Abstract:

The propagation and distribution of robusta coffee (Coffea canephora Pierre), clonal selections in
Uganda has been hampered by logistics. These clonal selections also exhibit a substantial degree of
genotype-environmental interaction. Our objectives were to further elucidate the differences between
these clones, the differences between individual clones and their corresponding seedling progenies and a
farmer's elite entry and to define the nitrogen levels required for the optimal performance of the various
clones and seedling progenies. A split-split plot, randomized complete block design with 4 replicates was
used. Mean yield data for the years 1988 and 1989 are presented. There were significant differences in
the response to nitrogen but a complete response curve was not established. Nevertheless, the data
confirmed that it is highly profitable to apply nitrogen to robusta coffee. The differences between the
yields of clonal cuttings and their corresponding seedling progenies were much higher for the erecta
types of robusta coffee than for the nganda type. The nganda clones had a higher level of general
combining ability than the erecta types. The correlations between the clonal parents and their corresponding seedling progenies were low for all entries but slightly higher for the nganda than for the erecta
entries. Using clonal cuttings resulted in higher yields for the erecta entries compared to their corresponding seedling progenies. This was not necessarily so with the nganda material.