ARS | Publication request: Natural Occurrence of Phytophthora Infestans on Black Nightshade (Solanum Nigrum) in Wales

Submitted to: Plant Pathology
Publication Acceptance Date: May 6, 2004
Publication Date: August 6, 2004
Citation: Deahl, K.L., Shaw, D.S., Cooke, L.R. 2004. Natural Occurrence Of Phytophthora Infestans On Black Nightshade (Solanum Nigrum) In Wales. Plant Disease. 88(7):771.

Interpretive Summary: Black nightshade is a weed of major economic importance in production of several vegetable crops in the world and because nightshades are in the same botanical family as tomato, pepper, eggplant and potato, control or elimination of nightshades in these crops is difficult. Since recent migrations of the late blight pathogen may have introduced new strains which could be more pathogenic to wild members of the potato/tomato family than were the old strains ,we characterized isolates obtained during 2001 from black nightshades weeds found among diseased potatoes in Wales. All isolates were determined to be part of the new population by genetic finger printing analysis ; isolates produced banding patterns characteristic of the genotypes of pathogenic isolates obtained from nearby blighted potato hosts.This information will be useful to extension agents and growers who should be aware that black nightshades weeds can be a reservoir for the pathogen.

Technical Abstract: Lesions of Phytophthora infestans were found on black nightshade Solanum nigrum) in a late blighted field in Wales in 2001. Pathogenicity and spore production of P. infestans isolates collected from potato (S. tuberosum) and S. nigrum was determined on several host plant species. Sporangial formation in naturally- infected and inoculated foliage of hosts was quantified. The present population of P. infestans in Wales is pathogenic on S. tuberosum and S. nigrum. Therefore, these plant species should be regarded as alternative hosts for the late blight pathogen. Although in Wales S. nigrum infection was apparently rare, further investigation of its occurrence is required since black nightshad may have a role in late blight epidemiology both as a source of inoculum and of pathogen variation.