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Title: Molecular, physiological and biochemical responses of Theobroma cacao L. genotypes to drought

Author
item SANTOSDOS, I - Universidade Estadual De Santa Cruz
item ANHERT, D - Universidade Estadual De Santa Cruz
item CONCEICAODA, A - Universidade Estadual De Santa Cruz
item PIROVANI, C - Universidade Estadual De Santa Cruz
item PIRES, J - Comissao Executiva Do Plano Da Lavoura Cacueira (CEPLAC)
item VALLE, R - Comissao Executiva Do Plano Da Lavoura Cacueira (CEPLAC)
item Baligar, Virupax
item ALMEIDADE, F - Universidade Estadual De Santa Cruz

Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2014
Publication Date: 12/26/2014
Publication URL: http://handle.nal.usda.gov/10113/63027
Citation: Santosdos, I.C., Anhert, D., Conceicaoda, A.S., Pirovani, C.P., Pires, J.L., Valle, R.R., Baligar, V.C., Almeidade, F.A. 2014. Molecular, physiological and biochemical responses of Theobroma cacao L. genotypes to drought. PLoS One. 9(12):e115746. DOI:10.1371/journal.pone.0115746.

Interpretive Summary: Frequent occurrence of long duration drought in cacao growing regions of South and Central America is severely affecting the yield potentials and health of the cacao trees. Planting of drought tolerant accessions could help to alleviate the situation. This research reports the molecular, physiological and biochemical responses of cacao genotypes to soil water stress. Methods developed in this research will be useful in identification of drought tolerance in cacao genotypes. Information gained from this research will be useful to plant physiologist in identification of drought tolerant cacao genotypes. Plant breeders could use this information in selection of drought tolerant crossing materials to breed drought tolerant cacao cultivars.

Technical Abstract: Six months-old seminal plants of 36 cacao genotypes with distinct morphological, genetical and geographical characteristics were subjected to two water regimes (control and drought) to assess, under greenhouse conditions, the effects of water deficit on growth, chemical composition and oxidative stress. In the control, soil moisture was maintained near field capacity with leaf water potentials ('WL) ranging from -0.1 to -0.5 MPa. In the drought, the soil moisture was reduced gradually by reducing the water volume applied until 'WL reach values between -2.0 to -2.5 MPa. The dehydration period varied from 40 to 60 days, depending on genotype. The most genotypes showed significant reductions in: dry biomass for all vegetative organs; total leaf area per plant (TLAP); leaves number per plant; net assimilation rate; relative growth rate (RGR); root volume and area of root system (ARS); stem diameter, and content of mineral macro and micronutrients at the leaf level. The genotypes PS-1319, MO-20 and MA-15 showed significant increases in the activity of guaiacol peroxidase, showing a more efficient antioxidant metabolism, whereas for the activity of polyphenol oxidase the highest variations were observed in CA-3, EET-103 and AMAZON-15.1. From principal components analysis, we found greater contribution of variables TLAP, RGR, ARS, shoot biomass, total dry biomass, leaf contents of N, Ca, and Mg in the formation of contrasting groups in relation to drought tolerance. From the results of these analyzes were selected six genotypes contrasting in tolerance to soil water deficit [CC-40, C. SUL-4 e SIC-2 (non-tolerant) and MA-15, MO-20, PA-13 (tolerant)] for assessment of expression of NCED5, PP2C, psbA and psbO. Increased expression of NCED5, PP2C, psbA and psbO genes was found for non-tolerant genotypes, while in tolerant genotypes there was repression, except for PA-13 that showed increased expression of psbA. We concluded that the cacao EET-53, ICS-9, MA-15, MA-14, MO-20, OC-77, PA-13, PS-1319, PA-150, RB-39 and SIAL-169 were the most tolerant genotypes to soil water stress; EET-103, EQX-107, ICS-98, IMC-27, SCA-6, SPA-5 and TSH-1188 proved to be moderately tolerant, while CA-1, CAB-139, CC-40, C. SUL-4, IMC-76, MOC-2, RB-48, SIC-2, SIC-17and TSA-792 were the least tolerant.