Genetic and environmental correlations between bean yield and agronomic traits in Coffea canephora

Anim-Kwapong Esther* and Boamah Adomako

Cocoa Research Institute of Ghana, P. O. Box 8, New Tafo-Akim, Ghana.

*Corresponding author. E-mail: ekwapong06@yahoo.com.

Accepted 17 January, 2010

   Abstract

Early identification and selection of genotypes with high yielding potential is a main breeding objective of Coffea canephora. Eighteen genotypes of C. canephora were assessed in three diverse environments over a 9-years period from 1996 to 2005. Genetic and environmental associations were assessed among 10 vegetative and five reproductive traits and yield. Genetic associations between yields over seven years and vegetative traits, except secondary branches per plant, were positive and significantly correlated with span (r_G = 0.65**), girth (r_G = 0.60**), diameter (r_G = 0.55*) and number of primary branches (r_G = 0.53*). The traits exhibited stronger genetic correlations with last 4 - 7 years yields (r_G =0.54* - 0.68**) than with first 1 - 3 years yields (r_G = 0.38 - 0.47*). Fruit-set observed in three fruiting seasons, when the trees were three, four and six years in the field, was consistently positive and significantly associated with yields over seven years (r_G = 0.60**; 0.63**; 0.66**). However, genetic associations between yields over seven years and flowers per node observed in the three fruiting seasons was consistently negative and significant for two seasons (r_G = -0.50*; -39; -0.62**). First 1 - 3 years yield was a better predictor (r²_G = 0.79***) of yields over seven years, than first 1 - 2 years (r²_G = 0.42**) and first year (r²_G = 0.012) yield. Selection for potential high yielding genotypes should, therefore, be based on an index involving span, girth, diameter and number of primary branches, first three years yield, fruit-set, and flowers per node. High positive environmental correlations were observed between bean yields and fruit-set, number of fruits per node, number of flowering and fruiting nodes, girth and number of primary branches. However, environmental conditions that reduced yields also increased flowers per node and promoted vegetative growth by increasing secondary branching, span, length, diameter and number of nodes per primary branch. Efficient selection for yield based on vegetative traits should, therefore, be undertaken under optimum growing conditions where there is a better balance between vegetative growth and yield.

Key words: Vegetative traits, reproductive traits, Coffea canephora, genetic correlations, environmental correlations, yields, indirect selection.