Effect Of Exogenous Selenium On Leaf Physiological Characteristics And Fruit Quality Of Blueberry (Vaccinium Spp.)

Blueberry is known as one of the‘five healthy fruits’because of its rich anthocyanins,antioxidant and anti-aging properties.Selenium,as an essential trace element for human beings,plays an important role in human health.However,selenium deficiency is still widespread in China and even in the world.It is currently believed that eating selenium-rich fruits is conducive to improving the situation of insufficient selenium intake in the human body.Therefore,the research on plant selenium biofortification technology has important practical significance for the development of safe and effective selenium-enriched fruits.In this experiment,‘O’Neal’blueberry was used as the test material,using the randomized block test design,amino acid foliar fertilizer,selenium-enriched organic fertilizer,bamboo charcoal selenium fertilizer and sodium selenite were selected as selenium sources.Foliar spraying was carried out at the beginning of flowering and the end of flowering.The spraying concentration was set to four levels:50mg/L,100mg/L,150mg/L and 200mg/L.By measuring the physiological indexes of leaves,fruit quality indexes,selenium content and mineral element content under different types of selenium fertilizer treatments,the principal component analysis method was used for comprehensive evaluation to screen out the selenium source suitable for‘O’Neal’blueberry and the best spraying concentration.In order to provide technical reference and theoretical basis for high quality and efficient production of selenium-enriched blueberry.The main results are as follows:（1）After spraying different concentrations of amino acid foliar fertilizer,selenium-enriched organic fertilizer,bamboo charcoal selenium fertilizer and sodium selenite,the chlorophyll content,soluble protein content and antioxidant capacity of‘O’Neal’blueberry leaves increased significantly（P<0.05）.The chlorophyll content and soluble protein content of leaves reached the maximum under the treatment of 150mg/L bamboo charcoal selenium fertilizer,which were significantly increased by 27.6%and14.93%（P<0.05）,respectively,compared with control.The activity of superoxide dismutase（SOD）reached the maximum value of 292.67(U·g^-1·min^-1)in all treatments when the concentration of amino acid foliar fertilizer was 100mg/L,which was significantly increased by 13.38%（P<0.05）,compared with control.After treatment with150mg/L bamboo charcoal selenium fertilizer,the activity of peroxidase（POD）significantly increased by 20.25%（P<0.05）,compared with control.The activity of catalase（CAT）reached the maximum value of 32.37(U·g^-1·min^-1)when the concentration of bamboo charcoal selenium fertilizer was 100mg/L,which was significantly increased by2.93%（P<0.05）,compared with control.（2）Different types of selenium fertilizer and spraying concentration had a certain effect on the external quality of fruit.With the increase of spraying concentration,the growth of fruit longitudinal diameter,transverse diameter and single fruit weight of fruit increased to a certain extent,and the fruit hardness decreased with the increase of spraying concentration.When spraying 200mg/L bamboo charcoal selenium fertilizer,the longitudinal diameter and transverse diameter of the fruit reached the maximum,the longitudinal diameter increased by 1.22%compared with control,and the transverse diameter increased by 1.6%compared with control.When the concentration of amino acid foliar fertilizer was 50mg/L,the fruit hardness was 0.37%higher than that of control.When the concentration of bamboo charcoal selenium fertilizer was 200mg/L,fruit firmness was significantly decreased by 4.82%（P<0.05）,compared with control.（3）The internal quality of fruits was significantly improved under different types of selenium fertilizer treatments,and the content of mineral elements changed significantly.The contents of vitamin C,soluble protein,soluble solids,total soluble sugar,sugar-acid ratio,total anthocyanin,total flavonoids and total phenols in the fruit increased significantly,and the total acid content decreased to a certain extent.Spraying exogenous selenium promoted the absorption of potassium（K）,sodium（Na）,magnesium（Mg）,manganese（Mn）,calcium（Ca）and zinc（Zn）,and the content of iron（Fe）and cuprum（Cu）decreased.（4）Spraying different types of selenium fertilizer can increase the selenium content in the fruit.Under the treatment of 150mg/L amino acid foliar fertilizer,the total selenium content of fruit was 0.0124mg/kg;Under the treatment of 200mg/L selenium-enriched organic fertilizer,the total selenium content of fruit was 0.0123mg/kg;Under the treatment of 150mg/L bamboo charcoal selenium fertilizer,the total selenium content in the fruit reached 0.0213mg/kg;when spraying 200mg/L sodium selenite,the total selenium content was 0.0149mg/kg.（5）Based on the above results,spraying appropriate concentration of exogenous selenium is beneficial to increase the chlorophyll content of‘O’Neal’blueberry leaves,improve the ability of stress resistance,improve fruit quality,and increase fruit selenium content.The comprehensive evaluation of different treatments was carried out by principal component analysis.In this experimental study,‘O’Neal’blueberry had the best effect under 150 mg/L bamboo charcoal selenium fertilizer spraying treatment.