Garlic Potyviruses Are Translocated to the True Seeds through the Vegetative and Reproductive Systems of the Mother Plant.

Abstract

Garlic lost its ability to produce true seeds millennia ago, and today non-fertile commercial cultivars are propagated only vegetatively. Garlic viruses are commonly carried over from one generation of vegetative propagules to the other, while nematodes and arthropods further transmit the pathogens from infected to healthy plants. A recent breakthrough in the production of true (botanical) garlic seeds resulted in rapid scientific progress, but the question of whether viruses are transmitted via seeds remains open and is important for the further development of commercial seed production. We combined morpho-physiological analysis, fluorescence in situ hybridization (FISH), and PCR analysis to follow potyvirus localization and translocation within garlic fertile plants and seeds. Spatial distribution was recorded in both vegetative and reproductive organs. We conclude that garlic potyviruses are translocated to the seeds from the infected mother plant during flower development and post-fertilization, while pollen remains virus-free and does not contribute to seed infection. Therefore, the main practical goal for virus-clean seed production in garlic is the careful maintenance of virus-free mother plants. Although garlic pollen is free of potyviral infection, the male parents’ plants also need to be protected from contamination, since viral infection weakens plants, reducing flowering ability and pollen production.