Genetic diversity in natural populations of Stylosanthes scabra Fabaceae using ISSR markers
Genetic diversity is the basis for genetic improvement as it can provide the basis for new cultivars. Stylosanthes scabra is a grasslands legume that presents potential economic importance in tropical and subtropical regions. Plants of the genus Stylosanthes naturally occur in semiarid native pastures in northeastern Brazil and are highly favored by grazing animals; therefore Brazil's Northeast stands out as an center of this genus. We evaluated the genetic diversity of S. scabra using ISSR molecular markers; naturally occurring samples were harvested from Santa Cruz do Capibaribe, Floresta, Sertânia and Petrolina in Pernambuco state, Brazil. We selected seven ISSR primers for amplification and analyzed 75 individuals, obtaining 88 bands, which amplified with 95% polymorphism at the species level. The AMOVA test revealed that 40% of the total genetic variation occurs within populations and 60% among populations. Population differentiation was 0.332 and the migrant number per generation was 0.5. Grouping analysis confirmed a high level of differentiation among populations and that the greatest variability was in Santa Cruz do Capibaribe and Petrolina regions. The ISSR markers were efficient for genetic diversity quantification in S. scabra, which presented greater variability among populations than within them. Overall, the population variability found will be useful for breeding programs for this species.