Effects of dual infections of Barley yellow dwarf virus (BYDV-PAV) and Wheat streak mosaic virus (WSMV) on WSMV titer, symptom severity and some yield components of wheat

Prevalence of effective sources of Wheat streak mosaic virus (WSMV) and Barley yellow dwarf virus (BYDV-PAV) and their mixed infections have been reported in several wheat growing regions in Iran. This research, investigates the effect of above mixed infections on viral titer and severity of one of the challenging viruses, WSMV, along with some yield components in three different wheat genotypes. The experiment was conducted in factorial design based on RCBD with 15 replications. Variables were viral treatments (six levels), genotypes (three levels) and the days post infection (DPI, three levels) of WSMV. The main and interactional effects of variables on above features were studied. Results showed that all doubly infections caused higher WSMV symptom scores and virus titer, those were accompanying with lower agronomic features. Among viral treatments, WSMV→BYDV-PAV inoculation and between genotypes, WSMV susceptible cultivar, Marvdasht, showed the maximum ELISA values and symptom scores. The highest viral content and symptom score were evaluated at 21 and 35 days post WSMV inoculation, respectively. Mutual interaction analysis between genotypes and viral treatments revealed the highest ELISA value and symptom score for WSMV→BYDV-PAV in Marvdasht and Rasul cultivars. Three ways interaction analysis of the above factors showed the highest ELISA value and symptom score for WSMV→BYDV-PAV treatment for Marvdasht and Rasul cultivars at 21 DPI. All doubly infections, particularly co-inoculation, resulted in the lower plant height, grain yield and shoot weight, comparing to single infections. For WSMV resistant genotype, Cross Adl, BYDV-PAV→WSMV inoculation was resulted in the higher ELISA value comparing to WSMV single infection, while, significant decrease in grain yield was observed in co-inoculation of two viruses.