Water and temperature relations and microconidial germination of Fusarium moniliforme and Fusarium proliferatum from maize

Abstract

The effects of water activity (aW, 0.994-0.85 = 0.4-21.0 (-)MPa water potential), temperature (5-42 degrees C), and their interactions on microconidial germination of three isolates each of Fusarium moniliforme and Fusarium proliferatum were determined in vitro on a maize meal extract medium. Temporal germination rates of microconidia of isolates of both species were significantly influenced by both aW and temperature. Germination was very rapid at > 0.94 aW with an almost linear increase with time. Germination rates of microconidia of F. moniliforme were slower than those of F. proliferatum isolates at marginal aW levels and 5-25 degrees C, while at higher temperature (30-37 degrees C), the former germinated more rapidly than the latter. The aW minima for germination of isolates of both species was 0.88, with none occurring at 0.85 aW over a 40-day incubation period. At 37 degrees C, isolates of F. moniliforme had slightly lower aW minima than those of F. proliferatum. The narrowest range of aW for germination was at 5 degrees C, and none occurred at 42 degrees C. The effect of aW x temperature interactions on the lag phases (h) prior to germination and the germination rates (h-1) were estimated using the Gompertz model and the Zwietering equation. This showed that lag phases were shorter at 25-30 degrees C and 0.994-0.98 aW, and were increased to 10-500 h at marginal temperatures (5-10 degrees C) for F. proliferatum and longer for F. moniliforme. At marginal aW levels (0.92-0.90), lag times were increased to > 250 h. Germination rates (h-1) were different for the two species. Microconidia of F. moniliforme germinated optimally at 25-37 degrees C and 0.96-0.98 aW, but this changed to 30 degrees C at 0.90-0.94 aW, while germination of microconidia of F. proliferatum remained optimum at 30 degrees C, regardless of aW. There were statistically significant (P < 0.01) effects of aW, temperature, isolate, and two- and three-way interactions for F. proliferatum, but there were no intraisolate effects for F. moniliforme. The ecological significance of these data for understanding colonization patterns of these important fumonisin-producing fungi are discussed.

Predictive modelling of temperature and water activity (solutes) on the in vitro radial growth of Botrytis cinerea Pers

“…The average diameter of each growing mycelial colony was measured daily in two perpendicular directions (Marín et al, 1996;Lahlali et al, 2005) without opening the Petri dishes.…”

“…Nevertheless, most of the models derive from models based on bacterial data due to the inherent difficulties in assessment of fungal growth rates and gathering of sufficient suitable and reproducible data (Gibson and Hocking, 1997;Dantigny et al, 2005a). Various workers have developed probability, mechanistic/semi-mechanistic, empirical and thermal death models for a variety of toxigenic and spoilage fungi (Pitt, 1993;Skirdal and Eklund, 1993;Gibson et al, 1994;Marín et al, 1996;Cuppers et al, 1997;El-Halouat and Debevere, 1997;Valík and Piecková, 2001;Sautour et al, 2002). The major objective of the present work was to construct and evaluate models describing the individual and combined effects of water activity and temperature on the radial growth rate of B. cinerea for each tested solute.…”

Studying and modelling the combined effect of temperature and water activity on the growth rate of P. expansum

“…The preservation of water content in media was checked by a w measurement of inoculated Petri dishes after 25 days at each temperature. The radius of each growing mycelial colony was measured daily in two directions at right angles to each other (Marin et al, 1996) without opening the Petri dishes. Three replicates were used per solute-a w -temperature combination.…”

The impact of environmental factors on the infection of cereals with Fusarium species and mycotoxin production – a review / Vpliv okoljskih dejavnikov na okužbo žit z glivami Fusarium spp. in tvorbo mikotoksinov – pregledni članek

“…Marín et al (1996) found that the aw minima for the microconidial germination of Spanish isolates of F. moniliforme and F. proliferatum were 0.88 on maize meal extract medium. (Marín et al, 1996;Etcheverry et al, 2002).…”

“…Marín et al (1996) found that the aw minima for the microconidial germination of Spanish isolates of F. moniliforme and F. proliferatum were 0.88 on maize meal extract medium. (Marín et al, 1996;Etcheverry et al, 2002). Earlier, Francis and Burgess (1977) found that the percentage germination of conidia, ascospores and chlamydospores of F. graminearum Group II isolates was reduced as water potential was lowered from −1 to −20 bars.…”