Response of sugar beet plants to ultraviolet-B (280-320 nm) radiation and Cercospora leaf spot disease.

Sugar beet (Beta vulgaris L.) plants injected with Cercospora beticola Sacc. as well as non-infeded plants were grown under visible light with or without ultraviolet-B (UV-B, 280-320 nm) radiation for 40 days. An interaction between UV-B radiation and Cercospora leaf spot disease was observed, resulting in a large reduction in leaf chlorophyll content, dry weight of leaf laminae, petioles and storage roots. Lipid. peroxidation in leaves also increased the most under the combined treatments. This was also true for ultraweak luminescence from both adaxial and adaxial leaf surfaces. However, no correlation between lipid peroxidation and ultraweak luminescence was observed. Ultraviolet-B radiation given alone appeared to have either a stimulating effect, giving an increase in dry weight of laminae and reducing lipid peroxidation. or no effect. This lack of effect was seen in the absence of change in dry weight of storage roots and chlorophyll content relative to! controls. The study demonstrated a harmful interaction between UV-B radiation and Cercospora leaf spot disease on sugar beet. [ABSTRACT FROM AUTHOR]