ACQUISITION, RETENTION AND TRANSMISSION OF FABA BEAN NECROTIC YELLOWSVIRUS BY 2 OF ITS APHID VECTORS, APHIS-CRACCIVORA (KOCH) AND ACYRTHOSIPHON-PISUM (HARRIS)

Faba bean necrotic yellows virus (FBNYV) belongs to a new group of pla nt viruses that have unusually small isometric virions and a multipart ite ssDNA genome. It is the causal agent of some virus diseases affect ing several food and fodder legumes in west Asia and north Africa. FBN YV is persistently transmitted by various aphid species of which Aphis craccivora appears to be the most significant natural vector. In atte mpts to obtain a better understanding of factors involved in FBNYV spr ead under field conditions, the interactions of the virus with A. crac civora and Acyrthosiphon pisum were studied. The two species were effi cient vectors and very similar in their minimum acquisition (AAP) and minimum inoculation access feeding periods which ranged from 15 to 30 min and 5-15 min, respectively. Following an AAP of 72 h and daily ser ial transfers of individual aphids to single plants, many individuals retained and transmitted the virus throughout their life span (up to 3 2 days) but at erratic efficiencies. In this persistence experiment A. pisum was a more efficient vector than A. craccivora. For both aphid species no decrease in transmission efficiency was observed, suggestin g that nymphs acquired large amounts of FBNYV virions which were not d epleted in their hemocoel during the experiment. Based on log-probit a nalysis, median latency period (LP50) values of 108.8 h and 105.0 h we re calculated for FBNYV in A. craccivora and A. pisum, respectively. F BNYV was not lost during moults and was not passed on to the parthenog enetic offspring by viruliferous adults. Aphids which acquired FBNYV a s adults were strikingly poor vectors as compared to nymphs.