Agriculture and Agri-Food Canada, Québec City, Canada.
Agriculture and Agri-Food Canada, Québec City, Canada.
Plant Sci. 2020 Mar;292:110388. doi: 10.1016/j.plantsci.2019.110388. Epub 2019 Dec 24.
Low freezing tolerance reduces the persistence of red clover under northern climate. The incidence of winter damages in perennial crops could increase in the future due to the adverse effects of the predicted warmer fall temperature on plant cold acclimation. To accelerate breeding progress, two cultivars of red clover Christie (C-TF0) and Endure (E-TF0) were exposed to a recurrent selection protocol for freezing tolerance performed indoor. New populations were obtained after five (C-TF5 and E-TF5), six (C-TF6 and E-TF6), and seven (C-TF7 and E-TF7) cycles of recurrent selection. These populations were overwintered under natural conditions and monitored for freezing tolerance and cold-induced molecular traits. Freezing tolerance was improved by up to 6 °C in recurrently selected populations when compared to initial cultivars confirming that further progress are achieved with advanced cycles of selection. Monthly analysis of biochemical changes shows that higher starch concentrations at the onset of the fall hardening period are contributing to the acquisition of superior freezing tolerance through its impact on sucrose accumulation. They also contribute to the vigor of spring regrowth by sustaining more pinitol and proline synthesis. Larger concentrations of these metabolites in populations with higher levels of freezing tolerance (TF7) hint at their involvement in winter survival of red clover. Among genes differentially expressed in response to both cold acclimation and recurrent selection, a concomitant cold induction of APPR9 and cold repression of 1-aminocyclopropane-carboxylate synthase suggests a link between the repression of a pathway regulated by ethylene and the improvement of freezing tolerance in red clover.
低温耐受性降低了红三叶草在北方气候下的持久性。由于预测的秋季温度升高对植物抗寒驯化的不利影响，未来多年生作物的冬季损害发生率可能会增加。为了加速育种进程，两种红三叶草品种 Christie（C-TF0）和Endure（E-TF0）在室内进行了耐冷冻性的反复选择试验。经过五次（C-TF5 和 E-TF5）、六次（C-TF6 和 E-TF6）和七次（C-TF7 和 E-TF7）的反复选择，获得了新的种群。这些种群在自然条件下越冬，并监测其耐冷冻性和冷诱导的分子特征。与初始品种相比，反复选择的种群的耐冷冻性提高了 6°C，这证实了通过选择的先进循环可以进一步取得进展。每月的生化变化分析表明，在秋季硬化期开始时，较高的淀粉浓度通过对蔗糖积累的影响有助于获得更高的耐冷冻性。它们还通过维持更多的肌醇和脯氨酸合成，为春季再生的活力做出贡献。在耐冷冻性较高的种群（TF7）中，这些代谢物的浓度较大，暗示它们可能参与了红三叶草的冬季生存。在对冷驯化和反复选择都有反应的差异表达基因中，APPR9 的伴随冷诱导和 1-氨基环丙烷羧酸合酶的冷抑制表明，乙烯调节途径的抑制与红三叶草耐冷冻性的提高之间存在联系。
