Frequency and molecular characterization of watermelon mosaic virus from Serbia

Abstract

Watermelon mosaic virus (WMV) is widespread in cucurbit crops, most commonly occuring in temperate and Mediterranean regions. In Serbia WMV has been detected in single and mixed infections with Zucchini yellow mosaic virus and Cucumber mosaic virus in field-grown pumpkin and squash crops. Among pumpkin-affecting viruses WMV is the most frequent one, both by the number of localities and its incidence at each location. During the growing season of 2009, samples from 583 plants of Cucurbita pepo cvs. Olinka, Belgrade zucchini and Tosca (Zucchini group), as well as from C. maxima and C. moschata showing symptoms of virus infection were collected from 12 commercial fields at eight localities and analyzed by DAS-ELISA using polyclonal antisera specific to six most important cucurbit viruses. Interestingly, WMV was detected at fewer sites and had lower incidence rate than in two previous years. In single infections, WMV was found in 11% of tested plants in three fields; in mixed infections with ZYMV, it was recorded in 9.9% of plants in five fields and with CMV in only 0.2% in one field. The partial coat protein gene and 3' non-translated region from two representative isolates of WMV originating from different localities and host plant species were amplified by RT-PCR, sequenced, and compared with the sequences available in GenBank database. The PCR-amplified fragment of predicted size of approximately 1017 bp was obtained. The sequences of isolates 137-08 (Acc. No. GQ259958) and 159-08 (GU144020) proved to be 94-99% identical at the nucleotide level with those from other parts of the world. The sequences of these two isolates differed from each other only at two nucleotide positions, without any amino acid substitution. Phylogenetic analysis of 57 isolates based on 750 bp sequences of the coat protein gene showed no correlation between isolates and their geographic origin, and it also indicated that these isolates fell into three molecular groups of strains. Serbian WMV isolates belong to group I, the most widespread group of isolates of this virus in the world.

Virus mozaika lubenice (Watermelon mosaic virus, WMV) široko je rasprostranjen u usevima vrežastih kultura, mada se najčešće javlja na Mediteranu i regionima sa umerenom klimom. U Srbiji, WMV je detektovan u pojedinačnim i mešanim infekcijama sa virusom žutog mozaika cukinija (Zucchini yellow mosaic virus, ZYMV) i virusom mozaika krastavca (Cucumber mosaic virus, CMV) u usevima tikava i bundeva gajenim na otvorenom polju. Od virusa tikava, WMV je često prevalentan virus, kako po broju lokaliteta u kojima je dokazan, tako i po učestalosti u samom usevu. Iz ukupno 12 komercijalnih useva na osam lokaliteta, 2009. godine sakupljeno je 583 biljaka Cucurbita pepo cvs. Olinka, Beogradska tikvica i Tosca (cukini forma), kao i C. maxima i C. moschata, sa simptomima virusnih zaraza, koje su analizirane na prisustvo šest najznačajnijih virusa tikava primenom DAS-ELISA metode. WMV je detektovan na manjem broju lokaliteta i u manjoj učestalosti u poređenju sa prethodne dve vegetacije. U pojedinačnim infekcijama, WMV je detektovan u 11% testiranih biljaka u tri useva, a u mešanim sa ZYMV u 9,9% testiranih biljaka u pet useva i sa CMV u 0,2% testiranih biljaka u jednom usevu. Deo gena za protein omotača virusa i deo 3' neprepisujućeg regiona dva odabrana izolata WMV poreklom iz različitih lokaliteta i biljaka domaćina umnožen je primenom RT-PCR metode, sekvencioniran i upoređen sa sekvencama dostupnim u GenBank bazi podataka. Dobijen je PCR produkt očekivane veličine od 1017 bp. Sekvence izolata 137-08 (Acc. No. GQ259958) i 159-08 (GU144020) pokazale su 94-99% nukleotidne identičnosti sa izolatima WMV iz drugih delova sveta. Sekvence ova dva izolata razlikovala su se jedna od druge samo u dva nukleotidna mesta što nije imalo za posledicu aminokiselinske supstitucije. Filogenetske analize 57 izolata, na osnovu 750 bp sekvence gena za protein omotača, nisu ukazale na korelaciju sa geografskim poreklom izolata, a pokazala su grupisanje izolata u tri molekularne grupe sojeva. Izolati WMV iz Srbije pripadaju grupi I, grupi koja obuhvata najrasprostranjenije izolate ovog virusa u svetu.