Lettuce in the field (photo courtesy of the author)
Las Cruces, NM Lettuce (Lactuca sativa) is a high-value crop cultivated worldwide. Harvested lettuce acreage in New Mexico, USA, trails the leading lettuce production states (California, Arizona), but growers in New Mexico are interested in expanding their production. For New Mexico farmers to increase lettuce production to reach new markets, information on heat-tolerant cultivar performance is needed.
Researchers from New Mexico State University have published new findings on the
performance of heat-tolerant lettuce cultivars in Southern New Mexico. The study,
conducted during the 2020-21 growing seasons, highlights the potential of specific
lettuce varieties to thrive in high-temperature environments, offering significant benefits
to local farmers and the agricultural industry.
The study evaluated six lettuce cultivars under the region’s challenging climatic
conditions. Southern New Mexico’s high temperatures and intense sunlight can be
detrimental to traditional lettuce varieties, making it crucial to identify cultivars that can
withstand heat stress without compromising yield or quality.
To determine which cultivars and types of lettuce are better suited for southern New
Mexico, researchers measured the following variables: marketable harvest weight,
number of days from transplant to first bolt, and number of days from transplant to 50%
bolted.
Temperature is one of the main factors affecting the germination and growth rate of
lettuce. Higher temperatures often reduce lettuce yield and cause physiological
disorders such as premature bolting, tipburn, and ribbiness (protuberances of the outer
ribs that prevent normal head development). One of the main methods of overcoming
temperature limitations for lettuce production is cultivar selection. Seed companies have
many listed heat-tolerant lettuce cultivars, some of which have been evaluated in
different locations and many cultivars have been found to be heat tolerant in specific
locations. Heat tolerance is the capacity of plants to function and remain productive
under high temperature stress.
Average marketable lettuce head weight, time to first bolt, and time to 50% bolted by cultivar for 2020 and 2021 growing seasons:
Bolting, when lettuce transitions from vegetative growth to reproductive growth, is
promoted in lettuce when temperatures exceed 86 °F. After bolting occurs, the edible
portion of lettuce can no longer be harvested. Early bolting could be related to a high
sensitivity to increased temperature and is not a desirable trait for lettuce cultivation in
warmer temperatures.
This research trial is the first to identify optimal lettuce cultivars for the southern New
Mexico region. The consistent high yield of romaine-type lettuce cultivar Sparx make it a
suitable option for growers in southern New Mexico. ‘Sparx’ was productive into the
warmer months of the summer, while ‘Mikola RG10’ (butterhead type) and ‘Muir’ (green
leaf type), demonstrated slower bolting in 2021. These cultivar performance results offer
an initial starting point for further research into appropriate planting dates for southern
New Mexico lettuce growers.
The full article can be found on the ASHS HortTech 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 ashs.org.
