Symptoms: Symptoms on pearl millet are expressed as a mild chlorotic mottle (Qiu et al. 1998). On switchgrass, stunting can be severe in susceptible plants. Mild green mosaic and mottling and yellow or light green blotchy mottling, mosaic, and streaking of leaves are characteristic. The entire plant or sectors of it can become chlorotic if badly stunted (Sill and Pickett 1957).
Pathogen and disease characteristics: 109S isometric virus, 28-30 nm in diameter. Single RNA (28S) and protein species (28,000 daltons). Six serotypes have been differentiated. A serological relationship exists between PMV and members of the phleum mottle virus group (Buzen et al. 1984).
The virus is mechanically transmitted. PMV is a warm-temperature virus. Incubation periods (7-18 days) are generally shorter at warmer, and longer at cooler, temperatures. Optimum symptoms develop on many hosts when temperatures are 29 to 35 °C. Virus remains infective in dessicated leaf tissue for up to 9 years (Sill and Talens 1962).
Host range: Switchgrass (Panicum virgatum L.), broomcorn millet (P. miliaceum L.), ticklegrass (P. capillare L.), panicgrass (P. scribnerianum Nash), Hall's panicum (P. hallii Vasey), foxtail millet [Setaria italica (L.) Beauv.], barnyardgrass [Echinochloa crus-galli (L.) Beauv.], crabgrass [Digitaria sanguinalis (L.) Scop.] (Sill and Pickett 1957). Also Panicum ramosum, P. decompositum, P. turgidum, Setaria verticillata (Sill and Talens 1962), S. lutescens (Sill and Desai 1960), maize (Zea mays), Panicum dichtomiflorum (Niblett et al. 1977), P. virgatum L., and St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] (Holcomb et al. 1989).
Note: Sill and Pickett (1957) indicate that pearl millet (P. glaucum) is immune to PMV. Buzen et al. (1984) indicated that PMV and its satellite virus were increased on pearl millet [Setaria italica (L.) Beauv.] [sic]. There was obviously a discrepancy in their host identification since S. italica is foxtail millet. Day et al. (1994) likewise referred to the host as pearl millet. Day sent a voucher specimen to me, and the host was confirmed to be pearl millet. Masuta et al. (1987) indicate that pearl millet was used to increase PMV.
Geographic distribution: USA (Kansas). St. Augustine decline stain (PMV-SADV) occurs in the USA (Arkansas, Louisiana, South Carolina, Texas), and Mexico (Holcomb et al. 1989).
Nomenclature discrepancies: Synonyms: St. Augustine decline virus (SADV) is a strain of PMV.
Primary citations: As indicated above.
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Original posting: June 5, 1999.