Crop improvement refers to the ways of developing and breeding of crop varieties which are better that the existing varieties in a number of characters.
Aims of Crop Improvement
The people that breeds new varieties of crop have their aims amd objectives in their mind. These aims include:
1. To increase yield: The varities of crops that is newly developed by plant breeders are capable of giving very high yield or quantity crops per unit land.The quantity is measured in kg/ha e.g high yield of tomatoes from 1000kg/ha to 1700kg/ha. There will be a great increase in income of farmer.
2. To improve the quality of produce: The quality of farm produce enhances its usefulness and value. Plant breeders can improve on the taste,colour, size, nutritive values and fibre content of crops.
3. To adapt to climatic conditions: Plant breeders develop a varities of crop that it will be capable of withstanding extreme conditions of cold,heat, drought and wind by making some changes in the growth cycle of the variety better to suit the available growing season of that crop.
4. To increase resistance to diseases: Plant breeders also develop varities of crops which are not only resistant to diseases but will be able to produce high yield even if there is diseases outbreak.
5. To meet the needs of growers: Improvement of crops to suit the farming methods of different farmers. For example, some large scale farmers will prefer short variety of maize which can be harvested with machine, instead of talk ones which can be harvested by hands or manual method.
6. To obtain uniformity of plants: One of the aims of plant breeder is to breed crops which can grow and mature with others at the same time to facilitate mechanisation or ease of harvesting.
7. Aim to breed crops with early maturing: Plant breeders try to breed plants that will mature early to ease the job of growers.This early maturing will make the growers to plant it many times in a year depending on the crops that is breeded.
8. To improve harvesting quality: Breeder develops new varities of crops that can be harvested without any damage and with ease .
9. To improve the nutritional value of the produce: It is the greatest aim of plants breeders to develop crops that have high nutritional value like high protein, minerals, vitamin etc. which are useful to man.This saves money for the consumer by avoiding to buy supplement.
Keywords in Crop Improvement
In order to understand the how to improve crops, it is very useful in plant breeding, it is important to know some words that we come across in crop improvement.
1. Character or Traits: These are the inherited attributes which the person breeding the crop will select. E.g seed colour,seed size, diseases resistance, plant heights, maturing age etc.
2. Chromosomes : These are rods or thread shaped boides that is found in the nucleus of a cell.All plants and animals have fixed number of chromosomes.
3. Genes : These are the units of inheritance. Genes are located in the chromosomes and it is responsible for the transmission of characters from parents to theirs offspring.
4. Gamete: This is a mature sex cell which takes part in sexual reproduction. There are two types make gamete or spermatozoa (in animals) and pollen grains (in plants) and female gamete or egg or ovum (in animals) and ovules (in plants). Gamete is usually haploid.
5. Phenotype: These are the physically and physiologically expressed traits of an individual e.g height
6. Genotype: This term is used to describe those traits or sum total of the genes inherited from both parents. Genotype includes both dominant and recessive traits.
Process of Crop Improvement
The process of crop improvement include:
1. Introduction
2. Selection
3. Breeding or Hybridization
Introduction: This is the importation of introduction or some varities of crops with desirable characteristics into areas where they have not existed before.In other words, it involves the movement of crops from it's origin or supposed centres of evolution to another region or area where it can adapt. Crops with breeders desired quality are identified in the place they exists and then procured. Such procured crops are then introduced into the country of the breeders for testing and multiplication. Such crops are always quarantined by the nation's quarantine service. Introduction is usually carried out to upgrade the qualities of the local varities of crops.
Advantages of Introduction in Crop Improvement
1. It helps to introduce new varieties of crops into areas where they have not existed.
2. It may enhances greater productivity.
3. It helps to upgrades the local varieties of crops
Disadvantages of Introduction in Crops improvement
1. There is a big possibilities of introducing new crop diseases if the crop not properly quarantined.
2. The new crop may not be able to adapt to the new area climatic conditions and it leads to waste of the money for importation.
Selection: This is the picking of desirable crops characteristics artificially which are most favoured by the environment. In another words, this is ability to choose certain crops which posses specific artificial or external characteristic which can be recognized easily by seeing them.
Method of selection includes
(I) Mass Selection : Crop plants are selected or rejected on the basis of their own advantages.Crop plants with desired characteristics are chosen in preference to those not possessing them from a large group of crops.
(ii) Pure line selection - This is the selection of only one crop having the good characteristics breedes want.
(iii) Progeny Selection: Crops plants are selected based on how it's offspring performed.
(iv) Pedigree selection: This is the selection of crops based on their ancestors performance. It is based on believe that the offsprings will perform like or even better than the ancestors.
Advantages of selection
(I) It ensures that the best crops are grown naturally.
(ii) It reduces the spread of diseases.
(iii) Crops with breeders undesirable characters are rejected immediately.
(iv) Crops with desired qualities are selected
Disadvantages of Selection
(I) It is very expensive in term of time amd money because breeder will have to travel to check and buy it desired crops.
(ii) Selection is tedious and time consuming.
(iii) It requires expertise which may not be available.
Breeding or Hybridization
Hybridization method is the one which two species of two different plant varities produces an offspring.
Types of breeding
(i) In-breeding : This is the pollination and fertilization of plants that are closely related in order to retain certain desirable characteristics.
(ii) Cross breeding : This is the fertilization of unrelated plants belonging to different breeds. This result in the production of offspring which is superior to the average performance of the parents.This is called hybrid vigour "heterosis"
Advantages of Breeding
(i) Production of pure line(in breeding)
(ii) Offspring can withstand variation of environment (cross breeding)
(iii) It is able to produce superior offspring resulting in hybrid figure (cross breeding)
Disadvantages of breeding
(i) It may lead to poor or low resistance to diseases attacks (in breeding)
(ii) There may be drop I production or yield of crops in terms of quantity and quality (in breeding).
Method of Improving Crop Productivity
(I) Crop Improvement Methods
(ii) Control of diseases of crops
(iii) Use of good crop varities.
(iv) Control of pest of crops
(v) Use of manure and fertilizers
(vi) Proper timing of planting
(vii) Use of resistant varieties
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