Assessment of Genetic Diversity in Phaseolus lunatus Landrace Germplasm for Use in Breeding Programs

The lima bean (Phaseolus lunatus L.) is an important food crop that is cultivated in temperate, arid, and semiarid tropical regions. It is a source of dietary protein for millions of people living in low-income countries. However, the genetic variability available for breeding programs is still poorly understood, which limits its productive potential. Knowledge of landrace germplasm through molecular and agromorphological markers could facilitate future breeding gains. Therefore, we evaluated the genetic variation of agromorphological and molecular markers in a lima bean collection. Twelve quantitative traits and microsatellite markers (SSRs) were used to determine genetic polymorphisms and differentiation among the 26 lima bean accessions. Considerable diversity was observed in traits related to agronomic performance, such as pod width, seed length, and seed width. At the molecular level, the expected mean heterozygosity (He = 0.486) was greater than the observed value (Ho = 0.128), indicating a deficiency of heterozygotes, which is a result of the reproductive system of the species. Although having a mixed system of reproduction, the lima bean is predominantly autogamous. The polymorphic information content (PIC) ranged from 0.04 to 0.67. Loci BM211 and BM156 were highly informative and are indicated for further studies with lima beans. The UFPI accessions 222, 234, 237, 228, 264, 230, and 251 showed the highest levels of similarity, while UFPI 230 and UFPI 276 were genetically distant and complementary in their traits; therefore, they could be used in crosses. Furthermore, the pairs of accessions UFPI 121/UFPI 173, UFPI 274/UFPI 276, and UFPI 271/UFPI 134 were duplicates found in the lima bean germplasm collection. The information generated in this study will play a significant role in future lima bean breeding programs.

Automated summary

This study evaluated the genetic variation of agromorphological and molecular markers in a collection of lima bean germplasm. The results showed considerable diversity in agronomic traits and a deficiency of heterozygotes at the molecular level. The information generated from this study will play a significant role in future lima bean breeding programs.