Studies on interactions between the infection of susceptible and tolerant sugar beet cultivars with different Rhizomania-viruses and aphids

By pot-experiments with sugar beets in the greenhouse, the effects of infec tions by the Rhizomania viruses BNVV, BSBV, and BNYVV + BSBV on populations of Aphis fabae and Myzus persciae were tested, using the cultivars 'Hilma' (susceptible for Rhizomania) and 'Corinna' (tolerant to Rhizomania). When compared with virus-free plants, in the case of cv. 'Hilma', infections by BNYVV + BSBV, and especially by BNYVV alone, led to a significant increase of A. fabae populations by 70 and 95%, respectively. This was not the case with M. persicae, but the population growth of M. persicae proved to be hig her than that of A. fabae. Infections by BSBV alone did not exert an influe nce on the aphids. In cv. 'Corinna', infections by Rhizomania viruses did n ot lead to an increased growth of aphid populations. The weight of leaves a nd of roots of cv. 'Hilma', attacked by viruses, proved to be reduced by ap hids. In the case of cv. 'Corinna', aphids only in case of infections by BN YVV + BSBV reduced the weighs of leaves, but in infections by all viruses, aphid attack reduced the weight of roots. The possible reasons of the inter actions between virus infections and aphid attack in sugar beers are discus sed. The possible significance of an increased aphid attack is pointed out.