Virological Studies On Some Potato Viruses Of Pepper In Egypt:

M.a Hafez

The present work was carried out at Laboratory, Greenhouse,and Farm of Faculty of Agriculture, Moshtohor, ZagazigUniversity, during J 996/97 - 1997/98 seasons, to isolate andidentified some pepper-associated potyviruses, which causedserious reduction in the pepper crops during the last seasons. Thiswork also aims to establish an effective means to produce virus-freepeppers by using natural antiviral SUbstances, and survey.occurrence and incidence of the isolated virus(es).A new potyvirus, suggesting called pepper severe mosaicpotyvirus (PSMV), was isolated from pepper crops (Capsicumannuum L. Balady) in Qalubia, Menofyia and Sharkia governorates.The distinguishing symptoms of this virus isolate were severemosaic on top leaves; necrotic spots on the stems, fruits and leaves;followed by premature foliar abscission. Infected plants, generally,showed severe stunting.Isolated virus was identified using sympomatology, hostrange, mode transmission, physical properties, and serological tests.The host range of pepper severe mosaic virus (PSMV) were18 species or cultivars (belonging 3 families, i.e., Amaranthaceae,Chenopodiaceae, and Solanaceae), during pot-trial undergreenhouse conditions.Only necrotic local lesions followed by no systemic infectionwere appeared on Amaranthus ascend ens Lois. Meanwhile,chlorotic ones appeared on mechanically inoculated leaves ofChenopodium amaranticolor Coste & Ryn., and C. quinoa Willd.Necrotic local lesions followed by systemic infectionproduced on Nicotiana debneyi Domin. While, chlorotic onesfollowed by systemic infection appeared on N rustica L., and Ntabaccum ”White Burley”.Systemic symptoms only and differentiated according to hostplant species or cultivars was appeared on Capsicum annuum L.cvs. ”Balady Hot, Balady Sweet, California Wonder”, Ci frutescens”Tabasco” Datura metel L., N. glutinosa L., N. clevelandii Gray, N.tabacum ”Samsun and Xanthi-ne” Petunia hybrid a Vilm., Physalisfloridana Rydi. and Solanum nigrum L.Physical properties of the isolated virus recorded as follows:Thermal inactivation point (TIP), was 80°C but not at 85°Cafter 10 min., dilution end point (DIP), was between 10~ and 10-7,and longevity in vitro (LIV), was between 28-35 days.Tested transmission means demonstrated that, the isolatedvirus was easily transmitted by mechanical inoculation and by greenpeach aphid, Myzus persicae Sulz. as non-persistent manner. Butnon-transmissible though pepper seeds.particles of the isolated virus, negatively stained with uranylacetate (2%), were filamentous fexuous and had a 760 nm lengthand 15 nm width when examined with electron microscope.Serological studies using tube precipitin, double diffusion testand directs system (double-antibody sandwich) of enzyme-linkedimmunosorbent assay (DAS-ELISA) tests were performed. Resultsdemonstrated that there is a clearly positive reaction betweenantiserum against isolated virus (PSMV) and antisera against someother potyviruses such as PSMV, PVY and TEV, but not withPVMV, which imported kindly from Argentina, Gennany, Finlandand Nigeria, respectively.This result clearly showed that, serologically, the isolatedvirus is a member ofPotyvirus group.Aqueous extracts of 12 plant species showing potent antiviralactivity belong to 10 families and containing different activeintegrated compounds used in the pot-trial.Extracts of Chenopodium amaranticolor Coste &Reyn.(leaves), Hibiscus rosa sinensis L.(flowers), Vinca roseaL.(leaves), and Pelargonium zonale L’Herit (leaves), showingmarked inhibitory effect, especially if sprayed 24h beforeinoculation with the tested virus.Leaves extracts of Lantana camara L., Euphorbiapulcherrima Willd., Datura metel L., Salvia officinalis L., and fruitextract of Azadirachta indica A. Juss came in the next in this trend.Slight inhibitory effect induced using leaves extracts of bothAdhatoda vasica Ness and Euphorbia peplus L. While, no effectshowed using leaves extract of Acalyphafruticosa Forsk.There were no significant differences between sprayed thetested extracts pre-, mixed or post-inoculation with the virus isolate.Response of some pepper cultivars, species and hybrids (mostfrequently cultivated in the greenhouse) against virus infection werestudied using pot experiment.Serrano (hot pepper), and Gedeon (sweet pepper) gave thesuperior resistant against infection by isolated virus. Came in thenext Cayenne Large, Anheium and Pical (hot pepper); Marconi,California Wonder and Yellow Banana, respectively.Generally, hot pepper showing more resistance to virusinfection than sweet peppers.Screening for existence pepper severe mosaic virus (PSMV)including some Northern Egyptian Governorates (e.g., El-Behera,Dakahlia, Domiat, Gharbia, Giza, Ismailia, Kafr El-Sheikh,Menofyia, Qalubia, and Sharkia) was carried out during summerseason (July-September), 1997.Young ,leaves and fruits of pepper plants (commercialCapsicum sweet and hot lines, species or varieties) naturallyinfectedwith typical potyvirus symptoms from different fields werecollected and investigated for the virus isolate. Crude sap frominfected leaves subjected to detection tests using double antibodysandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA)technique in indirect system at Agricultural Genetic Engineering,Research Institute (AGERI), Giza, Egypt. Meanwhile, fruit sampleswere subjected to vitamin C and capsaicinoids determination.Seven of ten screened Egyptian governorates (El-Behera,Ismailia, Menofyia, Sharkia, Giza, Gharbia and Qalubia, arrangeddescendingly according to severity infection) showed incidence ofthe isolated virus with different severity. Results clearly establishedwhen compared with the productivity of these governorates frompepper (recorded in the yearbook of Agriculture Ministry), wherefound consecutive correlation between severity infection andreduction in the productivity. Isolated virus not detected in the otherthree screening Egyptian governorates (Dakahlia, Domiat and KafrEI-Sheikh).Fruit samples collected from infected and healthy pepperplants during the screening were subjected to chemical analyses fortheir content of both vitamin C (ascorbic acid) and capsaicin.Correlation between virus infection and fruit pepper content ofvitamin C and capsaicin were estimated.Results showed marked reduction in the content of bothvitamin C and capsaicin in the virus infected pepper plants. Positive, correlation between pepper content of pungency ’capsaicin’ andresistance to virus infection was naturally found during the survey.Occurrence of the isolated virus during this study, suggestedcalled pepper severe mosaic potyvirus (PSMV), was the first recordin Egypt.