Effect of boron on mycelial growth, sporangiogenesis and zoosporogenesis of Phytophthora nicotianae and the possible inhibitory mechanisms

Phytophthora nicotianae is one of the most important soil-borne plant pathogens. Sporangia and zoospores of P. nicotianae are responsible for primary infection and disease dissemination. The disease caused by P. nicotianae was difficult to control by fungicide. Boron, an essential plant micronutrient, was found to have a direct effect on other pathogens. In this paper, the effects of B on the growth, antioxidant system and gene differential expression of P. nicotianae were tested. The results showed that 0.1 mM B could dramatically decrease the sporangiogenesis and zoosporogenesis of P. nicotianae. Mycelial growth of P. nicotianae was significantly inhibited when the concentration of B reached 8 mM. A high-quality differential expression sequence csn4 was obtained by gene differential expression analysis. Under the treated of B, csn4 expression was inhibited, activity of superoxide dismutase (SOD) and catalase (CAT) significantly decreased and the malondialdehyde (MDA) content notably increased compared to control. It is suggested that B could serve as a potential fungicide for the control of plant disease caused by P. nicotianae.