The Botrytis disease of gladiolus with special reference to the causal organism

Abstract

Summary 1. The symptoms of the disease studied are in substantial agreement with those described by Moore and the three types of corm symptoms mentioned by him are different phases of the same disease. 2. The symptoms are constantly associated with a species of Botrytis different from B. cinerea . Morphological and cultural examination of this fungus shows that it is B. gladiolorum Timm. 3. Inoculation experiments through wounds on corms showed that B. gladiolorum is more pathogenic on gladiolus than B. cinerea . The rate of attack is greatest at a storage temperature of about 15°C. 4. On flowers and shoots B. gladiolorum is also more pathogenic, but although under ideal conditions foliage attack caused subsequent corm rot, this is probably not of major importance in regard to storage rot. The evidence shows that the higher proportion of infection leading to storage rot occurs after lifting the corms, probably on the drying racks. 5. A useful measure of control of the disease is obtained by avoiding planting in heavy soil liable to waterlogging, by early lifting, by rapid drying at a high temperature, and by early cleaning. 6. B. gladiolorum was pathogenic on gladiolus whereas the isolates of B. cinerea were comparatively inert. Converse pathogenicity was observed when turnips, swedes and lettuce were used as hosts. 7. B. gladiolorum tends to be sterile in artificial culture. Media suitable for sporulation are a decoction of gladiolus leaves and glucose-peptone. Formation of conidia occurs only in good light and is also accentuated by moderate drying of the culture medium. 8. A description of B. gladiolorum is included which is in agreement with that of Timmermans. The features of this isolate are considered to be sufficiently distinctive to entitle it to specific status. The isolates of Botrytis from gladiolus made by earlier workers except Klebahn show in greater or less degree similarities with B. gladiolorum and were probably isolates of B. gladiolorum Timmermans.