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.

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 consistently high yield of romaine-type lettuce cultivar Sparx makes 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: https://doi.org/10.21273/HORTTECH05224-23

Source: ashs.org