No abstract

Plants protect themselves, after pathogen attack, through the passive and active defense mechanisms. The treatment of plants with various agents, including cell wall fragments, plant extracts, and synthetic chemicals, can induce resistance to subsequent pathogen attack both locally and systemically. In view of the capability of phytochemicals compounds found in fruits and vegetables with different proven health benefits to consumers, there are different strategies to enhance the concentration of these compounds, among which the use of elicitors. Elicitation has been used to trigger different defense responses in plants, which lead to different mechanisms, such as activation of enzymes related with secondary metabolism. In this study we investigated the effects of elicitors (Activane®, Micobiol®, Stemicol® in doses of 1.8 g L⁻¹, 3 m L⁻¹ and 2.5 g·L⁻¹) on the activity of two enzymes (polyphenoloxydase and peroxidase) in leaves as well as on the bioactive content (DPPH scavenging activity, total phenol and total flavonoid content) in fruits of Solanum lycopersicumL. The elicitors studied affected the production of enzyme and antioxidant activities in tomato, though showed a variable influence on the production of total phenolic and flavonoid content in tomato fruits. In general, the elicitors are able to increase polyphenoloxydase activity in leaves and phytochemical properties in fruits, with a significant negative correlation between the DPPH scavenging activity, total phenolic and flavonoids. These findings provide positive directions for the possible use of these elicitors in tomato (‘Bola’ and ‘Saladette’) production in greenhouse. Highlights - Elicitors increase the enzymatic activity of PPO in tomato leaves. - The production of total phenolic contents and flavonoids depends on type of elicitors. - No effects on the peroxidase content of the tomato leaves. - The antioxidant capacity of the aqueous fruits extract showed a significant difference (P = 0.05) between the treatments in the Saladette variety. - Positive relationship between total phenolic contents and flavonoids.

Many compounds available in the market act as elicitors and can be incorporated into agronomic management. But the focus is on elicitors frequently used for the induction of different responses related to the systemic resistance of plants to increase the production of bioactive metabolites, biomass accumulation, and yield. For that case, this work aimed to evaluate the effects of three elicitors on potato crops under field conditions. The potato cultivar "Fianna" was used, and a completely randomized design with four treatments and four repetitions. The effect of three elicitors at a dose of 2.5 g. L-1 for Activane®, 2.5 ml. L-1 for Micobiol® and 2.5 g. L-1 for Stemicol® was evaluated on growth, yield, enzymatic and antioxidant activity. Generally, the elicitors had a positive effect on the enzymes and antioxidant capacity of the potato plant. It was concluded that the application of elicitors Stemicol® (T4) had the most significant result on the number of tubers and weight per plant at harvest while allowing a more substantial number of tubers to be obtained. In comparison, Activane® (T2) influenced the growth variables of stem length and number of leaves per plant.

Optimum plant spacing ensures proper growth and development of crops resulting in maximum crop yield and economic use of land. The objective of this study was to evaluate the effects of different planting spacing on the growth and yield of California Wonder Bell Pepper (Capsicum annuum) on sandy loam soil of The Gambia, from January to May 2018. The design used for this experiment was a Randomized Complete Block Design (RCBD) with four treatments (T1: 50 x 50 cm, T2: 50 x 40 cm, T3: 50 x 30 cm and T4: 50 x 20 cm) and three repetitions and the parameter of plant height, stem girth, number of leaves, fruit length, fruit circumference, individual fruit weight, yield per plant, and yield per hectare. The plant spacing had a significant effect on plant height, stem girth and the number of leaves of the growth parameters, whereas for the yield parameters, individual fruit weight, yield per plant and total biomass yield were found significantly in treatments with the highest plant spacing (50 x 50 cm). In conclusion, wider plant spacing (50 x 50 cm) boosts the plants to develop the maximum number of branches and fruits.