DIFFERENTIAL INTERACTION BETWEEN PAV-LIKE ISOLATES OF BARLEY YELLOW DWARF VIRUS AND BARLEY (HORDEUM-VULGARE L) GENOTYPES

Four PAV-like isolates of barley yellow dwarf virus (BYDV) were identified as causing very severe (RG), severe (2t), moderately severe (3b) and mild symptoms (13t) in barley (Hordeum vulgare) cultivar Plaisant in a growth chamber at 25 days after inoculation. These isolates had different effects on a range of barley genotypes. Cultivar Vixen, which contains the Yd2 resistance gene, and 80-81BQCB10 were not affected by any isolate. Five other genotypes were significantly affected by at least one of the isolates. Line Ea52 (which is a mutant of the Japanese cultivar Chikurine Ibaraki) was more susceptible to BYDV-PAV than Chikurin Ibaraki 1. No serological differences were detected between the four isolates using monoclonal or polyclonal antibodies. Virus antigen concentration, estimated by enzyme-linked immunosorbent assay (ELISA), was correlated with the decrease in the shoot fresh weight for all isolates and all genotypes except for Vixen and 80-81BQCB10. In field tests, the severity of symptoms induced by the BYDV-PAV isolates was in accordance with that estimated in the growth chamber. However isolate 2t was more severe on cultivar Vixen and overcame the partial resistance of Chikurin Ibaraki 1 to the three other isolates. The results show that virus antigen concentration not only contributes to characterizing the resistance levels of barley genotypes but also the severity of BYDV-PAV isolates.