The 2012 ASHS Annual Conference

Protection of crop genetic resources is a key approach for securing food sources for the future generations. Crop diversity in part is maintained by farmers who share plant material, introduce new varieties and even select improved genotypes. Also the farmers keep and, in some cases without knowing, protect the wild relatives of many different species. The establishment of genetic relations within a crop is an important component in crop improvement programs. Correct assessment of genetic diversity is invaluable in any crops’ conservation and for diverse applications including the identification of new combinations with maximum genetic variability for further selection and introgression of desirable genes from diverse germplasm into the available genetic base. In this study, we report the first genetic diversity assessment of lima beans (Phaseolus lunatus L.) in the Caribbean. Lima bean, known as ‘pois souche’ in Haiti and ‘haba’ in Puerto Rico (PR) and the Dominican Republic (DR), is a drought and heat tolerant grain legume crop that is produced and consumed throughout the Caribbean. Most landrace varieties in the Caribbean are photoperiod sensitive (short-day) indeterminate plants that produce pods during the dry season. Fifty-five landraces collected from the PR, Haiti and DR were subjected to fluorescence-based Simple Sequence Repeat marker analysis on polyacrylamide gels. The number of alleles per loci ranged between 1 and 8 with the percentage of polymorphic loci being 74.17 ±12.64.  A high number of alleles were found per locus, at an average of 2.67 ±1.46. The percentage of polymorphic loci was highest in accessions from PR (75%) followed by DR (70.8%) and Haiti (62.5%). The average proportion of observed heterozygous individuals (H_o) was higher than expected in all three countries. The overall heterozygosity (H_t) in all accessions was 0.4110 ±0.1964 with approximately 40% of the diversity due to within country variation (H_s= 0.3969 ±0.1916) and only 3.65% (G_st = 0.0365 ±0.0512) due to differentiation among samples. The results reveal a low level of differentiation between country samples. The UPGMA analysis showed that all samples clustered with the known-check variety (Sieva) of Middle-American descent. Interestingly, all samples from Haiti grouped in a cluster that did not contain any samples from PR. Since lima bean is one of the few agronomical important crops that contain toxic cyanogenic glucosides, we also assessed all accessions for the presence of linamarin (the cyanogenic glucoside in lima beans) in leaves and seeds using a UPLC-TOF system.