Abstract
Downy mildew of pearl millet caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease which impairs pearl millet production causing huge yield and monetary losses. Chitosan nanoparticles (CNP) were synthesized from low molecular weight chitosan having higher degree of acetylation was evaluated for their efficacy against downy mildew disease of pearl millet caused by Sclerospora graminicola. Laboratory studies showed that CNP seed treatment significantly enhanced pearl millet seed germination percentage and seedling vigor compared to the control. Seed treatment with CNP induced systemic and durable resistance and showed significant downy mildew protection under greenhouse conditions in comparison to the untreated control. Seed treatment with CNP showed changes in gene expression profiles wherein expression of genes of phenylalanine ammonia lyase, peroxidase, polyphenoloxidase, catalase and superoxide dismutase were highly upregulated. CNP treatment resulted in earlier and higher expression of the pathogenesis related proteins PR1 and PR5. Downy mildew protective effect offered by CNP was found to be modulated by nitric oxide and treatment with CNP along with NO inhibitors cPTIO completely abolished the gene expression of defense enzymes and PR proteins. Further, comparative analysis of CNP with Chitosan revealed that the very small dosage of CNP performed at par with recommended dose of Chitosan for downy mildew management.
Highlights
Downy mildew of pearl millet caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease which impairs pearl millet production causing huge yield and monetary losses
The results of the present study clearly showed that, both PR-1 and PR-5 were activated early and in significantly higher amounts in the nanochitosan treated seedlings compared to the untreated seedlings; and the increase was more pronounced after the inoculation of the downy mildew pathogen
This study clearly showed that pearl millet seed treatment with nanochitosan particles will significantly promote seed germination and seedling vigor and effectively induced systemic and durable resistance against downy mildew disease under greenhouse conditions
Summary
Downy mildew of pearl millet caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease which impairs pearl millet production causing huge yield and monetary losses. Chitosan nanoparticles (CNP) were synthesized from low molecular weight chitosan having higher degree of acetylation was evaluated for their efficacy against downy mildew disease of pearl millet caused by Sclerospora graminicola. Seed treatment with CNP induced systemic and durable resistance and showed significant downy mildew protection under greenhouse conditions in comparison to the untreated control. Among the diseases of pearl millet, downy mildew caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease responsible for wide-spread yield and economic losses[2]. Chitosan pre-treatment primes the host plant defense responses by inducing earlier and higher phytoalexin synthesis, lignification, callose deposition, activities of reactive oxygen species, enhanced defense enzymes and PR proteins[3,4]. Plant protective efficiency of chitosan against a wide range of phytopathogens has been well established in several crops[4,5]
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