A Comparison of Fusarium Pseudograminearum and F. Graminearum from Wheat in Australia

In Australia both Fusarium graminearum and F. pseudograminearum cause head blight and crown rot of wheat and this work compares the aetiology and diversity between the two species. A total of 199 isolates of F. pseudograminearum and 118 isolates of F. graminearum obtained from wheat grown in Queensland and northern New South Wales and were identified using published species-specific PCR assays. The phenotypic measures used include aggressiveness on wheat, corn, sorghum, canola, barley, rye, oat and triticale, mycotoxins produced in autoclaved-wheat culture, growth rate on potato dextrose agar, spore size and the number of macroconidia produced in culture. To measure aggressiveness, the middle spikelet of wheat, oat, barley, rye and triticale was inoculated at flowering with 10-μL suspension of 105 macroconidia/ mL. Number of spikelets infected was recorded at 14 days after inoculation. Corn, sorghum and canola were inoculated using sterile toothpicks colonised by the pathogen by growing in potato dextrose broth for 7 days and the length of stem rot was recorded after 14 days. Genotypic relationship between the two species was evaluated using Amplified fragment length polymorphism with five primer pair combinations. Both species produced the same mycotoxins Deoxynivalenol (DON), Zearalenone (ZEA) and nivalenol (NIV). NIV concentration in all samples tested was less than 250 ppb, while DON concentration ranged between 2.5 ppm and 0.71 ppm in F. pseudograminearum and 4.4 ppm and 2.4 ppm in F. graminearum. ZEA concentration was considerably higher in F. graminearum (3.0-11.9 ppm) than in F. pseudograminearum (0.9-2.2 ppm). The symptoms and severity of diseases produced on the heads of the cereal crops were similar. Both species caused canker and stem rot in canola, and stalk rot in corn and sorghum. A high level of genotypic diversity was observed within each species. All F. graminearum isolates produced homothallic perithecia in culture but only 8% of F. pseudograminearum isolates produced heterothallic perithecia in culture. Although there were variations in all the phenotypic and genotypic measures for each species, the level of variation in F. graminearum was higher than in F. pseudograminearum. 2003 National Fusarium Head Blight Forum Proceedings 121 Epidemiology and Disease Management RECOVERY OF FUSARIUM GRAMINEARUM, CAUSE OF WHEAT HEAD SCAB, AND DEOXYNIVALENOL FROM INOCULATED LEAVES AT ADULT PLANT STAGE IN THE GREENHOUSE Shaukat Ali* Plant Pathology Department, North Dakota State University, Fargo, ND 58105 *Corresponding Author: PH: (701) 231-6467; E-mail: [email protected]