ABSTRACT
Eucalyptus globulus Labill is one of the most planted species in Chile, because of its fast growth and superior pulp qualities. Nevertheless, the incidence of drought and frost damage immediately after planting is frequent. The purpose of this work was to study the effect of drought hardening on frost resistance and on variations in morphological traits that may increase drought resistance at nursery phase in four genotypes of E. globulus Labill. Drought hardening treatments consisted in induced water stress by watering restriction, until pre-dawn stem xylem water potentials (Psi pd) reached -0.2, -1.8 and -2.6 MPa. Two water stress-rewatering cycles were applied during 54 days of hardening. Plant and root biomasses were affected by the interaction of drought hardening and genotypes. The rest of morphological and alometrical traits were affected independently by drought or genotype. Plant height, leaf area, specific leaf area (SLA), stem, and leaf biomasses decreased with drought hardening, while collar diameter was not affected. Genotypes responded differentially to drought hardening in plant height, leaf area, SLA, and stem, and leaf biomasses. Ice nucleation temperature (INT), and freezing temperatures (FRT), and 50 percent freezing damage index of leaves (LT50) were affected by the interaction between drought hardening and genotypes. EG-13, EG-23 and EG-22 genotypes became freezing tolerant with drought hardening (-2.6 MPa). Additionally, EG-14 genotype increased its freezing resistance at -1.8 MPa. Therefore, freezing resistance levels and mechanism depend on genotype and drought hardening treatment. The success in tree breeding by genetic selection should be facilitated by improved understanding of the physiology of stress resistance development and survival during water supply limitations. The knowledge of morphological and freezing resistance dependency on the interaction between genotype and drought hardening may be useful...
Subject(s)
Dehydration , Eucalyptus/analysis , Eucalyptus/antagonists & inhibitors , Plant Roots/anatomy & histology , Plant Roots/genetics , Agricultural Irrigation , Freezing , GenotypeABSTRACT
Objetivou-se, neste estudo, avaliar o grau de associação entre características de importância econômica de uma população de maracujá-amarelo (Passiflora edulis Sims f. flavicarpa Deg.) por meio da estimação dos coeficientes de correlação fenotípica e genético-aditivas. Cento e treze progênies de maracujá-amarelo foram obtidas conforme Delineamento I e avaliadas nas localidades de Viçosa, MG, e Miracema, RJ, em arranjos em três agrupamentos, com delineamentos em blocos ao acaso, com três repetições e três plantas por parcela. A característica número de frutos por planta demonstrou estar associada negativamente com peso, comprimento e largura de frutos, e positivamente com espessura de casca. Além disso, a característica peso de frutos apresentou correlações fenotípicas e genético-aditivas positivas com todas as demais, excluindo-se número de frutos por planta. Assim, o aumento nas dimensões do fruto pode resultar em diminuição da produção em números de frutos, de modo que métodos mais elaborados de seleção no melhoramento podem ser necessários para que se atinja uma população com alta produtividade e boas características comerciais. Por conseguinte, o uso de índices de seleção pode contribuir para obtenção de ganhos simultâneos em características de importância econômica em maracujá-amarelo.
The aim of this research was to evaluate the association among economically important traits of a yellow passion fruit population (Passiflora edulis Sims f. flavicarpa Deg.) through the estimate of the phenotypic and genetic-additive correlations. Hundred thirteen yellow passion fruit progenies were obtained by using nested design and evaluated in two environments, Viçosa, MG, and Miracema, RJ, in Brazil, grouped in three sets in a randomized block design, with three replications and three plants per plot. The trait number of fruits per plant demonstrated to be associated negatively with weight, length and width of fruits, and positively with peel thickness. Moreover, the trait weight of fruits expressed positive values for phenotypic and genetic-additive correlations with others, excluded number of fruits by plant. Thus, the increase in the dimensions of fruit may result in decrease of the production in numbers of fruits, so that elaborated methods of selection may be necessary for a high productivity population and good commercial traits. Consequently, the use of selection indexes can contribute to obtain genetic gain in traits of economical importance in yellow passion fruit.