THE GERMICIDAL AND HERMETIC EFFECTS OF UV-C LIGHT ON REDUCING BROWN-ROT DISEASE AND YEAST MICROFLORA OF PEACHES

The application of ultraviolet light-C doses (254 nm, UV-C) was used t o determine the germicidal and hermetic effects on reducing brown rot of 'Elberta' peaches which were naturally and artificially inoculated with Monilinia fructicola. The results showed that a negative relation ship existed between UV-C doses, colony forming units of the fungus, a nd the number of brown rot lesions. Also, the results of our study sho wed that the hermetic (beneficial) effect of low UV-C dose of 7.5 kJ m (-2) induced host resistance by controlling latent brown rot infection . The hermetic effects of UV-C on peaches was photoreversed with visib le light and resulted in the reduction of host resistance to brown rot . Furthermore, the results indicated that UV-C doses increased phenyla lanine ammonia-lyase activity, delayed ripening and suppressed ethylen e production. Additionally, the population of epiphytic yeast (Debaryo myces hansenii) increased curvilinearly on peach surfaces following UV -C irradiation up to 7.5 kJ m(-2). Evaluation of the yeast population on the peach surfaces showed an antagonistic activity against M. fruct icola. The possibility of the host peripheral defense by UV-C stimulat ion of the antagonist activity of a yeast is discussed. (C) 1998 Elsev ier Science Ltd. All rights reserved.