SUMMARYA study was performed in controlled conditions to reproduce cold and warm spring regimes in the east Po valley, northern Italy with a temperate subcontinental climate, to evaluate whether and to what extent spring weather regimes favour the attack ofRhizoctonia solaniorColletotrichum coccodeson potato, in view of predicted climate change. The main experiment, preceded by a controlled chamber set of tests to quantify response to temperatures ofR. solanianastomosis group (AG)-3 andC. coccodesstrains, showed that limit temperatures (minimum, maximum and optimum of colony radial growth) ofR. solaniAG-3 are 6 °C lower than those ofC. coccodes. Then, a trial to reproduce early growth stages of potato was performed in phytotrons with sprouts of cvar Hermes to simulate cold and warm spring regimes with two different relative soil moisture contents. That simulation was carried out on native non-sterilized soil samples which were co-inoculated artificially withR. solaniAG-3 andC. coccodes. Species-abundance findings of fungal root colonization in potato roots and molecular quantification (quantitative polymerase chain reaction) ofC. coccodesandR. solaniAG-3 inoculum growth in soil showed that: (i)C. coccodesis more competitive thanR. solaniAG-3 in colonizing potato root both in warm and cold spring regimes; (ii)R. solaniAG-3 infected potato roots only in the coldest spring regimes regardless of soil moisture content; (iii) soil temperature is the greatest factor that influences root colonization ofC. coccodesandR. solanias well as that of soil inhabiting fungi including some potential antagonists; (iv)R. solaniAG-3 andC. coccodesseem to greatly increase in soil under the relative driest and warmest spring weather regimes expected according to the mean scenarios of climate changing in northern Italy; (v) binucleateRhizoctoniaAG-A, a common non-pathogenic fungus indigenous to agricultural soil of that area, appears to be antagonistic towards root fungal pathogens of potato.