Susceptibility of some Papaveraceae plants to Fusarium oxysporum f. sp. papaveris

Abstract

The susceptibility of nine Papaver species commonly grown for gardens, cut flowers and potted plants, to Fusarium wilt, caused by Fusarium oxysporum f. sp. papaveris, has been evaluated. The susceptibility of Chelidonium majus L. and Papaver rhoeas L., both belonging to Papaveraceae family and naturally present in Italian flora, was also tested. Plants were inoculated by dipping the roots into the conidial suspensions of each of five single-spore isolates of F. oxysporum f. sp. papaveris isolated from P. nudicaule grown in Italy. After appearance of the symptoms, the disease index (D.I.) was evaluated for each tested species that was successively assigned to one of the following susceptibility classes: R = resistant (D.I. 0–5); PR = partially resistant (D.I. 6–20); MS = moderately susceptible (D.I. 21–50); S = susceptible (D.I. 51–75); and HS = highly susceptible (D.I. 76–100). None of the tested species was found to be totally or partially resistant to F. oxysporum f. sp. papaveris. However, Papaver atlanticum (Ball) Cosson, P. dubium L., P. glaucum Boiss. and Hausskn., P. pseudocanescens Popov, P. nudicaule L., P. rupifragum Boiss. and Reuter and Papaver “Daneborg” were susceptible or highly susceptible to the pathogen, while P. trinifolium Boiss. and P. orientale L. showed an average susceptibility to the tested isolates. The susceptibility classes of Chelidonium majus L. and P. rhoeas L. ranged from moderately to highly susceptible. About the origin of F. oxysporum f. sp. papaveris, two hypotheses are discussed. The first hypothesis is related to the susceptibility of C. majus L. and P. rhoeas to F. oxysporum f. sp. papaveris. This fact indicates that this pathogen might have been present in the wild of Italy and that the wild species belonging to the Papaveraceae may be a potential sources of disease outbreaks. The second hypothesis is related to the climatic conditions of subpolar areas in which P. nudicaule is indigenous. Low temperatures might limit the appearance of plant symptoms caused by F. oxysporum, which is generally favored by elevated temperatures, such as those typical of glasshouse cultivation in Liguria region (north of Italy) where the pathogen was reported for the first time on P. nudicaule. The first hypothesis should be validated with further monitoring activities in order to isolate the pathogen on wild flora, whereas the second hypothesis should be confirmed with epidemiology tests.