2013 Annual Report
1a.Objectives (from AD-416):
Identify cultivable plant species that are non-hosts for certain pests and pathogens common in the Pacific Northwest and achieve a measure of control or eradication without use of chemicals.
1b.Approach (from AD-416):
Test different plant species for host range against a panel of pests and diseases of the Pacific Northwest. Hosts should demonstrate egg hatching induction, but lack of successful parasitism and reproductions for nematodes, lack of successful initial inoculation events and propagation in the case of fungi. Successful candidates will be examined for ease of cultivation, flowering, seed production, root mass and rooting depth.
This project falls within the project Potato Germplasm Enhancement through Trait Discovery, Genetic Evaluation and Incorporation (5354-21220-010-00D) and addresses Sub-objective 1.B.: “Develop germplasm with resistance to pests and diseases, establishing effective and efficient screening protocols, determining range of expression, inheritance, heritability, and discover molecular markers, while mapping genetic factors where possible and useful.” Control of soil-borne pests and pathogens can be accomplished by chemical treatments, host resistance, or host resistance of another species with direct economic value, or value only as a controller of the disease problem. Green manure crops are sometimes planted in rotation with crops susceptible to Verticillium dahliae Kleb. (Vd) to reduce Vertcillium Wilt expression. Despite observed reductions in incidence of Verticillium Wilt, asymptomatic infections of rotational crops may result in formation of microsclerotia that serve as inoculum for subsequent crops. So trap crops, as they are called, may make things worse if they harbor the pest or pathogen in residue. We quantified Vd pathotypes of potato and mint from soil, roots, and stems of potato, mints and selected putative alternative hosts grown under greenhouse conditions. There was greater carry-over of Verticillium microsclerotia from corn preceding potato than with mint. If the potato following the trap crop is Russet Norkotah, a potentially serious case of early dying could occur in the potato crop. Mint can perpetuate Verticillium presence to present problems for other potato cultivars. With regard to Litchi tomato (LT) (Solanum sisymbriifolium) its value as a trap crop has only been documented so far against nematodes and Tobacco Rattle Virus vectored by stubby root nematode. LT will eradicate Pale cyst nematode (Globodera pallida), Root-knot nematode (Meloidogyne chitwoodi and M. hapla), Pratylenchus spp., but is a good host for stubby root nematode (Paratrichodorus allius) and for TRV. The take home message is that trap crops have interlocking advantages and disadvantages. When they are not themselves of economic value, the cost of keeping a field out of production and planting and disposing of a trap crop may be too high.