title: Molecular, physiological and biochemical responses of Theobroma cacao L. genotypes to soil water deficit.
abstract: Six months-old seminal plants of 36 cacao genotypes grown under greenhouse conditions were subjected to two soil water regimes (control and drought) to assess, 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 (ΨWL) ranging from -0.1 to -0.5 MPa. In the drought treatment, the soil moisture was reduced gradually by withholding additional water until ΨWL reached values of between -2.0 to -2.5 MPa. The tolerant genotypes PS-1319, MO-20 and MA-15 recorded significant increases in guaiacol peroxidase activity reflecting a more efficient antioxidant metabolism. In relation to drought tolerance, the most important variables in the distinguishing contrasting groups were: total leaf area per plant; leaf, stem and total dry biomass; relative growth rate; plant shoot biomass and leaf content of N, Ca, and Mg. From the results of these analyses, six genotypes were selected with contrasting characteristics for tolerance to soil water deficit [CC-40, C. SUL-4 and SIC-2 (non-tolerant) and MA-15, MO-20, and PA-13 (tolerant)] for further assessment of the expression of genes NCED5, PP2C, psbA and psbO to water deficit. Increased expression of NCED5, PP2C, psbA and psbO genes were found for non-tolerant genotypes, while in the majority of tolerant genotypes there was repression of these genes, with the exception of PA-13 that showed an increased expression of psbA. Mutivariate analysis showed that growth variables, leaf and total dry biomass, relative growth rate as well as Mg content of the leaves were the most important factor in the classification of the genotypes as tolerant, moderately tolerant and sensitive to water deficit. Therefore these variables are reliable plant traits in the selection of plants tolerant to drought.
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, Bahia, Brazil.
authors.forename: Ivanildes C Dos
authors.initials: IC
authors.lastname: Santos
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, Bahia, Brazil.
authors.forename: Alex-Alan Furtado de
authors.initials: AA
authors.lastname: Almeida
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, Bahia, Brazil.
authors.forename: Dário
authors.initials: D
authors.lastname: Anhert
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, Bahia, Brazil.
authors.forename: Alessandro S da
authors.initials: AS
authors.lastname: Conceição
authors.affiliation: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, Bahia, Brazil.
authors.forename: Carlos P
authors.initials: CP
authors.lastname: Pirovani
authors.affiliation: Centro de Pesquisas do Cacau, Comissão Executiva do Plano da Lavoura Cacaueira (CEPEC/CEPLAC). Rod. Jorge Amado, km 22, 45650-000, Ilhéus, Bahia, Brazil.
authors.forename: José L
authors.initials: JL
authors.lastname: Pires
authors.affiliation: Centro de Pesquisas do Cacau, Comissão Executiva do Plano da Lavoura Cacaueira (CEPEC/CEPLAC). Rod. Jorge Amado, km 22, 45650-000, Ilhéus, Bahia, Brazil.
authors.forename: Raúl René
authors.initials: RR
authors.lastname: Valle
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, Beltsville, Maryland, 20705-2350, United States of America.
authors.forename: Virupax C
authors.initials: VC
authors.lastname: Baligar
mesh_terms: D018533:Biomass; D002099:Cacao / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D008903:Minerals / Q000378:metabolism; D018384:Oxidative Stress; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D011891:Rain; D012987:Soil / Q000737:chemistry*; D014867:Water / Q000032:analysis*
chemical_list: D008903:Minerals; D010940:Plant Proteins; D012987:Soil; D014867:Water