Sequence diversity within the three agents of groundnut rosette disease

Sequence diversity was examined in the coat protein (CP) gene of Groundnut rosette assistor virus (GRAV), the overlapping open reading frames (ORFs) 3 and 4 of Groundnut rosette virus (GRV), and the satellite RNA (sat-RNA) of GRV obtained from field isolates from Malawi and Nigeria. These three agen ts cause groundnut rosette disease, a major disease of groundnut in sub-Sah aran Africa (SSA). Sequence analysis showed that the GRAV CP gene was highl y conserved (97 to 99%) independent of its geographic source. The nucleotid e sequence of the overlapping ORFs 3 and 4 of GRV was highly conserved (98 to 100%) from isolates within a geographic region but less conserved (88 to 89%) between isolates from the two distinct geographic regions. Phylogenet ic analysis of the overlapping ORFs 3 and 4 show that the GRV isolates clus ter according to the geographic region from which they were isolated, indic ating that Malawian GRV isolates are distinct from Nigerian GRV isolates. S imilarity within the sat-RNA sequences analyzed ranged from 88 to 99%. Phyl ogenetic analysis also showed clustering within the sat-RNA isolates accord ing to country of origin, as well as within isolates from two distinct regi ons of Malawi. Because the GRAV CP sequence is highly conserved, independen t of the geographic source of the GRAV isolates, the GRAV CP sequence repre sents the most likely candidate to use for pathogen-derived resistance in g roundnut and may provide effective protection against groundnut rosette dis ease throughout SSA.