DNA markers for Typhula resistance in timothy (Phleum pratense L.)

The objective of the study was to find DNA markers associated with resistance to Typhula ishikariensis in timothy (Phleum pratense L.) using bulked-segregant analysis. A progeny of 161 F1 individuals was created by crossing the Finnish resistant cultivar Tammisto II with the Japanese susceptible cultivar Nosappu. Six to ten clones of each F1 individual were tested for resistance in the greenhouse, and a survival index, which was based both on survival and the ability of plants to recover, was calculated for each F1 to describe resistance. Resistant and susceptible bulks of eight individuals in each were screened with a total of 292 primer combinations. Six DNA markers were found to be associated with resistance, together explaining 15% of phenotypic variation in Typhula resistance. Four of the markers formed one linkage group, which contained a QTL explaining 7% of the variation in Typhula resistance.

Nurmikasvien geneettinen tutkimus – haasteena timotei

Bioteknisillä menetelmillä, kuten DNA-merkeillä, pystytään nopeuttamaan myös nurmikasvien jalostusta. Nurmikasveista tutkituimpia ovat raiheinät (Lolium) ja nadat (Festuca), joilla on diploidi perimä (kaksinkertainen kromosomisto). Tutkimuksen kannalta haasteellisempia ovat polyploidiset kasvit, koska niiden periytyminen on monimutkaisempaa. Tämän tutkimuksen kohteena oli timotei (Phleum pratense), joka on heksaploidi (kuusinkertainen kromosomisto) ja jonka periyttämistapa on vielä epäselvä. Tutkimuksen pitkän tähtäimen tavoitteena on tehostaa timotein lajikejalostusta siten, että viljelijöillä olisi tulevaisuudessa käytössään satoisa, talvenkestävä, kasvurytmiltään optimaalinen ja sulavuudeltaan korkeatasoinen timoteilajike. Yhtenä tavoitteena oli tuottaa timoteijalostajien käyttöön valintatyökaluiksi DNA-merkkejä, jotka liittyvät soluseinän sulavuuteen ja talvituhosienten kestävyyteen. Tutkimusmateriaalina käytettiin kahta Boreal Kasvinjalostuksessa tuotettua timoteijälkeläistöä. Toisessa jälkeläistössä vaihteli rehun sulavuus. Kandidaattigeenianalyysin avulla haettiin rehun sulavuuteen liittyvien geenien edullisia geenimuotoja eli alleeleita. Toinen jälkeläistö testattiin Typhula ishikariensis -talvituhosienenkestävyyden suhteen, johon liittyviä kromosomialueita etsittiin bulkkianalyysin avulla. Kummankaan em. analyysin käytöstä timoteillä ei ole aiempaa kokemusta. Löytyneet DNA-merkit selittivät vain pienen osan ominaisuuksissa havaitusta vaihtelusta, mikä ei ole yllättävää ottaen huomioon timotein heksaploidin ja heterotsygoottisen perimän. Kuitenkin edulliseen alleeliin liittyvää DNA-merkkiä on mahdollista käyttää valintatyökaluna lajikejalostuksessa. Projektissa selvitettyjen rehun sulavuuteen vaikuttavien timotein ligniinibiosynteesigeenien sekvenssit tallennettiin Geenipankin tietokantaan. Tämä on merkittävä lisä timotein geenitietoon, sillä aiemmat timoteisekvenssit geenipankeissa ovat lähinnä siitepölyallergeenien geenejä. Nyt päättyneen hankkeen materiaalia ja tuloksia voi jatkossa käyttää paitsi käytännön kasvinjalostustyössä myös kotimaisissa ja pohjoismaisessa nurmitutkimuksessa.

Snow mold fungus, Typhula ishikariensis group III, in Arctic Norway can grow at a sub-lethal temperature after freezing stress and during flooding

Snow mold fungus, Typhula ishikariensis group III, in Arctic Norway can grow at a sub-lethal temperature after freezing stress and during floodingIsolates of the snow mold fungus Typhula ishikariensis group III, which is predominant in Finnmark (northern Norway) and Svalbard, are more resistant to freezing stress than group I isolates from the southern part of Norway. Group III isolates showed irregular growth on potato dextrose agar (PDA) plates when subjected to heat stress at 10°C. However, group III isolates showed relatively good growth on PDA at 10°C after freezing treatment. The optimal temperatures for mycelial growth were 5°C on PDA and 10°C in potato dextrose broth (PDB), and group III isolates showed normal mycelial growth at 10°C in PDB. Mycelium of group III isolates cultivated in water poured into PDA plates, and normal hyphal extension was observed only in the liquid media. Hyphal growth became irregular when mycelia had extended above the surface of the liquid media. These results suggested that group III isolates can grow at a sub-lethal temperature after freezing stress and during flooding. Soil freezing and thawing occurs regularly in the Arctic, and physiological characteristics of group III isolates are well adapted to climatic conditions in the Arctic.

Aggressiveness of Typhula ishikariensis Isolates to Cultivars of Bentgrass Species (Agrostis spp.) Under Controlled Environment Conditions

Speckled snow mold, caused by Typhula ishikariensis, is one of the most important Typhula snow molds in subarctic zones of the Northern Hemisphere. Nine isolates of three T. ishikariensis varieties (var. ishikariensis, var. canadensis, and var. idahoensis) isolated from infected turfgrasses on golf course fairways throughout Wisconsin were evaluated for their aggressiveness toward nine cultivars of three bentgrass species (three creeping, three colonial, and three velvet cultivars) under controlled environmental conditions. Speckled snow mold severity increased as inoculum concentration of T. ishikariensis was increased. In general, bentgrass susceptibility increased between 9 and 11 weeks after seeding but gradually decreased thereafter, suggesting expression of age-related resistance as plants matured. Significant differences in aggressiveness were detected within and among T. ishikariensis varieties. Significant interactions between T. ishikariensis varieties or isolates and bentgrass species were detected, but there was no interaction between pathogen isolates and bentgrass cultivars. Disease severity evaluations showed significant differences among bentgrass cultivars and species in their response to T. ishikariensis. Since bentgrass species exhibit differential responses to T. ishikariensis varieties, representative isolates of each variety should be employed for screening of bentgrass germplasm for resistance to speckled snow mold.

Antifreeze proteins from snow mold fungi

The psychrophilic fungi Coprinus psychromorbidus and Typhula ishikariensis produced unique antifreeze proteins (AFPs) in the extracellular space. Molecular masses of purified fungal AFPs of C. psychromorbidus and T. ishikariensis were approximately 22 and 23 kDa, respectively. Cloned genes of AFPs from T. ishikariensis do not have any similarity with known proteins. Purified fungal AFPs from cultural filtrate of T. ishikariensis and recombinant fungal AFP from methylotrophic yeast formed specific ice crystals resembling "Stone Age knives". These observations indicate that fungal AFPs do not form proper hexagonal ice crystals to inhibit their growth and that fungal AFPs can probably bind to surfaces of ice crystals in an irregular manner.Key words: antifreeze protein, snow mold fungi, Coprinus psychromorbidus, Typhula ishikariensis.