Efeito de Cercospora kikuchii em sementes de soja com tratamentos biológicos, fitorregulador e químico

Abstract

The use of quality seeds is one of the key factors for the success of soybean (Glycine max (L.) Merr) cultivation, although there are problems with contamination with pathogens that have the potential to cause diseases in plants, such as purple spot. The best results in controlling this pathogen are achieved via seed treatment. Therefore, the objective was to evaluate the physiological quality of soybean seeds and the development of seedlings and plants using two isolates of Trichoderma harzianum, a phytoregulator and a fungicide. The experiment was carried out in two stages, the first consisted of a completely randomized design (DIC) with a 3x5 bifactorial arrangement, with four replications, the first factor was seeds with purple spot symptoms, seeds without symptoms and artificially inoculated, the second factor was seed treatments with the products Trichodermil® (Trichoderma harzianum strain ESALQ-1306), Green Control® (Trichoderma harzianum strain SIMBI T5), Stimulate® (Cinetina+GA3+AIB), Fungicide (Vitavax® Thiram) and control with water. The variables analyzed were: germination speed index (IVG), germination, length and dry mass of the root system and aerial part of the seedlings. The second stage consisted of evaluating the latent infection of the disease, with the factors being seed types and seed treatments the same as in the previous trial, in this case, with five replications. For this, the seeds were sown in plastic cups placed on a shelf with UV light until they reached the V2 stage, in a controlled environment with air conditioning at 25°C. After this period, a cut was made at the neck of the plants to separate the root system and aerial part, which was placed in gerbox boxes in BOD and the aerial and root parts were dried in an oven. The variables analyzed were: observation of latent infection in the plant neck and the dry mass of the root and aerial system. The data were subjected to analysis of variance and the means were compared using the Tukey test at 5% probability using the SISVAR software. It was possible to conclude that seeds with natural symptoms of spot on the seed coat did not have any impairment in their development and stood out in relation to seeds without symptoms of the disease in the variables analyzed, on the other hand, artificially inoculated seeds were the most affected. The fungus C. kikuchii did not harm germination, except in artificially inoculated seeds. Biocontrol with T. harzianum and the phytoregulator did not promote a significant increase in the length and dry mass of seedling and plants in relation to the control. Regarding latent infection, there was colonization of the root by T. harzianum, however, the treatments did not inhibit the development of C. kikuchii.