New early phenotypic markers for cucumber green mottle mosaic virus disease in cucumbers exposed to fluctuating extreme temperatures

Abstract

Studies of early stages of cucumber green mottle mosaic virus (CGMMV) disease have been recently focused on plant molecular responses. However, extreme diurnal environmental temperatures, characteristic of global climate changes, could affect plant susceptibility and disease phenotype progression. Our studies of CGMMV disease progression, under simulated extreme temperature waves, have revealed two new disease initiation phenotypes that developed gradually, preceding severe symptom manifestations of post-recovery CGMMV systemic infections. 'Early post-recovery stage' bright yellow islands (BYIs) with defined boundaries amid asymptomatic leaf blades were first emerging followed by 'late post-recovery stage' BYIs with diffused boundaries. A deduced CGMMV disease progression scheme, postulating BYI symptom occurrence time-windows, revealed BYIs in field grown cucumber plants exposed to extreme diurnal temperatures. Profiling ontology of cucumber differentially expressed genes in BYIs vs the associated dark-green surrounding tissues disclosed activation of jasmonic acid (JA) pathway in 'early post-recovery stage' BYIs. JA signaling was inactivated in 'late post-recovery stage' BYIs concomitant with increasing expressions of JA signaling inhibitors and downregulation of JA responsive phenylpropanoid pathway. Our results disclosed a new phenotypic description of CGMMV disease initiation, characteristic of cucumbers grown under extreme environmental temperature fluctuations. The BYI phenotypes could define a time-window for CGMMV disease management applications.

Plant Disease Symptomatology: Cucumber Green Mottle Mosaic Virus (CGMMV)-Infected Cucumber Plants Exposed to Fluctuating Extreme Temperatures

“…Cucumber plants cvs. Romi and Senyal were cultivated, as previously described, and inoculated with CGMMV-Rd purified inoculum [18]. Treated plants were grown in temperature-controlled growth chambers and disease-symptom manifestations were monitored closely.…”

“…Serological analyses were performed, as previously described, using ELISA tests for systemically infected plants and Western blots for dissected equal sizes of EBYIs and the corresponding DGS tissues [18]. Meteorological data was extracted from records on the Israeli Meteorology Services (IMS) website: https://ims.gov.il/he/ObservationDataAPI (accessed on 10 November 2021).…”

“…A consecutive up-and down-regulation of jasmonic acid (JA) signaling and increasing JA inhibitory pathways have occurred, upon progression from early post-recovery stage BYIs (EBYIs) to late post-recovery stage BYIs (LBYIs). Interestingly, the cucumber plant response at the LBYI stage was associated with increasing activity of the phenylpropanoid pathway in the corresponding DGS tissues, apparently indicating high activity of plant resistance pathways towards the disease, including increasing levels of reactive oxygen species as well as interference with tobamovirus accumulation [18]. We have now expanded our study to include low temperatures of ≤16 • C in monitoring the effects of high DTR on CGMMV disease symptom manifestations at a post-recovery stage.…”

“…Disinfection studies of CGMMV-infected cucurbit seeds were unsuccessful, due to virus penetration to the perisperm endosperm envelope located underneath the seed coat, specifically in cucurbits [4][5][6]. Consequently, recent studies of CGMMV disease have focused on three major directions: (1) careful hygienic conducts combined with virus inactivation tests using various chemicals [7,8]; (2) selections of tolerant or resistant genotypes that could serve as rootstocks or cultivated plants [9][10][11][12][13]; and (3) molecular regulation studies of early disease stages that could pinpoint strategies for enhancement of plant resistance [14][15][16][17][18]. Importantly, all three approaches depend on a precise and detailed description of early disease manifestations, which could have been profoundly affected by the fluctuating extreme environmental temperatures occurring globally.…”

Disinfection Efficacy of Tobamovirus-Contaminated Soil in Greenhouse-Grown Crops

“…We have recently shown that the seasonal disease in tomatoes, which were observed primarily during the hot summer weather, has become more severe in the cold weather due to synergism occurring between ToBRFV and a mild potexvirus pepino mosaic virus (PepMV-IL) [19,20]. Regarding CGMMV, we have recently shown a tight correlation between disease manifestations and fluctuating environmental temperatures [21,22].…”