New Researches in Biotechnology - Facultatea de Biotehnologii ...

Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011EFFECT OF INORGANIC NITROGEN NUTRITION ON “IN VITRO”PRODUCTION OF POTATO MICROTUBERS*INCDCSZ Braşov, e-mail: nistorandreea06@gmail.comANDREEA NISTOR, NICOLETA CHIRU, CARMEN BĂDĂRĂUAbstract: The effect of inorganic nitrogen nutrition on production of microtubers was studied in twopotato genotypes Nicoleta and Christian. The objective of this study was to investigate whether areduction in total nitrogen level in the Murashige & Skoog medium would improve microtuberization.The effect of three levels of total nitrogen (30, 45 and 60 meq) on tuberization was studied at constant(20 meq K). Reducing the total nitrogen supply increased the number but decreased the size ofmicrotubers. The weight of microtubers per vessel was the highest at the highest nitrogenconcentration (60 meq): 1.91 g for Christian variety. A reduction in total nitrogen supply reduced thesize of microtubers, the lowest weight being at the lowest nitrogen level – 30 meq: 1.01 g for Nicoletavariety, with a difference of -0.66 g, significant in a negative way. Decreasing the total nitrogensupply caused increasing the number of microtubers/ vessel which was the highest at the lowestnitrogen concentration (30 meq): 19.67 microtubers, with a difference of 4.34 microtubers,significant in a positive way, for Christian variety. The number of microtubers per vessel was thelowest at the highest nitrogen concentration (60 meq): 15.33 microtubers, for both varieties.Keywords: microplants, mineral nutrition, microtubers, Solarium tuberosum L., tissue culture1. INTRODUCTIONSome cultivars are more sensitive than others to total nitrogen levels or relativeconcentration of nitrate: ammonium in the medium during micropropagation (Avila et al.1998) or microtuberization (Garner and Blake 1989; Sarkar and Naik 1998). Low nitrogenin the micropropagation and microtuberization media was best for microtuberization(Stallknecht and Farnsworth 1979; Wattimena 1983). Total nitrogen and nitrate:ammonium levels were used effectively to improve preconditioning, induction (Charles etal. 1995; Zarrabeitia et al. 1997; Sarkar and Naik 1998), and microtuber growth (Chen andLiao 1993; Sarkar and Naik 1998). Reduced ammonium levels during source plantpreconditioning resulted in increased numbers and better synchronization of subsequentmicrotuber induction (Charles et al. 1995; Zarrabeitia et al. 1997; Vreugdenhil et al. 1998).The amount of nitrogen had an effect on microtuberization (Cutter, 1978; Moorby,1978).Stallknecht and Farnsworth (1979) and Wattimena (1983) found that low nitrogenin both the explants and the tuberization media was best for induced tuberization in potato.In the absence of growth regulating substances in the medium, a reduction in total nitrogensupply or an increase in the ratio of ammonium to nitrate reduced the size and number ofmicrotubers (Garner & Blake, 1989).Hoque et al., (1996) reported that higher number of microtubers can be producedin MS medium by reducing KN0 3 by half of the total amount. Reduction in the amount ofNH 4 N0 3 to 1/8th of its amount present in MS medium, initiated early and highermicrotuberization after 4 wk (Zarrabeitia et ai., 1997). Nitrogen is one of the major nutrient51