291 10 th International Conference for Sustainable Agricultural Development 2-4 March 2020 Fayoum J. Agric. Res,&Dev.,Vol. 34 No. 1(B) March,2020 EFFECT OF SPRAYING CHITOSAN ON GROWTH , YIELD AND BERRIES QUALITY OF FLAME SEEDLESS GRAPEVINES By Mohamed, A.Khalil *; Ahmed, H.M. Abd Elaal*; Mohamed, A.M.Abada*; and Moustafa, A.A. Mohamed * * Viticulture Res. Dept. Hort. Res. Instit. ARC. Giza, Egypt. *Hort. Dept. Fac. of Agric. Al- Azhar Univ. Assiut, Egypt.** ABSTRACT This study was carried out during 2018 and 2019 seasons to examine the effect of spraying chitosan at 50 to 200 ppm once, twice or thrice on growth, vine nutritional status, yield and berries quality of Flame, seedless grapevines under Minia climatic conditions. Treating the vines once at growth start, twice at growth start and just after berry setting of thrice at growth start, just after berry setting and one month later with chitosan at 50 to 200 ppm substantially improved all growth again aspects, chlorophylls a , b, total chlorophylls total carotenoids, N, P, K, Mg, berry setting %, yield and both physical and chemical characteristics of the berries relative to the control. The promotion was related to the increase in concentrations and frequencies of application of chitosan. All the investigated parameters were unaffected with increasing concentrations from 100 to 200 ppm and frequencies of applications from twice to thrice. Conclusively, the best results with regard to vegetative growth aspects, leaf chemical components, yield and berries quality of Flame seedless grapevines grown under Minia climatic conditions were obtained due to treating the vines twice at growth start and again just after berry setting with chitosan at 100 ppm. Keywords: Chitosan, Flame seedless grapevines, yield, berry setting, berries quality INTRODUCTION The beneficial effects of chitosan on growth and vine nutritional status surely reflected on improving berry setting, yield and berries quality in Flame seedless grapevines. Chitosan is considered a biopolymer produced from chitin and is very safe for human being. It has bioactivity and biocompatibility (Dias et al., 2013) using it in plants resulted in improving the yield and reducing transpiration (Dzung et al., 2011 and Mondal et al., 2012). It is an important antioxidant and using it was accompanied with blocking relative oxygen species (ROS) and protecting the vines from their damage (Park et al., 2004). It is responsible for enhancing the tolerance of plants to bacterial, viral and fungal; attack (Al Hetar et al., 2011). The plants subjected to chitosan are less prone to all bitic and abiotic stresses (Lizarraga- Pauli et al., 2011; Jobeen and Ahmed, 2013 and Pongrayoon et al., 2013). It enhances vital processes and changing expression of genes (Limpanavech et al., 2008; Hadwiger, 2013 and Nguyen- Van et al., 2013). It stimulated plant reacting and the impact on microoragnisms and the molecular weight seems to be one of the most essential factors affecting the