Hilkka Koponen

Variability of Peronospora Sparsa (syn. P. rubi) in Finland as Measured by Amplified Fragment Length Polymorphism

Downy mildew caused by Peronospora sparsa (syn. P. rubi) is a serious threat to commercial cultivation of arctic bramble (Rubus arcticus subsp. arcticus) in Finland. P. sparsa is distributed throughout the country in cultivated and wild arctic bramble and in cloudberry (R. chamaemorus). A total of 36 isolates of P. sparsa collected from these hosts was analysed for amplified fragment length polymorphism (AFLP). Of the 226 markers scored, 223 were polymorphic and all isolates of P. sparsa had unique AFLP fingerprints, which indicated high levels of genetic variability. An UPGMA clustering analysis of the isolates did not reveal any genetically distinguishable strains. The isolates were grouped neither according to the geographic origin nor the host from which they were isolated. Isolates of P. sparsa obtained from wild arctic bramble and one from cloudberry readily infected the leaves of the cultivated arctic bramble (cultivar ‘Pima’). Also, P. sparsa isolated from cultivated arctic bramble infected the leaves of wild arctic bramble. These data suggest that P. sparsa may be disseminated from wild arctic bramble and cloudberry to cultivated arctic bramble in the field.

Infection of the Sunagoke moss panels with fungal pathogens hampers sustainable greening in urban environments

Drought and heat tolerance of the Sunagoke moss (Racomitrium japonicum) and the low thermal conductivity of the dry moss tissue offer novel greening and insulation possibilities of roofs and walls to mitigate the heat island phenomenon in urban environments. However, damage may appear in the moss panels under humid conditions in Japan. In this study we characterized fungi associated with the damaged areas of the Sunagoke moss panels. Fungi were identified by morphology and internal transcribed spacer (ITS) sequence analysis and tested for pathogenicity on R. japonicum (Grimmiaceae) and an unrelated moss species (Physcomitrella patens; Funariaceae) under controlled conditions. Alternaria alternata, Fusarium avenaceum and Fusarium oxysporum caused severe necrosis and death, whereas Cladosporium oxysporum and Epicoccum nigrum caused milder discoloration or chlorosis in both moss species. The fungi pathogenic on moss were closely related to fungal pathogens described from cultivated vascular plants. Ammonium increased severity of fungal diseases in moss. This study demonstrated that fungi can cause economically significant diseases in cultivated moss and hamper commercial use of the moss panels unless appropriate control methods are developed. Use of a single moss clone to cover large surfaces and the air pollutants such as ammonium may increase the risk for fungal disease problems.

Yield reduction caused by a soil-borne disease of naked, dwarf, and conventional oat in Finland

Kauran kasvu hidastui ja sadontuottokyky heikkeni tautiepidemian seurauksena Viikin koetilan pelloilla vuosina 1994 ja 1995. Erityisesti kasvuston alalehdissa ilmeni harmaanruskeita laikkuja, ja vuonna 1995 osa kasvustosta kuihtui. Oireellisten kasvien juuret ja varren tyvi olivat lahot. Taudinkuvaan kuului lisaksi hidas kasvuunlahto ja hidas kuiva-aineen kertyminen niin vegetatiivisiin kasvinosiin kuin itse sato-osaankin.Koesarjassa mukana olleista kauratyypeita erityisesti Minnesotassa jalostettu kaapiokaura (Pal) seka kuoreton kauralajike (Salomon) olivat voimakkaasti oireellisia. Kaapiokauran kasvustosta jopa 65 % kuoli ennenaikaisesti vuonna 1995. Pitkakortisen maatiaisen (Jalostettu maatiainen) ja modernien lajikkeiden (Virma ja Salo) oireet olivat voimakkuudeltaan lievia tai keskimaaraisia. Satotappiot aiheutuivat paaosin alhaisesta jyvamaarasta. Sen sijaan saastuneiden yksiloiden jyvien keskipaino saattoi jopa nousta. Oireellisista alalehdista eristettiin kaikkiaan 57 sieni-isolaattia, joista kaksi Fusarium-lajia olivat patogeenisia laboratorio- ja kasvihuonekokeissa. (F. culmorum ja F. sambucinum). Poikkeuksellisen lammin ja kuiva keskikesa vuosina 1994 ja 1995 ilmeisesti edisti maalevintaisten Fusarium-lajien aiheuttaman juuri- ja tyvitaudin puhkeamista, mika puolestaan aiheutti satotappiot. Alun pitaen huomion kohteena olleet lehtioireet lienevat johtuneet muista sienista, jotka tarttuivat heikentyneiden kasvien lehtia, eivatka siten liene olleet satotappioiden kannalta keskeisia.

The phytotoxicity of disinfectants and their effect at different temperatures

When disinfecting plastic growth containers, only sodium hypochloride (NaCIO) caused damage both to cucumber and lettuce seedlings grown on peat if the containers had not been washed with water after disinfection. Also the seedlings grown on rockwool cubes were susceptible to Menno-Ter-forte when the growthcontainers were not properly rinsed after disinfection. All tested disinfectants caused damage to cucumber, lettuce and cauliflower seedlings when mixed in the peat substrate. The efficiency of disinfectants was higher at +2O°C than at +5°C, especially against Fusarium culmorum, F. oxysporum and Rhizoctonia solani. A decrease in temperature affected least the efficacy of NaOCl and Menno-Ter-forte and most that of Virkon S.