Foliar application of ß-D-glucan nanoparticles to control rhizome rot disease of turmeric.

The soilborne Oomycete Pythium aphanidermatum is the causal agent of rhizome rot disease, one of the most serious threats to turmeric crops. At present, effective fungicides are not available. Researches on nanoparticles in a number of crops have evidenced the positive changes in gene expression indicating their potential use in crop improvement. Hence, experiments were carried out to determine the effect of ß-D-glucan nanoparticles (nanobiopolymer) in protection of turmeric plants against rot disease by the way of products that reinforce plant's own defense mechanism. Foliar spray of ß-D-glucan nanoparticles (0.1%, w/v) elicited marked increase in the activity of defense enzymes such as peroxidases (E.C.1.11.1.7), polyphenol oxidases (E.C.1.14.18.1), protease inhibitors (E.C.3.4.21.1) and ß-1,3-glucanases (E.C.3.2.1.39) at various age levels. Constitutive and induced isoforms of these enzymes were investigated during this time-course study. ß-D-glucan nanoparticles (GNPs) significantly reduced the rot incidence offering 77% protection. Increased activities of defense enzymes in GNPs-applied turmeric plants may play a role in restricting the development of disease symptoms. These results demonstrated that GNPs could be used as an effective resistance activator in turmeric for control of rhizome rot disease.

ß-D-Glucan nanoparticle pre-treatment induce resistance against Pythium aphanidermatum infection in turmeric.

In vitro experiments were carried out to test the efficacy of GNP (ß-D-glucan nanoparticle prepared from mycelium of Pythium aphanidermatum) against rhizome rot disease of turmeric (Curcuma longa L.) caused by P. aphanidermatum. GNP (0.1%, w/v) was applied to rhizome prior to inoculation with P. aphanidermatum (0 h, 24 h). Cell death, activities of defense enzymes such as peroxidase, polyphenol oxidase, protease inhibitor and ß-1,3 glucanase were monitored. Prior application of GNP (24 h) to turmeric rhizome effectively controls P. aphanidermatum infection. The increase in defense enzyme activities occurred more rapidly and was enhanced in P. aphanidermatum infected rhizomes that were pre-treated with GNP. Pre-treatment also induced new isoforms of defense enzymes. Increased activities of defense enzymes suggest that they play a key role in restricting the development of disease symptoms in the rhizomes as evidenced by a reduction in cell death. The results demonstrated that GNP can be used as a potential agent for control of rhizome rot disease.