of resisting disease’s attack and can mature early thereby increasing the yield of crops.
- Use of good crop varieties: There are some varieties of crops which naturally will grow well in different environmental conditions. Such crops do help to increase the overall production of such crops.