ABSTRACT Along the line that health-beneficial foods must also be accompanied by sustainable agricultural practices, the red alga Lithothamnium sp. (Rhodophyta), frequently used for animal and human nutrition, it was shown that it could be a biofertilizer, regarding their bioactive humic acid content, released by micronization. Also, onions present well-known benefits to health and are among the main vegetable crops grown worldwide. Thus, the objective this work was to evaluate the effects of foliar sprays with micronized Lithothamniun sp. on yield, mineral nutrients, flavonoids, phenolic content, and antioxidant activity before and after storage of bulbs of two organically grown onion cultivars. The yield, mineral content, antioxidant activity, and phenolic and flavonoid content in onion bulbs were improved through sprays, highlighting the dose of 1.5 g L-1 of Lithothamnium sp. in solution. Genotype interactions and storage effects were observed. The benefits with the use of Lithothamnium sp. as biofertilizer were towards the biofortification of organically grown onions by improving mineral nutrient acquisition as it was followed by upgrading antioxidant capacity.

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.