Green Leaf, Red Leaf, and Romaine Lettuce Breeding Lines with Resistance to Leafminer, Corky Root

Leafminer (USDA-ARS) Healthy & Corky Root Lettuce Downy Mildew of Lettuce

(USDA-ARS) (R.C. Grube)

Salinas, CA – A study released by the USDA-Agricultural Research Service announced the development of new breeding lines of green leaf, red leaf, and romaine lettuce with remarkable resistance to leafminer, corky root, and downy mildew. This advancement marks a significant step forward in sustainable agriculture, offering farmers robust options to combat common pests and diseases without relying heavily on chemical interventions.

The study details the rigorous selection and breeding processes used to develop these resistant varieties. The research aimed to address the pressing need for lettuce cultivars that can withstand common agricultural challenges while maintaining high yield and quality. The new breeding lines exhibited strong resistance to three major threats to lettuce crops: Leafminer infestation, Corky Root (a soil-borne disease that affects the plant roots, severely impacting plant health and productivity), and Downy Mildew, a pervasive fungal disease that thrives in moist conditions and can devastate lettuce crops.

Limited seed samples are available from the corresponding author for distribution to all interested parties for research purposes, including the development and commercialization of new cultivars. Samples will also be deposited in the National Plant Germplasm System. It is requested that appropriate recognition be made if the breeding lines contribute to research or the development of new germplasm, breeding lines, or cultivars.

The lettuce breeding lines were developed by Dr. Beiquan Mou, a Research

Geneticist with the USDA-ARS, Salinas, California. The enormous damages and economic losses caused by the insect and diseases prompted the author to seek genetic solutions for the problems. Leafminers are major insect pests of many important crops in the world including lettuce. Lettuce roots infected with the corky root disease develop yellow to brown lesions that later become longitudinal corky ridges and restrict the absorption of water and nutrients. Downy mildew is one of the most economically important diseases of cultivated lettuce worldwide.

The entire article can be read on the ASHS HortScience electronic journal website at:

Established in 1903, the American Society for Horticultural Science is recognized around the world as one of the most respected and influential professional societies for horticultural scientists. ASHS is committed to promoting and encouraging national and international interest in scientific research and education in all branches of horticulture.

Comprised of thousands of members worldwide, ASHS represents a broad cross-section of the horticultural community – scientists, educators, students, landscape and turf managers, government, extension agents and industry professionals. ASHS members focus on practices and problems in horticulture: breeding, propagation, production and management, harvesting, handling and storage, processing, marketing and use of horticultural plants and products. To learn more, visit

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