Occurrence of Maize rayado fino virus in Maize in Argentina.

Symptoms of fine chlorotic stipple-striping of the veins, chlorosis, numerous dots and stripes, formation of holes in the leaf blade, and ears reduced in size, bearing few grains, were observed in maize crops in Tafí del Valle (Tucumán Province), Orán, El Galpón (Salta Province), Tilcara and Yaví (Jujuy Province), the subtropical area of northwest Argentina where the leafhopper vector Dalbulus maidis (DeLong & Wolcott) is present. Maize rayado fino virus (MRFV) was detected in these samples by a positive reaction in double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) using an AGDIA kit. Electron microscopy revealed abundant isometric particles about 30 nm in diameter in the cytoplasm and vacuoles of phloem cells and xylem parenchyma cells. The virus was also detected by reverse transcription polymerase chain reaction (RT-PCR) using a primer pair MRFV-09/MRFV-10. Primers and PCR conditions were as previously described (1). Virus amplification was observed only in samples from symptomatic plants. In 1981 (2), the presence of MRFV in Argentina was revealed by serological assay in plants from temperate central areas. No further reports were released since then. This is the first evidence of MRFV in subtropical areas of Argentina and identification of the virus by combining DAS-ELISA, particle size, relation with plant tissues, and RTPCR. References: (1) R. W. Hammond et al. J. Gen. Virol. 78:3153, 1997. (2) S. F. Nome et al. RIA XIX:257, 1984.