The effect of additional viral infections on garlic plants initially infected with <Emphasis Type="Italic">Allexiviruses</Emphasis>

Yield losses caused by a second viral infection of garlic plants previously infected with either of the isolated Allexiviruses, Garlic virus-A (GarV-A) or Garlic virus-C (GarV-C), were evaluated in a field assay carried out over four consecutive growing seasons. The treatment groups included virus-free plants (VF), plants infected only with GarV-A isolates (A), plants infected only with GarV-C isolates (C), and plants infected with a mixture of viruses that naturally infect garlic, referred to as viral-complex plants (VC). From the first crop cycle the different treatments were infected by other viruses that naturally infect garlic. At the end of the first growth cycle, significant differences in yield were observed among the four treatments. The bulb weight for VF, C, and A treatments was respectively 137%, 116%, and 96% higher than the bulb weight for the VC treatment. After the fourth growth cycle, however, non-significant differences in garlic yield between the VC, C, and A treatments were observed, whereas the yield for the VF treatment was higher than the VC treatment by 22%. Garlic yield decreased more rapidly in plants infected previously with at least one Allexivirus and then infected with other naturally occurring viruses than the plants that were virus-free at the beginning (VF plants).