BIOLOGICAL AND MOLECULAR CHARACTERISTICS OF MAIZE YELLOW STRIPE VIRUS AND ITS RELATIONSHIP WITH THE LEAFHOPPER VECTOR

Abstract

ature oMaize yellow stripe virus (MYSV) causes a disease of maize in Egypt and is transmitted by the leafhopper Cicadulina chinai. Based on the morphology of the virus particles and on some other features, it was described as a tenuiviurs-like virus. Further studies were carried out to confirm this preliminary classification using molecular and biological approaches. Maize stripe virus (MStV), a definite member of the genus tenuivirus was used in most of the tests as a control. . The viral nucleic acid was extracted from purified virus or directly from infected plants. Four dsRNA fragments of 3.5, 2.6, 2.5 and 1.5 kb were obtained from MStV-R-infected maize plants and three from MYSV-infected maize plants of 33, 2.4 and 1.1 kb. Conserved sequences at the ends of tenuivirus RNAs (Tenuivirus-specific primer), were used to amplify the extracted RNAs by RT-PCR. Five PCR fragments of 2.5, 1.8, 1.6, 13 and 0.9 kb for MYSV and four major fragments of 2.5, 1.5, 0.64 and 0.42 kb for MStV-R were amplified when ds RNA was •used as template. Several eDNA clones were obtained by cloning of the PCR fragments. In Northern blot hybridization, 32P labeled eDNA probes hybridized with the homologous viral RNA extracted from virus infected plants and viruliferous insects. No hybridization was obtained with RNAs from healthy plants and no cross-reactions were detected between MYSV and MStV-R. In Northern blot hybridization, the 5 MYSV eDNA probes detected 6 single stranded formaldhyde-denatured RNA fragments of>9.5 kb (RNA!), 23 and 13 kb (RNA2), 2.1 kb (RNA3), 1.6 kb (RNA4) and 1.6 kb (RNA5). MStV­ R clones were hybridized with 2 viral RNA fragments RNA! and RNA3. At least four distinct RNA fragments were detected with the 5 eDNA probes confirming the segmente