Control of Phytophthora capsici, which causes root and stem rot, using encapsulated oligonucleotide DNA

Phytophthora rot, caused by the pathogen Phytophthora capsici, is one of the most destructive diseases affecting a wide range of plants, from vegetables to trees. This disease can attack the roots, aerial organs, and even the fruits of the affected plants. One of the latest control methods involves utilizing DNA interference (DNAi) technology, which employs short DNA oligonucleotides to disrupt the expression of pathogenic genes. In this research study, a 26-nucleotide double-stranded OligoDNA fragment, synthesized from the region of the cellulose synthase gene (CesA3), was used to regulate the expression of CesA3. The oligonucleotide sequence was encapsulated using gelatin and whey protein concentrate (WPC), separately, through electrospraying in an electrospinning machine. The physicochemical properties of the produced microcapsules were then evaluated. Pathogenicity tests were conducted using a completely randomized design, which involved baiting hemp seeds infected with P. capsici and treating the roots of bell pepper plants with the encapsulated OligoDNA. The development of the disease was monitored daily for two months, and the disease severity index was assessed. Statistical analysis, using the paired t-test, was performed on the collected data. The pathogen was cultured in a Corn meal agar (CMA) medium to investigate further the impact of the encapsulated OligoDNA on the growth of P. capsici. The results showed that OligoDNA encapsulated with the WPC polymer significantly reduced the disease index (DI) of P. capsici to approximately 16%, compared to other treatments, including the control, WPC, G, and G-Oligo, which exhibited DIs ranging from 35 to 40%. In the colony growth assay, both treatments, WPC and WPC-Oligo DNA, result in reduced growth compared to the control, with WPC-Oligo DNA having the most suppressive effect.