Shape of bean in Coffea arabica L. in Kenya

Abstract

Bean shape is an important quality factor in Kenyan coffee. The rounded Bombon type is preferred, and there should be no long, narrow, or other non-standard shaped beans in cross-section. In notched and double-blessed beans, the endosperm was found to have stopped growing shortly before reaching its maximum size, while in boat-shaped beans and many of the long, narrow beans, more serious endosperm abnormalities were found. The percentage of abnormal endosperms varied according to cultivar and location on the tree, with the apical part of the branch having more abnormal beans than the proximal part. In berries containing typically two seeds, double-blessed beans were also found to be more frequent when the seeds were symmetrically oriented. The frequency of double blessings appeared to be lower than average when typically shaped kernels were present in fruits in which the other seed had not developed, leaving only the empty parchment. The percentage of double-blessed kernels was positively correlated with kernel weight, but this trend was reversed in an irrigation experiment. Irrigation improved kernel shape and reduced the number of incompletely developed endosperms, probably by creating more favorable growth conditions during the dry season. Fruits and kernels that were too long by Kenyan standards were found to be no wider than those of average length. It is unlikely, however, that their presence can explain complaints about the prevalence of long, narrow kernels. The latter are more likely to be produced by cultivars possessing this kernel character or to arise from insufficient endosperm growth within a well-developed parchment.