Evaluation of the pathogenicity ofFusarium graminearumandFusarium pseudograminearumon soybean seedlings under controlled conditions

Abstract Fusarium graminearum, the cause of fusarium head blight of small-grain cereals and of gibberella ear rot of corn, has recently been reported to attack soybean, causing root rot and pod blight. A morphologically similar species, Fusarium pseudograminearum, is also an important pathogen of the roots and crown of cereals, but its pathogenicity against soybean has not been tested yet. Pathogenicity tests were conducted under controlled conditions to compare aggressiveness within and between isolates of F. graminearum and F. pseudograminearum in causing root rot of soybean. In each experiment, agar plugs (2 mm in diameter) from 7-day-old fungal cultures were placed on the primary root at the VE (vegetative emergence) growth stage. Twenty seedlings of each of three soybean cultivars were inoculated separately with six isolates each of the two Fusarium spp. All isolates caused visible infection 10 d after inoculation, but F. graminearum isolates were significantly more aggressive than those of F. pseudograminearum. The two species caused average disease severities of 2.3 and 1.1, reduced shoot lengths by 28.9% and 6.9%, and reduced plant dry masses by 12.8% and 7.9%, respectively. Significant differences (P < 0.05) were found among cultivars for all parameters and among isolates of F. graminearum in disease severity and shoot length, but there were no significant cultivar × isolate interactions. Further research is needed to verify, in soybean, genotypic difference and possible resistance to the two species. Keywords: pathogenicity Fusarium graminearum Fusarium pseudograminearum soybean Glycine max