REDUCING THE INCIDENCE OF ONION DOWNY MILDEW DISEASE USING BIO-FORMULATION OF Pseudomonas fluorescen

Under greenhouse and open field circumstances, the potential of Pseudomonas fluorescens isolate JY8, limonene (L), and acetyl salicylic acid (ASA) to reduce onion downy mildew disease severity was tested individually and in combination. At 0.25 percent, 0.5 percent, and 4 mM, foliar sprays of formulated P. fluorescens JY8, limonene, and acetyl salicylic acid were utilised, respectively. The prescribed fungicide, Acrobat MZ 69 percent WP, was used at a rate of 0.25 percent, on the other hand. In addition, two genes encoding enzymes in the flavonoids biosynthesis pathway in Allium cepa, chalcone synthase and chalcone isomarease (CHS and CHI), were discovered at the functional and transcriptional levels (mRNA level) in onion tissues under diverse treatments. Under greenhouse and open field circumstances, the foliar spray with prescribed fungicide was the most effective therapy for reducing onion downy mildew disease severity, followed by limonene and acetyl salicylic acid (L+ASA) and limonene (L) alone. Except for the treatment with the combination (JY8+L+ASA), which was the least successful, all treatments including P. fluorescens JY8 produced a high yield of onion bulbs. The electrophoretic pattern of PCR products used to detect CHS and CHI encoding genes revealed that CHS gene expression was induced at a primary transcriptional band of 420 bp, however CHI gene expression was detected at the main two transcriptional bands of 340 and 970 bp. In comparison to other treatments and the untreated control, increased expression of the CHS gene was discovered in the ASA treatment, whereas higher expression of the CHI gene was detected in the JY8, ASA, JY8+ASA, and L+ASA treatments. Finally, JY8 and ASA treatments induced encoded polyphenol synthesis genes in onion tissues, and these genes may play a significant role in the defence response to downy mildew disease infection. However, using limonene (L) as an antifungal substance reduced the severity of onion downy mildew illness.

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