Analysis of p25 in Three Iranian Populations of Beet necrotic yellow vein virus and the Role of Susceptible and Resistant Cultivars of Sugar Beet in the p25 Variation

Beet necrotic yellow vein virus (BNYVV, Benyvirus) is an economically important soil borne pathogen of sugar beet throughout the world. It is a multipartite virus in which RNA-3 encoded p25 protein controls disease symptoms in sugar beet. Under certain conditions, resistance-breaking variants are generated by amino acid changes at positions 67 and 68 in p25. In the present study p25 protein in three populations of the virus from Moghan, Lorestan and Fars were analyzed in susceptible and resistant sugar beet cultivars. Lorestan and Fars populations were serially passaged through resistant or susceptible sugar beet cultivars for 4 generations and p25 was monitored for possible amino acid changes. No significant amino acid changes were observed when the populations were passaged through susceptible cultivars. However, passage of the populations through resistant cultivars resulted in changes of amino acids at positions 30, 49, 67, 68, 129, 163 and 198. Changes were more frequent in position 67 in the tetrad amino acids. Biotype P of BNYVV which was found in Moghan and Lorestan may have appeared as a result of selection under pressure of resistant cultivars. Information on certain evolutionary parameters and motifs of p25 is included.