Voltammetric Determination of Total Phenolic Compounds in Cotton Leaves of Gossypium barbadense and Gossypium hirsutum Challenged with Spodoptera cosmioides (Walker)

A voltammetric method for phenolic compounds determination detected differences between Gossypium hirsutum and Gossypium barbadense , injured or not by caterpillars. G. barbadense seeds collected in Amazon were multiplied and compared to a commercial Brazilian variety ( G. hirsutum ). Plants were conducted in a net protected house for two assays where: i) floral buds were inoculated with boll weevil eggs and ii) leaves were infested with Spodoptera cosmioides (Walker) and leaf phenolic compounds determined by a voltammetric method based on the differential pulse technique and glassy carbon electrode. The proportion of emerging boll weevils was greater in G. hirsutum (0.24) than in G. barbadense (0.14). G. hirsutum non infested older leaves presented a higher amount of total phenolics than the younger leaves. For the infested plants, total phenolic levels were similar in both developmental stages and to the not infested younger leaves. The most intense current peak in the voltammetric profile was at the oxidation potential of 0.5 V for all samples, and more intense for G. hirsutum older leaves. Another less intense current peak at 0.8 V, found at all profiles, was great for G. barbadense attacked by caterpillars. Compounds coincident with these peaks may be related to insect tolerance.