New Hosts and Taxonomic Analysis of the Mississippi Native Species Tested for Reaction to Maize Dwarf Mosaic and Sugarcane Mosaic Viruses

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Abstract
A collection of 106 grass species, representing 50 genera, was tested for reaction to manual inoculation with maize dwarf mosaic virus strains A (MDMV-A) and B (MDMV-B) and sugarcane mosaic virus B (SCMV-B) and was found to contain 70 host and 36 nonhost species. Among the 70 suscepts, 56 were previously unknown hosts, which were divided into 55 grasses susceptible to MDMV-A, 46 grasses susceptible to MDMV-B, and 45 grasses susceptible to SCMV-B; the three virus strains had 40 new host species in common. Of the 36 nonhosts, 19 species had not been reported previously in nonsusceptible. Most of the hosts of MDMV-A were more susceptible to the Mississippi isolate than to the Ohio isolate. Those host gasses (12 of 14) that were more susceptible to the Ohio isolate than to the Mississippi isolate of MDMV-A do not occur in Ohio. Among 10 grasses tested during the warm and again during the cold time of the year, a trend was apparent for plants of the same species to be more susceptible to these viruses at the lower temperature and shorter photoperiod than at the higher temperature and longer photoperiod. The 106 grasses separated into 25 annuals and 81 perennials. All annuals in the subfamilies Panicoideae and Eragrostoideae were susceptible to one or more of the virus strains, whereas 10 of 12 annuals in the subfamily Festucoideae were resistant to all strains. An analysis of the comparative susceptibility of annual versus perennial grasses is presented. Available differential hosts for the separation of MDMV-A, MDMV-B, and SCMV-B are examined for their usefulness. Inclusive of the eight genera not previously tested and included in this study, representative species of all 89 genera that compose the grass flora in Mississippi have been tested now. On the basis of 293 out of 333 Mississippi grass species tested to date, it is concluded that about 70% of all native Mississippi grasses are susceptible to MDMV-A, MDMV-B, and/or SCMV-B.