The value of glasshouse tests with seedlings in selecting plants tolerant to beet yellows virus

Commercial strains of sugar beet, and breeders' lines of Beta vulgaris and B. vulgaris subsp. maritima, were exposed to infection with SBY and SBYN strains of beet yellows virus, using varying numbers of Myzus persicae as vectors, so as to cause a wide range of symptoms. The severity of the symptoms was assessed by scoring for superficial veinal necrosis ('etch'). All varieties of sugar beet tested were susceptible to infection, but the severity of the symptoms varied, particularly between the cultivated and wild beet types. The scores for severity of symptoms made in the glasshouse were positively correlated with similar scores made in a field experiment using two cultivated and two wild beet types. The symptom scores were also positively correlated with losses in root and sugar yields caused by the virus.