The Effect Of Different Fertilizer On The Growth Status And Nutrient Value Of Transgenic Alfalfa Expressing Stress Tolerance Genes From Zygophyllum Xanthoxylum Under Drought Condition

As a high-yielding and high-quality feed,alfalfa not only has economic value,but also can be used as green barriers to wind and sand to create ecological value.In China,the planting area of alfalfa is mainly in the Northwest,but the soil in Northwest is poor,and the climate is arid.The cost of fertilizer and water needed to grow alfalfa is high.In the current implementation of the policy “grain-by-feeding" ternary planting structure and the establishment of grass for the industry in the form.Cultivating alfalfa with strong stress resistance is more and more attention.Studies showed that vacuolar Na+/H+ antiporter(NHX)and H+-PPase(H+-PPase)play an important role in the ion compartmentalisation of plant cell,and overexpression of N HX or H+-PPase enhanced the salt tolerance and drought resistancein plants.Zygophyllum xanthoxylum is a succulent xerophyte which mainly grows in arid sandy land.As its strong capacity of Na+ compartmentalization,Z.xanthoxylum has a strong salt and drought resistance.Therefore,in this study,transgenic alfalfa(GM),which was successfully transferred ZxNHX and Zx VP1-1 gene and wild type alfalfa(WT)were used as experimental materials.The field experiment was designed to compare the plant height,cro wn width,branch number,yield,water use efficiency,stomatal conductance,transpiration rate,net photosynthetic rate and chlorophyll content of WT and GM under non-fertilization,halved fertilization and normal fertilization condition.In order to study the field production capacity of transgenic alfalfa,as an initial basis for future promotion.The main results are as follows:1.The plant height and shoot dry weight of GM were increased along with the increase of fertilization amount.Plant height and branch number of GM were significantly higher than WT.Thus,the ability of growth and field production about GM is better than WT.2.Under half fertilizer and no fertilizer conditions,crown diameter of WT was higher than corresponding GM plants due to lower nutrient absorption capacity of WT plants.It means that the WT tend to creeping growth and GM on the contrary.3.The content of chlorophyll in GM is accumulated more than WT under drought condition in field.Both of WUE,Gs,and Pn have significant discrepancy between GM and WT under regular fertilizer treatment.Pn of GM is increased 35.5% and 54% under regular fertilizer than half fertilizer and no fertilizer.Pn of WT is increased 31.4%% and 56% under regular fertilizer than other treatments.And the Pn of GM is 12% higher than WT under regular treatment.Compared with WT,the GM has stronger capacity for photosynthesis.4.With the increasing of fertilizer,both content of crude protein and crude ash are increasing gradually.Rude protein content in GM are significantly higher than WT under half fertilizer and regular fertilizer,as well as rude ash.The rude protein content of GM under half fertilizer is 11.8% higher than WT,7.1% under regular fertilizer.It means that GM can provide more protein for livestock than WT when giving half fertilizer.5.Both the content of acid detergent fiber(ADF)and neutral detergent fiber(NDF)are reduced by increasing fertilizer.The NDF of GM is 19.2% and 10.4% less than GM under the treatment of half fertilizer and regular fertilizer.Under the treatment of half fertilizer,the ADF of GM is 22.5% less than WT and is no significantly discrepancy under other treatments.After fertilization the relative feeding value(RFV)of GM is significantly higher than WT witch half fertilizer and regular fertilizer.However,there are no significant difference between GM and WT under no fertilizer.Thus,GM can be a better fodder than WT under half fertilizer and regular fertilizer.