A new disease of maize and wheat in USA
In USA, a new disease of unknown etiology has been observed on wheat and maize in the High Plains, since 1993. This disease has tentatively been called the high plains disease. Since mid-June 1993, maize plants showing severe symptoms (including stunting, chlorosis with flecking or streaking, reddening of leaf margins) were found in Colorado, Idaho, Kansas, Nebraska, Texas and Utah. In severe cases plants died. Since September 1993, wheat crops also showed severe symptoms (small chlorotic spots which rapidly expand into a mosaic and general yellowing of the plant) in the same areas that had diseased maize crops. By 1995, the high plains disease was observed in samples of maize and wheat from an area extending from the Texas panhandle to eastern Nebraska, to central South Dakota, to western Idaho and back through Colorado to eastern New Mexico and Texas. It appears also that the high plains disease can be found on barley and oat. Serological testing of diseased maize plants only identified wheat streak mosaic rymovirus (WSMV), but as symptoms were so severe and differed from those caused by WSMV, the presence of another virus was suspected. Pathogen nucleoproteins from infected tissues were concentrated and analyzed by electrophoresis, and revealed the presence of the coat protein of WSMV and a unique 32 kD protein. Electron microscopy of leaf-dip or semi-purified preparations did not give definite results, but in some cases many spherical or ovoid bodies with a double membrane were observed, in addition to the filamentous virus particules and pin-wheel cytoplasmic inclusions characteristic of WSMV. Preliminary studies have also shown that the high plains disease could be transmitted by the wheat curl eriophyid mite (Aceria tosichella). Further work is continuing on this disease to clarify its etiology, host range, vector transmission and interactions with WSMV.
Sources
Jensen, S.G.; Seifers, D.L. (1996) A new disease of maize and wheat in the High Plains.
Plant Disease, 80(12), 1387-1390.