Genetic diversity and erosion in lima bean (Phaseolus lunatus L.) in Northeast Brazil

Lima bean (Phaseolus lunatus L.) is a crop that stands out for its economic and social importance throughout the world, including in Northeast Brazil. Evidence points to high levels of genetic diversity in this crop in this region. Monitoring the levels of genetic diversity in lima beans is necessary for predicting the possible processes of genetic erosion. In this study, we compared the genetic diversity of 12 lima bean genotypes collected in the 1980s with that of 42 genotypes collected in 2014-2016 in Northeast Brazil, using eight microsatellite loci (SSRs), to assess the occurrence of genetic erosion. The genetic diversity (H-E) for the genotypes collected in 2014-2016 ranged from 0.144 to 0.47, indicating a wide diversity among the lima bean germplasms cultivated in Northeast Brazil. The Garza-Williamson index showed values below 0.70 for both the periods (1980s and 2014-2016). Moreover, the results obtained suggest a recent genetic bottleneck for the 2014-2016 genotypes, which may be related to the management and production techniques used by farmers owing to the growing market demand for improved lima bean varieties in recent years.