Nutritional Quality And Drought Resistance Evaluation Of 4 Alfalfa Varieties Grown In Different Ecoregions

4 alfalfa varieties that grown in different ecoregions and in different growth stages were used as test material to study the dynamics of nutritional qualities such as crude protein, crude fiber, crude fat, crude ash, phosphorus (P) and calcium (Ca). And, indoor pot culture with controlled water was used to determine the morphological and physiological indices of different organs (leaves, stems and roots) of the 4 alfalfa varieties, based on the 5 indices: relative water content (RWC), praline (Pro), malondialdehyde (MDA), superoxide dismutase (SOD) and soluble sugar (TSS), subordination function method was used to evaluate the comprehensive drought resistance capability.The main results are listed as follows:(1) During the whole growing season, the contents of crude protein, crude fat, crude ash, Ca and P decreased as the development of growth stage, the values of each nutritional indices were found the highest during branching stage and the lowest during fading stage; while the crude fiber content increased as the development of growth stage.(2) The external environmental factors play an important role on alfalfa nutritional qualities. Drought and high light intensity help to accumulate crude protein and crude fat and retard the formation speed of crude fiber.(3) Different nutritional qualities were found for the same variety that grown in different ecoregions due to different illuminations, altitudes, hydrothermal conditions and temperatures.(4) Among the whole growing seasons of the 4 varieties, the average crude protein content, crude fiber content and crude fat content were found the highest at 17.25%, 31.65% and 1.43%, respectively, for Medicago sativa L. cv.Qingshui, indicating that Qingshui alfafa is with relatively good nutritional value.(5) Shoot height, leaf length, leaf width and relative chlorophyll content of the 4 varieties decreased when exposed to different drought stress levels. Longdong alfalfa grew slowly, but with relatively high chlorophyll content and photosynthetic rate to resist the harm brought by drought.(6) On condition of drought stress, the RWC decrease of root was found the least, at 12.87% compared with CK, and for leaf and stem, the values were found at 21.13% and 23.06%, respectively, indicating that roots are with relatively stronger water holding capacity, while leaves and stems are prone to losing water.(7) On condition of drought stress, Pro and Tss accumulated massively, and on condition of severe drought stress, the Pro accumulated in the roots were found 2.37 times of the CK, and the accumulation of TSS was found 5.15 times of the CK, and were found higher than that accumulated in leaves and stems. The mass accumulation of Pro and TSS could be used in regulating osmotic pressure and keep the water in roots; SOD was also found the highest in root and the lowest in stem, indicating that root are the most sensitive to drought, and could resist and lower down the harm brought by drought more rapidly.(8) As for the accumulation of MDA, higher contents were found in leaves and stems than in roots, indicating that plasma membrane of leaf and stem were severely oxidized.(9) Comprehensive drought resistance capability was conducted on the 4 alfalfa varieties by subordination function method, the descending order was: native Medicago falcate (0.5897) > Medicago sativa L. cv. Longdong (0.5589) > Medicago sativa L. cv. Qingshui(0.5081)> Medicago varia Martin. cv. Gannong No.2 (0.4711).