Relative Susceptibility Among Alternative Host Species Prevalent in the Great Plains to Wheat streak mosaic virus

Abstract

Ito, D., IVIiller, Z., Menaüed, F., Moffet, M., and Burrows, M. 2012. Re!ative susceptibiüty among a!temative host species preva!ent in the Great P!ains to Wheat streak mosaic virus. Plant Dis. 96:1185-1192.Wild grasses, crops, and grassy weeds are known to host Wheat streak mosaic virus (WSMV) and its vector, the wheat cur! mite (WCM). Their relative importance as a source of WSMV was evaluated. A survey of smaü-grain fie!ds throughout Montana was conducted between 2008 and 2009. Cheatgrass was the most preva!ent grassy weed and the most frequent vira! host, with 6% infection by WSMV in 2008 {n = 125) and 15% in 2009 {n = 358). By mechanically inoculating plants with WSMV in the greenhouse, the highest susceptibiüty was found in rye brome (52.1%), jointed goatgrass (80.9%), and wi!d oat (53.9%). Quackgrass, not previous!y reported as a host, was susceptib!e to WSMV (12.7%). Mite transmission efficiency from susceptib!e grass species was lower than from wheat, and grass species must be a host for both WSMV and the WCM to serve as a virus source. WCM transmission was more efficient than mechanical transmission. Overall, results indicate that grass species can serve as a viral reservoir, regional variation in a weed species' susceptibiüty to WSMV cannot exp!ain geographic variation in epidemic intensity, and crop species and c!ose!y re!ated weeds (e.g., jointed goatgrass) remain the best reservoirs for both WSMV and the WCM.

Impacts of Crop Variety and Time of Inoculation on the Susceptibility and Tolerance of Winter Wheat to Wheat streak mosaic virus

“…A WSMV isolate from Conrad, MT (Conrad I) was used as the standard isolate for this studies (13). Isolate stocks were maintained at -80°C until use.…”

“…Plants were maintained as described by Ito et al (13). Two weeks after inoculation, these stock plants were used to inoculate flats (35 by 50 cm) of spring wheat at growth stage Feekes 2.…”

“…In all, 20 and 30 flag leaves were randomly sampled from the center 1.0 m of each row on 18 June 2008 and 22 June 2009, respectively. All leaves were processed individually with enzyme-linked immunosorbent assay (ELISA), as described by Ito et al (13). The absorbance (optical density) values of the negative controls (healthy wheat) were used to identify infected plants.…”

Impact of Timing and Method of Virus Inoculation on the Severity of Wheat Streak Mosaic Disease

“…Hunger et al (1992) reported a nonsignificant yield reduction (3 to 23%) in spring inoculation, a trend that was similar to our mechanical inoculation of Overland (13%), but these incidences are much lower compared with the 55% yield loss observed in this study with mite inoculation. Ito et al (2012) reported higher incidence of WSMV in barley (88%) with mite inoculation, while Lehnhoff et al (2015) reported very poor infection (average 13%) when barley was mechanically inoculated with WSMV under field conditions. The average yield losses due to mite inoculation in this study are generally greater but those due to mechanical inoculation are within the 32 to 74% reported in other studies that used mechanical inoculation in susceptible cultivars (Byamukama et al 2014;Fahim et al 2012;Miller et al 2014;Sharp et al 2002).…”

“…In addition, information on the effects of inoculation method (mites versus mechanical) on disease intensity and yield will be useful to researchers comparing response of wheat cultivars to WSMV infection. Laboratory experiments revealed a higher incidence of WSMV in barley plants inoculated using WCM compared with mechanical inoculation in the field (Ito et al 2012;Lehnhoff et al 2015), indicating that the method of inoculation can influence disease severity. A similar study by Miller et al (2014) revealed severe symptoms and yield loss in wheat plants mechanically inoculated with WSMV in the spring but not those inoculated during the fall.…”