A first step in the possible application of slime moulds as antagonists requires the isolation and identification of the organism. Myxomycetes were collected in a maize field at the end of the growing season (September and October 2015 and 2016). The maize field was mist irrigated in the month July and August (every second day, 15 seconds with 20 minutes time intervals) to simulate a big moist chamber. Each season about 200 collections were removed from the ripening maize plants. Identification of the samples was based on morphological characteristics according to the customary reference works (Nannenga-Bremekamp 1991, Neubert et al. 1995, Poulain et al. 2011)
Fructifications were detected mainly on specific plant tissues, including the silks of the ears, between the stalk and the leaves surrounding the stem, on the underdeveloped and in part decaying secondary maize ear surrounded by the leaves and also on the oldest leaves close to the soil. Five slime mould species were identified: Dydimium squamulosum, D. bahiense, Physarum pusillum, P. cinereum and P. compressum. In 2016 D. squamulosum was the most important species (45% of all isolates) followed by P. cinereum (26%). In 2015 however, P. pusillum was detected more frequently (46%) followed by D. bahiense (27%). In both seasons most isolates were recovered from the leaf and very rarely from the ear. P. pusillum occurred also frequently on the maize silks (44 and 43% in 2016 and 2015, respectively).
It appears that the myxomycetes prefer specific maize organs where the conditions for plasmodial development are optimal. Leaves surrounding the stalk collect and conduct water and all possible debris to the plant stem where it accumulates between the stem and the leaf. It is hypothesized that in this microenvironment plasmodia find optimal growth conditions. At the end of the season the plasmodia migrate to free plant tissues where they fructify and can readily be collected. All species we collected are soil born and thus must have the ability to compete with the soil micro-flora. This collection is used as source of bio-material for further investigations on antagonistic applications to control soil-borne plant pathogens (including bacteria and fungi).