I2I4 DISEASES OF VARIOUS CROPS 



942 - Sclerotinia libertiana, injurious to Forsythia vfridissima.— peglion 



VlTTORlO, in Rcndnonti dcilc scdutc dclla Rcalc A ccademia dei Lined . Clause di Scienze fisiche, 

 matematiche e naluraii, ^th Svrie^, Vol. XXV, 1st Half Year, Part o, pp. 665-657. Rome, 

 May 7, 191 6. 



As early as the spring of IQ15 the Writer, in some specimens of Forsy- 

 thia viridissima in the garden of the School of Agriculture of Bologna 

 (Italy), observed a withering of the shoots after flowering. An anatomical 

 study of the lesions disclosed a limited but very j^ronounced disorganisa- 

 tion of the bark, and the presence of small black isolated sclerotia, }nostly 

 placed at the point of intersection of the leaf stem on the twig. Accord- 

 ing to the \vriter, the fungus is Sclerotinia Libertiana. If fragments 

 of bark tissue are sown in nutrient gelatine, or if the withered shoots are 

 placed in a moist room, there follows within a very short time a vigorous 

 growth of mycelium and the differentiation of maii}^ large sclerotia. 



The origin of this infection is to be sought during the flowering of 

 the host. The flowers attacked adhere strongly to the stalk. On making 

 a longitudinal section of these flowers, the}' are seen to be the seat of an ex- 

 tensive mycelial infection. The mycelium of Sclerotinia starts from the 

 stigma and, passing along the style, enters the ovar}-, from which, traversing 

 the leaf-stalk, it spreads in the cortical zone of the twig. 



What here takes place is a mummification perfectly analogous to that 

 produced by several species of Sclerotinia of the sub-genus Stromatinia in 

 the female organs of various Rosaceae, and which, as is well known, are caus- 

 ed by the germination of ascospores or conidia {Monilia) on the stigma, 

 followed by the penetration of the mycelium into the ovary, and from the 

 latter into the branches. 



The infection takes place when the vitality of the flower is already on 

 the decline, because the germinal tube of the ascospores of Scl. Libertiana 

 cannot develop in healthy vegetable tissues in full vitality. The infection 

 is probably due to ascospores carried by the wind. The ascospores can ger- 

 minate as soon as they are expelled from the ascus. In the cases reported 

 by the writer they came from a plot cultivated with Jerusalem artichokes, 

 where 5. Libertiana is endemic. 



Thus S. Libertiana, the pathogenic position of which was known in 

 the typical forms of infection arising from injuries to the host (the writer 

 is of opinion that it is anormal case of " chancre " or " Sclerotia disease " 

 in hemp), from lesions following upon cold (as is the case with the Sclerotia 

 disease of beans), is found to possess other means of penetration into its 

 host, characterised by a more and more reduced period of life in the sapro- 

 phytic stage. Such is the special form of the Sclerotia disease in the bean, 

 described b}^ Petri {Rendiconti delta R. Accademia dei Lincei, Nov. 20, 1914), 

 in which the saprophytic stage develops at the expense of fragments of 

 petals adhering by chance to the growing shoots, and finally the pathologi- 

 cal process now in question which arises on the flowers of Forsythia and 

 causes considerable injury to the stem of the host. 



