Abstract Due mainly to the taste and appearance, the strawberry stands out in relation to the other fruits. and for the presence of antioxidant compounds. However, little attention has been devoted to the impact of abiotic stresses on the quality of strawberry and its agronomic performance. In the present study, we evaluated the effect of two levels of DS (L1 - 70% and L2 - 50% of crop evapotranspiration) on the quality of strawberry fruit and on some agronomic and physiological variables. There was a dose-dependent reduction in the evaluated agronomic variables in the DS plants, and the content of some minerals in the fruit and leaves was modified. The activities of the oxidative enzymes were higher in the fruit of L2 treatment, and the content of sucrose, reduced sugars, phenolic compounds and the total antioxidant activity were increased in the fruit from L2 treatment; while those of anthocyanins and L-ascorbic acid were reduced in L1 and L2 treatments, respectively. The phenylalanine ammonia lyase gene was upregulated and other genes related to phenylpropanoid and ascorbate pathways were downregulated in the fruit of stressed plants. Thus, our results indicate that DS seems to be a promising strategy to improve the content of antioxidant compounds and sugars.

O objetivo deste trabalho foi avaliar a influência de doses crescentes de nitrogênio sobre o crescimento vegetativo, a produção e os níveis foliares de nutrientes da amoreira-preta (Rubus spp.). O experimento foi realizado com as cultivares Tupy e Xavante, na região sul do Rio Grande do Sul, de 2008 a 2012. Os tratamentos consistiram da aplicação de cinco doses de N (0,0, 7,5, 15,0, 22,5 e 30,0 g por planta), aplicados na adubação de manutenção, após a implantação da lavoura. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições. Foram avaliadas as variáveis: densidade de hastes, massa de matéria seca de poda, índice de clorofila, produção por planta, número de frutos e composição nutricional das folhas (N, K, Ca, Mg e S). A adubação nitrogenada influenciou significativamente o crescimento vegetativo, a produção e a composição nutricional das folhas. As cultivares apresentaram resposta distinta à aplicação de N, em que 'Tupy' foi mais exigente que 'Xavante'. As doses de N atualmente recomendadas para a cultura da amoreira-preta são satisfatórias para a máxima produção de 'Xavante', mas insuficientes para 'Tupy'.

The objective of this work was to evaluate the influence of increasing doses of nitrogen on vegetative growth, yield and leaf nutrient levels of blackberry (Rubus spp.). The experiment was carried out with the cultivars Tupy and Xavante, in southern state of Rio Grande do Sul, Brazil, from 2008 to 2012. It was used a randomized block design, with four replicates. Treatments consisted of five N doses (0.0, 7.5, 15.0, 22.5 and 30.0 g per plant), applied as maintenance fertilization after the crop establishment. The following variables were evaluated: cane density, pruned dry mass, chlorophyll index, yield, number of fruit, and nutritional composition of leaves for N, K, Ca, Mg and S. The fertilization treatments significantly influenced the vegetative growth, yield, and nutrient composition of leaves. The cultivars responded differently to nitrogen application, with 'Tupy' being more demanding than 'Xavante'. The currently recommended nitrogen rate for blackberry cultivation is suitable for maximum yield of 'Xavante', but it is not sufficient for 'Tupy'.