Plants from the Caatinga biome harbor endophytic Trichoderma species active in the biocontrol of pineapple fusariosis

Abstract

Fusariosis incited by Fusarium guttiforme is the main limiting factor for pineapple cultivation in Brazil and other South American countries. Disease management based on biological agents is desired because resistant varieties are not yet widespread through the producing areas and there is no information on the durability of the resistance. Fungicide application has led to the selection of resistant populations of the fungus in the field, besides the negative effects of these chemicals on human health and the environment. Because pineapple cultivation is expanding in the Caatinga biome, this study is an attempt to employ Trichoderma species isolated as endophytes of plants from this region, which is characterized by low precipitation and high temperatures. A total of 109 isolates of Trichoderma were obtained from the sapwood of four plant species: Ananas comosus var. bracteatus (Bromeliaceae), Astronium fraxinifolium (Anacardiaceae), Bowdichia virgilioides (Fabaceae) and Caesalpinia pyramidalis (Fabaceae). The 109 isolates were clustered in 11 BOX groups and one isolate of each group was identified by sequencing the ITS and tef-1α regions. The isolates were subjected to a series of experiments in vitro in Petri dishes and pineapple stalk discs, and in vivo in a greenhouse and in the field. The number of isolates showing ability to inhibit the pathogen and control the disease at levels higher than 80% was 26 in Petri plates, 21 in stalk discs, and 3 in the greenhouse and field assays. These three isolates were consistently able to decrease disease severity by 68–84% across two field experiments.