THE INFLUENCE OF PLANTING LOCATION, PLANT-GROWTH STAGE AND CULTIVARS ON MICROFLORA OF WINTER-WHEAT ROOTS

The occurrence of parasitic and saprophytic microflora on roots of eig ht winter wheat cultivars was recorded at seven plant experimental sta tions with different climatic and soil conditions during four plant gr owth stages. The rates of recovery for pathogenic and sprophytic micro organisms were negatively correlated, and the negative correlations be came larger as the crop matured. Similarities were noted between the r atios of pathogen to saprophyte recovery in spring samplings as well a s between the root assays in early summer and early autumn. In spring, recovery of pathogenic Fusarium spp. was negatively correlated with r ecovery of saprophytic Trichoderma spp., and recovery of pathogenic Al ternaria spp. with saprophytic spp. of Trichoderma and Epicoccum. In s ummer and autumn, a negative relationship was found among saprophytic sterile fungi, saprophytic Mucor spp. and pathogenic Fusarium spp. Dif ferences among recovery ratios were found for the various plant breedi ng stations but not among individual cultivars. The average rates of r ecovery for pathogenic microorganisms thus depended on planting locati on and plant growth stage but the recovery ratios did not depend on cu ltivars. It suggests a stronger influence of these environmental compo nents than cultivars on pathogen recovery rates. Mutual interactions a mong microflora species, planting conditions, and plant development wi ll strongly influence field resistance to pathogens.