Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/2007
Publication Date: 7/28/2007
Citation: Olanya, O.M., Larkin, R.P., Honeycutt, C.W. 2007. Infection Potential of Hairy Nightshade By Phytophthora infestans and Epidemiological Implications of the Alternate Host. American Phytopathological Society Abstracts. Vol 97 (7): S87, 2007
Technical Abstract: Hairy nightshade (Solanum sarrachoides Sendt) is a common weed in the potato agro-ecosystem that can serve as an alternate host for late blight. The epidemiological significance of hairy nightshade to potato late blight has not been documented. Infection rates of P. infestans on potato and hairy nightshade and late blight development were assessed in replicated experiments at 14, 18, 22 and 26 C in controlled environments. Hairy nightshade susceptibility in relation to inoculum levels, weed ontogeny, and inoculum production potential were also investigated. The progress of late blight on potato and hairy nightshade hosts was best described by the logistic model. The pathogen infection rates ranged from 0.0232 to 0.4000 logits per day at 22 C and were generally higher on potato (cv Shepody) than on hairy nightshade. The disease levels varied on hairy nightshade with inoculum levels and the infection frequency ranged from 9 to 26% at low inoculum concentration (5 x 103) and 26 to 37% at high inoculum concentration (25 x 103). In contrast to diseased potato foliage, sporangia were only detected on symptomatic, detached hairy nightshade leaves. Late blight infection was recorded on hairy nightshade at different stages of growth, and disease was significantly lower (P < .05) on 4-6 week-old (6.3-8%) than on 8-10 week old plants (18-21%). These results suggest that inoculum levels and plant ontogeny can affect disease development on hairy nightshade; however, low infection rates and inoculum production suggest the likelihood of limited disease spread.