How does inbreeding depression affect plant fitness over generations?

Inbreeding depression decreases plant fitness over generations by reducing survival, fertility, and adaptability due to increased homozygosity and expression of harmful recessive alleles.

How It Affects Plant Fitness

1. Reduction in Genetic Variation- Inbreeding increases homozygosity, leading to less genetic diversity. This makes plants more vulnerable to diseases, pests, and environmental stress because they lack the genetic variability needed to adapt.
2. Expression of Deleterious Alleles- Harmful recessive alleles, which are usually masked in heterozygous individuals, become expressed in homozygous condition. This results in reduced seed viability, lower germination rates, and weaker offspring.
3. Loss of Vigor and Fertility- Over successive generations, inbreeding depression causes a steady decline in traits like plant height, yield, flowering rate, and pollen fertility. In crops such as alfalfa or maize, these effects are often evident after a few generations of selfing.
4. Reduced Evolutionary Potential- Lower genetic variability diminishes a plant population’s ability to evolve or adapt to new environmental conditions, thereby threatening long-term survival.
5. Transgenerational and Epigenetic Effects- Recent research shows that inbreeding depression can also involve epigenetic modifications such as DNA methylation, which further influence gene expression and fitness across generations.