| China is the most serious demand country for protein feed, a serious shortage of protein feed will be the key restricting factor in the development of animal husbandry in China.Alfalfa (Medicago sativa L.) is recognized as the world’s largest bank of plant protein and excellent forage due to its high stress resistance, high yield, good quality and good palatability etc., "alfalfa-based dairy industry" is the only way for safe raw milk. As the earliest areas introduction alfalfa of Shaanxi Province, there exist a lot of problems such as varieties confusion, unclear genetic backgrounds and other issues during the process of long-term cultivation, which affecting the industrial development of alfalfa. Based on above reason, the relevant regions of the study 22 alfalfa varieties from domestic and abroad were selected for this study, and RAPD is used to clarify their genetic relationship. At the same time, the agronomic traits, yield traits, and biological characteristics were studied under field conditions for five years, 7 strong heterosis varieties were screened and the flowering habits were observed, which a base work for hybrid and seed production .Finally, the regulatory mechanism of the antioxidant system of alfalfa were studied under salt stress. The results were concluded as follows:1. The genetic diversity and genetic relationship analysis of 22 alfalfa varieties22 alfalfa varieties can be clustered into three categories by RAPD:Algonquin and Sandili belong to the first group, Victoria、Total、Queen、Gold Empress、Affinity belong to the same group, the other 15 varieties include 3 domestic varieties were grouped together. Among the 15 varieties, Zhongmu No.1 and Guyuanzihua had relatively close genetic relationship and belonged to the same sub-class,while relatively distant relationship from Guanzhong alfalfa; Haygrazer from Canada had relatively distant relationship from the others and was single grouped, which means that significant heterosis are likely to produced by hybriding it with the other 21 alfalfa varieties.2. Comparison on the production and quality characteristics of 22 varieties of alfalfa(1) It was different of the growth stages between varieties, the most obvious difference existed at returning green stage, the earliest and latest gap is 15 days, but with the extension of the growth, the difference was shortened, almost no obvious differences between varieties at flowering period; (2) The yield of the first cut was higher than those of the 2nd and 3rd cuts in the seeding year. The varieties of Victoria, Total, Sandili, Derfy, Alfalfa 54 and Haygrazer had the better growth performance than those of Guyuanzihua, WL252HQ and Guanzhong alfalfa according to the plant height analysis.(3) The growth rate of the continuous three harvests showed significant difference (p<0.05) of the 22 alfalfa varieties, varieties of Victoria, Total, Sandili, Derfy, Derby, Alfalfa 54 and Haygrazer showed more advantages. Victoria and Sandili had the highest growth intensity, and the lowest Guanzhong alfalfa showed 6 times lower difference; The varieties that had the fastest regrowth rate include Victoria, Haygrazer, WL324, Alfalfa 54 and WH323ML, of which Victoria and Haygrazer reached 0.8cm / d or more, the worst were still local varieties of Guyuanzihua and Guanzhong alfalfa, only 0.49 cm / d or so;(4) Variance analysis showed that the fresh and hay yield difference of the 22 alfalfa varieties reached a significant level (p <0.01). The fresh yield of Victoria was significantly higher than the other varieties (p <0.05) except Total, Queen, AmeriGraze, Algonquin, Zhongmu No.1, WL324, Alfalfa 54 and Haygrazer.(5) WL324 had the highest protein yield of 3216.0 kg/hm2, higher than the lowest Guanzhong alfalfa by 115.0%, and had significantly differences in addition to varieties of Victoria, Alfalfa 54 and Haygrazer.(6) The Stand height/Plant height(S/P) which describe the erectness of grass showed significantly different among the 22 varieties (p <0.01). The S/P value of good erect Zhongmu No.1, Victoria, WL323HQ, WL232HQ and Derfy were all above 0.75, while the lowest Algonquin, H323ML and Derby only 0.55-0.59.In summary, 5 advantages varieties of Victoria, Total, Sandili, Affinity, and Haygrazer and two local varieties of Guanzhong alfalfa and Guyuanzihua were screened out for the following hybrid and seed production research.3. The seed production performance evaluation of 7 alfalfa varieties(1) The alfalfa flowers generally open at 7:00 to 19:00 in Guanzhong region, the keel petals open peak appeared at 9:00 to 15:00, which was also the peak of insect activity and the best time for alfalfa hybrid;(2) The correlation analysis showed that the correlation of the florets number and the pod number per inflorescence and seed number per pod were various between different varieties;(3) The two local varieties showed poor performance of the florets number and the pod number per inflorescence and seed number per pod than the other 5 introduced varieties from abroad.4. Regulation mechanism of antioxidant system in alfalfa under salt stress In order to study physiological and biochemical change, seedling of Medicago sativa L.cv. Golden Empress were treated with different NaCl concentration of 0、40、80、120 and 160 mmol/L. Superoxide, MDA, POD, SOD, CAT, Vc and T-AOC of alfalfa leaves and roots were measured. The results showed that the levels of superoxide and MDA increased. Moreover, the activities of POD, SOD and CAT, and antioxidant content of Vc and T-AOC increased in leaves and roots of alfalfa under different NaCl concentration of 0、40、80、120 and 160 mmol/L. Oxidative damage in alfalfa roots may be heavier than in leaves of alfalfa, which provide a theory support for alfalfa salt tolerance breeding. |
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