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United States Department of Agriculture

Agricultural Research Service

Research Project: Breeding Heat-Tolerant Lettuce and Spinach Varieties for Adaptation to Global Warming
2013 Annual Report


1a.Objectives (from AD-416):
To develop heat-tolerant lettuce and spinach germplasm that is adapted to global warming and low land cost areas of California.


1b.Approach (from AD-416):
We will use germplasm screening and breeding to find and create heat-tolerant lettuce and spinach germplasm, and test them in spring and summer trials conducted in coastal, Central and Imperial Valleys of California.


3.Progress Report:

This project contributes directly to the objectives 1 and 3 of the parent project, genetic improvement of lettuce and spinach. This report documents research conducted under a cooperative agreement with California Department of Food and Agriculture. Global warming and climate change pose serious challenges to California agriculture and place unprecedented pressures on the sustainability of horticulture industry. Adapting the leafy greens industry to future conditions is essential to meet the need of growing population and increasing demand for leafy vegetable products. Seeds were placed in Petri dishes to test their ability to germinate at high temperature (34oC) as compared to controls at 24oC. Three week-old seedlings were exposed to heat stress (43/35oC day/night) for a week before being assessed for leaf and plant damages as well as growth reduction. By using these methods we were able to identify different of lettuce genotypes that can tolerate heat stress and/or germinate under high temperature conditions. Some of lettuce cultivars and germplasm exhibited thermo-inhibition at 29oC, while others exhibited thermo-tolerance at higher temperature (34oC). Lettuce seed germination in the field was positively correlated with seed germination at 29 and 34oC. The results indicated that lettuce genotypes differ greatly in their ability to germinate at high temperatures as determined by the percentages and the rates of germination. We also identified heat-tolerant genotypes in different types of lettuce and spinach. The thermo-tolerant varieties could be used to expand lettuce production seasons in warm and low land cost areas and reduce the need for seed priming, lowering the production costs. The results from this study may help growers choose lettuce varieties to be grown in warm environment. The information may also help lettuce breeders to improve the crop for adaptation to global warming and climate changes.


Last Modified: 9/20/2014
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