Plant Breeding Steps

The steps involved in developing new varieties of plants are as follows:

Collection of Variability

Variability means variation in genetic composition (alleles of genes) which brings desired traits in progeny plants like tolerance to pests, extreme temperatures, etc. This can be achieved by the collection and preservation of natural genes of different wild varieties, species, and relatives of the cultivated species. This collection of plants/seeds with all the diverse alleles for all genes in a given crop is called germplasm collection. So, germplasm collection brings variability in plants. Once germplasm is collected, the next step is the evaluation and selection of parents.

Evaluation and Selection of Parents

Two or more plants with desired germplasm are known as parents. These parents are now selected and multiplied. For example-grain length in rice can be longer, intermediate, or shorter. If longer seeds are selected and sown then the next generation crop will have average and longer grains than the original population. Once parents are selected, the next step is cross-hybridization among selected parents.

Cross-hybridization among Selected Parents

Cross hybridization is the crossing of two or more types of plants with desired traits in such a way that future generations will have traits of both parents. For example, the high protein quality of one parent can be cross-hybridized with disease resistance from another parent. This will genetically combine the desired characteristics in the progeny plant. However, cross-hybridization is a very time-consuming and tedious process as first the pollen grains from the male parent have to be collected and placed on the stigma of the flowers female parent.  For example-wheat variety, HUW 468 took 12 years to develop. Once cross-hybridization is done, the next step is the selection and testing of superior recombinants.

Selection and testing of Superior Recombinants

This step involves the selection of progeny with desired character combination or called recombinants. The progeny crop is superior to both of the parents. The progeny obtained are self-pollinated for several generations till they reach a state of uniformity (homozygosity) so that the characters will not segregate in the progeny. The self-pollinated progeny for longer generations will produce a pure line. All plants in the pure line have identical genotypes. An example of the pure line is HUW 468 wheat variety. Once self-pollination is done, the next step is testing, releasing, and commercialization of new cultivars.

Testing, release, and commercialization of New Cultivars

The selected lines are evaluated for their yield and other agronomic traits like quality, disease resistance, etc. This can be achieved by growing these plants in the research fields and recording their performance under ideal fertilizer, irrigation, and other crop management practices, etc. for at least three growing seasons at different locations in the country. The evaluation in research fields is followed. The crop obtained is compared with the best available crop cultivar and seeds are multiplied and finally made available to farmers.

Plant breeding is made up of two words- plant and breeding. This means there is breeding among two different species of plant of desired varieties.  The desired varieties mean plants should have increased tolerance to environmental stresses (salinity, extreme temperatures, drought, etc.), resistance to pathogens (viruses, fungi, and bacteria), and increased tolerance to insect pests. All these qualities will help in getting better yield and disease-free plants. These all traits altogether, increase the yield of plants and make plant disease free. Plant breeding was first used during the green revolution. Let’s understand the green revolution.