Field trials on the effect of a Nigerian swollen‐shoot virus on the growth of different cacao types

SUMMARY Two brief field trials in Western Nigeria compared the effects of infection by a virulent strain of swollen‐shoot virus on growth of West African Amelonado cacao with those on other types. These included hybrid progenies from crosses with Upper Amazon cacao. Within each progeny, severity of leaf symptoms was correlated with growth rate, but the Amelonado showed more severe symptoms than the Amazon progenies, although infection decreased its growth rate proportionally less. However, most of the Amazon progenies are so much more vigorous that some infected ones grew more rapidly than the uninfected Amelonado. Three progenies were exceptionally tolerant and their growth rate was little affected by infection: such types may prove valuable in areas where attempts to eradicate swollen‐shoot disease have been abandoned.