Efficiency of Trichoderma harzianum and Trichoderma asperellum on Phytophthora palmivora control in vitro and in detached stems of peach palm

Abstract

Stem base rot, caused by Phytophthora palmivora, is the most important disease affecting peach palm. The present study aimed to develop a method for inoculating P. palmivora and Trichoderma spp. into detached peach palm stems and evaluating the efficacy of Trichoderma spp. on P. palmivora control both in vitro and in detached stems. The aggressiveness of P. palmivora and the colonization ability of Trichoderma spp. were investigated, as well as the preventive and curative effects of Trichoderma spp. against P. palmivora in detached stems. Additionally, the inhibitory effects of Trichoderma non-volatile metabolites on P. palmivora mycelial growth were assessed. Trichoderma harzianum TH2 and TH1, and T. asperellum TA1 and TA2 significantly reduced P. palmivora mycelial growth by 94.4% and 91.7%, and 61.8% and 80.9%, respectively. All four Trichoderma isolates colonized the internal tissues of the detached peach palm stem, exhibiting a growth rate of 1.42 cm/day and producing light-colored tissues, firm internal consistency and absence of soft tissues. When applied 24 and 48 hours before P. palmivora inoculation, T. harzianum TH2 and T. asperellum TA1 provided 40% and 38.7%, and 24.3% and 41.9% disease control, respectively. However, curative application was less effective than preventive treatments. Trichoderma harzianum TH2 colonized detached stems more rapidly than T. asperellum TA1. In stems treated with T. harzianum TH2 48 hours prior to Phytophthora inoculation, pathogen colonization was completely inhibited in all stem regions. The inoculation method employed in the current study proved effective for stem base rot investigation in detached peach palm stem. The present paper provides the first evidence of Trichoderma spp. penetration and endophytic colonization in peach palm tissues, besides pathogen control by this antagonist.