Effect of temperature during sclerotial formation, sclerotial dryness, and relative humidity on myceliogenic germination of sclerotia of Sclerotinia sclerotiorum

Abstract

A study was conducted to determine the effect of sclerotial dryness, temperature during sclerotia formation, and relative humiditiy during incubation on myceliogenic germination of sclerotia of two isolates of Sclerotinia sclerotiorum (Lib.) De Bary. In the absence of exogenous nutrients, sclerotia germinated more readily at 100% RH than at 95% RH or lower. Desiccation of sclerotia is an important factor affecting myceliogenic germination and hyphal growth. At high humidity, either in an atmosphere with 100% RH or on moist sand, desiccant-dried sclerotia germinated readily and produced vigorous hyphal growth that often developed into colonies. On the other hand, fresh, untreated sclerotia germinated less readily and produced limited growth of hyphae that rarely developed into colonies. There was generally no effect of temperature at which sclerotia formed on germination. The incidence of seed rot and seedling wilt of sunflower was significantly (p < 0.05) higher when desiccant-dried sclerotia were used as inoculum rather than fresh sclerotia.Résumé : Les auteurs ont étudié les effets de la dessiccation des sclérotes, de la température au cours de la formation des sclérotes, et de l'humidité relative en cours d'incubation sur la germination mycéliogène des sclérotes de deux isolats du Sclerotinia sclerotiorum (Lib.) De Bary. En absence de nutriments exogènes, les sclérotes germent plus facilement à 100% d'humidité relative qu'à 95% ou moins. La dessiccation des sclérotes est un facteur important affectant la germination mycéliogène et la croissance des hyphes. À haute humidité, ou à 100% d'humidité relative ou sur sable humide, les sclérotes séchées en présence d'un agent desséchant germent facilement et donnent une croissance mycélienne vigoureuse qui se développe souvent en colonie. Comparativement, les sclérotes frais et non-traités germent moins facilement et produisent des hyphes à croissance limitée qui forment rarement des colonies. La température à laquelle se forment les sclérotes est généralement sans effet sur leur germination. La présence de pourriture des graines avec flétrissement des plantules de tournesols était significativement plus élevée (p < 0,05) lorsque les sclérotes séchés en présence de desséchant ont été utilisés comme inoculum, plutôt que des sclérotes frais.

Evaluation of an Inoculum Production and Delivery Technique forValdensinia heterodoxa, a Potential Biological Control Agent for Salal

“…A cold storage of several months, which would imitate seasonal changes in the field, might enhance sporulation, but that gain would have to be balanced against a prolonged inoculum production period. Moisture might have an even greater effect on reproduction than temperature, as has been shown for Sclerotinia sclerotiorum where sclerotial dryness and relative humidity during incubation strongly affected myceliogenic (Huang et al , 1998). In our study, relative humidity in the incubation environment was not recorded but the substrates used showed differences in moisture content (ranging from 52 to 75%).…”

TaqMan Multiplex Real-Time qPCR assays for the detection and quantification of Barley yellow dwarf virus, Wheat dwarf virus and Wheat streak mosaic virus and the study of their interactions

“…Furthermore, Huang (1991) determined that conditioning sclerotia at sub-freezing temperatures induces vigorous myceliogenic germination in moist conditions. In a subsequent study, Huang et al (1998) revealed that relatively high temperatures (20 and 258C) during sclerotial development, in combination with sclerotial desiccation, led to vigorous myceliogenic germination under moist incubation conditions. It was proposed that the drying process again caused injury to the rind, which subsequently allowed the leakage of nutrients that were able to support vigorous hyphal growth (Huang et al 1998).…”

“…In a subsequent study, Huang et al (1998) revealed that relatively high temperatures (20 and 258C) during sclerotial development, in combination with sclerotial desiccation, led to vigorous myceliogenic germination under moist incubation conditions. It was proposed that the drying process again caused injury to the rind, which subsequently allowed the leakage of nutrients that were able to support vigorous hyphal growth (Huang et al 1998). Further research is required to confirm the effect of sclerotial desiccation and drying before myceliogenic germination.…”

“…Among sclerotia that myceliogenically germinated on moist sand, a range of phenotypes were observed. Previous attempts to capture this diversity categorised myceliogenic germination as non-vigorous ('germination') and vigorous (Huang et al 1998). To simplify statistical analyses, we used similar categories, but defined them based on the range of subtly different phenotypes we observed (see Materials and methods for definitions).…”

“…Most research on myceliogenic germination of S. sclerotiorum has used sclerotia collected from regions in Canada, where subfreezing temperatures routinely occur during winter (Huang and Dueck 1980;Huang 1985Huang , 1991Huang et al 1998). However, it has been reported that basal infection also occurs in dryland agricultural regions of the world with a Mediterranean climate (Khangura and Beard 2015).…”