Østrem Liv, Rapacz Marcin, Larsen Arild, Marum Petter, Rognli Odd A
Department of Grassland and Livestock, Norwegian Institute of Bioeconomy Research (NIBIO), Hellevik i Fjaler, Norway.
Department of Plant Physiology, University of Agriculture in Krakow, Krakow, Poland.
Front Plant Sci. 2018 Aug 20;9:1200. doi: 10.3389/fpls.2018.01200. eCollection 2018.
In a × population (FuRs0357) of parental origin × , selection of freezing tolerance by freezing tests on whole plants (FT) and chlorophyll (Chl-) fluorimetry on frozen detached leaves (CF) was assessed in high and low directions during two cycles of selection. The original population went through two cycles of random mating. All selections and non-selected intercrossed generations of the original population were established in field trials at a coastal site and a continental site in Norway. At the coastal site, analyses of Chl- fluorimetry parameters and leaf growth on individual plants in autumn and winter hardiness observed in field plots in spring showed that the first-generation selections for high freezing tolerance were associated with winter hardiness and early growth cessation. The second-generation FT-selections for high freezing tolerance were also associated with winter hardiness, whereas the CF-high selections diverged toward high photosynthetic activity. Both low selections were correlated with high photosynthetic activity. There were smaller variations between generations in unselected generations of the original population. Low accumulated leaf growth and early growth cessation were observed in the second-generation FT-selection for high freezing tolerance, whereas high normalized difference vegetation index (NDVI) were seen in Chl- selections. Both selection methods distinguished diverging selections with significantly different high and low freezing tolerance, but selection efficiency was comparable only for the first selection cycle. Moreover, due to mixed ploidy level in the original population, selection by FT and CF generated diploid and tetraploid plants, respectively, which intensified the response of selection, particularly in the diploid selections. Total dry matter yield (DMY) (mean of three annual cuts for 3 years) of the FT-high selections was lower than for the CF-selections. At coastal sites, selection intensity using freezing tests on whole plants should be adapted to actual climate conditions, to obtain genotypes that balance photosynthetic activity during autumn and good winter hardiness, making them persistent and high yielding.
在一个亲本来源为×的×群体（FuRs0357）中，通过对整株植物进行冷冻试验（FT）以及对冷冻离体叶片进行叶绿素（Chl-）荧光测定（CF），在两个选择周期内分别在高低两个方向上评估了耐寒性选择。原始群体经历了两个随机交配周期。原始群体的所有选择和未选择的杂交后代都在挪威的一个沿海地点和一个大陆地点进行了田间试验。在沿海地点，对秋季和冬季耐寒性的Chl-荧光测定参数以及春季田间小区中观察到的单株叶片生长进行分析表明，第一代高耐寒性选择与冬季耐寒性和早期生长停止有关。第二代高耐寒性的FT选择也与冬季耐寒性有关，而CF高选择则朝着高光合活性方向分化。两个低选择都与高光合活性相关。原始群体未选择世代之间的代际差异较小。在第二代高耐寒性的FT选择中观察到叶片生长积累低和早期生长停止，而在Chl-选择中则观察到高归一化植被指数（NDVI）。两种选择方法都区分了具有显著不同高低耐寒性的分化选择，但仅在第一个选择周期中选择效率相当。此外，由于原始群体中倍性水平混合，通过FT和CF进行选择分别产生了二倍体和四倍体植物，这增强了选择反应，特别是在二倍体选择中。FT高选择的总干物质产量（DMY）（3年每年三次切割的平均值）低于CF选择。在沿海地区，对整株植物进行冷冻试验的选择强度应适应实际气候条件，以获得在秋季平衡光合活性和具有良好冬季耐寒性的基因型，使其具有持久性和高产性。
