Studies on the transmission of groundnut rosette virus by Aphis craccivora Koch

Four strains of groundnut rosette virus were transmitted by a race of Aphis craccivora (Koch) from groundnut in Nigeria. Two of these strains, both from East Africa, were transmitted only by A. craccivora from Kenya. A fifth isolate, from Nigeria, was not transmissible by either race. The two races of aphids have been shown elsewhere to be distinct biotypes.

Most A. craccivora needed longer than 24 h feeding on infected groundnuts to acquire virus, and many needed 2–3 days of feeding on healthy plants to cause infection, even after several days on infected plants. The delays partly reflect the slow uptake of virus and possibly a period needed for virus multiplication in aphid tissue but some is lost through resistance of the test plants to infection.

In consecutive feeding experiments Natal Common variety could be infected soon after aphids had left the source of virus, but a more resistant Nigerian variety sometimes needed several more days. The frequency of inoculation by aphids, or the concentration of virus in the inocula or both, increased with time, but the times at which aphids were able to infect plants was also dependent on variety.