Effects of temperature, vapour pressure deficit and radiation on infectivity of conidia ofBotrytis cinerea and on susceptibility of gerbera petals

Abstract

The effect of vapour pressure deficit, temperature and radiation on the postharvest susceptibility of gerbera flowers to B. cinerea, on the water relations of gerbera flowers and on the lesion formation after conidial infection of B. cinerea was studied. The temperature range in which B. cinerea could germinate and grow in vitro is 5-30 ~ In climate chamber experiments flowers had more lesions of B. ctnerea at temperatures of 20 and 25 ~ than at 10 and 15 ~ At 15, 20 and 25 ~ the infectivity of B. cinerea conidia was negatively affected during a storage-period of 7 days. At a vapour pressure deficit (VPD) of 200 Pa significantly more conidia of B. cinerea were infective than at 800 Pa. At a VPD of 800 Pa the susceptibility of gerbera flowers for B. cinerea was not significantly different than at 200 Pa. High radiation levels in glasshouses in spring and summer negatively influenced the infectivity of conidia of B. cinerea on the flower surface, but did not affect the susceptibility of gerbera flowers for B. cinerea. In spring and early summer conidia lost their infectivity at high radiation levels, high temperatures and high levels of VPD. In summer gerbera flowers could be more susceptible to B. cinerea because of high temperatures in glasshouses, but the negative effect of radiation on the conidia of B. cinerea seemed to overrule the temperature effect. Thus, the numbers of lesions in spring and summer can be low compared with the numbers in other seasons, although the numbers of B. cinerea colonies on spore traps can be high. The effect of temperature on the susceptibility of gerbera flowers can probably be explained by changes of water status in the petals. At higher temperatures the number of lesions and the turgor (= water potential -osmotic potential) in the petals increased. Temperatures < 10 ~ during lesion formation (RH > 95% and VPD < 50 Pa) had a temporary negative effect on the number of lesions. After 3 days of incubation the numbers of lesions were about equal (> 30 lesions/cm 2) from 5 to 20 ~ At 30 ~ no lesion formation was observed even after 3 days.

Relationships of microclimatic variables to colonization of rose debris byBotrytis cinereaand the biocontrol agentClonostachys rosea

“…In general, growth of B. cinerea is strongly favoured by temperatures ranging from 18 to 228C, RH /85%, and presence of water on tissue surfaces (Jarvis 1992;Kerssies 1994). Once established in senescing tissues, the pathogen becomes less dependent of external environmental conditions for survival, but still requires high humidity for sporulation (Hausbeck & Moorman 1996).…”

Effects of Growth Conditions on Postharvest Botrytis Infection in Gerbera – a Nursery Comparison

“…This could be explained by the decreased spore vitality at high light levels as described by Kerssies (1994) or through the increased susceptibility of tissue grown under low light conditions due to a softer tissue structure. Usually Botrytis does not invade healthy green tissue unless an injured or dead area is present, where leaves in the lower canopy are often infected and then the fungus can spread (Körner and Challa, 2003).…”

“…However, the effect of high air humidity can be stronger or weaker depending on the specific susceptibility of the tissue as the fungus can easily invade soft flower petals (Marois et al, 1988). During daytime there are many more spores present in the greenhouse (Kerssies, 1994;Hausbeck and Pennypacker, 1991) and a dry microclimate around the flower petals can then prevent adhesion and germination (van Kan, 2005). During night humidity in greenhouses is generally higher than during day time and with very high humidity conditions or even free water on the leaves, the fungus can attack the leaf tissue through tiny wounds.…”

Relations between glasshouse climate and dry weight of petals, epicuticular wax, cuticle, pre-harvest flowering period and susceptibility toBotrytis cinerea of gerbera and rose flowers

“…Kerssies [1994] found that relative humidity and radiation had affected infectivity of conidia ofB. cinerea but not the susceptibility of gerbera flowers to the pathogen.…”