Question

What is plant breeding? Describe various steps involved in the classical breeding of plants.

Answer 1

Plants are crossbred to introduce traits/genes from one variety or line into a new genetic background of plants, so that the new plant has superior traits or genes. Plant breeding is a type of production of plants.

Complete Answer:
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.
Classical plant breeding involved crossing or hybridization of pure lines followed by artificial selection to produce plants with desirable traits of higher yield, nutrition and resistance to diseases.

Steps in plant breeding techniques:
1. Collection of variability:
- Genetic variability is the root of any breeding programme.
- Wild relatives of crops are a source of pre-existing genetic variability.
- Collection and preservation of all the different wild varieties, species and relatives of the cultivated species.
- Evaluation for their characteristics.
- 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 hybridization.
- Pure line is created wherever desirable and possible.

3. Cross hybridization among the selected parents:
- Cross hybridization of two selected parents by emasculation and bagging, to produce a hybrid of combined character of both parents.
- For example high protein quality of one parent may need to be combined with disease resistance from another patent.
- Usually one in a few hundred to a thousand cross offsprings shows desirable combinations.

4. Selection and testing of superior recombinants:
- Selection is done from the progeny of hybrids produced by cross hybridization.
- It requires careful scientific observations and evaluation of progeny.
- Hybrid plants that are superior to both of the parents are selected.
- These hybrids are self-pollinated for several generations till they reach a state of uniformity (homozygosity).

5. Testing, release and commercialization of new cultivars:
- Selected pure lines are evaluated for their yield and other agronomic traits of quality, disease resistance etc.
- This evaluation is done in the research fields and recording their performance under ideal fertilizer, irrigation.
- Testing is done in the farmers ‘fields’ at least for three generations.
- The material is compared with the best available local crop cultivar.

Note: The main objectives of plant breeding are to develop plants which are,
- Disease resistant.
- Increase the crop yield.
- Tolerant to extreme environment conditions.
- Plants with all the desired characteristics.