Effects of Trichoderma asperellum on Germination Indexes and Seedling Parameters of Lettuce Cultivars.

The aim of this study was to analyze the effects of Trichoderma asperellum on germination indexes and seedling parameters of lettuce cultivars. The trial was arranged in a completely randomized design with three cultivars (Cerbiata, Crespa Grand Rapids, and Mimosa), and two seed-treatment products (quality and organic) containing strain URM 5911 of Trichoderma asperellum plus a control group (untreated), with four repetitions. After seven days, six seedling characters were measured (shoot length, radicle length, total length, shoot diameter, radicle diameter, and seedling dry matter) and eight germination indexes were calculated (germination, first count, mean germination time, germination speed index, coefficient of velocity of germination, mean germination rate, Timson's germination index, and germination rate index). In general, regarding the germination indexes, the effect of the genotype factor predominated over the Trichoderma factor. The seedling characters showed significance for genotype × Trichoderma interaction for shoot length, shoot diameter, radicle diameter, and seedling dry matter. Such results demonstrate that the effects of Trichoderma asperellum on lettuce seedlings variate according to the cultivar used.