Ozone and sulphur dioxide effects on the lilac powdery mildew fungus
1975; Elsevier BV; Volume: 9; Issue: 2 Linguagem: Inglês
10.1016/0013-9327(75)90124-x
ISSN1878-2450
AutoresC. R. Hibben, Margery Poole Taylor,
Tópico(s)Powdery Mildew Fungal Diseases
ResumoAbstract Colonisation of lilac ( Syringa vulgaris ) by the powdery mildew fungus ( Microsphaera alni ) is often sparse in sites exposed to urban air pollutants. The influence of ozone (O 3 ) and sulphur dioxide (SO 2 ) on conidial germination and the establishment of infection by M. alni was studied. Although tolerant of O 3 , mildew infection was reduced by acute and chronic doses of SO 2 . Conidial germination and the appressorium phase were the stages most sensitive to SO 2 . Infection was unimpeded on leaves previously fumigated, thus confirming that these reactions were due more to the fungicidal, rather than the phytotoxic, properties of the pollutant. There was no synergism between the two gases that lowered the threshold of toxicity to conidia. A member of the Fungi Imperfecti, Hyalodendron album , sporulated on mildew colonies on lilac leaves. It was antagonistic to the mildew by reducing both conidial germination and the formation of appressoria. Conidia of H. album were more sensitive to O 3 and SO 2 than M. alni . These results suggest that the role of non-pathogenic microbial epiphytes should be considered when assessing the full impact of air pollutants on obligate parasites, and possibly on other foliar pathogens.
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