EFFECT OF BEET NECROTIC YELLOW VEIN VIRUS ON SUGAR BEET PLANTS GROWN UNDER SALINE CONDITIONS

Abstract

The combined effect of biotic stress, [Rhizomania, a viral root disease caused by Beet necrotic yellow vein virus (BNYVV)] & abiotic stress [salinity, NaCl 2000, 4000, 6000 and 8000 ppm] & time [Virus inoculated one day pre-salinity, Virus inoculated one week post-salinity and Virus inoculated one month post-salinity] were studied on sugar beet. This study reveals that the sensing of salinity stress and the subsequent cellular responses by only one week increase BNYVV symptoms in the host plant therefore lead to higher field crop losses. While sensing of salinity stress and the subsequent cellular responses by long time then occur viral infection in this case the effect of salinity is a predominant on the effect of virus although the presence of viral symptom on plant. A combination of salinity stress and virus infection in the same time counteract effect of each other. Virus infection improves plant tolerance to salt stress (4000 ppm) which correlates with increased osmoprotectant and antioxidant levels in infected plant. BNYVV infection and salinity treatments lead to a significant decrease in the protein content in shoot and root as in SDS-PAGE. The virus symptoms were interpreted through plant anatomical view where this study attribute the cracks and fisher which caused by virus and increased in presence of salt to the changes in periderm tissue (irregular and deformation in cambium layer and increase in cork cell layer.Also it was found that the decrease of sucrose content which caused by viral infection caused due to phloem disintegration which increased in presence of salt. This study reveals also a very important role of calcium in viral infected plant grown under salt stress, explaining the high severity and symptoms of viral infection under high salt concentration by the unbalancing calcium ion distribution theory in plant cell. And the role of Ca2+ in the enhancement of viral infection, by influx of Ca2+ may be involved in the regulation of viral gene expression after the integrity of the plasma membrane has been violated espiscially at high salt concentration. Salinity does not affect directly on virus particles (outside the plant cell) in vitro.Also it was found that NaCl directly effect on zoospore of Polymxa betae keskin specially in high concentration of salts (8000 ppm) (so salinity effect indirectly on virus) while at low concentration of salts (2000 and 4000 ppm) increasing disease severity of virus. Key words: Sugar beet, BNYVV, Salinity, Polymxa betae Combination of Stress, Viral Calciuomic, Anatomy, and X-ray Microanalysis.