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Abstract
High temperature tended to aggravate injury caused to tomato plants by flooding. Based on plant responses such as chlorosis, epinasty, and wilting, less than 0.2% (8 of 4630 accessions) of the world collection of the garden tomato (Lycopersicon esculentum Mill.) and related Lycopersicon species exhibited some level of tolerance to a short period of flooding associated with high temperature. The level of flood tolerance in one of the 8 flood tolerant accessions, L-123, was found to be less than that of 7 other vegetables tested.
Low hormetic doses of ultraviolet light (UV-C) stress on exposed peaches (Prunus persica). reduced brown rot resulting from field and artificial inoculation from Monilinia fructicola. To test the hypothesis that UV-C induced resistance through host responses the following tests involving biochemical changes (phenlyalanine ammonia-lyase activity (PAL) and ethylene production (EP)), bioassay of antifungal activity of tissue extracts to the fungus, and latent infection of rot free peaches previously treated with and without UV-C were determined. Exposure of peaches to UV-C dose of 7.5×104 ergs/mm2 promoted an increase in PAL and EP compared to the control. As the PAL activity increased, percent storage rots decreased. Antifungal activity to the fungal conidia in UV-C treated peach extract showed that the percent conidia germination was reduced 3 folds. Preharvest infection of brown rot which indicated latent infection was significantly reduced. To test for the germicidal effect of UV-C on M. fructicola on the surface of peaches, an artificial epiphytic population of the fungus was deposited on the peaches. A negative relationship between UV-C dose of 1.3 to 40×104 ergs /mm2, colony forming units and number of decaying brown rot lesions were found.