Optimisation of rooting and growth of grapevine cuttings through chitosan application and substrate selection

This study evaluated the effects of chitosan concentration and substrate composition on rooting efficiency, growth performance, and leaf colour parameters in hardwood cuttings of Vitis vinifera L. cv. 'Solaris'. Cuttings were soaked in 0.2% or 0.4% chitosan solutions and planted in five substrate types: peat, sand, perlite, pea-sand (50:50), and peat-perlite (50:50). The highest rooting percentage (92%) and most favourable biometric parameters were observed in cuttings treated with 0.2% chitosan and grown in the peat-perlite mixture. The tallest shoots (77 cm) were recorded with 0.4% chitosan, while the longest roots (52 cm) developed in the sand-perlite substrate. Although chitosan did not significantly affect shoot diameter, it enhanced root system development and overall plant quality, particularly in substrates with high air and water permeability. In addition, leaf colour analysis revealed that chitosan application in the peat-perlite substrate significantly reduced L* and a* values, indicating a deeper green foliage colour and enhanced chlorophyll accumulation. In contrast, sandy substrates showed minimal pigment response. These results confirm that chitosan acts as an effective biostimulant when applied in synergy with suitable substrates, and leaf colour metrics may serve as reliable indicators of physiological status during grapevine propagation.