Submitted to: The Americas Journal of Plant Science and Biotechnology
Publication Type: Review article
Publication Acceptance Date: 3/22/2007
Publication Date: 6/13/2007
Citation: Dugan, F.M. 2007. Diseases and Disease Management in Seed Garlic: Problems and Prospects. The Americas Journal of Plant Science and Biotechnology.1: 47-51. Interpretive Summary: Most garlic is propagated by the planting of seed cloves. Such "seed" is large relative to true seed of most crops. Although fungicides can be useful in some circumstances, pathogens and pests resident deep within clove tissues may be difficult to manage with chemicals, even those chemicals with systemic action. Moreover, the manner in which seed garlic is routinely stored between planting cycles is conducive to survival of pests and pathogens, some of which can also survive for long periods of time in the soil. However, various methods give the prospect of better management for pests and diseases. Tissue culture is being used to generate planting stock free of viruses and other pathogens. Breeding for disease resistance has achieved some successes. If the public will accept the resultant varieties, it may also be possible to attain resistance via new molecular-genetic techniques. In the meanwhile, however, users of garlic germplasm need to be aware of the potential for transfer of pathogens and/or pests with exchange of germplasm. This review concisely addresses all the above aspects and provides extensive references.
Technical Abstract: Although garlic is occasionally propagated via true seed, routine planting of garlic uses seed cloves as vegetative propagules. The size of seed cloves (large relative to seed of most agronomic crops), their vegetative habit, and routine storage conditions for seed cloves (permissive for most fungi), create opportunities for pathogens and problems for growers. Several phytopathogenic fungi, including some newly documented as pathogenic to garlic, are able to infest or colonize bulb tissues and remain latent for some time subsequent to harvest. Infested or infected bulbs may appear healthy at time of shipping or receipt, and even for protracted periods of storage, but incubation at suitable temperatures can result in the appearance of rot. The potential for planting seed cloves containing pathogens, plus the capacity of several of these fungal pathogens for prolonged survival in field soil, implies that pathogens may be introduced into and contaminate field soils. Systemic fungicides used as pre-planting and/or post-harvest dips can promote plant health, but the large size of seed cloves insures that deep-seated infections are not eradicated. Viruses also persist in vegetative material, are unaffected by fungicides, have been detected in a high proportion of garlic grown as planting stock, and often have arthropod vectors that are difficult to control. To circumvent these problems, tissue culture is increasingly used to generate disease free planting stock.