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SEPTORIA BIRGITAE BEDLAN AS A NEW PATHOGEN OF LACTUCA SA-TIVA L.
SEPTORIA BIRGITAE BEDLAN AS A NEW PATHOGEN OF LACTUCA SA-TIVA L. G BEDLAN1 1Federal Office and Research Centre of Agriculture, Institute of Phytomedicine, 1226-Vienna, Austria Backgrounds and objectives In the cool and mostly rainy year 1996 the leaves of lettuce (Lactuca sativa L.) frequently showed brown spots. After carrying out microscopic tests we found out that it was a fungus of the genus Septoria. The pycnidia are scattered over the spots and sometimes grouped together. The pycnidia are dark brown and blackish and give off the thready hyaline conidia, which are typical for Septoria, via the ostiolum. In humid or wet conditions the disease can occur very heavily. The conidia are dispersed through water drops (rain, irrigation). The fungus survives in the seeds and remainders of the lettuce. In absence of suitable hosts however the pathogen can only survive for a short time. The fungus is transported over long distances together with the seed, from plant to plant it is transferred by water drops (rain, irrigation), animals, tools and harvesting. The first samples were taken from biological farming in 1996 from the lettuce varieties ,,Kermit", ,,Libusa" and ,,Fiohai". Finally lots of lettuce varieties all over Austria were found to be infested. Septoria has also been found in lettuce quite frequently in Germany as well. Materials and methods Several herbarium specimen, types and original descriptions of Septoria-species occurring in Lactuca have been surveyed and checked: Septoria lactucae Pass. (=S. lactu-cae Peck, = Ascochyta lactucae Rostrup, = S. consimilis Ellis & Martin, S. lactucina Lobik, S. lactucicoia Ellis & Martin, S. schembeiii Meinik (=S. lac-tucina Petrak non Lobik), S. mulgedii de Thdmen, S. ludoviciana Ellis & Everh., S. fernandezii Unamuno, S. sikangensis Petrak, S. unicolor Wint. Pycnidia and conidia have been measured by digital image processing (model KS 400, version 1.2 respectively 2.0 by Kontron). Results and conclusions The Septoria-species occurring in Lactuca (and Mulgedium) differ from the isolates collected from Lactuca sativa L. in 1996 as far as the following features are con-cerned: the smallest diameter of the pycnidia is between 80 and 90 m, the biggest nearly 200 m with an average of a diameter of 132 - 139 m. The diameter found most frequently was 135 m. The ostiolum has a diameter of 22 - 45 m with an average of 33 m. The wall thickness of the pycnidia is between 5 and 20 m with an average of 11,7 m. The thready conidia are hyaline, straight, sometimes curved or sickle-shaped, at times slightly tapering to the ends, at the ends blunt, with 1 - 3 septa, 18,92 - 39,03 m long with an average of 28,87 m and 1,28 -2,30 m wide with an average of 1,81 m. PUNITHALINGAM & HOLLIDAY [2] described the pycnidia of Septoria lactucae Pass. as having a diameter of 100-200 p, conidia of a length of 25-40(-50) m and a thickness of 1,5-2 m dick 1-2(3) septa. These data however don't correspond to the type of Septoria lactucae
  • , but to the species collected in 1996 [11. Septoria lactucae Pass. has pycnidia with a diameter of 90 m. The thready, simple-celled conidia are hyaline, straight or slightly curved, 25 - 30 m long and 1,7 - 2 m wide. Comparing the new species with the other Septoria-species in lettuce we found out that it is a new species of Septoria that we call Septoda birgitae Bedian. References 1. BEDLAN G, 1996. Mitteilungsband der Ost. Pfianzenschutztage der OAIP, p.55. 2. PUNITHALINGAM E, HOLLIDAY P, 1972. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 335