Defense-related genes induced by application of silver nanoparticles, ascorbic acid and salicylic acid for enhancing the immune response system of eggplant against invasion of root–knot nematode, Meloidogyne javanica

Abstract

This study explored the nematicidal activity of silver nanoparticles (AgNPs), ascorbic (AA) and salicylic acid (SA) compared with Mycorrihizin (Myco) against Meloidogyne javanica infecting eggplants. The characterization and size confirmation of the AgNPs was done by ultraviolet–visual (UV–vis) spectrophotometry, surface zeta-potential and transmission electron microscopy. The results illustrated that 150 μg/mL AgNPs had nematicidal activity against the second-stage juvenile and egg hatching of M. javanica in vitro, and caused 100% mortality in juveniles after 48 h of exposure. In open-field conditions, the treatment with 100 µg and 150 µg AgNPs 24 h before transplanting killed almost all of the nematode eggs and galls per root system compared with the control. All treatments improved the eggplant growth in terms of plant height, root weight, number and weight of fruits, shoot and root length and fresh weight of shoot and root with various degrees as compared to control. The activities of oxidative enzymes, peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL), during the flowering stage, increased with all treatments comparing to healthy and infected plants. To assess the defense response of infected eggpant, the gene expression levels (PAL, POX and PPO) were monitored using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The PPO enzyme showed the highest rate on day 60 after infection when 50 µg AgNPs were used during transplanting. The POX enzyme activity showed the highest increase in all treatments during all stages of growth, on day 30, 45 and 60.

Keywords:

• Root–knot nematode (M. javanica)
• silver nanoparticales
• salicylic acid
• ascorbic acid
• mycorrihizin
• defense gene assessment

Disclosure statement

The authors do not have any relevant financial or non-financial competing interests.

Data availability

All data that support the findings reported in this study are available from the corresponding author upon reasonable request.