Discharge and germination of Eutypella parasitica ascospores

Abstract

LACHANCE, D. 1971. Discharge and germination of Elrtypella parasitica ascospores. Can. J. Bot. 49: 1111Bot. 49: -1118. Perithecia of Errtypella parasitica on cankered sugar maple in natural stands, discharged ascospores only when rainfall occurred. However, there was no relationship between amount of rainfall and intensity of spore discharge. High relative humidity alone did not induce spore ejection, but wetting of perithecia did. Variations in summer temperature appeared not to influence spore release. In laboratory studies, spore discharge from wetted clusters of perithecia on excised pieces of bark kept in moist chambers, was heavy at 20°C, light at 12"C, and nil at 4°C. Although near-freezing temperature inhibited ascospore discharge, exposure to warm temperature of previously frozen perithecia quickly induced release of viable ascospores. Ascospores germinated readily in water or on common agar media. Germination was rapid at 20°C, slow at 12'C, and nil at 4°C. Ascospores remained viable for several months when stored dry at 4°C; up to 13% still germinated after 20 months of storage. Ascospores stored dry at 20°C germinated poorly after 5 weeks.Des ptritheces du chancre Errtypelln parrrsitica sur des Crables a sucre en for&, ont libere des ascospores seulement a l'occasion de pluies. On a cependant decele aucune relation entre I'intensite de la precipitation et la quantite de spores libirees. Une periode de forte humidit6 relative n'a pu provoquer une sporulation; I'ecorce des arbres, et par consequent les perithtces, devaient Ctre niouilles pour obtenir une sporulation. Les variations de la temperature estivale n'ont pas influend la liberation des spores. En laboratoire, utilisant des morceaux d'icorce places en chanibre huniide et portant des peritheces d'E~ttypella, on a obtenu une sporulation abondante a 20°C, legere a 12°C et nulle a 4°C. Des peritheces geles durant 2 semaines ont sporule abondamment lorsque replaces dans des conditions favorables de temperature et d'humidite, et les spores liberees etaient presque toutes viables. Les ascospores d'Elrtypella germent bien dans l'eau et sur des milieux geloses conimuns. La germination est excellente et rapide a 20°C, lente a 12°C et nulle a 4°C. On a obtenu prbs de 13y0 de germination avec des spores conservees seches i 4°C durant 20 mois. Conservees a 20°C, ces spores n'etaient pratiquement plus viables aprks 5 semaines.

Taxonomic diversity of fungi deposited from the atmosphere

“…Indeed, agaricomycetes comprise a group of fungi that actively discharge spores primarily under humid conditions [ 5 ], including Stereum , Trametes , and Schizophyllum [ 54 – 56 ]. Peroneutypa has a closely related sordariomycete genus Eutypella [ 57 ] whose ascospores are discharged only when rainfall occurs [ 58 ]. Our observation suggests two non-mutually exclusive hypotheses: (1) spores serve as nuclei in clouds, and/or (2) spores are released selectively during precipitation.…”

Spread risk of Eutypella canker of maple in Europe1

“…Ascospore discharge is greatest at temperatures between 24 and 28°C (Johnson & Kuntz, 1979; Lachance, 1971). Laboratory tests show no ascospore discharge and dissemination at temperatures below 4°C and higher than 36°C.…”

“…Free moisture (rainfall) must also exist on mature perithecia to induce discharge of ascospores. At least 3 mm of rain has to penetrate the tree canopy to initiate discharge (Johnson & Kuntz, 1979; Lachance, 1971). Spore ejection begins about 2 h after rain has started.…”

Eutypella parasitica and Other Frequently Isolated Fungi in Wood of Dead Branches of Young Sycamore Maple (Acer pseudoplatanus) in Slovenia

“…Fruiting bodies (i.e., perithecia) develop in the central part of six to eight-year-old cankers. Their black necks protrude slightly above the surface [18] and release ascospores during wet periods at moderate temperatures [20,22]. The high number of discharged ascospores is an important factor of successful disease spread [21].…”

“…Spores are dispersed by wind, over long distances by trade of plants for planting or wood [23]. The optimal temperature for fungus growth is 24-28 • C [22,24].…”