CORESTA Meeting, Agronomy/Phytopathology, Montreux, 1997, PT9

Variability of Peronospora tabacina: an isoenzyme study

(1) D. Kostov Inst. of Genetics, Bulgarian Academy of Sciences, Sofia, Bulgaria. (2) SEITA, lnstitut du Tabac, Bergerac, France
The variability of P. tabacina A. populations was studied using the isoenzyme polymorphism of peroxidase, malate dehydrogenase and superoxidismutase. P. tabacina conidia from N. tabacum crops cultivated in distant areas of Europe (France-Bulgaria) were investigated during a long period of time (1978-1992). It was found that no variations of P. tabacina as a function of space and time occurred. The data point to the genetical stability of the presently spread strain of the pathogen. However, a significant variability of P. tabacina as a function of host plant was established. Conidia from N. tabacum ( Pt/Nt ) were used to inoculate another host plant, N. repanda , and compared with conidia produced on the new host ( Pt/Nr ). It was shown that isoenzymes present in Pt/Nt conidia (and common with N. tabacum host) were no more expressed in Pt/Nr . In Pt/Nr conidia new isoenzymes appeared, common with the corresponding host, N. repanda . The results reveal molecular mechanisms underlying relationships between host plants and obligate fungal pathogens. They may be used in blue mold epidemiology research.