Variation in bean morphology and biochemical composition measured in different genetic groups of arabica coffee (Coffea arabica L.)

The narrow genetic base of commercial arabica resulting from intensive selection for quality during domestication and self-pollination has been well documented, raising the need for new diverse germplasm sources. Beans of 232 diverse arabica coffee accessions originating from 27 countries were harvested from the germplasm collection at CATIE, Costa Rica. Substantial variation was observed for bean morphology including 100 bean weight, bean length, width, thickness and bulk density. Non-volatiles including caffeine and trigonelline were analysed and showed larger variation in range than has previously been reported. Results of targeted analysis of 18 volatiles from 35 accessions also showed significant variation, with coefficients of variation from 140% for 4-vinylguaiacol to 62% for geraniol. There were strong correlations between some volatile compounds, suggesting that representative volatiles used in selection would save analytical costs. However, no strong correlation was found between bean morphology and the levels of non-volatile or volatile compounds, implying that it is difficult to select for low or high composition of these compounds based on bean physical characteristics. Utilizing the large variation observed for bean morphology and biochemical traits, it should be possible to select for desirable combinations of traits in arabica coffee breeding.