Immunity Priming Compounds Have Variable Effects on Muskmelon ( <i>Cucumis melo</i> ) Resistance to Viral Pathogens

Plant defense activators, or elicitors, are compounds that can prime a plant's immune system to prepare for future challenge by pathogens. However, most have not been thoroughly explored for efficacy in priming plants to resist virus infections. In our previous work, we demonstrated that acibenzolar- S-methyl (ASM) reduces viral disease (symptoms) in cantaloupe ( Cucumis melo) when applied before being challenged with two distinct virus species but that this disease attenuation is short-lived. This study aimed to explore elicitor options for prolonging and improving this induced resistance in cantaloupe against two virus species, Zucchini yellow mosaic virus (ZYMV) and Cucurbit yellow stunting disorder virus (CYSDV). We evaluated the effects of two applications of ASM: the first at 3 days before inoculation and the second at 2 weeks postinoculation (wpi). We also evaluated single applications of other elicitor products applied before virus challenge, with active ingredients including chitosan, pyraclostrobin, silicon dioxide, laminarin, and an extract of Reynoutria sachalinensis. The results showed that an application of ASM before inoculation reduced virus symptoms, but a second application did not extend symptom reductions for plants challenged with either ZYMV or CYSDV. Evaluations of other elicitor products revealed that ASM, laminarin, and Reynoutria all reduced symptoms of ZYMV infection for up to 4 wpi. In contrast, chitosan and silicon dioxide reduced symptoms of CYSDV. These results suggest that elicitor products may be viable options for decreasing virus severity in cantaloupe, but careful attention must be paid to which products are effective against specific virus threats. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .