SALINE SOIL CONDITION DECREASES RHIZOMANIA INFECTION OF BETA VULGARIS

Abstract

Rhizomania, caused by the beet necrotic yellow vein virus (BNYVV), is a world-wide problem for sugar beet production. Although rhizomania was first detected in sugar beet in the northern Italian Po Valley, wild beet on the Adriatic coast near the Po estuary show no virus infection under natural conditions. Our aim was to examine whether this absence of virus infection is caused by endogenous wild beet resistance or by the saline soil conditions of coastal habitats. Greenhouse experiments were carried out with pot plants grown from coastal seed and with a BNYVV-susceptible sugar beet variety as control. The plants were grown in highly BNYVV infested soil. To simulate saline conditions, the pots were periodically irrigated with sea salt solutions of two different concentrations or with tap water as a control. The BNYVV levels in the plant were measured by ELISA. Without salt, a range of tolerances to BNYVV was observed in plants derived from different coastal populations. One population was highly virus resistant, two were more heterogeneous and three populations were highly susceptible. In the presence of salt the data showed a significant reduction of the number of infected plants. These results indicate that the absence of virus in wild beet populations is mainly due to the saline soil conditions in coastal habitats. This phenomenon will be important for the biosafety assessment of gene flow of BNYVV resistance genes from transgenic sugar beet to wild beet populations in coastal habitats.