Further evidence that dioscorea latent virus is a potexvirus

SUMMARY Dioscorea latent virus (DLV) was isolated from Dioscoreafloribunda but was not detected in any of 37 cvs of D. alata, D. bulbifera, D. esculenta or D. rotundata from eight countries. It was readily sap‐transmitted to 13 of 34 species from five of 12 families; it induced symptomless systemic infection in Nicotiana benthamiana and N. megalosiphon, but only symptomless local infection in other hosts. DLV was stable in vitro: sap from infected N. megalosiphon was still infective after 10 min at 75–80 oC but not 85 oC, after dilution to 10‐6 but not 10‐7, and after at least 12 months at 23 oC. DLV was not transmitted through seed, by contact or by the aphids Aphis gossypii and Myzus persicae. DLV had filamentous particles most of which measured c. 350–900 nm in purified preparations, with two modal lengths of 445 and 875 nm; the particles sedimented as two components with sedimentation coefficients of 111 S and 131 S and had a buoyant density in caesium chloride of 1–33 g cm‐3. The virus had a single nucleic acid species with a mol. wt of 2–3 ± 04 × 106 and usually produced two protein bands (mol. wts 24 900 and 23 100) in SDS‐PAGE, although virus preparations made in the presence of chloroform yielded only the larger polypeptide. DLV was serologically distantly related to commelina X and lily X viruses, but not to 11 other established or possible members of the potexvirus group. These results provide further evidence that DLV is a distinct but definitive potexvirus.