Single nucleotide polymorphisms for assessing genetic diversity in castor bean (Ricinus communis)

Area of Science:

• Plant genetics
• Population genetics
• Agricultural science

Background:

• Castor bean (Ricinus communis) is a globally cultivated crop and ornamental plant.
• Limited genetic variability has hindered understanding of castor bean population structure and cultivar distribution.
• Previous studies faced challenges in analyzing castor bean genetic diversity.

Purpose of the Study:

• To analyze the population genetics of Ricinus communis worldwide.
• To assess genetic diversity and population structure in castor bean germplasm and naturalized populations.
• To compare genome data of diverse cultivars with a reference genome.

Main Methods:

• Survey sequencing of seven diverse castor bean cultivars.
• Comparison with a reference genome assembly (Hale).
• Analysis of population genetic structure using single nucleotide polymorphisms (SNPs) at 48 loci in 676 samples.

Main Results:

• Bayesian clustering identified five main global groups with mixed genotypes prevalent in most countries.
• High population differentiation was observed, but it lacked a clear geographic basis.
• Most molecular variance occurred within populations (74%), with significant structuring in Florida's naturalized populations.

Conclusions:

• Low genetic diversity and genotype mixing limit geographic structuring in worldwide castor bean populations.
• Few, widely distributed lineages characterize castor bean genetic makeup.
• The SNP-based genome-wide approach offers a high-throughput framework for plant genetic diversity analysis, especially in species with limited variability.