Gas exchange, growth, yield and beverage quality of Coffea arabica cultivars grafted on to C-canephora and C-congensis

Gas exchange, leaf carbon isotope discrimination, growth, yield and beverag e quality were evaluated for two Coffea arabica cultivars (Catuai and Mundo Novo), grafted on to C, canephora and C. congensis progenies growing in op en fields. During the years 1994 to 1997, grafting resulted in an average i ncrease in bean yield of 151 and 89% for Catuai and Mundo Novo respectively . As analysed by sensory analyses and by the ratio between the mono-isomers and di-isomers of caffeoylquinic acid, beverage quality of the C. arabica was not altered by grafting. Shoot growth was significantly greater in graf ted plants, showing an increase of 52% in total leaf area compared with the non-grafted plants. Under conditions of water excess in the soil there was little difference in the transpiration and stomatal conductance rates betw een the grafted and non-grafted plants, I,ut the net photosynthesis was hig her in grafted plants. With an accentuated water deficit in the soil in til e dry period, the grafted plants showed significantly higher transpiration and stomatal conductance rates than the non-grafted plants, and similar val ues to those of C. canephora. Carbon isotope discrimination was greater in the grafted plants, suggesting greater root hydraulic conductance. The resu lts suggest that the better performance of the grafted plants during the dr y period was due to the greater capacity of the root system of C. canephora to provide water to the shoot thereby maintaining greater gas exchange in the leaves and consequently a greater carbon gain.