Breeding, application of genetic principles in animal husbandry, agriculture, and horticulture to improve desirable qualities. Ancient agriculturists improved many plants through selective cultivation. Modern plant breeding centers on pollination; pollen from the chosen male parent, and no other pollen, must be transferred to the chosen female parent. Animal breeding consists of choosing the ideal trait (e.g., fine wool, high milk production), selecting the breeding stock, and determining the breeding system (e.g., crossbreeding, inbreeding). See also animal breeding; plant breeding.
Read Pritish Kumar Halder’s article and get complete information about Plant Breeding.
What is Plant Breeding?
“Plant breeding is the purposeful manipulation of qualities in plants to create new varieties with a set of desired characteristics. Plants with higher qualities are selected and crossed to obtain plants with desired quality. This results in a plant population with improved and desired traits.
Plant Domestication: The Origin of Crops
For a given gene, mutations are rare events, but considering the large numbers of plants in a field and genes in a plant, mutations are quite frequent events in a population. (9) Most mutations are unfavorable for survival in the wild, being eliminated from the population in a few generations, as a consequence of natural selection. For more information please visit Pritish Kumar Halder ‘s page .
However, some of these mutations may result in more favorable phenotypes either in terms of cultivation or in terms of food quality. Some of those mutants were rescued by ancient farmers, who protected them against competition and established with those otherwise disabled plants a relationship of symbiosis.
Plant Breeding Based on Controlled Mating
Despite the great spontaneous diversity that can be found in the landraces, simply applying selection to preexisting diversity is an eroding process that eventually comes to a limit. The true creative power of plant breeding resides in promoting recombination for shuffling favorable alleles. The combination of different alleles in many loci results in a virtually infinite number of genotypes. One could conceivably start a commercial breeding program from a dozen well-adapted founding parents, with a clear focus on a specific target environment and evaluating large segregating progenies.
Let us have a detailed look at the objectives and steps involved in plant breeding.
Following are the major objectives of plant breeding:
- To increase the crop yield.
- raise plants with desired characteristics.
- develop a disease-resistant crop.
- develop plants that can tolerate extreme environmental stress.
There are the following different types of plant breeding:
a plant with desired traits is crossed with a plant that does not have the desired traits but has several other traits.
Self-fertilization occurs. The progeny produced is the same generation after generation. This helps to preserve the original traits.
In this, two different breeds are crossed to produce offspring that are more productive than the parents.
The mutations in plant genes result in new varieties. Mutations can also be induced in plants by exposing them to chemicals and radiation.
Genetic engineering helps in producing crops with desirable traits by inserting the gene of interest within the crop DNA. Such crops are known as genetically modified crops. E.g., Bt crops
Plant Breeding Steps
The plant breeding methods have undergone multiple amendments since it was started 9000 – 11000 years ago. The modern method of plant breeding is carried out in the following steps:-
Collection of Variability
Variability forms the root of all breeding practices. The first step involves the collection of plants or seeds for all possible alleles for all genes in a given crop, which is known as germplasm. This collection even involves wild varieties and relatives of the cultivated species.
Evaluation and Selection of Parent Plants
The germplasm is evaluated for the selection of parent plants with desired characteristics. The combination of these characteristics is expected in the hybrid progeny.
For example, a plant crop with high protein content can be selected to be crossed with a plant with higher disease resistance.
Cross-hybridization among Selected Parents
In the third step, the parents are cross-hybridized to develop pure lines of progenies. This is a tedious and time-consuming practice carried out in the conventional fashion of introducing pollen from one plant to the stigma of the other. Despite the labor involved, only one or two progenies in a few hundred show the desired combination of characteristics.
Selection and Testing of Superior Recombinants
The developed progenies are then evaluated and those with the desired combination of characteristics are self-pollinated to attain homozygosity.
Testing, Release, and Commercialization of New Cultivars
The new lines are grown in research fields where they are tested for their agronomic traits of quality, yield, resistance to diseases, etc. This is followed by the cultivation of these crops in farmers’ fields at different locations in the country which represent the different agroclimatic zones. With successful results, the crops are released commercially for public consumption.