Biocontrol of black rot on autochthonous cabbage cultivar ‘Futoški’

Abstract

The potential of two biocontrol strains, Bacillus velezensis X5-2 and Pseudomonas orientalis X2-1P to control black rot caused by Xanthomonas campestris pv. campestris was evaluated in vivo on autochthonous cabbage cultivar ‘Futoški’, under the condition of natural infection. Liquid formulations of biocontrol strains were prepared in fermenters (B. velezensis - 1010 CFU mL-1, P. orientalis - 109 CFU mL-1) and diluted with water in a 1:5 ratio, before use. Treatments were performed with each strain and their mixture (1:1). The experiment included the following: (i) seed treatments (15, 30, 60 min), (ii) foliar treatments (three treatments: when the first symptoms appeared and remaining every two weeks), and (iii) combined seed and foliar treatments. Experiments were conducted in four replicates, with 10 plants per replicate. Two controls were used, untreated and conventionally treated cabbage (pesticides). Assessment of disease intensity was rated one month after the last foliar treatment, using the Horsfall-Barratt scale (1-12). During ripening, cabbage heads’ weights were measured and data were statistically processed (Minitab). All performed treatments were effective in the control of black rot (85.7-98.9%). The highest efficacy was obtained in combined seed (60 min) and foliar treatments with P. orientalis, as well as its mixture with B. velezensis (98.9% both). All treatments influenced the increase of cabbage heads’ weight (up to 1.3 times), with the highest found in combined treatments (60 min seed + foliar) using a mixture of B. velezensis and P. orientalis. A negative correlation (P≤0.05) was found between disease intensity and cabbage heads’ weight.