Brassinosteroid analogues effect on yield and quality parameters of field-grown lettuce (Lactuca sativa L.)

Lettuce is a common crop in Spain. It is the most widely used fresh-cut vegetable product for salads in Europe, so increasing its yield is of great interest. The effects from two brassinosteroid (BR) analogues, DI-31 (BB16) and DI-100, were evaluated at concentrations of 4, 8 and 12 ppm together with a seaweed extract and amino acids called Tomex Amin (2.5 l/ha) to enhance their activity. These were sprayed fourfold to foliage of Lactuca sativa L. var. Beliva grown under field conditions. All treatments with BR analogues increased production. Treatments with DI-31 and DI-100 at a dose of 12 ppm (30 mg/ha) resulted in the highest production increases, which were 25.93% and 31.08%, respectively, relative to the control with Tomex Amin (T02). We could not correlate the slight increase in net photosynthesis with increasing yield produced by both BR analogues, except for treatment at the highest concentration of DI-100, which produced the maximum yield increase and also the biggest net photosynthesis with significant differences with respect to the control. This increased yield was caused by an increase in weight lettuce (which causes diameter and length increases) caused by increase of water absorption. These treatments produced no significant changes in the organoleptic quality of lettuce. The chemical variables related to lettuce quality, such as humidity, carbon and nitrogen content, sugar and organic acid content, total antioxidant activity (TAA) and phenolic content, were similar in the control and treated lettuces. The results showed that sprayed brassinosteroid analogues may play an important role in increasing the yield of field grown lettuces due to an increase in lettuce size without any undesirable effects on their nutritive and organoleptic properties.

► Effect spirostane BR analogues DI-31 and DI-100 on the growth of lettuce.
► The DI-31 and DI-100 lettuce plant spray treatments were effective in increasing total yield.
► The optimal concentration was found to be 12 ppm for both compounds.
► BR analogues produced no significant changes in the organoleptic quality of lettuce.