Assessing temporal changes in genetic diversity of maize varieties using microsatellite markers

Area of Science:

• Agricultural Science
• Genetics
• Plant Breeding

Background:

• Maize (Zea mays L.) is a vital global crop.
• Understanding genetic diversity in cultivars is crucial for sustainable breeding programs.
• French maize cultivars have evolved over the last five decades, necessitating an assessment of their genetic makeup.

Purpose of the Study:

• To quantify and compare genetic diversity among maize cultivars from different historical periods in France.
• To assess the genetic differentiation between these historical maize groups.
• To provide insights for future French maize breeding strategies.

Main Methods:

• Fingerprinting of 133 maize varieties using 51 simple sequence repeat (SSR) markers.
• Grouping varieties into four distinct historical periods.
• Computation of allelic richness, Nei's unbiased heterozygosity, and analysis of molecular variance (AMOVA).

Main Results:

• A total of 239 alleles were identified across all varieties.
• Genetic diversity (Nei's unbiased heterozygosity) ranged from 0.56 to 0.61, with the highest in the earliest period.
• Most genetic diversity (H(S)=0.57) was found within periods, with low differentiation among periods (G(ST)=0.04).
• A significant, though low, genetic differentiation was observed between periods, except for the last two.
• A 10% reduction in genetic diversity was noted in pre-1976 cultivars compared to post-1985 cultivars.

Conclusions:

• French maize cultivars have experienced a reduction in genetic diversity over the last five decades.
• Low genetic differentiation among recent cultivars suggests a narrowing of the genetic base.
• Breeders should prioritize expanding the genetic diversity in future French maize breeding programs.