Analysis On Variety Difference Of Chinese Cabbage Under Different Phosphorus Concentration

Phosphorus is one of the necessary nutrient elements in the process of plant growth and development.Although the content of phosphorus(P)in soil is very high,the growth of plant is majorly limited by low content of available phosphorus.China is a major country of vegetable production and consumption and vegetable land accounts for a high proportion of agricultural land.Phosphate fertilizer was used to promote the growth of vegetables,improve the qualities of vegetables,and reduce the nitrate content of leafy vegetables.However,excessive and blind application of phosphate fertilizer has caused a series of problems,such as eutrophication of water body,waste of phosphate fertilizer resources,decline of vegetable quality,increase of production cost and so on.Therefore,developing strategies to reduce the use or increase utilization efficiency of P fertilizer is one of the important tasks for vegetable industry.Chinese cabbage(Brassica.rapa ssp.pekinenesis)is a biennial plant,belongs to Cruciferae,and highly favored among the Chinese.As the main vegetables stored for the winter,Chinese cabbage was widely planted in northern China and play an important role for stabling prices and supply of the market.To reduce the use or increase utilization efficiency of P fertilizer,some planting techniques were developed.However,these techniques were so limiting due to the differences between soil types among locations.Therefore,screening the low P tolerant genotype of Chinese cabbage,discovery the regulatory mechanisms of phosphorus uptake and transport in Chinese cabbage,may lay a foundation for developing new P tolerant variety based on marker assisted breeding and gene editing technologies.In this study,1)the physiological and morphological characteristics of 25 Chinese cabbage varieties collected from market were analyzed under different phosphorus levels to screen the low phosphorus tolerant genotype.2)we systematically analyzed the coding members of PHT and SPX gene family which play an important role in phosphorus uptake and transport of plant;3)the expression patterns of PHT and SPX genes in the root of Chinese cabbage were analyzed.The main results are as follows:(1)Based on the morphological and physiological data,25 Chinese cabbagevarieties were divided into three types,ow phosphorus tolerance type,intermediate type and sensitive type with the evaluation of principal component analysis and systematic clustering.(2)According to the protein sequence of PHT gene in Arabidopsis thaliana,52 coding members of BrPHT gene family in Chinese cabbage were isolated by Blast analysis.Using low phosphorus sensitive rubber vegetable Qiuwang(17)and low phosphorus tolerant space 6(12)as materials,semi-quantitative PCR and fluorescence quantitative PCR were used to analyze the expression pattern of BrPHT gene in root system of Chinese cabbage.Among the 52 genes,6 BrPHT were detected to respond to low phosphorus stress,which were BrPHT1,BrPHT21,BrPHT46,BrPHT47,BrPHT48 and BrPHT50.The six genes of variety 17 were all induced by low phosphorus,and the four genes of BrPHT21,BrPHT47,BrPHT48 and BrPHT50 of variety 12 were also induced by low phosphorus,while the expression of BrPHT1 and BrPHT46 was inhibited by low phosphorus.It is speculated that BrPHT1 and BrPHT46 may be negatively correlated with low phosphorus tolerance of Chinese cabbage.(3)With Arabidopsis thaliana SPX gene protein sequence as a reference,a total of 40 BrSPX gene family coding members were isolated from Chinese cabbage by Blast analysis.Using low phosphorus sensitive rubber vegetable Qiuwang(17)and low phosphorus tolerant space 6(12)as materials,semi-quantitative PCR and fluorescence quantitative PCR were used to analyze the expression pattern of BrSPX gene in root system of Chinese cabbage.Among the 40 genes,six genes,BrSPX2,BrSPX3,BrSPX7,BrSPX9,BrSPX10 and BrSPX12,were detected to be related to phosphorus absorption and transport.Among them,six genes of variety 17 were induced by low phosphorus,and five genes of variety 12 except BrSPX10 gene were also induced by low phosphorus.However,the histogram of BrSPX10 of variety 12 showed that its expression was inhibited by low phosphorus.