The Studies On Physiological, Biochemical And Molecular Mechanisms Of The Adaptation To Drought Stress Of Sugar Beet (Beta Vulgaris L.) Seedlings

Sugarbeet(Beta vulgaris L.) is an important sugar crop in the world, but its yield and quality are attacked severely by drought stress. Reducing it's sensitivity towards water deficiency and increasing the drought resistance will be important field of sugar beet breeding research. So, making known the mechanism of drought resistance during seedling stage, speeding up the proceedings of drought resistance breeding research are great significantly. The paper got comprehensive evaluation on the drought resistance of 30 sugarbeet genetic resources from home and abroad, two varieties (represented respectively the high and low drought resistance)are selected for study materials according to the above mentioned evaluation results. The physiological, biochemical and molecular mechanisms of the adaptation to drought stress are analyzed widely. The major results studied in the paper are abstracted as follows:1,The drought resistance of 30 sugarbeet genetic resources are evaluated comprehensively by the viability test combining principal component analysis and factor analysis, verification is conducted by field experiments, which provided new technology for drought–resistance screening during seedling stage for sugar beet.2,By the combined action of the protective enzyme systems (SOD and POD) and antioxidants (Car and GSH), the HI0466 genotype showed higher drought resistance due to the better cell structure protection with significant lower active oxygen and less membrane lipid peroxidation production etc..3,The action of proline, betaine, soluble sugar and soluble protein in osmotic adjustment were extremely remarkable, the first two factors of which(proline and betaine) became the main osmotic adjustment substances with the P5CS and BADH genes'real–time expression.4,Drought stress may interfere with sugar beet photosynthesis, causing Photoinhibition. The net photosynthesis rate and primary light energy translation of PSⅡwere decreased under drought stress but the variety with higher drought resistance was less affected, which can repair itself after flooding and had higher non-photochemical quenching. The results also showed that stomata was the major influencing factor on photosynthesis under slight drought stress, while the opposite for serious one.5,The ABA content increased both in the two beet genotype and IAA content increased first, and then decreased under drought stress, this trend contributed to the drought stress regulation. The two hormones work cooperatively to enhance root growth and stomatal closure.6,The changes of water in sugar beet were closely related to 54KD protein under drought stress. The 54KD protein may participate to drought resistance process presenting in large quantity during the later period of stress. Mass Spectrometric Analysis showed that its main component was ribulose-1,5-bisphosphate carboxylase(Rubisco), which can regulate photosynthesis to enhance the drought resistance adaption.