Identification of Zebra Chip Tolerant Diploid and Tetraploid Potato Genotypes with Good Processing Quality

Abstract

Zebra chip (ZC) disease, caused by the bacteria ‘Candidatus Liberibacter solanacearum’ (Lso), and vectored by the potato psyllid (Bactericera cockerelli Šulc.) causes significant yield and quality losses in potatoes. Potatoes infected with the Lso bacteria make chips with zebra-like patterns that are unacceptable for consumers. Currently, insecticides are applied to minimize plant contact with the potato psyllids. The use of tolerant potato cultivars is being considered as an important part of an integrated approach to manage the disease and reduce insecticide use. Comprehensive screening of commercial and breeding clones over multiple years indicated that very little resistance was available in chipping clones. The objective was to screen additional tetraploid clones containing introgressions from crop wild relatives and also a collection of diploid clones derived from recurrent selection to identify tolerance to Lso that could be incorporated in potato breeding programs. Artificial infestation with Lso-infected psyllids was conducted in greenhouse controlled and field experiments isolated from natural insect presence. Tubers were chipped and evaluated for chip quality and ZC score. Insect mortality and egg numbers were counted to characterize insect response. Among diploids with good chipping quality and low ZC score, one highly tolerant diploid clone (DD853-02) and two tolerant clones (CC831-03 and DD812-02) were identified. Among tetraploid potatoes with good chipping quality and low ZC score, some members of the A07781 and TX12484 families showed promising tolerance in the field and greenhouse. The findings indicate that genetic tolerance to ZC is available in potatoes with high chip quality and could be used for future breeding work.