Lesquerella fendleri seed oil content and composition: harvest date and plant population effects

Abstract

Yield losses of Lesquerella fendleri L. seeds, caused by shattering and seed oil content reduction by excessive desiccation could be minimized by the appropriate choice of harvest dates. However, no information is available on harvest dates to maximize economic returns at any planting density. This research was undertaken to study the effects of harvest dates and plant populations on oil yield and composition in L. fendleri. Mechanically seeded field plots of L. fendleri were thinned at 103 days after sowing (DAS) to density treatments of 250,000, 500,000, 750,000, 1,000,000, and an nonthinned control of 1,500,000 plants/ha. These plants were grown in 1993–1994 at The University of Arizona, Maricopa Agricultural Center in central Arizona, and were harvested at 203, 229, 243, and 264 DAS. Eight fatty acids, which make up 87–96% of mature seed oil, were investigated. These included palmitic (C16: 0), palmitoleic (C16: 1), stearic (C18: 0), oleic (C18: 1), linoleic (C18: 2), linolenic (C18: 3), lesquerolic (C20: 1-OH), and auricolic (C20: 2-OH) fatty acids. Generally, seed at the earliest harvest of 203 DAS had lower concentrations of palmitoleic, stearic, oleic, lesquerolic, and auricolic acids, and lower total oil content than those harvested at 229, 243, and 264 DAS. Also at 203 DAS, the 750,000 plants/ha treatment produced the highest fatty acid content yield, although both this oil and that from the 1,000,000 plants/ha treatment lacked auricolic acid. During this period, the major contributing fatty acids to oil content were oleic, linoleic, linolenic, and lesquerolic. Harvest at 229 DAS resulted in an increase in oil content for all treatments except the 750,000 plants/ha. Lesquerolic acid was the dominant oil for the nonthinned control. At 243 DAS, higher oil contents were observed in the 250,000, 750,000, and 1,000,000 plants/ha densities, with lesquerolic acid again the dominant fatty acid. At final harvest (264 DAS), lesquerolic acid content was virtually the same among the density treatments. No significant differences for seed yield, fatty acid composition or content were found among plant populations. The seed yield averaged over all population densities was 1344 kg/ha with a fatty acid content of 21.9%, giving an oil yield 267 kg/ha (calculated as total fatty acid content).