Ecophysiology of the cacao tree

Abstract

Cacao, one of the world's most important perennial crops, is almost exclusively explored for chocolate manufacturing. Most cacao varieties belong to three groups: Criollo, Forastero and Trinitario that vary according to morphology, genetic and geographical origins. It is cropped under the shade of forest trees or as a monocrop without shade. Seedlings initially show an orthotropic growth with leaf emission relatively independent of climate. The maturity phase begins with the emission of plagiotropic branches that form the tree crown. At this stage environmental factors exert a large influence on plant development. Growth and development of cacao are highly dependent on temperature, which mainly affects vegetative growth, flowering and fruit development. Soil flooding decreases leaf area, stomatal conductance and photosynthetic rates in addition to inducing formation of lenticels and adventitious roots. For most genotypes drought resistance is associated with osmotic adjustment. Cacao produces caulescent flowers, which begin dehiscing in late afternoon and are completely open at the beginning of the following morning releasing pollen to a receptive stigma. Non pollinated flowers abscise 24-36 h after anthesis. The percentage of flowers setting pods is in the range 0.5 -5%. The most important parameters determinants of yield are related to: (i) light interception, photosynthesis and capacity of photoassimilate distribution, (ii) maintenance respiration and (iii) pod morphology and seed fermentation, events that can be modified by abiotic factors. Cacao is a shade tolerant species, in which appropriate shading leads to relatively high photosynthetic rates, growth and seed yield. However, heavy shade reduces seed yield and increases incidence of diseases; in fact, cacao yields and light interception are tightly related when nutrient availability is not limiting. High production of non-shaded cacao requires high inputs in protection and nutrition of the crop. Annual radiation and rainfall during the dry season explains 70% of the variations in annual seed yields. Key words: root growth, flowering, pod set, flushing, mineral nutrition Ecofisiologia do cacaueiro: O cacau, um dos mais importantes cultivos perenes no mundo, é quase exclusivamente explorado para a fabricação de chocolate. A maioria das variedades de cacau pertence a três grupos: Criollo, Forasteiro e Trinitário, que variam de acordo com a morfologia, genética e origem geográfica. É cultivado sob sombra de árvores de floresta ou como monocultivo sem sombra. As plântulas inicialmente mostram um crescimento ortotrópico com emissão de folhas relativamente independente do clima. A fase de maturidade inicia-se com a emissão de ramos plagiotrópicos que formam a copa. Nesse estádio, fatores ambientes exercem grande influência no desenvolvimento da planta. O crescimento e o desenvolvimento do cacaueiro são dependentes da temperatura, que afeta principalmente o crescimento vegetativo, florescimento e desenvolvimento do fruto. O alagamento do solo diminui a área fol...

Floral Phenology of Upper Amazon Cocoa Trees: Implications for Reproduction and Productivity of Cocoa

“…World cocoa production increased at a rate of 2.2 percent a year, from 1998 to 2010 culminating in a production level of 3.7 million tons over the period [4]. Studies in other parts of the world suggest that the yield of cocoa is related to the floral phenology of the trees ( [5,6]). Clarke [7] reported that a good understanding of the floral phenology of tree crops provides significant insights into the functional attributes of growth and reproduction of the trees.…”

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

“…However, at the end of the receptivity period, 50% to 75% of the flowers are unpollinated and drop from the tree [11,12]. Finally, only 2% of the flowers produce mature fruit [13][14][15] due to fruit abortion [16][17][18]. More recently, it has been reported that the number of pollinated and fertilized flowers that progress to fruit is, on average, three out of 1000 flowers [19].…”

“…Appraisals on the mechanism of self-incompatibility in cocoa indicated that incompatible pollination did not inhibit pollen germination or pollen tube evolution [25]; compatible and incompatible pollination resulted in similar pollen tube growth rates [25,26]. As such, Theobroma symbolizes a classic illustration of an ovarian auto-incompatibility method, to a certain extent different from most plant incompatibility methods in nature [18,27].…”

Genetic mapping of Theobroma cacao (Malvaceae) seedlings of the Parinari series, carriers of the lethal gene Luteus-Pa

“…This tree species, under natural conditions, may grow from 20 to 25 m in height (Lachenaud et al, 1997). Under cultivation, it normally is smaller, reaching 6 m. This species is native to South America (Motamayor et al, 2002); populations can be found in the Amazon and Guiana (Almeida and Valle, 2007). Cacao grows in tropical areas of the Central and South Americas, Asia and Africa (Marita et al, 2001).…”

“…The fruits of T. cacao are commercially explored for the production of seeds destined to the preparation of cocoa derivatives and sub-products, mainly in its most popular form, chocolate. It may also be manufactured as cosmetics, refined beverages, jellies, ice creams, and juices (Almeida and Valle, 2007).…”