Anna Rytkönen

Effects of sugar beet chitinase IV on root-associated fungal community of transgenic silver birch in a field trial

Heterogenous chitinases have been introduced in many plant species with the aim to increase the resistance of plants to fungal diseases. We studied the effects of the heterologous expression of sugar beet chitinase IV on the intensity of ectomycorrhizal (ECM) colonization and the structure of fungal communities in the field trial of 15 transgenic and 8 wild-type silver birch (Betula pendula Roth) genotypes. Fungal sequences were separated in denaturing gradient gel electrophoresis and identified by sequencing the ITS1 region to reveal the operational taxonomic units. ECM colonization was less intense in 7 out of 15 transgenic lines than in the corresponding non-transgenic control plants, but the slight decrease in overall ECM colonization in transgenic lines could not be related to sugar beet chitinase IV expression or total endochitinase activity. One transgenic line showing fairly weak sugar beet chitinase IV expression without significantly increased total endochitinase activity differed significantly from the non-transgenic controls in the structure of fungal community. Five sequences belonging to three different fungal genera (Hebeloma, Inocybe, Laccaria) were indicative of wild-type genotypes, and one sequence (Lactarius) indicated one transgenic line. In cluster analysis, the non-transgenic control grouped together with the transgenic lines indicating that genotype was a more important factor determining the structure of fungal communities than the transgenic status of the plants. With the tested birch lines, no clear evidence for the effect of the heterologous expression of sugar beet chitinase IV on ECM colonization or the structure of fungal community was found.

Introduced pathogens found on ornamentals, strawberry and trees in Finland over the past 20 years

Kansainvalinen kasvikauppa on edesauttanut vieraslajien ja suotuisat tuulet tulokaslajien leviamista maasta toiseen. Varsinkin Phytophthora-suvun mikrobit ovat hyotyneet koristekasvikaupan vilkastumisesta. Suomeen kulkeutui 1990-luvun alussa taimien mukana Phytophthora cactorum-mikrobi, jota voidaan kutsua jo vakiintuneeksi vieraslajiksi. Mansikassa se aiheuttaa seka tyvi- etta nahkamataa ja saman lajin toinen kanta levalaikkutaudin koivun taimissa. Myohemmin, vuonna 2000 mansikan mustalaikun aiheuttaja Colletotrichum acutatum, loytyi mansikan tuontitaimista. Phytophthora ramorum-mikrobi, joka Amerikassa aiheuttaa tammenakkikuolemaa ja joka on Englanissa tuhonnut vierasperaisia Japaninlehtikuusiviljelmia, eristettiin ensimmaisen kerran 2004 tuontitaimista, mutta myohemmin myos kotimaassa tuotetuista versopoltteisista alppiruusuista. Seka C. acutatum etta P. ramorum nayttavat sailyvan viljelyaloilla havitystoimenpiteista huolimatta. Uusimmat vieraslaji ovat Phytophthora plurivora ja P. pini, jotka tartutuskokeissa ovat osoittatautuneet erittain haitalliseksi monille luonnossa tavattaville kasveille. Aasiasta kotoisen oleva ruostesieni, Melampsoridium hiratsukanum, levisi meille tuulten mukana 1997 ja on siita lahtien ruskettanut paikoitellen leppien lehtia. Muita tulokaslajeja ovat Dothistroma septosporum ja Chalara fraxinea. Ensinmainittu aiheuttaa punavyokariste-taudin monilla mantylajeilla, ja sen esiintyminen meilla metsamannylla varmennettiin useammalla paikkakunnalla 2008. C. fraxinea puolestaan liitetaan saarnensurmaksi nimettyyn tautiin, joka on tappanut saarnimetsikoita Euroopassa kohta 20 vuotta. Ensimmaiset oireet taudista havaittiin Ahvenanmaan saaristossa ja myohemmin 2007 mantereella, lukuunottamatta saarnen levinneisyysalueen itaosaa.

Identity and potential pathogenicity of Phytophthora species found on symptomatic Rhododendron plants in a Finnish nursery

Abstract In this study, microbial isolations were made from symptomatic Rhododendron plants from a large Finnish nursery, known to be harbouring Phytophthora based on PCR screenings. The nearby waterways were also sampled. A diversity of common Nordic plants was screened for Phytophthora susceptibility. Isolates recovered from Rhododendron plants included P. ramorum, P. cactorum, P. plurivora, P. pini and Pestalotiopsis sp. Baits floated in water samples from nearby waterways did not become infected with Phytophthora. In infection trials, all Phytophthora detected here were pathogenic to Rhododendron but nonpathogenic to Pinus sylvestris and Quercus robur. Phytophthora plurivora infected Betula pendula, Alnus glutinosa, Picea abies, Viburnum lentago, Vaccinium myrtillus, V. uliginosum, V. angustifolium and Fragaria × ananassa, the latter four species being new host records for this pathogen. Phytophthora ramorum caused small lesions on B. pendula, A. glutinosa and V. uliginosum, and more serious symptoms in Rhododendron, Viburnum lentago, V. lantana, Vaccinium myrtillus and V. angustifolium. Phytophthora pini was pathogenic to most plants tested, including Rhododendron, V. lentago and P. abies. In spite of an annual eradication programme in the nursery, P. ramorum was detected in annual samples taken during 2004–2010. Microsatellite analysis revealed that all isolates of P. ramorum belonged to the EU1 lineage.

Soaking effects on seed germination and fungal infection in Picea abies

Abstract The effect of soaking on germination and occurrence of fungal infections on Norway spruce (Picea abies (L.) Karst.) seeds and germinants was studied in three commercial seed lots. Treatments in which seeds were soaked in water for 24 h or in which the water was changed during the soak did not have an effect on the species diversity or on the abundance of the fungi isolated from the seeds. Different fungi were found in different seed lots. Most of those isolated are saprophytic or weakly pathogenic, but pathogens such as Sirococcus conigenus (D.C.) P.F. Cannon & Minter and Trichothecium roseum (Pers.) Link were also isolated. Soaking increased germination energy but had no effect on final germination percentage. The number of mouldy seeds and germinants with disease symptoms was different among seed lots when seeds were germinated on water agar. When germinated in low humified Sphagnum peat, no differences in the emergence of disease symptoms were observed among seed lots. The frequency of disease was lower in peat than in water agar. Soaking had no effect on disease emergence in germination trials on either water agar or in Sphagnum peat.

Irrigation water and Phytophthora cactorum in a forest nursery

Abstract Phytophthora cactorum (Lebert and Cohn) J. Schröt is known to cause stem lesions on Betula pendula Roth in Finnish nurseries. It has been suggested that irrigation water may be one source of infection. Therefore, P. cactorum was baited from pond water used for irrigation and direct isolations were made from necrotic stem lesions in a forest nursery during the years 2004–2006. Morphological characteristics, as well as sequencing of the β-tubulin gene and ITS1 region, confirmed the isolates as P. cactorum. The pathogen was present in the pond every year, but no diseased seedlings were found in 2005. The cultural and morphological characteristics showed high variation among the isolates, but it was not possible to identify the origins of the isolates according to them. In random amplified microsatellite (RAMS) analysis and DNA sequencing, the isolates from the pond and from the stem lesions were genetically similar, and the tested isolates were pathogenic. The results indicate that irrigation water is one source of stem lesion disease, and the microbe can overwinter in the pond. Two separate forms of the β-tubulin gene were detected in all the studied isolates, suggesting that the P. cactorum here carries two β-tubulin gene loci in its genome.