HIGH-OLEATE OILSEEDS FAIL TO DEVELOP AT LOW-TEMPERATURE

The fad2 mutants of Arabidopsis thaliana are deficient in activity of the endoplasmic reticulum oleate desaturase that is the main enzyme re sponsible for polyunsaturated lipid synthesis in developing seeds of o il crops. A comparison of wild-type and fad2 seeds developing on heter ozygous (FAD2/-) plants was used as a model far genetically engineered high-oleate oilseeds of species such as soybean and canola. When fad2 seeds developed at normal temperatures (22 degrees C), they showed hi gh viability compared to wildtype seeds. When a portion of seed develo pment took place at 6 degrees C, germination of the wild-type siblings remained high but germination of fad2 segregants declined considerabl y. This was true even when exposure to low temperature was limited to the final stages of seed filling and maturation. Compared to wild-type seeds, fully viable fad2 seeds produced at 22 degrees C had reduced l ipid contents and were slower to germinate at 10 and 6 degrees. Taken together, these results indicate that for some oilseed species at leas t, molecular genetic manipulation of oleate levels in the oil may resu lt in plant lines with unacceptable performance in the field.