Transgenic leek (Allium porrum) and garlic (Allium sativum) plants have been recovered by the selective culturing of immature leek and garlic embryos via Agrobacterium-mediated transformation using a method similar to that described by Eady et al. (Plant Cell Rep 19:376-381, 2000) for onion transformation. This method involved the use of a binary vector containing the m-gfp-ER reporter gene and nptII selectable marker, and followed the protocol developed previously for the transformation of onions with only minor modifications pertaining to the post-transformation selection procedure which was simplified to have just a single selection regime. Transgenic cultures were selected for their ability to express the m-gfp-ER reporter gene and grown in the presence of geneticin (20 mg/l). The presence of transgenes in the genome of the plants was confirmed using TAIL-PCR and Southern analysis. This is the first report of leek and "true seed" garlic transformation. It now makes possible the integration of useful agronomic and quality traits into these crops.

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Allium white rot (AWR), caused by the soil-borne fungus Sclerotium cepivorum, is the most devastating disease in onion crops worldwide. Integrated pest management strategies involving cultural practices, biocontrol agents, genetic engineering and selective breeding are being investigated to control this disease. A major obstacle to evaluating these different methods is the lack of a simple, accurate, rapid assessment technique for AWR pathogenesis. An assay for quantifying AWR tissue resistance in Allium species has been developed. Lesion development on Allium seedlings was used as an indicator of susceptibility to infection. A difference in AWR resistance between leek and onion seedlings was detected using this assessment technique, with infection scores of 13% and 54-56%, respectively. Leek seedlings exhibited less frequent and less extensive lesions than the onion seedlings. Engineered germplasm, onion cultivars and other related Allium species with varying degrees of susceptibility to AWR will be screened using this assay to calibrate levels of AWR resistance.

This chapter is concerned with the genetic manipulation of crop Allium species. Section 1 starts by briefly covering aspects of crop Allium history, industry, and flavor characteristics. The section ends on cultivation and breeding of Alliums, which leads into a justification for the use of genetic modification technologies for these crops. Section 2 covers herbicide‐resistant, disease‐resistant, and insect‐resistant traits and techniques such as RNA interference and targeted expression that are currently under investigation in crop Alliums through the use of genetic modification technology. The section finishes with a comprehensive overview of the current techniques available for the genetic modification of Allium species. Section 3 outlines the future prospects for the use of genetic modification of crop Alliums.