Pathogenetic roles of beet necrotic yellow vein virus RNA5 in the exacerbation of symptoms and yield reduction, development of scab‐like symptoms, and Rz1‐resistance breaking in sugar beet

Beet necrotic yellow vein virus (BNYVV) generally has a four‐segmented positive‐sense RNA genome (RNAs 1–4), but some European and most Asian strains have an additional segment, RNA5. This study examined the effect of RNA5 and RNA3 on different sugar beet cultivars using a Polymyxa‐mediated inoculation system under field and laboratory conditions. In field tests, the degree of sugar yield served as an index for assessing the virulence of BNYVV strains. Japanese A‐II type isolates without RNA5 caused mostly 15%–90% sugar yield reductions, depending on the susceptibility of sugar beet cultivars, whereas the isolates with RNA5 induced more than 90% yield losses in the seven susceptible cultivars, but small yield losses in one Rz1‐resistant and Rizor cultivars. However, a laboratory‐produced isolate containing RNA5 but lacking RNA3 caused higher yield losses in Rizor than in susceptible plants, and induced scab‐like symptoms on the root surface of both susceptible and resistant plants. In laboratory tests, A‐II type isolates without RNA5 had low viral RNA accumulation levels in roots of Rizor and Rz1‐resistant plants at early stages of infection, but in the presence of RNA5, viral RNA3 accumulation levels increased remarkably. This increased RNA3 accumulation was not observed in roots of the WB42 accession with the Rz2 gene. In contrast, the presence of RNA3 did not affect RNA5 accumulation levels. Collectively, this study demonstrated that RNA5 is involved in the development of scab‐like symptoms and the enhancement of RNA3 accumulation, and suggests these characteristics of RNA5 are associated with Rz1‐resistance breaking

Additional volumetric modulated arc therapy to vertebral metastases abutting the previously irradiated site

Introduction: Lung cancer frequently causes metastases to the spine, especially to the thoracic vertebrae, which sometimes compress the spinal cord and induce irreversible palsy. Many patients suffering from metastatic spinal tumors need to undergo repetitive radiotherapy. In such situations, intensity-modulated radiotherapy including volumetric modulated arc therapy can reduce the dose delivered to the spinal cord at the junction.&nbsp;Case Report: The authors describe a case of thoracic vertebral metastases from lung cancer treated with two courses of radiotherapy. In the second course, volumetric modulated arc therapy was adopted and a columnar-shaped planning target volume with a concave portion was configured.&nbsp;Conclusion: The authors propose an approach aimed at realizing both junctional safety and the conformality of the spinal column, which may be an option for repetitive irradiation to heterochronic spinal metastases.</p