A Whole-Plant Screening Test to Select Freezing-Tolerant and Low-Dormant Genotypes

Breeding for low fall dormancy is an efficient approach to increase the annual yield of perennials by extending their growing seasons from late summer through early winter. Improvement of plant winter hardiness has historically been based on field selection of plants that survive winters while selection for reduced fall dormancy is based on the height of plants in the fall. However, the unpredictability of test winters and of fall conditions due to large variations between and within locations and the environmental conditions to which the plants are exposed severely limits the predictability of these approaches. As a result, costly assessment of many plants at multiple locations over many years is often used to select plants with high potential. Thus, new approaches are needed by breeding programs to accelerate and reduce the cost of assessment of freezing tolerance and fall dormancy. Here we describe a whole plant assay entirely performed indoor in growth chambers and walk-in freezers to identify low-dormant plants with superior freezing tolerance. The equipement required as well as a step-by-step description of our selection method are detailed in this publication. The method has been shown to be efficent to improve the freeaing tolerance and reduce the dormancy in alfalfa and couild be used for other perennials.