Plant Breeding - Definition - Practice Questions & MCQ

• Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant.
• Conventional plant breeding has been practised for thousands of years, since the beginning of human civilisation; recorded evidence of plant breeding dates back to 9,000-11,000 years ago.
• Many present-day crops are the result of domestication in ancient times.
• Classical plant breeding involves crossing or hybridisation of pure lines, followed by artificial selection to produce plants with desirable traits of higher yield, nutrition and resistance to diseases. 

Various Steps Required For Developing New Varieties:

1. Collection of variability: 

• Genetic variability is the root of any breeding programme. 
• In many crops, pre-existing genetic variability is available from wild relatives of the crop.
• Collection and preservation of all the different wild varieties, species and relatives of the cultivated species (followed by their evaluation for their characteristics) is a pre-requisite for effective exploitation of natural genes available in the populations. 
• The entire collection (of plants/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.

2. Evaluation and selection of parents:

• The germplasm is evaluated so as to identify plants with a desirable combination of characters.
• The selected plants are multiplied and used in the process of hybridisation. 
• Pure lines are created wherever desirable and possible.

3. Cross hybridisation among the selected parents:

• Hybridisation is crossing of two or more types of plants for bringing their traits together in the progeny. 
• It brings about useful genetic/ heritable variations of two or more lines together. 
• This is a very time-consuming and tedious process since the pollen grains from the desirable plant chosen as the male parent have to be collected and placed on the stigma of the flowers selected as the female parent.
• Also, it is not necessary that the hybrids do combine the desirable characters; usually, only one in a few hundred to a thousand crosses shows the desirable combination.

4. Selection and testing of superior recombinants :

• This step consists of selecting, among the progeny of the hybrids, those plants that have the desired character combination.
• This step yields plants that are superior to both of the parents.
• These are self-pollinated for several generations till they reach a state of uniformity so that the characters will not segregate in the progeny.

5. Testing, release and commercialisation of new cultivars:

• The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc. 
• This evaluation is done by growing these in the research fields and recording their performance under ideal fertiliser application irrigation, and other crops management practices.
• The evaluation in research fields is followed by testing the materials in farmers’ fields, for at least three growing seasons at several locations in the country, representing all the agroclimatic zones where the crop is usually grown.