FROST TOLERANCE OF WHEAT, OATS, BARLEY, CANOLA AND MUSTARD AND THE ROLE OF ICE-NUCLEATING BACTERIA

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Abstract
Each year in western Canada, millions of dollars are lost in crop production due to untimely spring and fall frosts. For example, on 11 June 1985 and 6 June 1986, frosts of -7 and -6.degree. C, occurred in Saskatchewan. From Saskatoon North, on 13 Aug. 1979 a frost of -6 to -8.degree. C completely devasted all unripe crops. The seeding of frost-sensitive crops such as canola and mustard must be delayed in certain areas to avoid spring frosts. This results in a yield reduction and a delay in maturity which, in turn, can result in crop loss due to fall frosts. If seeding is delayed to avoid killing frosts, early-maturing, lower yielding varieties must be sown. In addition to reducing yield, frosts may induce lesions which provide a means of infection by bacteria and fungi. Fall frosts may result in either a complete loss or reduced quality. Frosted wheat may not be suitable for milling and is often graded as feed. Frost at the soft dough stage can result in poor seed germination which makes seed unacceptable for registration. Fall frosts result in green seeds which are unacceptable to the crushes because green oil is produced. Certain spring crops such as wheat, barley and oats possess a certain degree of frost hardiness. Some of our current cultivars can withstand a frost of -5.degree. to -7.degree. C with little or no apparent injury. The current cultivars of canola and mustard cannot tolerate -4.degree. C of frost in the cotyledon stage without being severely injured or killed.