No abstract

The strawberry is susceptible to several pests which cause a reduction in productivity. The use of mechanisms which repel or prevent these pests to establish, represent a sustainable environmental technology to reduce the frequency of agrochemical use. In this context, the aim of this study was to evaluate the effect of salicylic acid (SA) on resistance induction against two-spotted spider mite in strawberry cultivars (Aromas and Sweet Charlie). Five concentrations of SA (0, 25, 50, 75 and 100 mg L-1) were tested in order to verify the antixenosis effects. In SA concentration of 50 mg L-1, a reduced number of mites in the two strawberry cultivars was noticed. For the number of eggs deposited on leaflet, we verified an effect of SA concentration with quadratic adjustment in the equation. Sweet Charlie cultivar was more effective than Aromas in relation to the reduction of mite oviposition on leaflets treated with SA. SA concentrations of 25, 50 and 75 mg L-1 were the most efficient for the evaluated traits allowed to infer its potential as antixenotic resistance inducer against two-spotted spider mite in strawberry crop.

The inoculation of arbuscular mycorrhizal fungi (AMF), increasing the rhizospheric influence, might provide higher levels of bioactive compounds. Thus, the objective was to evaluate the influence of the AMF inoculation on the physicochemical components of fruit’s quality in field. Strawberry fruits from cultivars Camarosa, Aromas, Camino Real, Monterey, Portola, San Andreas and Albion in 2016, and Camarosa, Camino Real, Monterey and Albion in 2017 were either inoculated or non-inoculated with AMF. The analyzed physicochemical components of fruit’s quality were ascorbic acid, titrated acidity, pH, soluble solids, soluble solids/titrated acidity ratio, phenolic compounds, anthocyanins, and firmness. The inoculation with AMF on strawberry plants in field improved the fruit’s physicochemical attributes, increasing pH, soluble solids content, soluble solids/titratable acidity ratio and phenolic compounds content in both cultivation years (2016-2017). The inoculation of AMF has improved the characteristics of post-harvest quality in strawberry fruits.

Seeking the development of nature-friendly agronomic techniques, the use of natural sources to promote plant growth and increase agricultural yield has gained relevance. In this context, the use of biofertilizers or biostimulants obtained from microalgae has been studied, as these microorganisms have in their composition a great diversity of bioactive molecules. This study aimed to evaluate the effect of microalga Asterarcys quadricellulare (CCAP 294/1) on organic onion production, verifying its action on metabolism, growth and yield of two cultivars. Thus, two experiments were carried out: (i) foliar applications on onion plants grown in pots in a greenhouse; (ii) foliar applications on field-grown onion under an organic system. Both experiments were undertaken using solutions with spray-dried microalga biomass at concentrations of 0.05, 0.15, 0.25 and 0.4 g L−1. Biometric variables, yield of bulbs and biochemical variables were evaluated indicating that the use of A. quadricellulare promoted plant growth and increases in bulb caliber and yield of both onion cultivars. The microalga biomass stimulated plant metabolism by increases in contents of chlorophyll, carotenoids, amino acids, and the nitrate reductase enzyme activity in leaves, also free amino acids and total sugar contents in bulbs, highlighting the biomass concentration of 0.25 g L−1.

The demand for soybean has increased in the international market, and water restriction is an important factor in reducing its yield. Therefore, the development of technologies aimed to reducing the damage caused by water stress becomes strategic. Thus, the objective was to demonstrate the role of the amino acid L-glutamic acid in mitigating water stress in soybean plants. A study was conducted in a greenhouse using soybean plants in vegetative stage subjected to water restriction and foliar applications of biofertilizer obtained from bacterial fermentation, containing 25% of the amino acid L-glutamic acid, sprayed three days before the imposition of water restriction and when the substrate moisture reached 50% of the water retention capacity (WRC).  Stomatal resistance was determined throughout the days and three collections of plant material were carried out: at the beginning of water restriction, one and four days after rehydration for biochemical and enzymatic analyses. Plants that were supplied with biofertilizer at the beginning of water restriction showed lower stomatal resistance, while plants that received application three days before 50% WRC showed increases in sugar accumulation, in free amino acids and proline content, and in nitrate reductase and peroxidase enzymes activity, consequently, reducing lipids peroxidation, mitigating the effects of oxidative stress.

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.

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The use of arbuscular mycorrhizal fungi (AMF) is a strategy to increase the absorption of nutrients by plants, stimulate the plant defense system, and promote the synthesis of bioactive compounds. In addition, AMF can reduce production costs and improve the agricultural and environmental sustainability of farming systems. The objective of this study is to evaluate the effect of AMF on production and physiological parameters of strawberry cultivars. The cultivars Camarosa, Aromas, Camino Real, Monterrey, Portola, San Andreas, and Albion were evaluated in the year 2016, and Camarosa, Camino Real, Monterrey, and Albion were analyzed in the year 2017. These cultivars were grown either with or without AMF. The analyzed production variables were the total number of fruits and fruit yield and weight. Gas exchange and leaf area were also determined in 2017. Fruit yield in treated and control plants was assessed in the two study years. AMF inoculation augmented the leaf area in all cultivars except for Monterrey, photosynthetic performance in the cultivars Camarosa and Camino Real, and the transpiration rate in the cultivar Camarosa. These results indicate that AMF improve agronomic and physiological characteristics of strawberry cultivars.