Abstract
Drought is worldwide considered one of the most limiting factors of Theobroma cacao production, which can be intensified by global climate changes. In this study, we aimed to investigate the phenotypic correlation among morphological characteristics of cacao progenies submitted to irrigation and drought conditions and their partitions into direct and indirect effects. Path analysis with phenotypic plasticity index was used as criteria for estimation of basic and explanatory variables. The experiment was conducted in a greenhouse at the Cacao Research Center (CEPEC), Ilhéus, Bahia, Brazil, in a randomized block 21 x 2 factorial arrangement [21 cacao progenies obtained from complete diallel crosses and two water regimes (control and drought)] and six replications. In general, drought conditions influenced biomass production in most progenies, causing significant reductions in total leaf area, leaf number, leaf biomass, fine-roots length (diameter <1 mm), root volume and root area for considered drought intolerant. All progenies showed alterations in growth due to drought. Phenotypic plasticity was most strongly pronounced in root volume. Stem and root diameters, as well as stem dry biomass were the growth variables with the greatest direct effects on root volume under drought conditions, these characters being indicated in screening of cacao progenies drought tolerant.
Highlights
Climate oscillations, especially those related to quantity and distribution of rainfall, have been a major cause of variation in cacao (Theobroma cacao L.) productivity [1, 2]
Regarding plant height (H) and stem diameter (SD), under drought conditions, only progenies originated from MOC-01 x TSH-1188 (11) and PUCALA x Catongo (14) crosses showed significant reductions of their averages, with values below the overall average
Reduction in the leaf number (LN) and of total leaf area (TLA) was observed in progenies subjected to soil water limitation
Summary
Especially those related to quantity and distribution of rainfall, have been a major cause of variation in cacao (Theobroma cacao L.) productivity [1, 2]. Cacao is considered a very sensitive to drought species and can be greatly affected by climate changes and water availability [3, 4]. Few studies have been conducted to identify cacao adaptation strategies to water deficit [5, 6, 2] and eventual use of water under drought conditions [7]. Some authors have described morphological alterations as indicators for early selection of drought tolerant genotypes [8, 9, 10] as they have a direct impact patterns of plant growth and development [11, 12].
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