Creating a new variety of plants, often called a cultivar, involves specific breeding techniques focused on selecting or combining plants with desirable traits.
Developing new plant varieties relies on leveraging genetic variation within a plant population to select or create individuals with improved characteristics, such as higher yield, disease resistance, or unique colors. This is achieved through various breeding methods.
Key Techniques for Creating New Cultivars
The creation of a new plant variety typically involves techniques focused on selection or controlled breeding to isolate and propagate desired genetic traits.
According to the provided reference, the techniques used in creating a new cultivar are: mass selection, recurrent selection, top crossing, and synthetic variety development.
Let's explore these methods:
1. Mass Selection
This is one of the oldest and simplest breeding methods. It involves selecting individual plants from a population based on their physical characteristics (phenotype).
- Process: In mass selection, the source population is examined and desirable plants or seed from those parent plants are selected. The seed from these selected plants is then bulked and planted for the next generation.
- Goal: To increase the frequency of genes that contribute to the desirable traits in the population.
- Best Suited For: Traits that are highly heritable (strongly influenced by genetics rather than environment) and easily observed, like flower color or plant height in self-pollinating crops, or for initial improvement in cross-pollinating crops.
2. Recurrent Selection
A method designed to improve the performance of a population over multiple cycles of selection and intermating.
- Process:
- Select superior plants from a population.
- Intermate these selected plants (cross them with each other).
- Grow the offspring population.
- Repeat the selection and intermating process in the new generation.
- Goal: To accumulate favorable genes and increase the overall genetic merit of a population for complex traits (like yield) controlled by many genes.
- Best Suited For: Improving cross-pollinating crops for traits with low heritability.
3. Top Crossing
This technique involves crossing selected individual plants or lines with a common, superior parent, often called a "tester."
- Process: Superior plants or inbred lines are crossed with a specific, often genetically broad-based or known-good, tester parent. The performance of the resulting hybrids is evaluated.
- Goal: To identify parent plants or lines that combine well with the tester, indicating their potential for use in hybrid varieties or as components in other breeding programs.
- Best Suited For: Evaluating the combining ability of parent lines, particularly in hybrid breeding programs.
4. Synthetic Variety Development
A synthetic variety is developed by intermating a specific number of selected, proven inbred lines or clones that combine well with each other.
- Process: Selected parental lines (often 5-10) are allowed to inter-pollinate freely. The resulting seed is harvested in bulk to plant the first generation of the synthetic variety. Subsequent generations are maintained by open pollination.
- Goal: To create a population variety that maintains good performance and genetic diversity over generations of open pollination, while being relatively easy to produce compared to hybrids.
- Best Suited For: Cross-pollinating crops where hybrid seed production is difficult or expensive, or where some level of genetic diversity is desired for stability across environments.
Comparing the Techniques
Here's a simple comparison of these methods:
| Technique | Primary Mechanism | Focus | Application Area |
|---|---|---|---|
| Mass Selection | Phenotypic Selection | Direct improvement of observable traits | Self & Cross-pollinating crops |
| Recurrent Selection | Selection & Intermating Cycles | Accumulating favorable genes | Primarily Cross-pollinating crops |
| Top Crossing | Crossing with a Tester | Evaluating combining ability | Hybrid breeding programs |
| Synthetic Variety Dev. | Intermating Selected Lines | Creating stable, diverse populations | Primarily Cross-pollinating crops |
These techniques, often used in combination or as part of larger breeding programs, form the foundation for developing the diverse and improved plant varieties we rely on today.
