ECOPHYSIOLOGICAL TRAITS OF ADULT TREES OF CRIOLLO COCOA CULTIVARS (THEOBROMA CACAOL.) FROM A GERMPLASM BANK IN VENEZUELA

Abstract

We studied physiological traits of 12 Criollo cocoa cultivars growing in a germplasm bank in the southern region of Maracaibo Lake Basin, during the rainy (RS) and dry seasons (DS) of 2007. A further evaluation of photosynthetic responses to changes in environmental parameters was done on three cultivars: Los Caños 001 (LCA001), Sur Porcelana 010 (SP010) and Escalante 001 (ESC001) in 2009 and 2010. Leaf water potential ( L ) of most cultivars decreased during the DS of 2007, with the exception of ESC001. Maximum photosynthetic rate (A max ), stomatal conductance and water use efficiency varied among cultivars and seasons. The CO 2 -saturated photosynthetic rate (A CO2sat ) was higher in LCA001 and ESC001 than in SP010, with no differences in carboxylation efficiency. Light curve responses of the three cultivars were similar. In all cultivars, no evidence of chronic photoinhibition was observed, since maximum quantum yield of photosystem II was high (0.77-0.81). We conclude that ESC001 has the best physiological performance ( L remained unchanged, highest A max , A CO2sat and photochemical activity), and it seems to be a promising cultivar for cocoa agroforestry systems in the southern region of Maracaibo.

Does Criollo cocoa have the same ecophysiological characteristics than Forastero?

“…Water status. High values of Ψ early in the morning were in agreement to those reported for young plants in well-watered conditions in an agroforestry system (Jaimez et al 2008;Tezara et al 2009;Araque et al 2012) and in young trees in a germplasm bank (Pereyra 2007;Ávila-Lovera et al 2016). By the time of the study (November and January) when monthly rainfall average was high, Ψ at noon of these trees indicated a low transpiration rate which may well be the result of an environment of low evaporative demand.…”

“…The very low average A observed for both cultivars might be associated with low g s . Similarly, A values have been found to range from 0.7 to 6.5 µmol m -2 s -1 with low g s (20 -150 mmol m -2 s -1 ) in different studies Daymond et al 2011;Araque et al 2012;de Almeida et al 2014;Ávila-Lovera et al 2016). Higher instantaneous A and lower E determine a significant higher WUE in Criollo compared to Forastero, suggesting that Criollo cocoa could grow well in regions with limited water availability.…”

“…Low photosynthetic rates (A) and stomatal conductance (g s ) have been reported in cocoa trees with reductions due to water deficit, high vapor pressure deficit (VPD) and high photosynthetic photon flux density (PFD) among other abiotic factors that could cause stress (Deng et al 1989;de Almeida and Valle 2007;Acheampong et al 2013;Ávila-Lovera et al 2016). There are limited studies on ecophysiological responses to water and light availability of different genotypes of adult cocoa trees, both in agricultural ecosystems and natural habitats (Moser et al 2010;Araque et al 2012;Jaimez et al 2013;Ávila-Lovera et al 2016).…”

Compatibility of Ten Elite Cocoa (Theobroma cacao L.) Clones

“…This may be due to environmental effects. Indeed, the environment may have played a role in the expression of some compatibility genes or traits [3,36]. The different levels of compatibility observed were a visible phenomenon indicated by the dropping of flowers, which could also be due to physiological traits and or environment conditions such as wind, rainfall, etc.…”

“…T. cacao is a heterozygous plant with a high variability for agronomic and quality traits [2,3]. Several studies have shown that the flowers of cocoa are androgynous and essentially fertilized by midges (Forcipomyia spp.)…”