Coffee Research

Coffee research is an important part of the HARC diversified crops program. Industry support from the Hawaii Coffee Growers' Association (HCGA) was received in 1998 which, together with state, federal, and other private sources, supports coffee research in genetic improvement, control of flowering and ripening, weed control, and insect control. HARC also successfully developed a genetic transformation system for coffee under a state-funded project with the University of Hawaiʻi. Other privately funded coffee work includes a training program for coffee field management and experiments on fertilizer and nutrition.

Selection and Breeding

The primary objective of coffee breeding and selection program is to develop high yielding, excellent bean quality cultivars which are adapted to specific growing conditions in Hawai'i. Disease resistance (especially rust) and mechanical harvestability are also important criteria.
Four major goals have been set for this year:

• Develop strategies for breeding and selection of coffee cultivars in Hawaii with the assistance of a coffee breeding consultant
• Develop techniques required to implement the breeding program
• Develop procedures for vegetative propagation
• Select potentially elite individual trees from existing coffee farms and vegetatively propagate them

An important part of the coffee improvement program is to efficiently vegetatively propagate elite coffee tree selections; thus, work on vegetative propagation was also initiated. The preliminary results are very encouraging. The development of micropropagation techniques will also be pursued.

Coffee rust resistance

In 1992, HARC imported, under quarantine, the rust resistant cultivars PROMECAFE1 and 2 from Guatemala and the germplasm was established at the HARC Maunawili Breeding Station. During March and April 1997, crosses were made between the rust resistant lines of Promecafe and the cultivars 'typica' and 'catuai.' Promecafe lines were also self-pollinated to obtain progenies of individual Promecafe trees for evaluation. In addition, 34 individual trees from 5 coffee growing areas in Hawaii have been selected. Plants derived from seed and vegetative cuttings were planted at one of the HARC substations on Oahu. Additional crosses among these trees are being made.

Coffee Physiology: Control of Flowering and Ripening ​

Coffee growing in many subtropical and tropical production areas is characterized by poorly synchronized floral development and a prolonged hand-harvesting period. Because of the high cost of hand-harvesting, mechanical harvesting will be required for successful establishment of an extensive coffee industry in low elevation, irrigated leeward areas of Hawaii. Cultural practices that synchronize fruit development are needed to optimize mechanical harvesting.

Fruit development in coffee can be synchronized by treatments designed to synchronize flower opening (anthesis), or fruit ripening or both. Previous research in Hawaiʻi and elsewhere has shown that anthesis in coffee is stimulated and synchronized by a period of drought followed by irrigation or rainfall. Imposition of drought followed by irrigation may be a practical approach for synchronizing anthesis of coffee grown in regions with a prolonged, predictable dry season. The feasibility of this approach in Hawaiʻi will depend on the intensity of the water deficit required to stimulate anthesis and on the interval between significant rainfall events.

The use of plant growth regulators also offers an opportunity for more dependable and precise timing of floral development and ultimately fruit ripening in coffee. The effectiveness of gibberellin for synchronizing anthesis and ethylene for synchronizing fruit ripening is being evaluated in commercial field trials. Results to date suggest that this approach is feasible.