Native Cadmium-Tolerant Trichoderma Associated with the Rhizosphere of Inga sp. and Quararibea sp. in Amazonian Cocoa Agroecosystems of Peru.

Cadmium (Cd) contamination of Amazonian cocoa soils threatens Theobroma cacao production, and shade-tree rhizospheres may harbour Cd-tolerant fungi useful for bioremediation. Trichoderma associated with Quararibea sp. remain unexplored. We isolated native Trichoderma from rhizospheres of Inga sp. and Quararibea sp. in Bagua (Peru), and evaluated Cd tolerance (25-200 ppm) through growth inhibition percentage (GIP) and IC50 from dose-response models selected via the Akaike Information Criterion (AIC). Of 16 Trichoderma-like isolates, five met stringent multilocus quality criteria: JSRA09 (Quararibea sp.) and JSRA16, JSRA22, JSRA28, JSRA30 (Inga sp.). Independent Maximum Likelihood trees (ITS, tef1, rpb2) assigned JSRA09 to the T. spirale/T. subuliforme clade, JSRA16 to the T. harzianum complex (affinity to T. lentiforme), JSRA22 and JSRA28 to a clade within the T. koningii/T. koningiopsis complex, and JSRA30 to T. afroharzianum. To the best of our knowledge, JSRA09 represents the first Trichoderma report in Quararibea sp. No strain exceeded 35% inhibition at 200 ppm: JSRA09 and JSRA16 were highly tolerant (GIP < 10%), JSRA28 and JSRA30 moderately tolerant, and JSRA22 tolerant. AIC selection yielded linear responses for JSRA09 and JSRA16, log-logistic (LL.4) for JSRA22, JSRA28 and JSRA30. These native strains are candidates for further screening towards microbial consortia for Cd bioremediation.