The effect of short-term vs. long-term soil moisture stress on the physiological response of three cocoa ( Theobroma cac
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ORIGINAL PAPER
The effect of short-term vs. long-term soil moisture stress on the physiological response of three cocoa (Theobroma cacao L.) cultivars Wiebke Niether1 · Alexandra Glawe2 · Katharina Pfohl3 · Noah Adamtey4 · Monika Schneider4 · Petr Karlovsky3 · Elke Pawelzik2 Received: 29 January 2019 / Accepted: 12 June 2020 © The Author(s) 2020
Abstract Understanding water stress signaling mechanisms and screening for tolerant cocoa cultivars are major challenges when facing prolonged dry and rainy seasons in cocoa-producing areas. While abscisic acid (ABA) and proline are supposed to enhance drought tolerance in cocoa, the role of polyamines remains unclear. The aim of this study was to investigate the biochemical response and phenological adaptation of cocoa (Theobroma cacao) on different soil moisture conditions, with a focus on short-term (20 days) and long-term (89 days) stress conditions, and to compare the performance of three cocoa cultivars. In a split plot design with four blocks, cocoa seedlings of an international high-yielding cultivar (TSH-565) and two locally selected cultivars (IIa-22 and III-06) from the drought-exposed Alto Beni region, Bolivia, were arranged in pots under a roof shelter (cultivar: three levels). The seedlings were exposed to strong (VERY DRY) and moderate (DRY) soil moisture deficits, water logging (WET) and regular irrigation (MOIST) that served as a control (moisture: four levels). We examined the growth performance and the levels of ABA, proline, and polyamines in the leaves. Growth was reduced already at a moderate drought, while severe drought enhanced seedling mortality. Severe drought increased the levels of ABA by 453% and of proline by 935%, inducing a short-term stress response; both compounds were degraded over the long-term period. The polyamine concentration was unrelated to soil moisture. The cocoa cultivars did not differ in their biochemical response to soil moisture stress (proline: p-value = 0.5, ABA: p-value = 0.3), but the local cultivar III-06 showed a stronger height growth increment than the international cultivar TSH-565 (237%, p-value = 0.002) under drought conditions. Keywords Drought · Flooding · Abscisic acid · Polyamines · Water stress
Introduction
Wiebke Niether conducted the experimental trial, analyzed the data and wrote the first draft of the manuscript. Alexandra Glawe and Katharina Pfohl contributed to the measurements and data analyses. Monika Schneider and Noah Adamtey established the experimental design. Petr Karlovsky and Elke Pawelzik supervised the analyses of the samples and the data. All co-authors contributed to the manuscript by detailed reading and revision. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10725-020-00638-9) contains supplementary material, which is available to authorized users. * Wiebke Niether [email protected]‑goettingen.de Extended author information available on the last page of the article
Cocoa (Theobroma cacao L.) is produced in the humid tropics
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