Cultivar-Specific Effect of Chitosan on Chitinase and Glucanase Activity in the Roots of Garlic Allium sativum L.

Abstract

Chitosan is a natural polysaccharide and, when applied externally, is able to stimulate both growth and defense of the plant, enhancing its resistance to abiotic stresses and suppressing the development of many phytopathogens. Immune response includes the activation of defense proteins, carbohydrases such as chitinases and glucanases, which are also known to participate in the regulation of morphogenesis. In this study, for the first time, the effect of treatment with unfractionated (hydrolysate) chitosan of low (CH1) and medium (CH2) molecular weight on chitinase and glucanase activities, as well as on the expression of chitinase and -1,3-glucanase genes in the roots of two cultivars of garlic Allium sativum L. differing by resistance to Fusarium rot was examined. It was shown that the effect of chitosans on the enzymatic activity and expression of the genes encoding -1,3-glucanases (AsPR2a, AsPR2b, and AsPR2c) and chitinases (AsCHI1, AsCHI3, AsCHI7, AsCHI17, and AsCHI23) is cultivar-specific, which may be due to different susceptibility of the cultivars to Fusarium. The expression pattern of chitinase genes AsCHI10, AsCHI27, and AsCHI34, similar between varieties, suggested their involvement in root tissue morphogenesis. The results indicated a greater stimulatory effect of CH2 in comparison with CH1 on chitinase and glucanase activity. The stronger inhibitory influence of CH2 (as compared with CH1) on the expression of chitinase and -1,3-glucanase genes correlated with the lower fungicidal effect of CH2 on Fusarium proliferatum. The findings may be used in breeding biotechnology to increase the resistance of garlic to Fusarium.