Genetic transformation of taro

Abstract

Taro (Colocasia esculenta (L.) Schott) is cultivated worldwide for its edible corms and leaves. It was the world's fourteenth most-consumed vegetable and the fifth most-produced root crop in the world during 2010. However, various pests and diseases, especially fungal and oomycete diseases, are major problems causing steep declines in taro production. Conventional breeding of disease resistant cultivars is ongoing, although it is a lengthy process. Tissue culture and genetic transformation of taro are alternative options to improve yields, quality, and disease resistance. Compared with conventional breeding, genetic engineering has unique advantages, such as a much broader gene pool for selection of genes of interest and the capability of transferring only a few transgenes, thus maintaining all other desirable crop characteristics. Only a few reports are available on the regeneration and genetic transformation of taro. The first report of taro transformation described insertion of a reporter gus gene and a selection gene hpt into a Japanese taro cultivar via particle bombardment with a very low transformation efficiency. More recently, particle bombardment and Agrobacterium-mediated transformation methods have been used to transform a Chinese taro cultivar with a disease resistance gene chi11 from rice. The Agrobacterium-mediated method had much higher transformation efficiency than particle bombardment. Insertion of this rice chitinase gene into taro resulted in moderately increased disease resistance against the fungal pathogen Sclerotium rolfsii. These results demonstrate the potential usefulness of genetic transformation to increase disease resistance of taro, particularly in instances where there are no naturally occurring resistances within the taro germplasm or the elite taro cultivars are difficult to breed conventionally.