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Title: Physiological and biochemical responses of Theobroma cacao L. genotypes submitted to flooding

item BERTOLDE, F - University Of Santa Cruz - Brazil
item ALMEIDA, A-A - University Of Santa Cruz - Brazil
item PIROVANI, C - University Of Santa Cruz - Brazil
item AHNERT, D - University Of Santa Cruz - Brazil
item Baligar, Virupax
item VALLE, R - University Of Santa Cruz - Brazil

Submitted to: Photosynthetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2012
Publication Date: 6/25/2012
Citation: Bertolde, F.Z., Almeida, A.F., Pirovani, C.P., Ahnert, D., Baligar, V.C., Valle, R.R. 2012. Physiological and biochemical responses of Theobroma cacao L. genotypes submitted to flooding. Photosynthetica. 50(3):447-457.

Interpretive Summary: In cacao growing regions of South America, soil flooding due to frequent high intensity rains is causing substantial damage to cacao sustainability. Soil flooding is also serous growth limiting factors for successful production of cacao seedlings in nursery. Identification and use of flood tolerant cacao genotypes could reduce the damage caused by flooding. In this paper we report the effects of flooding on plant traits such as growth and physiological processes. Plant traits identified in this research are useful in selection of flood tolerant cacao genotypes. Flood tolerant genotypes will be excellent plant materials for breeding of flood tolerant cacao cultivars. Findings of this study will be helpful to farmers, to improve cacao production in lowland areas where flooding is a problem. The information generated will be of use to scientists and commercial cacao seedling growers to manage irrigation more efficiently in the nursery and in cacao plantations.

Technical Abstract: Flooding is common in lowlands and areas with high rainfall or excessive irrigation. One major effect of this stress is the deprivation of O2 in the root zone, which affects several biochemical and morphophysiological plants processes. This study aimed to elucidate biochemical and physiological characteristics associated with tolerance to O2 deficiency in two clonal cacao genotypes. The experiment was conducted under greenhouse conditions with two flood tolerant contrasting clones (TSA-792 – tolerant and TSH-774 – susceptible). Leaf gas exchanges, chlorophyll fluorescence emission, chemical composition and oxidative stress were assessed during 40 days on control and flooded plants. Flooding induced a decrease in net photosynthesis, stomatal conductance and transpiration on both genotypes. Under flooding, the flood-susceptible clone showed changes in fluorescence emission, reduction in chlorophyll content and increased activity of peroxidase and polyphenol oxidase. Flooding also caused changes in macro and micronutrients, total soluble sugars and starch concentrations in different plant organs of both genotypes. PN x PAR results did not permit to differentiate genotypes for tolerance to flooding as both genotypes curves showed similar behavior when waterlogged. However, it was observed that the flood-susceptible clone under flooding showed (i) non-stomatal limitations of photosynthesis since decreases in Fv/Fm values indicate possible damage to the PSII light-harvesting complex; (ii) oxidative stress; (iii) increases in the incidence of leaf chlorosis; (iv) decreases in root carbohydrate levels resulting in death of several plants after 30 days of flooding.