Genetic Diversity of Arabica Coffee (C. arabica) Based on Morphological and Biochemical Analysis

Selection of improved quality coffee genotypes can be supported by the use of association genetics linking phenotypic data (morphological and biochemical components in the coffee bean determining coffee quality) with genotypic data. The choice of germplasm representing diversity is very critical for the success of an association study. The narrow genetic base resulting from a genetic bottle neck in domestication and self-pollination of commercial arabica has been well documented. However, the sub/spontaneous accessions have higher genetic diversity assessed by molecular markers.  In this work, beans of 235 coffee genotypes were selected from a population of 1800 genotypes growing in Costa Rica. These comprised 232 genotypes of C. arabica, two of C. canephora (robusta) and one of C. brevipes, representing samples from 24 countries with 82 cultivars/varieties/selections, 38 hybrids and 112 wild types. Bean morphology including weight of 100 beans, the ratio of bean length to width, bean thickness and bulk density has been measured and showed significant variation. Compositional analysis was also performed to identify diversity in the population in regards to biochemical compounds linked to coffee quality (both volatile and non-volatile components). The results of this study could help in direct selection of desired genotypes in coffee breeding or could be used in association genetics to identify genes or markers linked to coffee quality. Further, correlations between bean physical properties and composition could determine whether or not bean physical properties could be used for selection of desired quality genotypes.