Long-term effects of asparagus virus 2 infection on growth and productivity in asparagus

An asparagus field trial was established with clonal plants to determine th e long-term effects of asparagus virus 2 (AV2) infection on spear productio n. Yield data, analysed by ANOVA, showed that AV2 infection caused signific ant (P < 0.05) decreases in spear yield which became more pronounced as the trial progressed. Mean marketable spear yields were reduced by 14%, 28%, 2 0%, 48% and 57% and reject spear yields were increased by 93%, 105%, 207%, 352% and 167%, during harvest years 1-5 respectively. Marketable spear yiel ds from AV2-free plants increased annually to yr 5, but for AV2-infected pl ants, yields increased to yr 3 and decreased annually thereafter. Spears fr om AV2-infected plants were thinner than those from AV2-free plants, result ing in more reject thin spears by 109%, 88%, 220%, 499% and 216% during har vest yr 1-5, respectively. Further, data collected in yr 4 and 5 showed tha t AV2 infection had caused a 31% reduction in mean spear diameter and reduc tions of 27% and 22% respectively, in diameter and height of fern stalks. C learly, plants with smaller fern stalks were less able to accumulate carboh ydrate reserves and therefore produced fewer, smaller spears and fern stalk s the following spring. This may result in annual cycles of diminishing pro ductivity in which the size and number of spears and fern stalks decrease w ith each successive year. The type and timespan of symptoms caused by AV2 i nfection in this trial are similar to those reported for asparagus decline syndrome and therefore it is likely that AV2 infection is a factor contribu ting to asparagus decline.