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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #342340

Research Project: Genetic Enhancement of Lettuce, Spinach, Melon, and Related Species

Location: Crop Improvement and Protection Research

Title: Variation within lactuca spp. for resistance to impatiens necrotic spot virus

Author
item Simko, Ivan
item Richardson, Claire
item Wintermantel, William - Bill

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2017
Publication Date: 1/22/2018
Citation: Simko, I., Richardson, C.E., Wintermantel, W.M. 2018. Variation within lactuca spp. for resistance to impatiens necrotic spot virus. Plant Disease. 102(2):341-348. https://doi.org/10.1094/PDIS-06-17-0790-RE.
DOI: https://doi.org/10.1094/PDIS-06-17-0790-RE

Interpretive Summary: Lettuce production in coastal California, one of the major lettuce-producing areas of the US, is affected by outbreaks of Impatiens necrotic spot virus (INSV). Transmission of INSV among lettuce crops in this growing region has been attributed mostly to the western flower thrips. INSV is acquired by first or second instar thrips nymphs feeding on infected host plants (not necessarily lettuce). The virus replicates within the insect vector, and is transmitted to new plants by adult thrips as they feed on plants. All currently grown cultivars of lettuce are susceptible to the disease. Screening lettuce for resistance to INSV under the field conditions is problematic because natural infections appears sporadically and the virus is not evenly distributed across infected fields. We have developed a greenhouse-based assay that uses viruliferous thrips in combination with mechanical inoculation that allows dependable, year-round screening for resistance. Eighty-nine cultivars, breeding lines, and plant introductions of cultivated lettuce were evaluated for resistance to INSV. All tested material was susceptible to INSV to varying degrees. A partial resistance to INSV was observed in cultivars Amazona, Ancora, Antigua, Commodore, Eruption, Iceberg, La Brillante, Merlot, Telluride, and Tinto. Limited comparison of the greenhouse-based screening results with the data from six field trials indicates consistency of results from both greenhouse and field environments. The most resistant lettuce accessions are being incorporated into our breeding program for introgression of resistance into breeding lines.

Technical Abstract: Lettuce (Lactuca sativa L.) production in coastal California, one of the major lettuce-producing areas of the US, is affected by outbreaks of Impatiens necrotic spot virus (INSV) from the genus Tospovirus. Transmission of INSV among lettuce crops in this growing region has been attributed mostly to the western flower thrips (Frankliniella occidentalis). INSV is acquired by first or second instar thrips nymphs feeding on infected host plants (not necessarily lettuce). The virus replicates within the insect vector, and is transmitted to new plants by adult thrips as they feed on epidermal and mesophyll cells. All currently grown cultivars of lettuce are susceptible to the disease. Screening lettuce for resistance to INSV under the field conditions is problematic because natural infections appears sporadically and the virus is not evenly distributed across infected fields. We have developed a greenhouse-based assay that uses viruliferous thrips in combination with mechanical inoculation that allows dependable, year-round screening for resistance. Eighty-nine cultivars, breeding lines, and plant introductions of cultivated lettuce, together with 53 accessions from 11 other Lactuca species, four accessions from two dandelion (Taraxacum) species, and four tomato (Solanum lycopersicum L.) lines were evaluated for resistance to INSV. All tested material was susceptible to INSV to varying degrees, with the exception of two tomato lines that carry the Sw-5 gene that confers resistance Tomato spotted wilt virus (TSWV), a virus closely related to INSV. In cultivated lettuce, a partial resistance to INSV was observed in cultivars Amazona, Ancora, Antigua, Commodore, Eruption, Iceberg, La Brillante, Merlot, Telluride, and Tinto. Limited comparison of the greenhouse-based screening results with the data from opportunistic evaluations of resistance on 775 lettuce accessions from six field trials indicates consistency of results from both greenhouse and field environments. The most resistant lettuce accessions are being incorporated into our breeding program for introgression of resistance into breeding lines.