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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #383271
Research Project: Genetics and Breeding of Lettuce, Spinach, Melon, and Related Species to Improve Production and Consumer-related Traits

Location: Crop Improvement and Protection Research

Title: Update on breeding lettuce for resistance to Impatiens necrotic spot virus

Author
item Richardson, Kelley
item Nayak, Santosh

Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/7/2021
Publication Date: 8/7/2021
Citation: Richardson, K.L., Nayak, S. 2021. Update on breeding lettuce for resistance to Impatiens necrotic spot virus. American Society for Horticultural Science Annual Conference, August 5-9, 2021, Denver, Colorado.

Interpretive Summary:

Technical Abstract: Lettuce production in the Salinas Valley, California has suffered devastating losses from increasing incidence of Impatiens necrotic spot virus (INSV) and its vector, Western flower thrips (Frankliniella occidentalis). The number of infected fields and disease incidence within fields have risen significantly in recent years, with incidence as high as 80% in some fields. Infected heads are not marketable and often result in abandoned, tilled under fields without a harvest. Genetic resistance is considered the most economical and environmentally sound disease control method, but no cultivars have been identified that completely prevent infection. High incidence and symptom severity of INSV in field trials in 2018 and 2019 at the USDA in Salinas provided a unique opportunity to evaluate 500 entries of breeding lines and commercial varieties for resistance in four experiments. Selected lines from the 2018 and 2019 trials were planted in an August 2020 field trial to evaluate germplasm during the period of heaviest disease pressure. Natural INSV infection occurred uniformly in the five trials but varied in disease incidence. The August 2020 trial had the highest disease incidence, calculated as the proportion of symptomatic plants per plot. Across all trials, the red leaf varieties ‘Eruption’, ‘Cavalry’, and ‘Rubens Red’ showed the fewest diseased plants (less than 10%). Under heaviest disease pressure, the varieties ‘Defender’, ‘Conquistador’, and ‘Outback’ showed the most diseased plants (greater than 80%). We are presenting preliminary results of germplasm evaluated under moderate (2018 and 2019 trials) and heavy (2020 trial) INSV disease pressure. This information is useful for variety selection for early (lower pressure) versus late (higher pressure) planting times and for fields with a history of INSV infection.