Light-induced Resistance of Broad Bean against Botrytis cinerea

This study was designed to investigate the ligh t-induccd resistance of broad bean ( Vicia Jaba) against BOlrYlis cillerea. Yellow (590 nm max) and red (650 nm max) light significantly inhibi ted the formation of infection hypha from appressoria of B. cillerea on bOlh detached and a llached broad bca nleaflets. Pretrea tment of leaflets with yellow or red light for 24 h before inocula tion. also inhibited the formation of infection hypha from apprcssoria. This indicates that the fai lure in appressorial penetration of B. cinerea under yellow or red light was not due to the effect of these wavelengths (575 nm to 700 nm) of light on fungal infection behaviour. but due to lightinduced resistance in the broad bean against B. cinerea. Spore germination of B. cil/erea. in supernatants of spore suspension droplets or B. cinerea recovered from inocula ted broad bean leaHets kept under red light for 48 h after inoculation, was significantly inhibited to a germination rate of 8.2%. However, under darkness the spore germination in infection droplets was not inhibited. with a germination rate of 92.30/0. On the other hand. stich antifungal activity was also observed in water droplets without spores of B. cinerea on broad bean leflflets kept under red light for 48 h. However. suppressive activity was lower than in infection droplets. These results indicate that irradiation of broad bean leaftets with red light activated production of antifungal substa nee(s) in the leaf ti ssues which seem to be responsible for the induced resistance of broad bean against B. cil1erea . Further. it was demonstrated that the accumulation of antifungal substa nce(s) in leaf ti ssues was increased by infection of B. cinerea .