Studies On Coldhardiness Evaluation And Related Morphological And Physiological Variation For Different Alfalfa Cultivars

Five various alfalfa cultivars, three from China and two from Canada, were used as materials in the present work. The research work studied coldhardiness and the relations between coldhardiness and morphological characters of various seasons, nonstructural carbohydrates (NSC) status in taproot, and tissue structure by controled and field trials. The study of associations between morphological characters and coldhardiness provided very useful tools for evaluation of alfalfa coldhardiness in production practice, which are rarely investigated in China. Accumulation of NSC in alfalfa cultivars with contrasting coldhardiness was known in detail in this field. The results were shown as follows:Zhaodong>Xinjiangdaye>Xunlu>Zhongmuyihao>Huangguan, Coldhardiness sequence of five cultivars, was get by evaluating various regrowth characters following controlled and natural hardening conditions. This hardiness sequence didn't consistent with their fall dormancy scores that were usually determined by regrowth vigor in height during the fall and used to evaluate winterhardiness among cultivars. In addition, coldhardiness of cultivars were weakened by fall harvest. Among morphological characters of seedling, shoot height from axil of first true leaf is significantly related with coldhardiness (R=0.929, P<0.05). Unifoliate internode length was used as a trait for fall dormancy of alfalfa, but here didn't show a higher association with coldhardiness (R=-0.625). Among the regrowth traits after fall defoliation, regrowth plants height that is generally used to give cultivars dormancy score was also not associated closely with coldhardiness since the correlation coeffiencents of them for total five cultivars and native cultivars are –0.521, -0.039, respectively. And that phenotype score of fall regrowth after first cutting had a positive relation with coldhardiness (R=0.929, P<0.05). The other traits such as early fall regrowth, later fall regrowth and tap root mass were all negatively related with coldhardiness. On the contrary, total shoots number and crown buds number had fairly positive correlation coefficients with coldhardiness although they didn't get the significant level.Sugar concentration in fall was positive related with coldhardiness of cultivars. Whereas starch concentration appear negative correlation with coldhardiness while TNC concentration negatively related with coldhardiness in a certain extent. However the total amounts of sugar, starch and TNC per plant had little relation with coldhardiness among cultivars. Nonhardiness cultivar, Huangguan had larger xylem part in cross section of stem as compared with hardiness cultivar, Zhangdong. However, the secondary xylem and cambium in tap root of hardiness cultivars were more distinct and contained larger amounts of cells than nonhardiness one.Master candidate: Liu Xiangping Major: Grass ScienceSupervisor: Prof. Cui Guowen...