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ARS Home » Midwest Area » Madison, Wisconsin » Vegetable Crops Research » Research » Publications at this Location » Publication #334932
Title: Potato stem cuttings to study Verticillium dahliae infection for resistance breeding and ‘omics’ studies

Author
item KUMAR, ARUN - University Of Wisconsin
item Jansky, Shelley
item Halterman, Dennis

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2016
Publication Date: 1/27/2017
Citation: Kumar, A., Jansky, S., Halterman, D. 2017. Potato stem cuttings to study Verticillium dahliae infection for resistance breeding and ‘omics’ studies. American Journal of Potato Research. 94(3):270-274. doi: 10.1007/s12230-016-9563-z.

Interpretive Summary: Verticillium wilt is a serious disease in potato and is caused by a soil-borne vascular wilt fungus. Breeding for resistance is a promising control strategy, but it is difficult and expensive to evaluate populations for resistance in field trials. This paper describes a greenhouse assay for resistance based on the inoculation of stem cuttings. It reliably distinguishes between resistant and susceptible clones. This protocol can be used for breeding and for studies of host pathogen interactions.

Technical Abstract: The use of consistent and effective methods for early discrimination of resistance to pathogens and selection of appropriate times for tissue sampling are important for experiments focused on global gene expression and metabolomics. Assays for resistance to the vascular pathogen Verticillium dahliae (Vd), the causal agent of Verticllium wilt (VW) are particularly difficult because escapes are common in field assays. Seedling dip assays offer a potential solution, but homogeneous populations are not typically available. As an alternative strategy, we have developed a protocol for studying spatiotemporal infection dynamics of Verticillium dahliae Kleb. using Russet Norkotah stem cuttings. The protocol was validated using four other potato genotypes varying in resistance/susceptibility to VW under greenhouse conditions. Plants were propagated by making stem cuttings and allowing them to root for six weeks. Thereafter, plant roots were inoculated with a liquid culture of Vd and grown in a warm greenhouse. Stem samples were collected at 7, 10, 14, 21 and 30 days post inoculation (dpi), sliced into thin sections, and placed on semi-selective media to observe fungal growth. Although there were no visual symptoms in the plants, stem sections were found to be infested with Vd as early as 7 dpi. The protocol has potential applications in resistance breeding and -omics studies where populations derived from true seeds are not available.