Aloe Vera Extract Gel-Biosynthesized Selenium Nanoparticles Enhance Disease Resistance in Lettuce by Modulating the Metabolite Profile and Bacterial Endophytes Composition

The use of nanotechnology to suppress crop diseases hasattractedsignificant attention in agriculture. The present study investigatedthe antifungal mechanism by which aloe vera extract gel-biosynthesized(AVGE) selenium nanoparticles (Se NPs) suppressed Fusarium-induced wilt disease in lettuce (Lactuca sativa). AVGE Se NPs were synthesized by utilizing sodium selenite as aSe source and AVGE as a biocompatible capping and reducing agent.Over 21 d, 2.75% of total AVGE Se NPs was dissolved into Se ions,which was more than 8-fold greater than that of bare Se NPs (0.34%).Upon exposure to soil applied AVGE Se NPs at 50 mg/kg, fresh shootbiomass was significantly increased by 61.6 and 27.8% over the infectedcontrol and bare Se NPs, respectively. As compared to the infectedcontrol, the shoot levels of citrate, isocitrate, succinate, malate,and 2-oxo-glutarate were significantly upregulated by 0.5-3-foldas affected by both Se NPs. In addition, AVGE Se NPs significantlyincreased the shoot level of khelmarin D, a type of coumarin, by 4.40-and 0.71-fold over infected controls and bare Se NPs, respectively.Additionally, AVGE Se NPs showed greater upregulation of jasmonicacid and downregulation of abscisic acid content relative to bareSe NPs in diseased shoots. Moreover, the diversity of bacterial endophyteswas significantly increased by AVGE Se NPs, with the values of Shannonindex 40.2 and 9.16% greater over the infected control and bare SeNPs. Collectively, these findings highlight the significant potentialof AVGE Se NPs as an effective and biocompatible strategy for nanoenabledsustainable crop protection.

Automated summary

This study investigated the antifungal mechanism of aloe vera extract gel-biosynthesized selenium nanoparticles (Se NPs) in suppressing Fusarium-induced wilt disease in lettuce. The results showed that the release rate of AVGE Se NPs was higher than that of bare Se NPs, and they significantly increased the growth of lettuce and regulated the levels of endogenous substances. Moreover, AVGE Se NPs increased the diversity of bacterial endophytes.