EARLY DETECTION OF VERTICILLIUM WILT RESISTANCE IN A POTATO BREEDING PROGRAM

Nine potato clones/cultivars selected for varying degrees of Verticill ium wilt (VW) resistance based on degree of vascular colonization, wer e intercrossed and outcrossed to 13 uncharacterized clones. Based on g rowth characteristics of 3,535 seedling transplants and an assay quant ifying V. dahliae in potato vascular tissue, 404 clones were selected for further tests. The average number of Verticillium dahliae colony f orming units (CFU) expressed as Log10(CFU + 1)/0.1 ml of plant sap for the 404 clones was 2.3, and 1.3 and 3.7 for resistant Reddale and sus ceptible Kennebec checks, respectively. Thirty-five clones (8.66%) had CFU values equal to or less than Reddale suggesting that VW resistanc e is a readily transmitted trait.