| Pitaya also known as red dragon fruit,honey immortality,belongs to cactus family Hylocereus genus,which is a kind of tropical fruit with rich nutrition and good health care value.Comparatively,pitaya is drought-tolerant,but can not withstand waterlogging,however water stress is an inevitable environmental stress during its cultivation process.In order to investigate the resistance and adaptability of pitaya to different soil moisture gradients,we used red meat dragon fruit as the material to study the changes of morphology,physiological and biochemical indicators of pitaya cutting seedlings under different soil moisture gradients(normal watering(control),severe drought,moderate drought,mild drought and near saturation soil water)by means of potted artificial water control.Moreover,the annual seedlings of red meat pitaya were used as test materials to clone and analyze the genes related to water stress in pitaya and the expression of these genes were examined under severe drought and flooding treatments.The aim was to provide a theoretical basis for the cultivation of pitaya from the physiological and molecular levels.The results of this study are as follows:1.Severe drought,moderate drought and near saturation soil water hinder the growth of pitaya stem.The obstruction of severe drought is more obvious,and mild drought promotes the growth of pitaya stem to a certain extent.2.Under water stress treatment,with the elongation of duration the relative water content of pitaya stem is gradually decrease,malondialdehyde content is gradually increase,and the content of soluble sugar shows a trend of ‘rise-fall-rise',and the relative electrical conductivity,chlorophyll,proline,soluble protein content,and antioxidant enzymes activities show a certain degree of ‘rise-down' trends.Under water stress,the content of chlorophyll decreased with the increase of stress,and the content of other indicators and enzyme activity increased.3.In this study,the open reading frames and partial fragments of seven genes of three gene families of pitaya were obtained by gene cloning.Among them,alcohol dehydrogenase genes ADH1 C,ADH2,ADH class-3 and ADH-like 7 contain open reading frames of 1197 bp,1140 bp,1140 bp and 1161 bp,respectively.The Pyruvatedecarboxylase 2 gene is 2046 bp in length and contains an 1815 bp ORF.Pitaya PDC2 had the closest relationship with PDC2 of Beta vulgaris,followed by Brassica rapa.The length of the PDC1 fragment is 1191 bp.The calcineurin B-like proteins 2 is 861 bp in length and contains 678 bp ORF.Its amino acid sequence had the highest similarity with Beta vulgaris and Chenopodium quinoa,which is 96% and 95%,respectively.The fragment length of CBL4 and CBL9 is 208 bp and 107 bp,respectively.4.The water stress related genes expression of pitaya were tested.The results indicated that the expression of ADH1 C,ADH2,ADH class-3,ADH-like 7,PDC1,CBL2,and CBL4 of pitaya seedlings show a significant ‘rise-fall-rise-fall-rise' trend during the entire drought stress period.CBL9 showed a significant ‘up-down-up-down' trend.PDC2 showed a significant ‘up-down-up' trend,and the timing of up-regulation of each gene was different.The expression trends of each gene in pitaya seedlings were not the same under flooding stress,and all genes exhibited more complex fluctuations.The results showed that these genes have a certain regulation on water stress,but their sensitivity and expression levels are different. |
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