Towards disease resistance in potatoes using intragenic approaches.

Disease resistance is an important objective of global potato breeding programmes. The use of resistant cultivars is a significant tool for disease management. Recent advances in plant molecular genetics have identified several genes for resistance to potato diseases from within the germplasm pool available to potato breeders. Antimicrobial peptides, such as Snakin-1 (StSN1) and Snakin-2 (StSN2), have been isolated recently from potato tubers. Overexpression of the StSNI and StSN2 genes in potato is known to provide broad spectrum activity against a wide range of bacterial and fungal pathogens. We describe the use of intragenic gene transfer technology towards disease resistance in potatoes. An expression cassette was constructed with the 5' promoter and 3' terminator regions of a potato gene encoding a chlorophyll a/b binding protein (StLhca3). The coding regions of the StSN1 and StSN2 genes of potato were cloned individually between these regulatory regions. The resulting Lhca3-StSNi-Lhca3 and Lhca3-StSN2-Lhco3 chimeric genes were individually cloned into a potato-derived T-DNA-like region for potato transformation. Potato cultivar Iwa was co-cultivated with Agrobocterium harbouring intragenic binary vectors with the StSN1 and StSN2 genes. Regenerated potato plants were screened using PCR to identify lines transformed with the disease resistance genes without the presence of foreign DNA.