The LTR-retrotransposon MAGGY is found sporadically in isolates of Pyricularia grisea (Magnaporthe grisea). Based on a dendrogram constructed by RFLP analysis of rDNA, isolates that carry MAGGY elements were classified into a single cluster that comprised four rDNA types. However, in a few members of this cluster, exemplified by isolates from common millet (Panicum miliaceum), the MAGGY element has distinct features. Southern analysis suggested that these isolates possessed a single copy of a MAGGY-related sequence whose restriction map differed from that of MAGGY itself. Sequence analysis revealed that the MAGGY-related sequence was a degenerate form of MAGGY, characterized by numerous C:G to T:A transitions, which have often been reported to result from RIP (Repeat-induced point mutation) or RIP-like processes. However, the favored target site for C:G to T:A transitions in this fungus, determined by examining a total of 501 sites, was (A/T)pCp(A/T), which differs from that for the RIP process originally reported in Neurospora (CpA), and from that reported in Aspergillus (CpG). The fact that certain members of the cluster of MAGGY carriers retain a single copy of a degenerate MAGGY element implies that the ancestor of these isolates successfully "captured" the invading MAGGY element.

Pyricularia isolates from various gramineous plants were subjected to RFLP and sequence analyses of rDNA to clarify their genetic relationships.Based on rDNA-RFLP patterns produced by digestion with two restriction enzymes, 71 isolates from 27 plant species were grouped into 13 rDNA types. To estimate their genetic relatedness, a UPGMA dendrogram was constructed based on the rDNA-RFLP profiles. The ITS2 regions of 13 representative isolates were also amplified by PCR and directly sequenced to construct another dendrogram.In both dendrograms, isolates from agronomically important crops (rice, foxtail millet, common millet, finger millet, wheat and oats) and their relatives were classified into a single cluster. Isolates from weeds, such as crabgrass and buffelgrass, were located outside the crop isolate cluster, and Japanese bamboo or bamboo grass isolates were farthest from the crop isolate cluster. In surveying the distribution of a retrotransposon, MAGGY, in these isolates, MAGGY was present in multiple copies in isolates from rice, foxtail millet and six other hosts, which formed a single subcluster within the crop isolate cluster. Multiple copies of MAGGY were also detected in an isolate from buffelgrass, which was distant from the other MAGGY carriers in the rDNA dendrograms. These results suggest that the horizontal transfer of MAGGY occurred during the differentiation of Pyricularia.