Produção e qualidade fisiológica de sementes de alface tratadas com rizobactérias e cultivadas em diferentes substratos

Abstract

Due to intensive management area for the production of vegetable crops and the large consumption of raw materials and natural resources, it is urgent investment in research and incentives for the development of sustainable production models. In order to get high seed quality and yield, rhizobacteria association with substrates offers promising results, preserving and reducing the impact of pesticides on the environment. Therefore, this study aimed to evaluate the production and physiological quality of lettuce seeds, cultivar Grand Rapids TBR, treated with rhizobacteria and grown on different substrates. The experiment was conducted in a heated greenhouse and at the Unimontes Seed Analysis Laboratory, Campus Janaúba-MG, during the months of April to August 2015. The experimental design was a randomized block in a factorial 3x5, involving seed treatment with rhizobacteria Bacillus pumilus 01 and B. subtilis 34, and control (no microbiolization) and five substrates soil+sand+Bioplant (1:1:1), soil+manure (2:1), soil+manure+sand (1:1:1), soil+Bioplant (2:1) and Bioplant", with five repetitions. For seed microbiolization, bacterial suspensions were prepared in Plant Pathology and Microbiology Laboratory. Each isolate was increased in TSB medium (Trypic Soy Broth) at 28 °C for 48 hours under stirring of 150 rpm. Then the suspension was placed in tubes and centrifuged at 10,000 rpm and the supernatant was discarded. Next, salt solution was added (0.85% NaCl) on the pellet and manually shaken. The seeds were immersed in the bacterial suspensions and kept under constant stirring for 15 minutes. They were then preserved in sterile Petri dishes and immediately conducted to planting. Seedlings were produced with Bioplant. At 23 days, transplant was carried out to plastic pots (7,5 L) with their respective substrates. Seed harvest was performed at 125 days after planting. After the harvest, the following agronomic evaluations were performed: number of fruits, number of seeds per fruit, shoot height, fresh and dry shoot mass, stem diameter, root length, fresh and dry root mass and seed yield. Seed physiological quality was evaluated by determining the water content, germination test, first germination count, mean germination time, seedling emergence, emergence speed index, seedling length, fresh and dry seedling mass and accelerated aging. The interaction between substrates and seed treatments was significant for all variables studied. "The tested rhizobacteria and substrates had influence over lettuce physiological quality and yield, cultivar Grand Rapids TBR. The microbiolization of lettuce seeds, cultivar Grand Rapids TBR, with the rhizobacteria B. pumilus 01 and B. subtilis 34, and the use of substrate soil+manure+sand (1:1:1) provided better crop agronomic performance. Seed treatment with the rhizobacterium B. pumilus 01 associated to substrates soil+manure+sand (1:1:1) and soil +Bioplant (2:1) improved seed physiological quality.