Effects Of Methanol Application On The Growth Of The Radish (Raphanus Sativus), And Host Preference And Damage By Plutella Xylosterra, Phyllotreta Striolata, Myzus Persicae, And Liriomyza Sativae To Methanol-Treated Radish

Methanol, along with isoprene, is quantitatively the most important volatile organic compounds found in the atmosphere. On one hand, methanol application changes plant gene expression profile and proteome to elicit the defense and to enhance the growth. Methanol, on the other hand, may mediate the chemical communication between pest insects and their host plants. This study was conducted to test the effect of methanol application on the growth of the radish(Raphanus sativus), and to evaluate the host preference and the damage to methanol-treated radish by two oligophagous pests, the diamondback moth(Plutella xylosterra) and the striped flea beetle(Phyllotreta striolata), and two polyphagous species, the green peach aphid (Myzus persicae) and the vegetable leafminer(Liriomyza sativae).The effects of aqueous methanol solutions applied as a foliar spray or via irrigation were investigated in the radish(Raphanus sativus). Both foliar and root methanol -treated seedlings showed higher water content,the turgid leaves and lower wilted leaf rate. Treated leaves exhibited an increase of surface area, thickness and improved photosynthesis. Consequently, methanol application increased fresh and dry vegetative weight of treated radish seedlings.The radish seedlingss were treated with the foliar and root application of 2%,5% and 10% methanol aqueous solutions, and the host preference and damage to treated plants by two oligophages, the diamondback moth(Plutella xylosterra) and the striped flea beetle (Phyllotreta striolata), were compared. It was found that methanol application causes increased damage and larval populations in both pests. This demonstrated that methanol-treated plants may attract and/or arrest the diamondback moth(Plutella xylosterra) and the striped flea beetle(Phyllotreta striolata), enhance daily food consumption.Similar treatments to the radish seedlings were carried out, and the host preference and damage to treated plants by two polyphages, the green peach aphid(Myzus persicae) and the vegetable leafminer(Liriomyza sativae), were evaluated. Methanol application decreased damage and larval populations in both pests, indicating that methanol-treated plants may repel the green peach aphid(Myzus persicae) and the vegetable leafminer (Liriomyza sativae), reduce their daily food consumption..In summary, methanol application stimulated growth of the radish seedlings. This indicated that method application may elicit cytokinin sigaling pathway to accerate cell division,and/or may trigger auxin signaling pathway to stimulate cell elongation. Methanol-treated radish seedlings may attract and/or arrest two oligophagous pests and stimulate their feeding. In contrast, methanol-treated radish may repel two polyphagous species and inhibited their feeding. It seems that methanol application also triggers defense relative signaling pathway mediated by jasmonate, salicylic acid or abscisic acid, and enhances the synthesis of isothiocyanates.