Seed-borne cucumber mosaic virus in New Zealand lentil crops: yield effects and disease incidence

Cucumber mosaic virus (CMV) has been detected in lentil (Lens culinaris L.) seed grown in New Zealand. In 1994 experimental plots of lentil plants 'Ra jah' inoculated with CMV yielded 15% less seed than uninoculated. In 1995, seed losses were similar for 'Rajah' and 'Titore', but losses were greater at 17 and 19%, respectively. Plant numbers were also reduced by CMV infecti on-by 18% in 'Rajah' and 7% in 'Titore'. Thousand seed weight was not affec ted by infection. Surveys of commercial lentil seed lines detected CMV inci dences of between 0.05 and 2.5%. In a field experiment in 1996, using four levels of seed-borne CMV (0, 0.5, 1, and 2%) obtained by blending infected and healthy seed, mean seed-borne incidences in harvested material of betwe en 1.5 and 6% were recorded. No reductions in seed weight or subsequent ger mination rate were recorded. Plant numbers were slightly reduced by seed-bo rne CMV. Transmission of CMV from infected seed was measured. A linear rela tionship was observed from 1% transmission in plots sown with clean seed to 4.9% transmission in plots sown with seed having a 2% level of infection.