EFFECTS OF ONION YELLOW DWARF AND LEEK YELLOW STRIPE VIRUSES ON SYMPTOMATOLOGY AND YIELD LOSS OF 3 FRENCH GARLIC CULTIVARS

This study was conducted to determine the effect of two potyviruses, o nion yellow dwarf virus (OYDV) and leek yellow stripe virus (LYSV), on the symptoms, growth, and potential yield loss of garlic (Allium sati vum). For 2 consecutive years, the impact on leaf length, pseudostem d iameter, and bulb weight was evaluated after mechanical inoculation of cultivars Messidrome, Germidour, and Printanor, the three main garlic cultivars grown in France. The reduction in bulb weight due to OYDV r anged from 39% for Germidour to about 60% for the two other cultivars. For LYSV, the reduction in bulb weight was less on Messidrome (17%) a nd Germidour (26%) than on Printanor (54%). Coinfection with both viru ses further reduced growth and bulb weight. When cloves originating fr om bulbs infected by each virus alone or a mixture of both viruses wer e planted, results indicated that such chronic infection induced furth er yield reduction. An assay designed to evaluate the role of LYSV ino culation date an yield revealed that yield losses were the-lowest for late-season infections. However, yield loss was greater than 30% when the inoculation was performed at the end of April, the time when natur al contamination generally occurs in southern France. A comparison of the impact of mixed infections of OYDV and LYSV from different origins suggested that the isolates did not differ significantly in their eff ects on yield loss.