Disclosed is an agricultural composition which comprises an association of an at least partially depolymerised chitosan having an average molecular weight of from about 1,000 to about 10,000 and a bivalent copper chelate which is a copper ethylenediaminetetraacetic acid (EDTA) complex. Further disclosed is the use of a composition as defined above for improving resistance of crops to infection by phytopathogenic agents (such as a virus or an oidium infection) and/or for phytotherapeutically treating said crops and/or for increasing the tolerance thereof to abiotic stress and/or as a fertiliser for stimulating plant and fruit growth and/or for extending the shelf life of fruit and seeds.
