Seed and pollen transmission of asparagus virus 2

Asparagus virus 2 (AV2) is widespread in asparagus crops worldwide and is known to be seed-transmitted. To determine the effect of AV2- infected parental source on development of infected seed, male and female asparagus plants which were AV2-infected or AV2-free were cross-pollinated and allowed to develop seed in an insect-proof greenhouse. ELISA tests of shoots from the resulting seedlings showed that AV2 was transmitted into 17 % of germinated seedlings when only the male parent was infected, into 47 % when only the female was infected and to 95 % when both parents were infected. Infection of parent plants resulted in reductions in successful pollination (21–29 %), weight (11–18 %) and number of seed (12–46 %), as well as germination (8–23 %) and seedling viability (4–15 %). Most of the AV2-free female plants pollinated with infected pollen became infected; ELISA tests showed that 83 % of plants and 36 % of shoots tested positive the following year, and by the second year RT-PCR testing showed that 75 % of plants and 55 % of shoots were infected. The significance of vertical transmission via infected seed and horizontal transmission by pollination is discussed with respect to control strategies.