The investigated effect selenium selenite on some quantitative and qualitative characteristics and accumulation of selenium and reduction nitrate accumulation in potato tubers (Solanum tuberosum L.).

The potato (Solanum tuberosum L.) tuber is the third most important food crop in the world after rice and wheat for human consumption and makes an important contribution to the diet of people worldwide (Haverkort et al. 2009). Global cultivation area of about 19.35 million hectares in 2014 and annual production of nearly 382 million tons and nearly 5 million tons has been reported in Iran (FAO, 2016). Selenium (Se), as an essential part of human nutrition, plays a significant role in a number of metabolic functions and also shelters plants from several abiotic and biotic stresses (Schiavon et al. 2017). Se can affect the quality of vegetables and fruit. Increased cellular content of linoleic acid and sterols and a decreased oleic acid content have been observed in Camelia oleifera plants treated with Se (Song et al. 2015). Se spraying has been used to enhance the selenium content in broccoli (Sindelarova et al. 2015), radishes (Schiavon et al. 2016), basil (Mezeyova et al. 2016), tomatoes (Zhu et al. 2016), grapes (Zhu et al. 2017) and other crops (Puccinelli et al. 2017).

Two field experiments were carried out in Jiroft (57 90 E L. 28 13 N Lat., 625 m above sea level), Kerman, Iran, during 2016-17 (October to Jan) and 2017 (Jan to Apr) with Sante cultivar. In Jiroft minimum and maximum temperatures over growing season were 8 and 40 °C, respectively in first season and 8 and 43 ºC, respectively in the second. Relative humidity was 55-60% in every two years. The soil had a sandy-loam texture, and the acidity (pH), electrical conductivity (EC), absorbable potassium, absorbable phosphorus, total nitrogen and selenium content of the soil extract were 7.50, 2.41 ds m-1, 159 mg/l, 8.80 mg/l, 0.03 % and 0.17, respectively (table 1). This study was carried out as a split plot with three replicates. Experimental treatments included foliar application of nitrogen fertilization on 2 level normal (150kg/h) and high nitrogen (300kg/h) and selenium (Se) (0, 15, 30 and 60 mg/l) as sodium selenate (Na2SeO4) 35 days after plant emergence. During the experiment, morphological traits including plant height, plant fresh weight, tuber weight and tuber yield and chemical and biochemical traits including selenium and nitrogen levels, starch, ion leakage and malondialdehyde, chlorophyll content, Catalase enzymes, nitrate reductase and superoxide dismutase, and some amino acids were evaluated.

Result and disscution:

Overall, it has been shown that nitrogen uptake increases the quantitative traits and decreases the quality of potato tuber cultivars. Selenium application, improving yield, qualitative and quantitative traits, increased selenium accumulation and reduced nitrate accumulation in potato tubers. The lowest amount of nitrate accumulation and the highest selenium accumulation were obtained from 150 mg/l selenium treatment. The highest yield of the tuber was obtained from 150 mg/l Selenium treatment. Although Se is not yet confirmed as an essential micronutrient in higher plants (Turakainen et al. 2004; Rani et al. 2005), many researchers have already shown that selenium (Se) could increase the tolerance of plants exposed to stressful environments (Djanaguiraman et al. 2005; Djanaguiraman et al. 2010). In the present study, potato plants treated with Se resulted in an increase in shoot fresh weight and tuber yield. Se increases the allocation of phytosimulates to grow tubers, so tubers act as a rich source for carbohydrates and selenium accumulation. They also attributed the positive effect of selenium on potatoes to the antioxidant effects of selenium on the plant's aging delay. They reported that selenium fertilization could improve the nutritional value of potato by increasing the level of organic compounds containing selenium in the tubers.