Coffee Plants come in two main varieties :- Arabica and Robusta
Arabica beans are mild in the cup, with comparatively less caffeine, while Robusta has more aromatic. The Robusta tree appears bushier, the leaves are larger and the berries form in clusters
Coffee Research Foundation (CRF) currently produces four commercial cultivars (varieties) of Arabica coffee. Different varieties are recommended for various altitudes.
i) K7 – low altitude coffee areas with serious Coffee Leaf Rust (CLR).
ii) SL 28 – medium to high coffee areas without serious CLR.
iii) SL 34 – high coffee zone with good rainfall.
iv) Ruiru 11 – all coffee growing areas. Resistant to both Coffee Berry Disease (CBD) and CLR.
K7 cultivar was selected at Legetet Estate in Muhoroni from the French Mission Coffee. It is distinguished by its spreading habit on young laterals although older primaries tend to be decumbent or drooping. It has characteristic medium to narrow leaves with young shoot-tips that are intermediate bronze in colour. The cultivar has resistance to some races of CLR as well as partial resistance to CBD. It is suited for lower altitudes where CLR is prevalent. The bean and liquor qualities are good.
The SL 28 cultivar was selected at the former Scott Laboratories (now the National Agricultural Laboratories, NARL situated at Kabete) on a single tree basis from the Tanganyika Drought Resistant variety selected in Northern Tanzania in 1931. The prefix SL in the variety name are acronymous for Scott Laboratories where the variety was selected. The name is completed by a serial number (28) for the selection. The variety is suited for medium to high altitude coffee growing zones.
SL 34 was also selected at the former Scott Laboratories from French Mission Coffee. The cultivar is adapted to high altitude areas with good rainfall. It is majorly characterized by dark bronze shoot tipped plants with a few green-tipped strains. The laterals have semi-erect habit which tend to become decumbent or drooping on older primaries. The cultivar produces high yields of fine quality coffee but is susceptible to CBD, CLR and BBC.
Ruiru 11 variety was released in 1985. The variety name has the prefix “Ruiru” referring to the location of the Kenyan Coffee Research Station where the variety was developed. The name is completed by an additional two code numbers, 11. The first code number denotes the type of variety as a one way cross between two designated parent populations and the second number defines the sequence of release, in this case the first release. The variety is not only resistant to CBD and CLR but is also compact allowing farmers to intensity production per unit land especially in high potential areas where population is high and coffee is in competition with other crops and farm enterprises required for food security and income. Ruiru 11 is planted at a density of 2500/3300 trees/ha compared to 1300 trees/ha for the traditional varieties. This translates into a higher production per unit area of land. The variety comes into production earlier, hence earlier realization of benefits to the farmers. The development of Ruiru 11 also took into consideration the importance of quality as a major marketing parameter. Since the quality of the traditional varieties was already popular among consumers of Kenyan coffee, Ruiru 11 was developed with quality attributes similar to the traditional varieties.
True breeding Arabica coffee variety resistant to Coffee Berry Disease and Leaf Rust
Type: True breeding Arabica coffee
Growth habit: A tall statured plant with vegetative features similar to those of Cultivar SL28. The cultivar produces many primary branches with horizontal but occasionally erect branching habit which tends to become semi-drooping after successive crop bearing seasons. It produces average to profuse secondary branching, and is ever green throughout the year under good management.
Leaves:The young leaves have medium purplish colouration giving a bronze colour but occasionally absent or weak, giving a green-bronze colouration. Mature leaves have medium width which compares closely with SL28.
Internodes: The cultivar has long internodes on both the main stem and branches that compares closely to SL28.
Berry:Ripe cherries are larger than those of SL28, elliptical in shape and deep red in colour.
Beans:Mature beans are large and bold, endosperm is green while the centre cut is mostly singled and straight.
The planting materials are available at Coffee Research Foundation.
To convert the traditional varieties (disease susceptible) to the new coffee variety, topworking on mature plants in the field is recommended. This can be done when the suckers are at pencil thickness stage.
Similar to other nursery management practices for traditional coffee varieties.
Spacing of 2m x 2m giving a plant population of 2500 trees per ha.
Nutritional requirements are similar to those recommended for traditional varieties.
Weed management is as per recommendations contained in Technical Circular no. 502 available from CRF.
i.Batian should be raised on single head in the first cycle and then one or two heads in subsequent cycles.
ii.Remove primary branches that touch the ground.
iii.Due to the profuse vegetative growth, frequent handling is necessary.
iv.Change of cycle can be done by stumping or side pruning system at five year intervals.
Sequential replacement of the old varieties with Batian is ideal. This would enable attainment of the right population per hectare.
Batian is resistant to CBD and Leaf Rust. Bacterial Blight of Coffee (BBC), Fusarium spp, Berry blotch, Crinkle leaf, etc should be controlled as recommended for the other varieties.
Insect pests’ control
Proper insect pest survey and monitoring is essential before the appropriate control measures are taken. Where chemical control is considered best, the rates are similar to those for traditional varieties.
Merits of Batian
i.Batian is a true breeding variety. Seed production is therefore easier.
ii.Batian comes into production in the second year while traditional varieties do so in the third year, hence early flow of benefits.
iii. Cherry ripening comes earlier than SL28 and Ruiru 11.
iv.There are appreciable savings from the cost of fungicides and labour used to control CBD and Leaf Rust.
v.It is a high yielding variety with good bean and cup quality.
vi.It is suited for all coffee agro-ecological zones.
Other coffee varieties
Although the varieties mentioned above are the most commonly grown, some coffee plantations have blue mountain and the original French Mission Coffee in the Arabica range as well as Robusta coffee especially in the low altitude and humid areas such as Western Kenya.