Intracellular inclusions associated with white spike disease of wheat

Light microscopic examination of epidermal strips from leaves of wheat (Triticum sativumL.) showing typical symptoms of the white spike (WS) disease, demonstrated the constant occurrence of huge, fibrous and whorled intracellular inclusions. Occasionally cells adjacent to those having inclusions contained needle-like formations. The whorled inclusions appeared in ultrathin section profiles as loose aggregates of threadlike elements, 7-10 m¼ in diameter and of indeterminable length, within the cytoplasm. They seem to represent filamentous particles found in leaf dip preparations from affected plants, in situ. Nucleolus hypertrophy, chloroplast degeneration and changes in endoplasmic reticulum were frequently noticed in affected tissues. Occasionally small crystalline inclusions were found nearby or within the nucleus. The presence of these fibrous, whorled inclusions associated to WS condition, reinforces the suggested viral etiology, due to the similarity of these inclusions with virus aggregates found in tissues infected with several other viruses of the beet yellows virus group. Besides symptomatology, the particle and inclusion morphology of rice "hoja blanca" virus are very similar to WS of wheat, suggesting that both diseases are induced by viruses of the same complex. The ease with which the inclusions are detected in epidermal strips, constitutes a quick and secure method to diagnose the WS disease.