Early selection for yield in robusta coffee based on juvenile growth traits
Variety development, particularly for tree crops is a long-term exercise requiring significant resource investments, over many years of evaluation. Identification of traits at early growth stages that are predictive of future performance would facilitate the breeding process. The objective of this study was to assess the value of juvenile trunk cross-sectional area (TCSA) and number of laterals for selecting high-yielding Robusta coffee (Coffea canephora) genotypes, early in a breeding programme. Seventy-two Robusta coffee clones developed by either ortet selection, from previous progeny trials/clonal trials carried out at the Cocoa Research Institute of Ghana (CRIG), were planted in 2011 in a randomised complete-block design with five replications, at CRIG’s experimental fields. Juvenile TCSA and number of laterals were effective predictors of yield. Genotypes that combined small TCSA and less number of laterals at the juvenile growth phase had the lowest cumulative yields, and vice versa. TCSA was significantly associated with yearly yields (2015: r = 0.49, P < 0.001; 2017: r = 0.35, P < 0.001) and cumulative yield (r = 0.41, P < 0.001). Similarly, a significant (P < 0.001) correlation was observed between juvenile number of laterals and yearly yields (2015: r = 0.58, 2016: r = 0.24; 2017: r = 0.48), and cumulative yield (r = 0.57, P < 0.001). A selection index that combines large juvenile TCSA and many number of laterals has the potential of identifying productive genotypes early in a Robusta coffee breeding programme.
Key words: Coffea canephora, number of laterals, trunk cross-sectional area