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SEASONAL CHANGES IN GAS EXCHANGE AND YIELD OF 21 GENOTYPES OF COFFEA ARABICA

Abstract:

Background: Coffee breeding programs in Ecuador have information on production and disease tolerance in many genotypes; however, they lack physiological information, especially on photosynthetic characteristics and their response to drought. Questions: Whether high genetic variability among coffee genotypes will explains the photosynthetic and production differences expected? Will the physiological response to the dry season (DS) be different between genotypes? Studied species: Coffea arabica L. Study site and dates: Pichincha canton, Manabí province, Ecuador during March-April 2017 (rainy season, RS) and June-July 2017 (DS). Methods: Leaf relative water content (RWC) and gas exchange of 21 coffee genotypes were measured during DS and RS. Coffee production during a period of three years was evaluated. Results: Significant differences were found in RWC, photosynthetic rate (A), stomatal conductance (gs) and water use efficiency (WUE) among genotypes, between seasons, an interaction effect of genotype × season. Drought caused a significant reduction in A and gs of 30 and 44 % respectively, while WUE was not affected. A positive linear relationship was found between A and gs, and a negative relationship between A and the leaf-air vapor pressure gradient (ΔW) and between gs and ΔW. Differences in coffee production were found among genotypes. Conclusions: The high genetic variability of C. arabica genotypes may explain the significant differences in RWC and gas exchange and interaction genotypes x season, suggesting a differential response of each genotype to drought. Eleven of the 21 coffee genotypes were sensitive to drought, but showed different responses, suggesting possible genotypic differences in tolerance.