RESPONSE OF THE ‘POLESIE’ RASPBERRY CULTIVAR TO FOLIAR APPLICATION OF CHITOSAN WITH DIFFERENT MOLECULAR WEIGHTS

This study explored the effects of chitosan, a biodegradable and non-toxic natural polymer derived from chitin, on the yield and quality of raspberries. Various molecular weights (3.3–950 kDa) were assessed to determine the impact on raspberry plants and fruit development. These applications were made during key growth phases – the start of the vegetation period, during flowering and at the fruit-bearing stage – using a foliar method to ensure full coverage of both leaves and fruit without runoff. The results indicated that chitosan application influenced various parameters of fruit quality, including firmness, colour and antioxidant levels. Notably, chitosan with a molecular weight of 21 and 50 kDa significantly enhanced fruit yield and size compared with the control. Conversely, chitosan with a higher molecular weight (500 and 950 kDa) did not improve yield and appeared to induce stress in plants, although they did contribute to increased fruit firmness and potentially extended the shelf life due to their film-forming capabilities. The findings suggest that while chitosan can improve the yield and quality of raspberries, the effectiveness is highly dependent on its molecular weight. These results support the potential of chitosan as an alternative to traditional chemical treatments, promising a reduction in chemical inputs while sustaining or enhancing agricultural productivity and fruit quality.