ANALYSIS OF THE SEQUENCE DIVERSITY OF THE P1, HC, P3, NIB AND CP GENOMIC REGIONS OF SEVERAL YAM MOSAIC POTYVIRUS ISOLATES - IMPLICATIONS FOR THE INTRASPECIES MOLECULAR DIVERSITY OF POTYVIRUSES

Partial sequences from serologically characterized yam mosaic potyviru s (YMV) isolates were determined in conserved (helper-component protei nase, HC; nuclear inclusion b, NIb) and variable (first protein, P1; t hird protein, P3; and coat protein, CP) regions of the potyviral genom e in order to investigate the intraspecies molecular diversity of YMV, Multiple sequence alignments and pairwise comparisons were used to qu antify the sequence polymorphism in these regions, Two levels of diver sity were observed among YMV isolates: above 90% nucleotide (nt) seque nce identities were found between YMV isolates of the same group (intr agroup) regardless of the region considered, whereas identities betwee n isolates from different groups (intergroup) were lower and depended upon the protein chosen, For instance, the average intergroup nt seque nce identity between YMV isolates was about 65% in the P1 protein and the N terminus of the CP while there was more than 80% nt identity in the HC, P3 and NIb proteins, Thus P3 appeared to be conserved between YMV isolates even though this region was variable between potyvirus sp ecies, Similar analysis of the intraspecies molecular diversity of oth er potyviruses (potato virus Y, zucchini yellow mosaic virus, plum pox virus, pea seed-borne mosaic virus) led to the same results: (i) two levels of intraspecies molecular diversity were found (intragroup and intergroup); (ii) intraspecies molecular diversity differed from inter species molecular diversity in the P3, P1 and N-terminal regions.