INFLUENCE OF HOST VIRUS CONTENT ON THE ACQUISITION AND TRANSMISSION OF BARLEY YELLOW DWARF VIRUS BY VECTORS (CEREALS, ELISA, APHIDS, LUTEOVIRUS)
Abstract
Symptomatic resistance to BYDV in cereals is cultivar- and virus-specific but can be associated with reduced virus productivity in infected plants. Cereal plants, whether symptomatically resistant or susceptible to barley yellow dwarf virus (BYDV), showed wide variations in virus content (as assessed by ELISA) among different leaves on the same plant, and also between leaves in the same position (i.e. of the same age) on different plants. These variations were more pronounced with Clintland 64 oats than with several barley cultivars tested. Selected entire plants or individual leaves were compared as virus sources for the acquisition and transmission of three BYDV isolates by their specific (i.e. efficient) or non-specific (i.e. inefficient) vectors. With one isolate, acquisition by an inefficient vector showed good correlation with virus content of the source leaf, but only with an 18 hr acquisition feeding time. Overall, there was no convincing evidence of differences in virus acquisition efficiency due to differences in virus content. In membrane feeding experiments, where virus was readily available to aphids, correlation between virus content and efficiency of acquisition and transmission was evident for both efficient and inefficient vectors. Aphids also acquired virus more efficiently when feeding on virus concentrates through membranes than by feeding on individual leaves. The combined results indicated that virus content is not the primary factor affecting the acquisition of BYDV by vectors, but that acquisition is probably strongly influenced by uneven distribution of virus within the leaf. DAS-ELISA in Immulon 2 plates is at present the most reliable method for detecting BYDV in plant and aphid extracts. Use of nitrocellulose membranes in a direct dot-immunobinding, or in indirect dot-ELISA, permitted the rapid detection of BYDV in small quantities of purified preparations; but with the polyclonal antisera available, it offered no significant improvement over conventional DAS-ELISA for detecting BYDV in plant or aphid extracts. BYDV can be frozen in intact tissue or leaf extracts; however, the stability of ELISA activity depends on the isolates used, on freezing conditions, and on the period of storage.
Degree
Ph.D.
Subject Area
Plant pathology
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