Estudo genealógico e variáveis biométricas, bioquímicas e agroindustriais de genótipos de cana-de-açúcar sob diferentes condições hídricas

Abstract

Water deficit is one of the main environmental factors that significantly limits agricultural production. The state of Paraíba is located in the brasilian northeast region and has expressive agricultural areas, where sugarcane (Saccharum spp.) has been exploited under the influence of different edaphoclimatic conditions, which sometimes triggers the water deficit. Plants have several adaptation strategies to low water availability that mitigate the effects of stress by activating defense mechanisms through enzymes of the antioxidant system. Knowledge of the relationship between individuals is indispensable for breeding programs, especially helping to understand the behavioral similarities between genotypes. Performance evaluations related to the biometric, biochemical and agroindustrial aspects of a set of genotypes are of fundamental importance to determine the feasibility study of its use in commercial scale considering the different production and management environments. These behavioral differences can be further verified when substantially justified and correlated through biochemical analysis by determining enzyme antioxidant system activity, catalase (CAT) and ascorbate peroxidase (APX) activity, in addition to concentrations and activities of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and lipid peroxidation products, malondialdehyde (MDA). The objective of this thesis was to estimate the agroindustrial performances of a group of sugarcane genotypes through biometric and biochemical variables in the stages of crop development, in view of different water conditions in Paraíba coastal areas, using two simultaneous experiments and differentiating them between irrigated environment, meeting 50% of crop water demand and dry environment, without irrigation. Field work was conducted at Miriri Alimentos e Bioenergia, Santa Rita, Paraíba, during the 2015/2016 agricultural year. Ten sugarcane genotypes were used, using a randomized block design with three replications. Through the analysis of the main components (ACP) and groupings (AA) for the analyzed variables, groups I, II, III and IV were originated for the irrigated environment and groups I, II and III for the dry environment. Significant genetic relationship coefficients (COP) were verified between the RB931011, RB992587 and RB867515 genotypes, probably due to the participation of common parents in the genealogical constitution of those involved. H2O2 signaling stimulated the activation of the antioxidant enzymatic system, contributing to tolerance to water deficit. Agroindustrial incomes for the irrigated environment ranged from 13.14 to 16.09 TAH, with emphasis on Group II (RB92579), with the best agroindustrial incomes. In the dry environment the highest sugar production per hectare was presented by group III and II, with 10.98 and 10.91 TAH, respectively.