Background Locating the optimal varieties for coffee cultivation is increasingly considered a key condition for sustainable production and marketing. Variety performance varies when it comes to susceptibility to coffee leaf rust and other diseases, adaptation to climate change and high cup quality for specialty markets. But because of poor organization and the lack of a professional coffee seed sector, most existing coffee farms (and even seed lots and nurseries) do not know which varieties they are using. DNA fingerprinting of coffee planting material will contribute to professionalize the coffee seed sector. Objective The objective of this paper is i) to check in a large scale the robustness of the existing coffee DNA fingerprinting method based on eight Single Sequence Repeats markers (SRR) and ii) to describe how it can help in moving the needle towards a more professional seed sector. Method 2533 samples representing all possible genetic background of Arabica varieties were DNA fingerprinted with 8 SRR markers. The genetic diversity was analyzed and the genetic conformity to varietal references was assessed. Results The DNA fingerprinting method proved to be robust in authenticating varieties and trace back the history of C. arabica breeding and of the movement of C. arabica varieties. The genetic conformity of two important coffee varieties, Marseillesa and Gesha, proved to be 91% and 39% respectively. Conclusions DNA fingerprinting provides different actors in the coffee sector with a powerful new tool—farmers can verify the identity of their cultivated varieties, coffee roasters can be assured that marketing claims related to varieties are correct, and most of all, those looking to establish the a more professional and reliable coffee seed sector have a reliable new monitoring tool to establish and check genetic purity of seed stock and nursery plants. Highlights While C. arabica is primarily self-pollinating, even fixed line varieties appear to be drifting away from their original genetic reference due to uncontrolled cross pollination. A set of 8 SSR markers applied to the largest possible genetically diverse set of samples prove to discriminate between a wide range of varieties Figures confirm that genetic non conformity of coffee varieties can represent up to 61% of checked samples.

Cultivated Arabica coffee outside Ethiopia is plagued by low genetic diversity, compromising disease resistance, climate resiliency and sensory potential. Access to the wider genetic diversity of this species may circumvent some of these problems. In addition to Ethiopia, South Sudan has been postulated as a center of origin for Arabica coffee, but this has never been genetically confirmed. We used simple sequence repeat (SSR) markers to assess the genetic diversity of wild and cultivated populations of Arabica coffee from the Boma Plateau in South Sudan, against farmed accessions (of wild origin) from Ethiopia, Yemen, and global cultivars. Our results not only validate Boma Plateau as part of the natural distribution and as a center of origin for Arabica coffee but also indicate that wild populations in South Sudan are genetically distinct from Ethiopian Arabica. This newly identified genetic diversity within Arabica could have the potential for crop improvement through selection and use in breeding programs. Observations and analyses show that the extent and health of the wild population of Arabica in South Sudan have declined. Urgent action should be taken to conserve (in situ and ex situ) the unique, remaining genetic diversity of wild Arabica populations in South Sudan.