Variation and association among characters genetically related to yield and yield stability in Coffea canephora genotypes

Abstract

Water deficit stress is a main factor determining yield and yield stability in Robusta coffee (Coffea canephora P.). Studies were conducted to identify agronomic traits that offer genetic sources of drought tolerance associated with yields and yield stability. In a nine-year experiment, 18 genotypes were assessed for mean value and variation in three diverse environments, for nine vegetative traits, five reproductive traits and bean yield. Drought tolerance was expressed by a visual scale of leaf scorching from 0 to 5: tolerant – susceptible on the genotypes in 2000 when there was drought, and genetic associations between leaf scorching and the traits established. Significant interaction (P ≤ 0.05), and location (P ≤ 0.05) effects were observed for leaf scorching scores and all the traits, except stem diameter and diameter of primary branches. Significant (P ≤ 0.05) genotypic effects were also observed for all the traits, except fruits per node. Canopy diameter (Span), number of primary branches per plant (NPB), fruit-set (FS) and bean yield over seven years (MY1-7) were inversely and significantly (P ≤ 0.05) correlated with leaf scorching scores. Span, NPB and FS were also significantly (P ≤ 0.05) correlated with MY1-7. Span was highly correlated with stem diameter, length and diameter of primary branches. Eight genotypes each with high mean performance for (MY1-7) and fruit set (FS), seven for Span, and five for NPB, were among the top 10 genotypes which recorded the lowest leaf scorching scores. The results indicate that, Span and its associated traits, NPB, and FS could be exploited, through indirect selection for superior Coffea canephora genotypes, for direct utilisation or for breeding for adaptation to drought-stress. Key words: Drought tolerance, leaf scorching, agronomic traits, yield, yield stability, genetic correlations, genetic variation, indirect selection, Coffea canephora.