Safflower Winter Survival and Selection Response Relates to Fall Growth Morphology and Acclimation Capacity

Abstract

Fall‐planted safflower (Carthamus tinctorius L.) offers potentially higher yield than spring‐sown types. Yet winter survival in relation to fall growth and physiological aspects of acclimation has not been determined. Our objectives were (i) to determine the relationship between fall growth and winter survival in safflower, (ii) to assess if selection improved winter survival, and (iii) to determine if water relations and membrane leakage distinguished safflower varying in winter survival. Fall growth, leaf water relations, and leaf membrane leakage were measured in fall 2004 and 2005 at Pullman and Central Ferry, WA, and winter survival was determined. Average minimum winter temperatures were 1.0°C at Central Ferry and −3.9°C at Pullman, with extremes of −7.2°C at Central Ferry and −19.5°C at Pullman. For the 21 accessions evaluated, low fall plant habit was required for survival, but survival also varied substantially among low‐habit types. Two cycles of recurrent mass selection on five low‐habit types improved winter survival from 21 to 59% at Central Ferry and from 8 to 18% at Pullman. The highest survival was for BJ‐27 after two selection cycles, averaging 90% at Central Ferry and 38% at Pullman. Accession BJ‐27 maintained higher leaf pressure potential during fall acclimation in 2004–2005 and in 2005–2006 had higher pressure potential and membrane stability on the 8 January sampling than less‐hardy types. The results show that both low habit and physiological acclimation capacity are needed for high winter survival in safflower.