Re-examining the relationship between fall dormancy and winter survival of 27 alfalfa (Medicago sativa) populations under field conditions

Alfalfa (Medicago sativa L.) is an important forage legume in Canada. Fall dormancy (FD) of alfalfa is a common predictor for its winter hardiness because of their close genetic linkage. However, there is an increasing scientific debate that these two traits can be manipulated independently. This study was conducted to re-examine this relationship from 2019 to 2022 at two experimental sites in Quebec and Saskatoon, Canada using 27 alfalfa populations with a varying range of FD scores. These populations were selected from 11 genetic backgrounds of Norseman (FD 1), 6010 (FD 1), Peace (FD 1) and Yellowhead (FD 2), Apica (FD 4), Saranac (FD 4), 55v48 (FD 5), Lahontan (FD 6), Mesilla (FD 6.5), CUF 101 (FD 9), and Wadi Qurayat (FD 10). Phenotypic traits including dry matter yield, fall plant height and spring vigor were measured. Three populations from cultivars Wadi Qurayat (FD 10) did not survive the first winter in 2019. High winter survival rate (>90%) was observed in Lahontan (FD 6), 55v48 (FD 5), Apica (FD 4), and Saranac (FD 4), Peace (FD 1-2) and Yellow (FD 1) at the two sites. Fall regrowth was positively correlated with the subsequent year spring vigour. Cultivar 55V48 (FD 5) produced maximum dry matter in Quebec, followed by 6010 (FD1), Apica (FD 4), and Yellow (FD 1), whereas in Saskatoon maximum dry matter was produced by Peace (FD 1-2), followed by Apica (FD 4), Yellow (FD 1) and Saranac (FD 4). Fall regrowth of different dormancy classes was in the order of FD 9>FD 6.5>FD 4>FD 5>FD 6 in Quebec, when the order was FD 5 > FD 9 >FD 1 >FD 5 >FD 6.5 in Saskatoon. Our results showed that it is possible to select less dormant, but high yielding and high winter hardy alfalfa populations.