Fall dormancy is a vital component of alfalfa (Medicago sativa L.) yield in northern climates, but selection for the trait is often done at the expense of winter survival. We performed one cycle of selection to reduce fall dormancy in two winter hardy cultivars (Yellowhead and Peace) using a new indoor screening method. We compared the reduced dormancy populations with their respective initial cultivars for fall dormancy, yield, and winter survival at four sites across Canada. During the establishment and the first production years, plants of the reduced dormancy populations were generally taller in the fall than their respective cultivar, which resulted in a one unit increase of their fall dormancy class. Under field conditions, plants of the reduced dormancy populations had a similar winter survival than those of the initial cultivars. Under simulated winter conditions, freezing tolerance was not affected by selection for reduced dormancy in Peace, whereas a decrease from −24.0 to −21.5 °C was observed in Yellowhead. However, in this cultivar, we noted a 37% yield increase under field conditions and a 40% more vigorous regrowth under simulated winter conditions in the reduced dormancy population. These results showed that the indoor selection method effectively reduced fall dormancy and that indirect responses for yield and winter survival were dependent on the genetic background used as selection material. This selection method could therefore be promising to develop alfalfa cultivars adapted to northern latitudes with high winter hardiness and improved late season yield.

中文翻译：

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室内筛选法选择低休眠苜蓿种群的农艺学评价

秋季休眠是紫花苜蓿（Medicago sativa ）的重要组成部分L.) 在北方气候条件下产量，但通常以牺牲冬季生存为代价来选择性状。我们使用一种新的室内筛选方法进行了一个选择周期，以减少两个耐寒品种（黄头和和平）的秋季休眠。我们在加拿大的四个地点比较了减少的休眠种群与其各自的初始品种的秋季休眠、产量和冬季存活率。在建立和第一个生产年份，减少休眠种群的植物在秋季普遍高于其各自的品种，这导致其秋季休眠等级增加了一个单位。在田间条件下，休眠种群减少的植物与初始品种的植物具有相似的冬季存活率。在模拟冬季条件下，耐寒性不受选择在和平中减少休眠的影响，而在黄头中观察到从-24.0 到-21.5°C 的降低。然而，在这个品种中，我们注意到在田间条件下产量增加了 37%，在模拟冬季条件下，在减少的休眠种群中，再生长旺盛了 40%。这些结果表明，室内选择方法有效地减少了秋季休眠，并且对产量和冬季存活的间接反应取决于用作选择材料的遗传背景。因此，这种选择方法有望开发出适应北纬地区的具有高抗寒性和提高晚季产量的紫花苜蓿品种。我们注意到在田间条件下产量增加了 37%，在模拟冬季条件下，在减少的休眠种群中，再生长旺盛 40%。这些结果表明，室内选择方法有效地减少了秋季休眠，并且对产量和冬季存活的间接反应取决于用作选择材料的遗传背景。因此，这种选择方法有望开发出适应北纬地区的具有高抗寒性和提高晚季产量的紫花苜蓿品种。我们注意到在田间条件下产量增加了 37%，在模拟冬季条件下，在减少的休眠种群中，再生长旺盛 40%。这些结果表明，室内选择方法有效地减少了秋季休眠，并且对产量和冬季存活的间接反应取决于用作选择材料的遗传背景。因此，这种选择方法有望开发出适应北纬地区的具有高抗寒性和提高晚季产量的紫花苜蓿品种。这些结果表明，室内选择方法有效地减少了秋季休眠，并且对产量和冬季存活的间接反应取决于用作选择材料的遗传背景。因此，这种选择方法有望开发出适应北纬地区的具有高抗寒性和提高晚季产量的紫花苜蓿品种。这些结果表明，室内选择方法有效地减少了秋季休眠，并且对产量和冬季存活的间接反应取决于用作选择材料的遗传背景。因此，这种选择方法有望开发出适应北纬地区的具有高抗寒性和提高晚季产量的紫花苜蓿品种。