Moderate Dosages of Ozone Enhance Infection of Onion Leaves byBotrytis cinereabut not byB. squamosa

Publisher Website
Google Scholar
Abstract
Exposure of onion plants to moderate chronic dosages of ozone under controlled conditions resulted in predisposition of the older leaves to enhanced infection by B. cinerea. More lesions/cm2 of leaf surface were induced by B. cinerea on the 2 oldest nonsenescing leaves of plants of ozone-sensitive onion cv. Autumn Spice and Fiesta inoculated after 4 h exposure to 0.16 ppm (314 .mu.g/m3) of ozone (a dosage rarely, if ever, encountered in New York [USA]) than were induced on the corresponding leaves of nonexposed plants. This effect occurred in both the presence and absence of macroscopically visible, ozone-induced leaf injury. Similar results were obtained following inoculation with B. cinerea of plants exposed or not exposed to the relatively high chronic dosage of 0.12 ppm (235 .mu.g/m3) of ozone for 5 h/day for 4 days. More lesions/cm2 of leaf surface were induced by B. squamosa on the 2 oldest nonsenescing leaves of exposed than on nonexposed plants (cv. Autumn Spice) but only after exposure to the relatively high acute dosage of 0.25 ppm (490 .mu.g/m3) of ozone for 4 h (a dosage rarely, if ever, encountered in New York). Exposure of onion plants (cv. Autumn Spice) infected with B. cinerea or B. squamosa to the relatively high chronic dosage of 0.14 ppm (274 .mu.g/m3) ozone for 5 h/day for 5 days had no detectable effect on expansion of preestablished lesions induced by these pathogens.