Nitrogen fertilization in the contents of secondary compounds in cassava cultivars

Abstract

The production of chemical substances is a strategy of plants to defend against the attack of pest insects. The synthesis of secondary compounds in plants is influenced by genotype and cultural management, such as the use of nitrogen fertilizers. Thus, the objective of this work is to evaluate the effect of doses of nitrogen fertilizer over time on the production of secondary compounds in two industrial cassava cultivars. The experiment was carried out in a greenhouse (25 ± 5 °C) of Embrapa Soybean in Londrina, Paraná, with the cultivation of potted plants (4l) in a 2 × 4 × 3 factorial scheme, with five replications. Two genotypes of industrial cassava (‘Baianinha’ and ‘Caiuá’) and four different nitrogen doses (0, 30, 60, and 90 kg ha-1) were used, with sampling at 15, 30, and 45 d after fertilization. Nitrogen fertilization was performed 50 d after sprouting. In the apical leaves, the levels of rutin, caffeic, p-coumaric and ferulic acids were evaluated in a high performance liquid chromatograph (HPLC). Exploratory analyses were performed on the data variables to verify the assumptions for analysis of variance (ANOVA), such as the independence and normality of errors, homogeneity of treatment variances and non-additivity of the model (they were submitted to analysis of homogeneity and normality, respectively. After these tests, ANOVA and Tukey’s test (p ? 0.05) were performed. For the quantitative data concerning the N rates, regression study analyzes were performed. The Caiuá cultivar was found to have a higher ferulic acid content. The caffeic acid content decreased over time after the application of N in both cultivars. The rutin content in both cultivars did not increase with an increase in nitrogen dose. At a dose of 90 kg ha-1, both cultivars presented a lower p-coumaric acid content after 30 d.