Studies On The Effect Of Selenium On Physiological Characteristics And Qualities Of Tomato And Its Molecular Regulation

Tomato (Solanum lycopersicum Mill.) is one of the solanaceae family vegetables and loved by people for its fruit nutritious and unique flavor. In our country,tomato has a larger acreage. Selenium (Se) is one of the essential trace elements and important to human health, and it is known as ’the protective agent of life’. In1988, Chinese Nutrition Society has been listed Se as one of15kinds of daily dietary nutrients and recommended its dose between50-250ug·d-1.. Deficiency of selenium could lead to cardiovascular disease, Keshan disease, Kashin-Beck disease and so on. Se also plays an important role in plant, and it is conducive to plants for the growth and development at suitable concentrations. For further understanding of effects of Se on the growth and quality of tomato, pot experiment were carried to study effects of different levels of Se on tomatoes’biomass, physiological and biochemical indexes, mineral nutrition element content, and Se content in different organs in tomato. Moreover, we have separated several genes related to Se accumulation in tomato with quantitative PCR technology, dected the expression levels of genes related to Se metabolism preliminary explored the molecular mechanism of Se regulation in tomato. We hope that these could provide a theoretical basis for the study of the effect of Se on tomato.The results are as follows:(1) Selenium can increase KT30and Defu mm-8’s yield(fruit dry weight), but reduce the yield of Luobeiqi when soil Se concentrations was5mg·kg-1, the yield of KT30and Defu mm-8increased by10.73%and2.61%than the control (CK), respectively. There was a significant difference between tomato yields under treatment of different levels of Se, the order was Defu mm-8>KT30> Luobeiqi.(2) Selenium significantly increased Se content in fruit, root, stem and leaf of tomato, the higher the soil Se concentrations, the higher Se content in different organs of tomato. When soil Se concentrations was10mg·kg-1, Se content in fruit of KT30, Defu mm-8and Luobeiqi were18.77,28.79and23.95times of the control, respectively, The order of Se content in fruit was Luobeiqi> KT30>Defu mm-8. Selenium content in different organs were significantly different, the order was root>leaf>stem(?)fruit. With the increase of soil Se concentrations, Se trended to be enriched in aboveground, such as stem, leaf and fruit. (3) Selenium improved the physiological characteristics of tomato, increased SOD and POD activity, reduced MDA content in leaf. When soil Se concentrations was5mg·kg-1, SOD and POD activity in leaf in KT30, Defu mm-8and Luobeiqi were the highest, increased by84.94%,56.65%and12.46%than CK, respectively, and MDA content reduced by16.97%,13.27%and16.95%than CK, respectively. With the increase of soil Se concentrations, SOD and POD activity decreased and MDA content increased in leaf. CAT activity changed irregularly. SOD and POD activity MDA content changes in root were similar with leaf.(4) Selenium improved the quality of tomatoes, increased content of Vc, free amino acid, reducing sugar and reduced the nitrate content in fruit. Selenium increased Vc content in fruit, the highest of Vc content in fruit of KT30and Luobeiqi were found at soil Se concentrations of5mg·kg-1, and Vc content in fruit of Defu mm-8increased by increasing with soil Se concentrations, the highest Vc content in fruit was observed at soil Se concentrations of10mg·kg-1. Selenium reduced the nitrate content in fruit, the highest nitrate content in fruit of Defu mm-8and Luobeiqi were found at soil Se concentrations of10mg·kg-1. Se increased free amino acid content in fruit, except for KT30and Luobeiqi reduced a little at soil Se concentrations as5mg·kg-1. Selenium also increased reducing sugar content in fruit, the highest reducing content of all of varieties of tomato’s were observed at soil Se concentrations of5mg·kg-1.(5) Selenium affected the absorption, accumulation and distribution of mineral nutrition elements in tomato. On the whole, Se improved the absorption of N, K, Ca and Mg element in tomatoes, increased their content in different organs, especially in fruit of tomato. However, Se reduced the content of Fe, Mn, Cu and Zn element. Selenium irregularly affected on P element, and difference of P content was found among varieties and organs of tomato.(6) The expression levels of APR and the other6genes varied both with tomato cultivars and Se levels. Soil Se application inhibited the expression levels of APR in KT30; while that of Defu mm-8was not significantly influenced by Se application. Selenium application facilitated the expression of APS in all tomato varieties. The expression quantities of CysD in KT30and Defu mm-8decreased at first, and then increased with increasing levels of soil Se applicatio,, and the expression level of CysD in all Se treatment reduced compared to the control; while that in leaves of Luobeiqi increased with increasing levels of Se. The expression levels of MMT in all tomato varieties decreased with soil Se application except for the5mg·kg-1Se treatment in Defu mm-8. Selenium inhibited the expression of SAT in KT30and Defu mm-8while enhanced the expression of SAT in leaves of Luobeiqi. In addition, the expression of SMT in leaves of KT30and Luobeiqi were obviously inhibited with soil application of Se, while that of Defu mm-8increased with Se treatment compared to the control.