title: Diallel Analysis and Growth Parameters as Selection Tools for Drought Tolerance in Young Theobroma cacao Plants.
abstract: This study aimed to estimate the combining ability, of T. cacao genotypes preselected for drought tolerance through diallel crosses. The experiment was conducted under greenhouse conditions at the Cacao Research Center (CEPEC), Ilhéus, Bahia, Brazil, in a completely randomized block design, in an experimental arrangement 21 x 2 [21 complete diallel crosses and two water regimes (control and stressed)]. In the control, soil moisture was kept close to field capacity, with predawn leaf water potential (ΨWL) ranging from -0.1 to -0.5 MPa. In the drought regime, the soil moisture was reduced gradually by decreasing the amount of water application until ΨWL reached -2.0 to -2.5 MPa. Significant differences (p < 0.05) were observed for most morphological attributes analyzed regarding progenies, water regime and their interactions. The results of the joint diallel analysis revealed significant effects between general combining ability (GCA) x water regimes and between specific combining ability (SCA) x water regimes. The SCA 6 genetic material showed high general combining ability for growth variables regardless of the water regime. In general, the water deficit influenced the production of biomass in most of the evaluated T. cacao crosses, except for SCA-6 x IMC-67, Catongo x SCA, MOC-01 x Catongo, Catongo x IMC-67 and RB-40 x Catongo. Multivariate analysis showed that stem diameter (CD), total leaf area (TLA), leaf dry biomass (LDB), stem dry biomass (SDB), root dry biomass (RDB), total dry biomass (TDB), root length (RL), root volume (RV), root diameter (RD) <1 mm and 1 <(RD) <2 mm were the most important growth parameters in the separation of T. cacao genotypes in to tolerant and intolerant to soil water deficit.
authors: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, BA, Brasil.
authors: Emerson Alves
authors: EA
authors: Dos Santos
authors: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, BA, Brasil.
authors: Alex-Alan Furtado de
authors: AA
authors: Almeida
authors: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, BA, Brasil.
authors: Dario
authors: D
authors: Ahnert
authors: Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado, km 16, 45662-900, Ilhéus, BA, Brasil.
authors: Marcia Christina da Silva
authors: MC
authors: Branco
authors: Centro de Pesquisas do Cacau, Comissão Executiva do Plano da Lavoura Cacaueira (CEPEC/CEPLAC), Rod. Jorge Amado, km 22, 45650-000, Ilhéus, BA, Brasil.
authors: Raúl René
authors: RR
authors: Valle
authors: United States Department of Agriculture, Agricultural Research Service, Beltsville, MD, 20705-2350, United States of America.
authors: Virupax C
authors: VC
authors: Baligar
mesh_terms: D000483:Alleles; D002099:Cacao / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D055864:Droughts; D005838:Genotype; D006824:Hybridization, Genetic; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil