DETECTION OF SWEET-POTATO FEATHERY MOTTLE POTYVIRUS IN SWEET-POTATO GROWN IN NORTHERN AUSTRALIA USING AN EFFICIENT AND SIMPLE ASSAY

A convenient virus detection assay was required to screen sweet potato cultivars being grown commercially for the first time in the Darwin region of northern Australia. Initially an enzyme-linked immunosorbent assay (ELISA) was used to screen plant samples for a range of viruses but results were unreliable and there were high background levels. A previously reported membrane immunobinding assay was modified to give a reliable detection assay for sweet potato feathery mottle virus (SPFMV). Using this assay SPFMV was detected in sweet potato cultivars and a native Ipomoea sp. The pattern of SPFMV distribution in runners was determined and as reported by other workers virus was detected in the older leaves of runners and only occasionally in younger leaves. Samples taken from petioles gave more reliable results than laminae and a chloroform treatment prior to immunoblotting improved visualization of positive reactions. The incorporation of a biotin step marginally increased the sensitivity of the assay. The modified assay and sampling practices described here represent a reliable, efficient and simple approach for detecting SPFMV in sweet potato and serves as a model for detecting other sweet potato viruses.