Plant Protection Institute in Poznaniu, Sosnicowice Branch, Gliwicka St. 29, 44-153 Sosnicowice, Poland

Background and objectives
In June and July of 1997, the amount of rainfall in the south of Poland was high above the average. Under conditions of long-lasting rainfall and rapid cumulation of water in the rivers, many hectares of land were flooded, including winter wheat fields. Wheat plants at GS 77-91 remained totally or partly flooded for various periods of time. Weather conditions in the spring and summer of 1997 were favourable for Fusarium infection of seedlings, culm bases and other plant parts, and the disease continued to develop under flooding conditions. Wheat could be harvested only from partly flooded crops where the upper parts of plants still remained above the water table.

Materials and methods
We investigated the composition of mycoflora of seeds from fields flooded for 2, 4 or 7 days. Special attention was given to the pathogenic species of Fusarium which frequently occur on cereal seeds in Poland and other European countries under favourable weather conditions [1, 2]. Seeds were air-dried, disinfected for 120 s in 1% H9C12, and plated on acidified PDA. A strong disinfectant and a long time of disinfection had to be used, because of the abundant development of storage fungi: Mucor, Rhizopus and Penicillium. Thus we were able to estimate the mycoflora present in dipper layers of kernels.

Results and conclusions
Irrespective of length of time under water (including non-flooded control), the most frequent species of Fusarium, in decreasing order, were: F. avenaceum, F. culmorum, F. graminearum, F. nivale. Other species of Fusarium rarely occurred. The percentage of pathogenic Fusaria was significantly higher on seeds from flooded than non-flooded areas. The percentage of F. avenaceum was highest in seeds from nonflooded areas. The percentage of F. graminearum was least on seeds from areas flooded for 7 days, and the percentage of F. nivale was always higher from flooded than non-flooded areas, although this fungus was not common among the seed samples studied. Significantly more colonies of Epicoccum and Alternaria were isolated from seeds harvested from non-flooded than from flooded areas.

1. Tacicowa B, Sulek-Pista D, Wagner A, 1987. Zeszyty Problemowe Postepow Nauk Roiniczych 307, 165-173.
2. Diehi T, Fehrmann H, 1990. Zeitschrift for Pflanzenkrankheiten und Pflanzenschutz 96, 393-407.