Impact of soil salinity on fungal vector of rhizomania virus infecting beta vulgaris

Abstract

Polymyxa betae Keskin is the only natural transmitting vector of the Beet necrotic yellow vein virus (BNYVV) among the cultivated sugar beet. This work aims to study the impact of salt stress on fungus-virus-host relationships. The fungal infected fine roots of sugar beet plant naturally infected with BNYVV were collected and treated with different salt concentrations (0, 2000, 4000, 6000 and 8000 ppm) of NaCl for one day prior to mixing it with a sterile soil. After virus symptoms appeared on leaves, disease severity has been determined, leave and roots tissues were collected for BNYVV detection. It was found that severe symptoms on sugar beet inoculated with treated roots by low salt concentrations (2000 and 4000 ppm) while at high salt concentrations, 8000 ppm less injury approximately as control treated with H2O. On the other hand it was found the cystosorial colonization was increased in low salt concentrations (2000 and 4000 ppm) while decrease in high salt concentrations (6000 and 8000 ppm) especially in 8000 ppm. The same trend results were observed in virus concentration in roots where as the BNYVV concentration was increased in low salt concentrations (2000 and 4000 ppm) while decrease in high salt concentrations (6000 and 8000 ppm). So the relation between capacity of fungal vector to infect the plant by virus and salinity concentration are antagonistic. Soil salinity extremes most often lead to decrease infection of BNYVV via effect on fungal zoospore. Key words: Polymyxa betae, sugar beet, rhizomania, beet necrotic yellow vein virus (BNYVV), salinity.