Transgenic American Chestnuts Exhibit Intermediate Resistance to Chestnut Blight

American chestnut (Castanea dentata) is a native keystone species that was nearly eradicated by chestnut blight caused by the fungal pathogen, Cryphonectria parasitica. A new approach to producing American chestnut trees with enhanced blight resistance is through Agrobacterium-mediated transformation. This report describes the progress towards producing a blight-resistant American chestnut tree.

The transgenic American chestnut ‘Darling4,' which expresses a wheat oxalate oxidase gene, exhibited an intermediate blight resistance. It was found to be more resistant than American chestnut but less resistant to Chinese chestnut (Castanea mollissima), the source of the resistance genes. Enhanced resistance was first observed in an assay of young chestnuts grown indoors. It was then confirmed with traditional stem inoculations on field-grown trees.

Pollen from ‘Darling4′ were also used to produce transgenic T1 seedlings. The T1 seedlings expressed the enhanced resistance trait. This is vital for propagation and development of transgenics since outcrossed transgenic seedlings have several advantages over tissue-cultured plantlets. These advantages include increased genetic diversity and faster initial growth.

For more on the development of the transgenic chestnuts, feel free to visit: http://www.sciencedirect.com/science/article/pii/S016894521400079X.