Impact of Salicylic Acid and Juniperus procera Extract as a Defense Mechanism against Zucchini Yellow Mosaic Virus and Host Biochemical Characterization

摘要

Plants have developed numerous approaches to resist infection by viruses. Severe mosaic symptoms commonly occur in leaves of cucurbit plants infected with Zucchini yellow mosaic virus (ZYMV). The present study is conducted to investigate the effect of salicylic acid and Juniperus procera extract on systemic acquired resistance against ZYMV and metabolic changes of Cucurbita pepo plant. Infected plants leaves with ZYMV showed many symptoms, including severe mosaic, chlorosis and deformation, while treated leaves with salicylic acid (SA) or J. procera extract showed lower level of symptoms. Most of the detected amino acids of ZYMV infected C. pepo plants were found lower in concentration than the control, while the amino acid proline was detected at the highest concentration (217μg/gm) in infected compared with healthy plant (71 μg/gm). Proline content of inoculated ZYMV plant was 136 and 187 μg/gm with the treatment of SA or J. procera extract respectively. Chlorophyll a & b content of virus inoculated C. pepo . plant was (5.31 and 2.46 mg/g fresh weight) compared with the healthy control (7.68 and 3.21mg/g fresh weight), respectively. On the other hand, treatment with SA increased the total content of chlorophyll a &b comparing with the infected plant without treatment. Jasmonic acid, SA, phenolic and protein contents of C. pepo plant were increased, while carbohydrate and lipid contents decreased as a result of viral infection comparing with the healthy plant. With SA treatment jasmonic acid, SA and phenolic content are noticeably increased, while decreased with treatment of J. procera extract. Current results showed many metabolic changes affected by either viral infection or treatments with SA and J. procera extract. Also, the results indicate that exogenous SA plays an important role as a defence mechanism against ZYMV infection.