Tolerância à seca e adapatação a solos com camadas coesas de genótipos de citros em estádios jovens de desenvolvimento

Abstract

Identification of citrus genotypes tolerant to stress factors such as water deficiency and mechanical stress is of paramount importance for Brazilian citriculture. Experiments were conducted at Embrapa Mandioca and Fruticultura - Cruz das Almas - BA facilities to evaluate both water deficit tolerance and mechanical stress characteristics in citrus genotypes. For this, an experiment was installed to test the water stress and five other experiments to evaluate the mechanical stress. The evaluation of water deficiency was done in Fitotec (controlled environment: light, temperature and relative humidity), evaluating the effect of two water management (control and water deficit) on 15 genotypes obtained by Embrapa's Citrus Genetic Improvement program Yucca and Fruticultura, potential of use as rootstocks. In the mechanical stress experiments conducted under greenhouse conditions, an artificial cohesive layer methodology with several resistances was evaluated. In two experiments we tested systems of direct sowing {(no-till) and planting of seedlings (conventional planting - PC) under five levels of artificial physical impediment (0.14, 1.04, 1.67, 1.92 and 2.05). In three other experiments the penetration of the root system was evaluated on the following resistances: 0.14; 0.24; 0.31; 0.59; 0.80; 1.05; 1.67; 1.92 and 2.05 MPa. The experimental designs used were in blocks and completely randomized. In the experiments, soil moisture, growth parameters, physiological parameters and root density were determined. Among the evaluated genotypes, those with moderate tolerance (MT) to water stress were TSKC x CTSW 028, 064; LVK x LCR 018, 017. In the evaluation of planting systems under artificial physical impediment, it was found that compacted structures decrease the root system with resistance ≥ 1.67 in both systems of planting. In the evaluation of the root system on the artificial cohesive layer the genotypes that presented the best performance to the mechanical stress, with resistance below 1.67 were: TSKC x (LCR x TR) 059, 073, 040; LVK x LCR 038, 030. The results obtained from these studies have implications for the selection of rootstocks adapted to environments subject to water stress and to soils with cohesive, compacted layers.