Hydraulic resistances in seedlings of Coffea arabica accessions under contrasting shade regimes in southwestern Ethiopia

摘要

The study was carried out to determine the variations among different Coffea arabica germplasm lines in hydraulic resistances under controlled nursery settings at the Jimma Agricultural Research Center in southwest Ethiopia. The experimental treatments included contrasting shade conditions (moderate shading v. full sunlight) and seedlings of 12 arabica coffee accessions of varying geographical areas in Ethiopia. Root hydraulic conductance and hydraulic resistances in the whole-shoot and different shoot parts were measured using a high-pressure flow meter. The results depicted significantly lower hydraulic resistances in the whole-shoot and in various shoot segments from the full sunlight exposed seedlings. The contribution of root and shoot resistances varied significantly in response to shade treatments. Likewise, seedlings of coffee accessions exhibited significant variation in the resistance contribution of the main stem-cut to whole-shoot resistances. The maximum hydraulic resistances in main stemcut were noted in the order of Bonga > Berhane-Kontir > Yayu > Harenna coffee populations, suggesting a direct relationship between growth and hydraulic characteristics. The resistance contributions declined across seedling growth parts: roots > leaf > whole-shoot > lateral branch > petiole, which is consistent with hydraulic gradients and thus sensitivity to drought stress. Moreover, the findings indicate the possibility of predicating the latter stage performances of coffee genotypes at specific field locations. In support of the hypothesis, the effects of both environmental and genetic factors need to be considered in fully understanding drought tolerance strategies in coffee genotypes. In view of the continuous multifaceted threats on the untapped coffee genetic resources, due mainly to, among others, anthropogenic activities coupled with climate change, there is an urgent need for global collaborative actions for future development of the coffee sector in Ethiopia and worldwide.