Effective Population Size during Grass Germplasm Seed Regeneration

Area of Science:

• Plant breeding and genetics
• Population genetics
• Conservation biology

Background:

• Effective population size (N(e)) is vital for managing genetic drift during germplasm regeneration.
• Variation in seed production among individual plants is a primary factor reducing N(e) below census population size (N(c)).
• Understanding and mitigating genetic drift is essential for maintaining genetic diversity in plant populations.

Purpose of the Study:

• To estimate the ratio of effective population size to census population size (N(e)/N(c)) in three grass species, considering variation in seed production.
• To identify cost-effective sampling methodologies that maximize N(e)/N(c) during seed regeneration.
• To provide recommendations for minimizing genetic drift in outcrossing grass germplasm regeneration.

Main Methods:

• Three perennial grass species (Lolium perenne, Festuca pratensis, Pseudoroegneria spicata) were grown in field trials.
• Variation in seed number per plant and mean seed production were analyzed.
• N(e)/N(c) was estimated using whole plant samples and samples of two inflorescences per plant.

Main Results:

• N(e)/N(c) varied significantly among species and accessions, with whole plant estimates ranging from 0.42 to 0.63.
• Sampling two inflorescences per plant yielded higher N(e)/N(c) ratios (0.69–0.88) by reducing variation associated with inflorescence number.
• Results indicate a substantial potential for genetic drift in small regeneration populations.

Conclusions:

• Variation in seed production, particularly inflorescence number, strongly influences genetic drift.
• Sampling a constant number of inflorescences per plant is a more effective method to maintain N(e)/N(c) than sampling whole plants.
• Increasing population size and standardizing inflorescence sampling are recommended to minimize genetic drift in grass regeneration.