RESUMO O desenvolvimento de soluções sustentáveis visando aumentar a produtividade agrícola é crucial para atender à crescente demanda por alimentos. As microalgas são organismos cuja composição é rica em moléculas bioativas e podem ser produzidas em escala, com baixo custo. Dessa forma, a hipótese desse trabalho é de que a microalga Asterarcys quadricellulare (CCAP 291/1), uma fonte de L-aminoácidos livres, pode aumentar o crescimento e o rendimento de plantas de tomate. Para investigar seu potencial como biofertilizante, foi realizado um trabalho de dois anos, aplicando biomassa A. quadricellulare através de pulverização foliar em plantas de tomate. No primeiro experimento, foram realizadas aplicações semanais durante o ciclo completo da cultura. O efeito das soluções contendo 0.05; 0.15; 0.25; e 0.40 g L-1 de biomassa de A. quadricellulare sobre o rendimento do tomate foi medido através de análise de regressão. No segundo experimento, a concentração com melhor performance (0.25 g L-1), foi testada em duas cultivares de tomate com pulverizações de frequência semanal e quinzenal. Como resultado, para ambas as cultivares, as aplicações aumentaram a área foliar, o rendimento e o conteúdo de açúcares, aminoácidos e proteínas livres. Assim, mostrando efeito biofertilizante em tomate.

ABSTRACT The development of sustainable ways to increase crop productivity is essential to meet the growing demand for food. Microalgae are rich in bioactive molecules and can be produced on a large scale and at a low cost. Therefore, we hypothesized that the microalga Asterarcys quadricellulare (CCAP 294/1), a rich source of free L-amino acids, can increase the growth and yield of tomatoes. To determine the potential of A. quadricellulare, we performed a two-year study by applying A. quadricellulare biomass using a foliar spray on tomato plants. In the first season, weekly applications were performed during the full cycle of tomatoes. The effect of A. quadricellulare biomass of 0.05, 0.15, 0.25, and 0.40 g L-1 on tomato yield was determined through regression analysis. In the second season, the solution of 0.25 g L-1, which showed the best results, was tested on two tomato cultivars using a weekly and a biweekly frequency of application. Both cultivars were positively affected by the application of biomass, which promoted the increase in leaf area and yield, along with higher contents of sugar, free amino acid, and protein. Thus, we determined the role of A. quadricellulare as an effective biofertilizer in tomatoes.

ABSTRACT Potato scab caused by different species of phytopathogenic Streptomyces is considered one of the main bacterial diseases of economic crop importance worldwide. Several studies are being carried out in order to control the disease, but until now, there is no efficient way to do this. Some management strategies have been investigated including application of chemical and biological products and utilization of resistant cultivars of potato but there are few reports about the impact of pH and irrigation regimes on the disease. The present study aimed to evaluate the effects of these last two factors on the incidence and severity of potato scab caused by S. scabiei, S. acidiscabies, Streptomyces sp., S. caviscabies and S. europaeiscabiei in assays at pH 4.0, 4.5, 5.0, 5.5, 6.5 and 7.5; and irrigation regimes of once a week, alternate days and daily in greenhouse conditions. The experimental design for the pH tests was randomized blocks arranged in a 5x2 factorial scheme, with 5 replications and 3x2 for the irrigation regimes with 5 replications. The pH tests showed significant differences between the treatments and pH 4,0 - 4,5 presented lower incidence and severity of the disease for the most species tested but no significant differences were observed between the irrigation regimes. The soil acidification is considered a classic strategy for management of the disease and the results obtained herein corroborated this hypothesis.