Initial Evaluation of Spinach Collections for Drought Tolerance

Spinach (Spinacia oleracea) production in California represents 73% of all production in the United States covering more than 28,000 acres with a value over $150 million in 2012.  California has abundant fertile farmland along with a climate favorable to leafy vegetable production, but a combination of factors are building to threaten the future viability of spinach production in the state. Irrigation water supplies are being increasingly constrained due to reduced precipitation along with regulatory changes reducing water allotments for growers. California is currently in a historic drought with Governor Brown declaring an official drought emergency in 2014. Furthermore, climate change is estimated to increase these types of extreme weather events further reducing water availability. Leafy vegetables, such as spinach, have high water content, which makes these crops particularly vulnerable to water stress.  Reducing the irrigation water required for a spinach crop can represent not only a substantial cost savings to the grower, but can also help growers to meet tightening water quality regulations. To identify spinach cultivars adapted to drought-stress conditions, more than 400 spinach varieties and germplasm were initially screened for drought-tolerance traits in greenhouse trials by evaluating leaf relative water content, wilt-resistance, and shoot fresh weights in response to limited water availability. Candidate varieties identified through initial greenhouse trials, were further evaluated in fields in the Salinas Valley under carefully controlled water-stress conditions to identify spinach exhibiting drought-tolerance traits. Through a combination of greenhouse and field trials, differences were observed in the ability of spinach genotypes to adapt to limited-water environments. This initial screening of spinach germplasm is a significant step toward developing commercial cultivars that are specifically adapted to production in regions that are facing tightening freshwater supplies and will serve as a tool for breeders to utilize in the ongoing development of abiotic-stress tolerant spinach.