Effect of environmental conditions on spore production by Fusarium verticillioides, the causal agent of maize ear rot

Abstract

Silk infection by Fusarium verticillioides is caused by conidia produced on maize crop residues and results in kernel infection and consequent accumulation of fumonisins. Studies were carried out in both controlled and field conditions to understand the dynamics of sporulation on maize residues. The effect of temperature (5°C to 45°C) and incubation time (3 to 41 days) on spore production on maize meal agar was described by a logistic model that accounted for 85% of variability. The rate parameter depended on the length of incubation and the asymptote on temperature. Maximum sporulation occurred at 27°C, with a progressive increase between 5°C and 27°C and then a rapid decline, with no sporulation at 45°C. Fusarium verticillioides strains from different geographic origins showed different sporulation capabilities, with similar optimum temperatures. Pieces of stalk residues inoculated with F. verticillioides and placed above the soil between rows of maize crops, in 2003 to 2005, produced conidia continuously and abundantly for some weeks, particularly during the period after silk emergence, with an average of 1.59×10 7 conidia g −1 of stalk, over a wide range of environmental conditions. Sixty-seven percent of variability of the spore numbers found on stalks was accounted for by a multiple regression model. Precipitation (rain or overhead irrigation) in the 14 days before stalk sampling decreased the number of spores, whilst the number of days with conducive conditions of moisture (i.e. days with rainfall, average relative humidity >85% or vapour pressure deficit <4 hPa) and greater degreedays (base 0°C) in the 14 and 3 days before sampling, respectively, increased sporulation.

Climate change impacts on mycotoxin risks in US maize

“…Some of these results were summarised by Maiorano et al (2009). Sporulation, germination, and growth of F. verticillioides are optimised at 25-30 °C (Maiorano et al, 2009;Rossi et al, 2009). Most studies have found optimal conditions for fumonisin production are a temperature close to 30 °C and high water activity (Marin et al, 1999;Reid et al, 1999).…”

“…Chauhan et al, 2008;De la Campa et al, 2005;Maiorano et al, 2009;Rossi et al, 2009;Schaafsma and Hooker, 2007), none of these was conducted in US maize. The creation of a climatemycotoxin prediction model would enable growers and their buyers to anticipate future fungal disease occurrences and mycotoxin contamination incidents.…”

Impact of increasing temperature on the fitness of Fusarium pseudograminearum causing crown rot in wheat

“…In this study, temperature was found to be the most influential factor affecting spore production (Rossi et al, 2009). Rossi et al (2009) also reported that spores were produced across a wide range of temperatures (5-45 o C) with optimal production at 30 o C. In another study, Paul et al (2007) showed that for the dominant head blight pathogen in North America, F. graminearum, the number of spores sampled from wheat spikes was also significantly related to weather variables including air temperature and rain intensity. Spore production amongst three important crown rot pathogens in Australia, including F. pseudograminearum, was investigated in a recent study by Tunali et al (2012) where the fungi had been grown on PDA at 25 o C. In this study, Tunali et al (2012) found that spore production was significantly different for the three species and also for isolates within each species, and overall being lowest for F. pseudograminearum.…”

“…This was demonstrated in a recent in vitro study by Rossi et al (2009) where temperature and the length of incubation time significantly influenced sporulation of F. verticillioides, the causal agent of maize ear rot. In this study, temperature was found to be the most influential factor affecting spore production (Rossi et al, 2009). Rossi et al (2009) also reported that spores were produced across a wide range of temperatures (5-45 o C) with optimal production at 30 o C. In another study, Paul et al (2007) showed that for the dominant head blight pathogen in North America, F. graminearum, the number of spores sampled from wheat spikes was also significantly related to weather variables including air temperature and rain intensity.…”

“…temperature and moisture) (Little et al, 2012). This was demonstrated in a recent in vitro study by Rossi et al (2009) where temperature and the length of incubation time significantly influenced sporulation of F. verticillioides, the causal agent of maize ear rot. In this study, temperature was found to be the most influential factor affecting spore production (Rossi et al, 2009).…”