Impact of multiple selective breeding programs on genetic diversity in soybean germplasm

Area of Science:

• Plant genetics and breeding
• Agricultural science
• Genomics

Background:

• Soybean (Glycine max) has been cultivated for over 3,000 years, evolving from wild soybean (Glycine soja).
• Modern soybean cultivars are crucial sources of global oil and protein.
• Breeding programs significantly alter genetic diversity from unimproved germplasm to elite cultivars.

Purpose of the Study:

• To evaluate the molecular impact of selective breeding on soybean genetic diversity.
• To compare genetic diversity patterns across different soybean gene pools and breeding strategies.
• To identify the extent to which independent breeding programs preserve unique genetic variation.

Main Methods:

• Analysis of 391 soybean accessions, including US cultivars, progenitors, and two novel gene pools (AGP, SGP).
• Assessment of nucleotide genetic diversity (π) and population differentiation (FST) across gene pools.
• Population structure analysis to compare allelic compositions and identify private alleles.

Main Results:

• Nucleotide genetic diversity decreased with selection within gene pools.
• Artificial selection in the exotic G. max germplasm (AGP) retained more diversity than the USDA Soybean Germplasm Collection (CGP).
• Independent breeding resulted in elite lines with similar allelic compositions in AGP and CGP, while SGP elite lines were distinct but lower yielding.
• Both AGP and SGP retained significant private alleles not found in CGP.

Conclusions:

• Multiple selective breeding programs can generate highly productive elite soybean lines with similar genome-wide allelic compositions.
• Breeding programs utilizing different ancestral lines can retain private alleles, contributing to unique genetic diversity.
• Distinct breeding populations, even when producing similar elite lines, preserve unique genetic variation, enhancing overall soybean genetic resources.