A NEW UV-B LIGHTING SYSTEM CONTROLS POWDERY MILDEW OF STRAWBERRY

We have produced a new UV-B lighting system comprising a UV-B florescent lamp, a reflective aluminum plate, a timer, and a control board. UV-B radiation induces resistance to strawberry against pathogens, especially powdery mildew (Sphaerotheca aphanis var. aphanis). We demonstrated control of powdery mildew with UV-B radiation in soil culture and in drip fertigation.
The lighting system was suspended from the ceiling at intervals of 5 m in a line in the middle of a vinyl house. The lamp height was ca. 2 m above the strawberry plants. Strawberry plants were radiated using UV-B fluorescent lamps daily during 9:00-15:00. Plants received light energy of ca. 2-7 kJ m^-2 d^-1. The lighting system suppressed powdery mildew. Control was 100% at best.
UV-B radiation induced transcription of strawberry genes associated with disease resistance, such as phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), β-1,3-glucanase, and osmotin-like protein. Furthermore, production of antifungal substances was induced in leaves. UV-B radiation also made strawberry fruits more red than the control, reflecting the accumulation of anthocyanin in fruits.
Consequently, the new UV-B lighting system prevents powdery mildew of strawberry and improves fruit quality.