Sequence diversity and virulence in Zea mays of Maize streak virus isolates

Full genomic sequences were determined for 12 Maize streak virus (MSV) isol ates obtained from Zee mays and wild grass species. These and 10 other publ icly available full-length sequences were used-to classify a total of 66 ad ditional MSV isolates that had been characterized by PCR-restriction fragme nt length polymorphism and/or partial nucleotide sequence analysis. A descr iption is given of the host and geographical distribution of the MSV strain and subtype groupings identified. The relationship between the genotypes o f 21 fully sequenced virus isolates and their virulence in differentially M SV-resistant Z. mays genotypes was examined. Within the only MSV strain gro uping that produced severe symptoms in maize, highly virulent and widely di stributed genotypes were identified that are likely to pose the most seriou s threat to maize production in Africa. Evidence is presented that certain of the isolates investigated may be the products of either intra- or inters pecific recombination. (C) 2001 Academic Press.