Cold Resistance Of Different Alfalfa Materials

It is very cold in winter and late spring chilly always happen in North China. In order to evaluateaccurately the cold resistance of alfalfa varieties, this paper, using temperature controlled method andthe field experiment. Do analysis between the winter hardiness and the resistance to late spring coldthrough the aboveground morphological indexes and root characters after regrowth. The varianceanalysis, the correlation analysis, the principal component analysis, the cluster analysis were conducted.And the relationship between cold resistance and chlorophyII fluorescence parameters was also studied.The results are as follows:1Different alfalfa varieties have different winter hardiness and spring hardiness. In the springhardiness test, Caoyuan NO.2, Zhungeer, Zhaodong and YL-2have strong anti-late spring chillingperformance; while Zhongmu No.1, Aohan, Algonquin, YL-1and Longmu No.801have poor late springresistance. From the winter survival rate, we can see that the ability of winter hardiness of LongmuNo.801and Gongnong No.1are relatively strong; but Aohan has weak cold hardiness. In the simulationtest,the cold resisitance of Longmu No.801and YL-80are strong; Algonquin and Gongnong No.1arenormal;while Aohan is poorer.There has a little difference between the field and simulation test.Fromthe experiment, we know that the same material maybe have different resistance to winter hardiness andlate spring chilly. And YL-2and YL-4can be used as breeding materials for anti-late spring chilling.2The regrowth plants from frozen have a strong correlation between the form indicators andbiological production. The total weight has highly significant positive correlation with plant height,branch number, node number, bud number, crown diameter; taproot diameter and lateralroot number;and has significantly negative correlation with laterialroot position; but the correlation with crown depthis not significantly.3Principal component analysis indicated that the first component includes taproot diameter andcrown diameter; the next is plant height, taproot length and lateralroot number; the third is branchnumber and node number.4The chlorophyII fluorescence parameters of alfalfa leaves changed significantly after lowtemperature stress. As the temperature decreased, Fo increased firstly, and then decreased;furthermore,the efficiency of PSII maximal photochemistry (Fv/Fm),the maximum quantayield(Yield),the transport rate of photosynthetic electron (ETR) and the efficiency of PSII potentialphotochemistry (Fv/Fo) decreased under the low temperature stress, which caused damage to the PSIIreaction center.Because fluorescence parameters changed significantly at-5℃,so at the low temperaturestress of-5℃, alfalfa will occur obvious photoinhibition.Due to the fluorescence parameters aresensitive to temperature, and Fv/Fm is specsial,so we can use the Fv/Fm at-5℃to distinguish the coldresistance of different alfalfa varieties.