Assessment of Genetic Variability of 142 Sweet Sorghum Germplasm of Diverse Origin with Molecular and Morphological Markers

Abstract

Sorghum bicolor (L.) Moech is the fifth most important crop in the world. Recently, its agronomics and genetics have drawn interest among scientists. Sweet sorghum, a variety of sorghum, may po-tentially become a bioenergy source because of the high sugar content in its juicy stems. Exploring the diversity of sweet sorghum around the world is important to the development and improve-ment of the crop as an energy source. In exploring the diversity of sweet sorghum, three types of markers (simple sequence repeats [SSR], sequence-related amplified polymorphisms [SRAP], and morphological markers) are used on 142 sweet sorghum accessions from around the world. The accessions show a high significance (P < 0.05) for all the morphological traits measured. The morphological markers cluster the accessions into five groups based primarily on plant height (PH), anthesis data (AD), and moisture content (ML), with the principal component analysis (PCA) showing these traits to explain 92.5% of the total variation. The furthest accessions were PI571103 from Sudan, and N99 from the United States. The Nei's genetic standard distances ranged from 0.024 to 1.135 and 0.078 to 0.866 for SSR and SRAP, respectively. As expected, accessions of the same origin or breeding history had the lowest genetic distance (e.g. Mokula and Marupantse, both from Botswana; NSL83777 and NSL83779 from Cameroon). Neighbor joining clusters the sweet sorghum accessions into five major groups using SSR and four major groups using SRAP, based on their origin, or breeding history. The three marker types complement each other, and the presence of accessions of different origins across clusters indicate similar genetics, and evi-dence of germplasm movement between countries.