Genetic variance and drift in selfed and intermated populations derived from backcrossing

Area of Science:

• Plant breeding
• Quantitative genetics
• Population genetics

Background:

• Backcrossing is a common technique in plant breeding to introgress desirable genes.
• Understanding genetic variance in derived lines is crucial for effective breeding strategies.
• Random-mated lines and BCgF2-derived lines represent different genetic bases for selection.

Purpose of the Study:

• To investigate the impact of backcross generation (g) and the number of crossed plants (n) on genetic variance.
• To compare genetic variance between BCgS1 and BCgF2-derived lines.
• To provide recommendations for optimal plant numbers in recurrent selection to avoid donor allele loss.

Main Methods:

• Analysis of genetic variance in random-mated lines derived from backcrossing (BCgS1 lines).
• Evaluation of the effect of the number of BCgF1 plants crossed (n) on genetic variance.
• Comparison of genetic variance between BCgS1 and BCgF2-derived lines across different backcross generations (g).

Main Results:

• Genetic variance is dependent on backcross generation (g) and the number of crossed plants (n).
• The number of crossed plants (n) has minimal effect on genetic variance when n > 6.
• Genetic variance is consistently greater in BCgF2-derived lines compared to BCgS1 lines for all g.
• Specific numbers of BCgF1 plants (8, 16, 32, 64 for BC1-BC4) are recommended for recurrent selection to prevent donor allele loss.

Conclusions:

• The choice of backcross generation and the number of plants used in crosses significantly influence genetic variance.
• BCgF2-derived lines offer a higher genetic variance base for selection compared to BCgS1 lines.
• Adhering to recommended plant numbers in recurrent selection is vital for maintaining genetic diversity and avoiding the loss of valuable donor alleles.