Growth and physiological responses of chestnut calli to crude extracts of virulent and hypovirulent strains of Cryphonectria parasitica

Abstract

The effect of crude extracts (CEs) of virulent (V‐E4) and hypovirulent (H‐E13) Cryphonectria parasitica strains on growth and physiological activities of chestnut calli was investigated on cell cultures obtained from either a susceptible Castanea sativa or a resistant Castanea mollissima chestnut species. The V‐E4 CEs significantly reduced calli fresh weight in both species when used at 50 and 500 μg g–1 and, in general, showed an inhibitory effect on either O2 uptake and H+‐ATPase activity. Only the highest (500 μg g–1) concentration of H‐E13 CEs had a detrimental effect on callus growth, whereas the lowest one (5 μg g–1) induced a slight, but significant early increase in callus fresh weight of both genotypes. The O2 uptake and H+‐ATPase activity were enhanced by the presence of H‐E13 CEs. The decrease of callus growth and physiological activities, caused by V‐E4 CEs, was attributed to toxic compounds produced by the C. parasitica virulent strain, whereas the stimulatory effects of H‐E13 CEs on the overall callus metabolism seemed to be due either to the lack or very reduced amount of phytotoxic compounds and to growth‐regulating substances produced only by the hypovirulent strain of the fungus.