Intraspecific variation in growth response to drought stress across
geographic locations and genetic groups in Coffea
canephora Pierre ex A. Froehner
Abstract
Uganda lies within the drier end of the natural distribution range of
Coffea canephora and contains unexplored genetic material
that could be drought-adapted and useful for developing
climate-resilient varieties. Using experimental treatments, (i) ample
and (ii) restricted-water, response of 148 genotypes were studied
comprising wild, feral and cultivated C. canephora. Biomass allocation,
standing leaf area and leaf area growth data were collected. Linear
mixed effect models and PCA were used to analyse effect of drought on
genotypes from different: (i) cultivation status, (ii) genetic groups
and (iii) locations. We assessed the relationship between drought
tolerance for relative growth rate in leaf area (RGRA), total number of
leaves (TNL), total leaf area (TL) and total leaf dry weight (TLDW) of
genotypes at final harvest. Restricted-water reduced RGRA across genetic
groups (3.2 – 32.5%) and locations (7.1 – 36.7%) but not cultivation
status. For TNL, TL and TLDW, genotypes that performed well in
ample-water performed worse under restricted-water, indicating
growth-tolerance trade-off. Drought tolerance in RGRA and TNL were
negatively correlated with wetness index suggesting some degree of
adaptation to local climate. Findings indicate a growth-tolerance
trade-off within this tropical tree species and drought tolerance of
Uganda’s C. canephora is somewhat associated with local
climate.