6.41
THE EFFECT OF LOW DOSE ULTRAVIOLET LIGHT-C SEED TREATMENT ON INDUCED RESISTANCE IN CABBAGE TO BLACK ROT, (XANTHOMONAS CAMPESTRIS PV. CAMPESTRIS

C STEVENS2, TY LU1, JE BROWN1, VA KHAN2, JY LU2, CL WILSON3, DJ COLLINS 1, MA WILSON4, ECK IGWEGBE2, E CHALUTZ5 and S DROBY5

1Alabama Agricultural Experiment Station, Auburn, AL 36849, USA; 2George Washington Carver Agricultural Experiment Station, Tiiskegee University, AL 36088, USA; 3USDA-ARS, Appalachian Fruit and Research Station, Kearneysville, WV 25430, USA; 4Department of Agriculture, Southeast Missouri State University, Cape Giradcall, MO, USA; 5ARO, The Volcani Center, Bet Dagan 50250, Israel

Background and objectives
Numerous studies have supported low dose(s) of gamma rays, X-rays and ultraviolet light-C (UV-C), as hormetic radiation can stimulate induced resistance to plant diseases in crops. Hormetins such as physical stress LIV-C stimulate a beneficial plant response such as induced resistance, an effect called hormesis [1]. Recent reports have shown that the application of LTV-C (254 nm) light at low hormetic doses reduced post-harvest decay of various fruits and vegetables [2]. The objectives of this study were: (i) to determine an optimum low hormetic dose of UV-C to elicit host resistance to black rot of cabbage; and (ii) to determine the effect of UV-C on seed germination, vegetable quality and the effect of seed storage time of UV-C treated cabbage seeds on black rot development in cabbage plants in greenhouse studies.

Results and conclusions
Low-dose hormetic UV-C (1.3-20 kJ/m2) seed treatments were used to elicit host resistance to black rot and improve the quality of cabbages. The optimum UV-C dose of (3.6 kJ/m2) was effective in reducing black rot and population density of Xanthomonas campestris pv. campestris of infected cabbage plants. UV-C-irradiated cabbage seeds showed no significant decrease in seed germination among treatments in greenhouse studies. Seeds treated with UV-C at 3.6 kJ/m2 produced plants with healthy green colour and the highest weight and largest head diameter among the UV-C treatments compared to the controls. Hormetic UV-C resistance response to black rot was observed in cabbage from irradiated seeds and stored at room temperature for 2 days and 1, 5, and 8 months before transplanting. Seeds stored for the shortest time gave the best reduction of black rot in cabbage plants. It has previously been reported that when corn seeds were treated with UV-C prior to sowing, resistance was induced to both root and stem rots [1]. To the best of our knowledge this is the first report on the treatment of cabbage seeds by UV-C to reduce black rot of cabbage plants produced from systematically infected seeds.

References
1. Lickey TD, 1980. Hormesis with ionizing radiation. CRC Press, Boca Raton, Florida, p. 121.
2. Wilson CL, El Ghaouth A, Chalutz E et al., 1994. Potential of induced resistance to control post-harvest diseases of fruits and vegetables. Plant Disease 78, 837-884.