engleski

Spontaneous host of Radish mosaic comovirus (RaMV) among weed plants

Radish mosaic virus (Comoviridae), a beetle- transmitted virus naturally infecting crucifer plants (Brassicaceae), has isometric particles ca. 28 nm in diameter and a biparrite ssRNA genome. Its strains, neotype and European, differ serologically and natural host range. In nature, the neotype stran, which includes North American (Californian), Japanese and possibly Far East (Russian) isolates, predominantly infects radish (Rraphanus sativus L. var. sativus L., R. sativus L ssp. chinensis/ Mill./Sazon) but is a potential danger to some Brassica oleracea L. (cauliflower, Brussel sprouts, etc.) and B. napus L. (swede, rutabage) cultivars. The European strain has often been found in Brassica rapa L. ssp. rapa (turnip) ; besides, in the hybrid Brassica Perko PVH, in B. napus and B. oleracea cultivars (as above, also perennial kale) and Eruca sativa. Some of these plants species (e.g. radish, turnip, Perko PVH) suffer serious. From plants generally known as wild plants and weeds, only Sinapis arvensis L., Brassica nigra (L.) Koch, Diplotaxis erucoides L., Erysimum spp., Raphanus raphanistrum L. and B. napus L. ssp. olaifera (DC.) Janch, have been found (in Europe) to be spontaneously infected with RaMV. The latter species was earlier referred to as B. rapa L. ssp. sylvestris. In the present account, one season's (May to July) investigation of RaMV spread in weed plants in restricted region of central Croatia (the broader Zagreb area) are reported. Plants, quite frequently stunted, showing foliar virus-like symptoms, i.e., mosaic, veriegation and vein banding (B. rapa ssp. sylvestris) together with blistering and leaf malformation, (Rapistrum rugosum (L.) All ssp. rugosum) or strong mosaic, leaf malformation, veinal and complete necrosis (S. arvensis), were tested for virus presence ; the persentage of such plants in populations varied approximately from 10 to 40 %. The double radial immunodiffusion (DRID) method was applied, using crude leaf extracts and an antiserum to the RaMV European HZ strain. Identification of replicativeform of the RaMV genome was attempted following dsRNA isolation by a micromethod. Both methods were applied directly to plants taken from nature. The new natural hosts, B. rapa ssp. sylvestris and R. rugosum ssp. rugosum were found. Spontanous infection of S. arvensis and (occurring as an ephemerophyt ) B. napus ssp. oleifera was confirmed. All these plants are remarkable reservoirs of RaMV in nature. The DRID method was reliable in identifying RaMV in natural host plants. Isolation of dsRNA from the investigated RaMV-infected plants showed that, in general, the concentration of RaMV replicative genome RNA was insufficient to give clearly recognizable dsRNA patterns. The investigations are continued.

Radish mosaic virus ; spontneous host ; weed plants

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