Question

Describe briefly various steps of plant breeding methods.

Answer 1

Hybridization involves the following steps:

1. Collection of variability:

1. Wild species and relatives of the cultivated species having desired traits are collected and preserved.
2. The entire collection having all the diverse alleles (i.e. variations) for all genes in a given crop is called germplasm collection.
3. Variations are useful in the selection. Germplasm conservation can be done in the following ways.

a. In situ conservation: It can be done with the help of forests and natural reserves.

b. Ex-situ conservation: It is done through botanical gardens, seed banks, etc.

2. Evaluation and selection of parents:

1. The collected germplasm is evaluated (screened) to identify plants with desirable characters.
2. The selected parents must be healthy, vigorous, and should show desirable but complementary features.
3. The selected parents are selfed for three to four generations to make them pure or homozygous.
4. It is made sure that only pure lines are selected, multiplied, and used in the hybridization.

3. Hybridization:

1. The variety showing maximum desirable features is selected as a female (recurrent) parent and the other one as a male parent (donor) which lacks good characters found in a recurrent parent.
2. The pollen grains from anthers of male parents are collected and then artificially dusted over stigmas of emasculated flowers of the female parents.
3. Pollination is followed by seed and fruit formation in due course.
4. The seed thus obtained represents the hybrid generation.
5. The hybrid F₁ progeny is selected and evaluated for the desired combinations of characters.

4. Selection and testing of superior recombinants:

1. The F₁ hybrid plants showing superiority over both the parents and having high hybrid vigour are selected.
2. Such hybrids are then selfed for a few generations to make them homozygous for the said desirable characters till there is a state of uniformity so that the characters will not segregate further.

5. Testing, release, and commercialization of new cultivars:

1. The newly selected lines are evaluated for productivity and other features like disease resistance, pest resistance, quality, etc.
2. Initially, these plants are grown under controlled conditions of water, fertilizers, etc. and their performance is recorded.
3. The selected lines are then grown for three generations at least in the natural field, in different agroclimatic zones.
4. Finally, variety is released as a new variety for use by the farmers.