Tropical and Subtropical Agroecosystems

Background: Mexico is the seventh largest producer of jamaica in the world, Guerrero represents the entity with the largest area planted and produces >60% of the country's jamaica. The crop has numerous phytosanitary limitations, among which the chalice staining associated with a fungal complex stands out. The main damage occurs in flowering, reporting losses of 50 to 100% in areas without adequate phytosanitary management. The use of strains of Trichoderma spp. with antagonistic capacity, it represents a viable ecological alternative for the ecological management of the disease. Objective: to identify native strains of Trichoderma spp. and to evaluate its antagonistic capacity in vitro on important phytopathogenic fungi in the cultivation of hibiscus. Methodology: the research was developed in the 2018-2019 cycle in the Microbiology Laboratory of the Faculty of Agricultural and Environmental Sciences of University of Guerrero, Iguala, Guerrero. Systematic soil samplings were carried out in jamaica producing areas in Tecoanapa, Guerrero. The isolates were obtained by serial decimal dilutions and consecutive re-isolates until obtaining pure monosporic colonies. The isolates generated were identified morphologically and molecularly. The antagonistic capacity in vitro of each Trichoderma isolate was evaluated against purified monosporic strains of Phytophthora parasitica, Fusarium oxysporum, Corynespora cassicola and Coniella diplodiella. A completely randomized design was established with four repetitions per interaction, an analysis of variances and multiple comparison of means (Tukey, p <0.05) of the variables was performed: percentage of radial growth inhibition (PICR), days until first contact between hyphae (DCH) and area of intersection. Four isolates of Trichoderma spp. with particular morphological and growth characteristics. Results: with the help of the keys of Barnett and Hunter (1998) and Samuels (2006), and the sequences resulting from the molecular tests, it was possible to identify with 99% similarity to T. virens and T. longibrachiatum as Trichoderma species dominant in soils of jamaica producing areas of Guerrero. The results indicated that all the isolates significantly reduced the size of the colonies of the phytopathogens; the Tl4 isolates consistently presented the highest PICRs (75-95%); Phytophthora parasitica was the organism for the most part, and Coniella diplodiella presented the greatest resistance to invasion by antagonist agents. Isolate Tl4 was identified as the one that most inhibited the development of all pathogenic agents (89.25%). In dual confrontations, the hyphae of both microorganisms made contact at 3.25 days after sowing on average. Isolate Tl4 (T. longibrachiatum) was identified as the one with the highest levels of interaction zone and based on the linear regression analysis and Pearson's correlation coefficient, a wide relationship between the zone area of interaction and the percentage of inhibition of the control agents. Implications: It is proposed to continue the study in the field phase, incorporating what was obtained in an integrated pest management (IPM) system. Conclusions: these results contribute to the agronomic management of jamaica in the region as a precedent in the search for alternatives for managing diseases with low environmental impact, also contributing to the determination of the etiology of the disease.

isolate; biological control; dual culture; disease; Hibiscus sabdariffa; Trichoderma spp.