Relationship between tipburn and leaf mineral composition in strawberry

Malformation of emerging leaves with distortion of leaf tips, a condition known as tipburn, is frequently observed in strawberry. Calcium (Ca) deficiency has been considered the main cause of tipburn. The aim of the present study was to analyse the relationship between leaf mineral composition and the incidence of tipburn in three short-day strawberry (Fragaria x ananassa Duch.) cultivars (‘Ventana’, ‘Camarosa’ and ‘Candonga’) submitted to different concentrations of Ca. The studies were conducted in a hydroponic system in a greenhouse. Calcium was added as Ca(NO3)2 at 2 mM, 3 mM, 4 mM and 5 mM. A completely randomized block design (4 Ca concentrations × 3 cultivars) with three replications was used. Each replicate consisted of 12 plants grown in a polyethylene bag (100 cm × 18 cm × 3 cm) filled with coconut peat. Crown diameter and tipburn incidence were evaluated throughout the experimental period, and at the end of the experiment leaf mineral composition was assessed. In general, plants with larger crown diameters had a greater incidence of tipburn. The ‘Candonga’ cultivar had the smallest incidence of tipburn, while the ‘Camarosa’ and ‘Ventana’ cultivars were more susceptible. There was no correlation between level of Ca applied and incidence of tipburn. The incidence of tipburn was associated with foliar K:Ca and K:Mg ratios. Ratios above 3.40 for K:Mg and 1.77 for K:Ca represented a risk of more than 50% of tipburn incidence, when overall means for all cultivars and levels of Ca were used.

Research highlights▶ In the present experiment tipburn incidence was closely associated with the balance between Ca, Mg and K, as shown by the strong correlations of tipburn incidence with K:Ca and K:Mg ratios. ▶ The concentrations of K, Mg, Ca, Zn and Mn in leaves differed between cultivars, with the ‘Ventana’ cultivar having the greatest concentrations of K, Zn and Mn, and the ‘Candonga’ cultivar the greatest concentrations of Mg and Ca. Only leaf Mg was affected by Ca application, but there were also significant interactions cultivar × level of Ca for K, Mg, Ca, and Cu concentrations. ▶ There were differences between cultivars on tipburn susceptibility, with cv. ‘Candonga’ being less susceptible to tipburn, with an incidence smaller than 35% until April.