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.