THE FUSABIUM BULB ROT OF NARCISSUS

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Abstract
IV SUMMARY: A brief review is given of diseases affecting the underground parts of Narcissus plants, with especial reference t o the bulb rot associated with F. bulbigenum Cke. and Mass., the symptoms of which are described both in stored bulbs and in the field. In isolations made from stored bulbs P. bulbigenum was found most frequently. Two strains of this organism are briefly described. Two other organisms of frequent occurrence in Narcissus bulbs, F. moniliforme and Cylindrocarpon radidicok, are also described. Inoculations into healthy bulb tissues with strains of F. bulbigenurn were found to produce the typical symptoms of the storage rot, and the fungus was reisolated without difficulty. In general, wounding of the tissue was necessary for infection to take place. In a few cases where infection was obtained without artificial wounding, naturally produced wounds are suspected. Inoculations of roots failed to produce the disease. Inoculatioas with F. moniliforme and Cylindrocarpon radicicola, which are frequently found on diseased bulbs, failed to give infection, and it is concluded that F. bulbigenium is the causal agent of the bulb rot. There is considerable variation in the resistance of different varieties to the fungus. F. bulbigenurn was occasionally found entering &a the nose of the bulb, but usually it attacked from the base upwards. A very frequent point of attack was at the junction of the two components of a doublenosed bulb. So far no clear evidence was obtained of the fungus entering the base of the bulb from infected soil through the dying‐back roots, as stated by Weiss to be the case in America. High temperature and high humidity during storage were found to aggravate the disease in an infected stock, but in healthy stocks these same factors did not harm the bulbs or reproduce the disease. The beneficial effect claimed for early planting of stocks as a means of checking the disease has not been substantiated. In the light of the figures obtained, the question must be considered to be open. Support was found for the view put forward by Weiss that the disease may be spread during the hot‐water treatment against eelworm. The surface sterilisation of bulbs with fungicides appears to offer promise as a method for reducing the amount of rotting during storage. Experiments are described in which tests were made of the effect of various concentrations of fungicides on the health of the bulbs themselves and on the germination of F. bulbigenum spores. This investigation was carried out in the Department of Plant Pathology, Imperial College of Science and Technology, South Kensington, and a t the Biological field Station of the. College a t Slough, Bucks. In addition t o acknowledgments made in the text, thanks are due to Prof. Munro, Director of the Field Station, for the facilities afforded there; to Dr G. H. Pethybridge and Mr W. C. Moore, of the Plant Pathological Laboratory, Harpenden, for much assistance in the way of material and references to literature; to Messrs G. R. Ban and H. R. Barr for many facilities for study at their Taplow Xursery and Covent Garden Warehouse; to Messrs the Proprietors of Hay's Wharf for cold‐store accommodation, and finally to Prof. W. Brown for his continual interest and assistance throughout all stages of the investigation.

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