Heat and Drought Effects on the Oil Formation of Winter Canola

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Winter canola is a potential bioenergy crop for the southern Great Plains (SGP) as acres planted in Oklahoma, Kansas, and Colorado have increased to record levels in recent years. These increases can be attributed to improved cultivars, observed rotational benefits to wheat, as well as growing U.S. demand for canola oil. However, drought and heat stress often limit grain production in the SGP. Canola is sensitive to drought and high temperatures at flowering period and grain fill as the crop progresses towards the summer months. Yield, oil content, and quality can also be severely reduced.

A short period of heat stress during canola flowering is more detrimental than drought stress exposure for the same duration. Several days of high temperatures can cause significant damage to canola yields. Drought can also decrease oil content if it occurs between flowering period and maturity. For this reason, specific climatic conditions that reduce oil content in winter canola are needed.

Agronomist Michael Stamm of the Department of Agronomy at Kansas State University (KSU), teamed up with Drs. Krishna Jagadish (KSU), and Sangdu Angadi (New Mexico State University) to investigate the effects heat and drought stress on the oil formation and quality of winter canola. The project aimed to quantify the impacts of drought and heat stress on the production and quality of oil in canola seeds; identify cultivars that produce greater oil content and oil yield under challenging weather conditions; endorse best production practices under limited irrigation and dryland conditions that enhance oil formation; and manage limited irrigation resources to benefit canola yield, oil content, and oil yield.

“We quantified the impacts of high night temperature (HNT), high day temperature (HDT), and their combination (HDNT) on the formation and quality of oil in canola seeds. We identified cultivars that produce greater oil content and oil yield under elevated risk for low oil production,” Stamm said.

Four heat tolerant and high oil producing hybrid cultivars (46W94†, Edimax CL, Mercedes, and Popular) and two heat sensitive open-pollinated cultivars (DKW44-10 and DKW46-15) were identified by the research group.

“High night temperature (HNT) significantly decreased seed weight and oil content in susceptible open-pollinated cultivars more than in tolerant hybrids. Susceptible cultivars had significantly reduced biomass, total pod numbers, and total pod weight, while the same traits were not significantly affected in the tolerant hybrids,” Stamm added.

The research team observed that among the four unsaturated fatty acids measured, oleic acid, linoleic acid, and linolenic acid were not significantly affected by temperature treatments. However, HNT stress significantly reduced the gadoleic acid content in the seeds of susceptible cultivars. “Under optimum conditions, high oil producing cultivars are more likely to produce greater oil contents under stress conditions than low oil producing cultivars,” Stamm said.

Timing of stress events, particularly a delay in flowering, can significantly affect oil content. “We found that seed oil content and oil yield were substantially affected by inflorescence removal at the bolting and full bloom stages,” Stamm said. “Inflorescence removal at flowering stage produced seed with the lowest seed oil content and oil yield.”

“We also demonstrated best production practices, such as optimum swathing timing and direct cutting, which enhance or maintain seed oil content,” Stamm said. “We observed that swathing at the later stages of seed color change had a positive effect on oil content. Direct cutting harvest method produced highest oil content, but not the highest yield. Over two years of research, swathing resulted in higher yields than direct cutting,” Stamm added.

Researchers also assessed the effect of drought stress on biomass production, seed yield, and oil formation in three different winter canola cultivars. “Overall, drought stress reduced biomass and seed yield. Among the three cultivars tested, DKW46-15 cultivar had the highest oil content, although it did not have the highest seed yield,” Stamm said.

This project will enhance development of a biobased canola economy, develop potential heat and drought tolerant canola germplasm, and engage producers through extension and outreach to expand adoption of winter canola into wheat-based systems.

Funding of this project was provided by the U.S. Department of Agriculture-National Institute of Food and Agriculture (USDA-NIFA) through the South Central Sun Grant Program.