Population dynamics of Monosporascus cannonballus ascospores in marsh soils in eastern Spain

The population dynamics of Monosporascus cannonballus ascospores in the soils of four muskmelon fields located in a marsh area in Castellon province (eastern Spain) was studied for a 3 year period. Two of these fields were cropped to muskmelon with fallow periods between muskmelon cropping, and the others were in fallow and had extensive flooding periods. Muskmelon cultivation resulted in a progressive increase of the number of ascospores in soil, reaching a maximum 7 months after muskmelon planting (2-4 months after plant death), and a subsequent decline during fallow periods between muskmelon crops. During muskmelon cropping, in-bed and between-bed ascospore numbers were compared and, in general, there were no statistical differences between them. In the fields which were in fallow and flooded, the dynamics found was a progressive decline of the population of ascospores. Soilborne inoculum was viable and capable of infecting muskmelon at the end of the 3 year period in all fields, demonstrating that ascospores of M. cannonballus are able to survive for this period of time in the absence of muskmelon cultivation and also that this fungus seems to be well adapted to survive in soils which maintain a high water table during the crop or under flooding conditions.