Seed trade in the Nordic region in a plant health perspective Seed-borne and seed transmitted microbes

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1 Photo: Arja Lilja/Metla Seed trade in the Nordic region in a plant health perspective Seed-borne and seed transmitted microbes Katri Himanen Finnish Forest Research Institute NordGen Skog Conference 9th of September 2014 Son, Norway Seeds and microbes 1

2 Seeds and microbes All tree seeds are covered with microbes, typically with different fungi. Also Phytophtora species, bacteria etc. are found The microbes can also infect or exist (as endophytic) inside the seed The fungal contamination can happen at many stages of seed (and cone) handling and the significance of it varies greatly Seeds and microbes Some fungi can destroy the whole cone or seed crop and some are serious pathogens causing problems during storage, germination or in the seedlings / trees Mostly the significance of the microbes is mild / non-existent or even beneficial, and typically problems occur when something else has also gone wrong 2

3 Cone rusts The biggest fungal problems in conifer seed production occur up in the tree. Cone rusts infect the flower or young cone and usually destroy the entire cone, even >90% of all cones! Chrysomyxa pirolata (inland) spruce cone rust Thekospora areolata cherry-spruce rust No easy eradication method exists, but these fungi do not infect other seed in seed lots Photo: Tiina Ylioja/Metla Photo: Pekka Voipio/Metla 3

4 Infection during flowering or seed ripening Seeds of broadleaved trees can also be infected during seed development Different Ciboria species can infect birch and alder seed Ciboria batschiana (black rot) infects acorns of different oak species either in the tree or when they touch the forest floor. By using proper collection methods infection levels can be reduced and acorns can be sanitized by hot water treatment. Photo: Tiina Ylioja/Metla Infection during flowering or seed ripening Recent findings show that the fungus (Hymenoscyphus pseudoalbidus) assosiated with ash dieback can be seed transmitted as well The contamination happens apparently during seed development in the infected mother tree However, it is not know can the existence of this fungus in seed actually cause the disease 4

5 Fungal contamination during collection and seed handling Most important source of fungal contamination is cone / seed collection and handling in the field Most species are typical fungi for soil and decaying plant material, such as Penicillium species Most are saprophytic or weekly pathogenic, but many can cause damping-off in the nursery and some are associated with current season needle necrosis (in Abies spp.) Photo: Tiina Ylioja/Metla 5

6 Seed lot Treatment Penicillium Trichoderma Fusarium Acremonium Trichothecium Cladosporium X Seed lot Treatment Alternaria Thysanophora Sirococcus Aureobasidium Apiospora Y Sirococcus conigenus 6

7 Fungal contamination during collection and seed handling Later in the seed processing chain and during storage these microbes can spread Right procedure in all phases of seed handling, storage and use is key to diminish the effect of these microbes 7

8 Cone cleaning removal of debris Kilning C, 2 3 days Seed sorting De-winging Seed storage High quality seed holds best in storage C 5 6% moisture content for orthodox seed If you have to compromise one, choose temperature! 8

9 New (invasive) pathogens Caloscypha fulgens = Geniculodendron pyriforme A common storage pathogen in North and South America in conifers, including Sitka spruce Causes the seeds not to germinate The fungus is reported to have been found in seed lots imported to Europe New (invasive) pathogens Diplodia pinea = Sphaeropsis sapinea Is know to infect over 30 different Pinus species around the world. Found recently in Estonia, Sweden and around St. Petersburg Causes cankers and other symptoms in nurseries and in the field. Often the symptoms appear after stress or damage to the seedling /tree Infects old pine cones and the spores are transmitted to seeds 9

10 New (invasive) pathogens Gibberella circinata = Fusarium circinata, Pitch canker A chronic problem in pine plantations and seedling production in south-eastern USA. Spread also to Europe (Spain, Italy) as well as to South America and South Africa Can cause damping-off type symptoms, root infections and infection in other tree parts as well Seed-borne, can exist both on surface and inside the seed. No clear explanation for the occurrence of the infection in seed. The disease can travel from tree to tree via insects etc. Lessons to seed trade Seeds always contain microbes do not expect anything else Therefore regulations exists and changes in rules may occur Mostly there is little need for worry, BUT Seed producers, sellers and users should use the best practice methods to decrease risks 10

11 Thank you 11