Soil-borne mosaic viruses in winter barley: Effects of variety and management on BaYMV and BaMMV expression

Abstract

In each of the three years of the project, field trials were conducted at two sites within 2.5 miles of each other in Gloucestershire, one heavily infested with barley yellow mosaic virus (BaYMV) and the other with barley mild mosaic virus (BaMMV). In each year, eight winter barley cultivars (Willow, Firefly or Epic, Target, Fighter, Sprite, Pipkin, Halcyon, Puffin) were sown at each site at malting N levels and the four feeding cultivars (Willow, Firefly or Epic, Target, Fighter) were additionally grown at feed N levels. There was a single sowing date at the BaYMV site, but at the BaMMV site four autumn sowing dates were planned. At the latest two dates, two spring cultivars (Alexis and Blenheim) were also sown and these were also sown at this site on two dates in the spring.

Disease incidence and yield data showed that the malting cultivars Pipkin, Halcyon and Puffin were much more susceptible to BaMMV than to BaYMV. Indeed, on BaYMV sites, their yields were sometimes comparable to those of the resistant cultivars. By contrast, the feeding cv. Fighter proved to be equally susceptible to both viruses. Although cv. Sprite is not immune to the viruses, it showed partial resistance to BaMMV and, like the other malting cultivars, was not very prone to BaYMV. Spring cultivars developed symptoms if sown in the autumn, but not in the spring.

At the BaMMV site, disease incidence on the susceptible cultivars decreased as sowing was delayed. Yields of resistant cultivars were usually greatest from the first sowing date, declining steadily as sowing was delayed. Amongst the fully susceptible cultivars (Fighter, Pipkin, Halcyon, Puffin) yields at the first sowing date (which developed the greatest levels of disease) were the lowest of any of the dates and were better at the later dates, although they never reached those of the resistant cultivars at the earliest sowing. Thus delayed sowing (e.g. from late September to late October) can produce greater yields of susceptible cultivars because the gain from decreased disease outweighs the negative effects on plant growth.

The results highlight the need for farmers to know which of the viruses is present on infested fields. Resistant cultivars should give the highest yields on infested land, but susceptible malting cultivars should perform well on sites infested only with BaYMV. If BaMMV is present, early sowing of malting cultivars should be avoided.