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Biological studies and characterization of the High Plains Disease pathogen
High Plains Disease (HPD), which is a recently recognized affliction causing up to 80% yield losses in corn and wheat, has been suspected to be of viral origin, however no clear evidence existed to validate this claim. In order to determine the nature of the infectious agent, its transmission and movement, the relationship with Wheat streak mosaic virus (WSMV) and the particle composition, studies were performed to compare the features of HPD with known viral characteristics. The eriophyid mite vector Aceria tosichella was found capable of transmitting the HPD pathogen in single infections from an established single-infection colony. Using the mites for transmission, the HPD pathogen was observed to move in a classical virus-like systemic manner in How-Sweet-It-Is sweet corn initiating from the originally infested or inoculated leaf to the roots and ultimately moving into the new shoots. However, movement in Siouxland wheat was limited to the roots. Co-infection of wheat with WSMV permitted movement of the HPD pathogen not only to the roots, but also to the new growth in the shoots. Conversely, HPD was not detected in the roots nor the shoots in corn co-infected with WSMV. In addition, a recovery-like phenomenon was observed, with the HPD pathogen no longer being detected 45 days post infestation in any of the treatments for wheat or corn. A purification protocol was established for isolation of the double-membrane particles associated with HPD from wheat leaves. When viewed under transmission electron microscope these purified ovoid particles varied in size from 80-200 nm in diameter and were identical to those previously observed with thin tissue sections of infected leaf tissue. Strand-specific RNA probes, generated from one of four RNA species previously shown to be associated with HPD infection, revealed the presence of negative-sense single-stranded RNA encapsidated in the particles. In addition, immunomicroscopy using the 32kDa protein antiserum showed that the 32 kDa protein is most likely acting as a nucleocapsid protein, complexing with the encapsidated RNA. These studies suggest that HPD is caused by a newly recognized plant virus.
Issued also on microfiche from Lange Micrographics.
Includes bibliographical references (leaves 94-104).