Plant Breeding is defined as the science of changing the genetic traits of the plants in order to create the desired plant types that are better suited for cultivation, gives better yield and have good resistance to diseases.
Plant breeding technology incorporates many traits:
- Increased tolerance to insect pests.
- Increased resistance to pathogens
- Increased tolerance to environmental stresses such as salinity, extreme temperatures, drought and frost
- Improved quality
- Increased crop yield
What is Hybridization?
Craigieburn nursery breeds closely related plants that are genetically different to produce a hybrid offspring. Scientist such as Gregor Mendel and Charles Darwin developed this process and many plant breeders later improved it.
Plant breeding is a systematic process. The entire process of plant breeding starts from choosing the desirable qualities of the plant to the final product which is broadly divided into 5 steps.
1. Collection of Variability
A particular plant species has different varieties depending on which part of the region it is growing in; each variety will have a different set of traits and this differentiation of a variety of a plant in the same species is called genetic variation.
For example, there are about 121 natural variants of ragi on this planet. Each one of them is different from the other by few traits such as some are resistant to bugs, and give low yield, others are drought resistant and give a high yield. To create a new high quality of Ragi, it would be better if scientist knew about all the variation of Ragi and their traits, to select the best traits to create a new hybrid.
2. Evaluation and Selection of Parents
Craigieburn nursery collects the varieties based on easily distinguishable characteristics such as medium inflorescence, big kernel, thin stem, etc. However, plant variation can be due to the environmental conditions which are temporary.
For example, if a dwarf plant collected from a drought region when grown under normal circumstances grows tall then dwarfism is not actually a trait. In order, to avoid such errors careful evaluation and characterization are required to know about the composition of the germplasm and the diversity of the given crop. Before the plants are selected, they are tested for pureness. Plants which have more than one allele are called heterozygous, such plants are rejected and only pure plants or homozygous plants are subjected to further study.
3. Cross-hybridization among the selected parents
Craigieburn nursery selects the pureline parents from the desired characteristics that are cross-hybridized. It helps to produce hybrid progeny which further helps to bring desired traits from different plant lines into one plant line.
For example, if we crossbred, a low yielding, high disease resistance ragi plant with high yielding, low disease resistance ragi plant since the parent plants crosslined are pure the F1 hybrid ragi plant obtained will have a high yield and high disease resistance. This tendency of hybrids to obtain superior characteristics of both parents is known as heterosis or hybrid vigour.
4. Selection and testing of superior recombinants
The hybrid obtained is scientifically checked for desired characters and if the test is passed the plants are self-pollinated for several generations. Since F1 hybrid has both dominant as well as recessive alleles at every next generation we will get a wide variety of combinations, desirable and undesirable. The undesirable combinations are eliminated and the process is continued for 7-8 generations until uniformity or homozygosity is obtained, creating a pureline where characters don’t segregate forming a pureline called as cultivars.
5. Multiplication of improved seeds
The seeds of the approved cultivars are multiplied by growing them in suitable conditions. The seeds are then tested for quality and certified by National Seed Corporation NSC. The certified seeds are then distributed to farmers and license seed sellers.