Efeitos da adubação foliar com silício na resistência do cacaueiro (Theobroma cacao L.) à vassoura-de-bruxa (Moniliophthora perniciosa (Stahel) Aime & Phillips-Mora)

Abstract

The economic interest of cocoa (Theobroma cacao) isbecause, mainly, of using itsseeds to produce cocoa butter and chocolate. However, this business has encountered a crisis caused, mainly, by witches’ broom, caused by the fungal Moniliophthora perniciosa, that could induce losses of until 90% of the production,beenconsidered one of the most destructive disease of cocoa. One management alternative of diseases that has been used it’sthe inducedresistance, that could be obtained by treatments using products with silicon. Therefore, we verified the efficiency of different dose of silicon in protection against the disease witches’ broom in the clonal Catongo of cocoa inoculated with M.perniciosaby analysis of morpho-physiological and biochemical characteristics. The experimental design wasinrandomized blocks (DBC), with four replications in a factorial 2 x 4, consistingof two factors of inoculation (inoculated and non-inoculated) and four dosesof silicon (0 mg mL-1 ; 0,5 mg mL-1; 1,0 mg mL-1e 2,0 mg mL-1)with the product AgriSil (98% ofSiO2), resulting in 32 plots with 10 plants each,totaling 320 plants. The results obtained were submitted to analysis of variance and regression. Evaluations about enzyme analysis, gas exchange, foliar silicon content and stomatal density were conducted.Inoculated plants presentedincreased of photosynthesis and of chitinase and polyphenoloxidase activities with application of growing dosesof Si. Already stomatal density showed maxim in the dose 0,79 mg/mL of Si, while the foliar silicon content was obtained in the dose 0,7 mg/mL of Si. The results suggestthat growing doses of silicon demonstrated beneficial to ease the effects caused by M. perniciosain cocoa seedlings