Effects of Calcium Concentrations in Medium on Microtuberization of Potato (Solanum tuberosumL.)

It is now widely accepted that calcium (Ca) deficiency is linked to potato (Solanum tuberosum L.) tuber disorders and improved tuber health is expected through increased Ca availability. The purpose of this study was to optimize the Ca concentration in Murashige-Skoog (MS) basal medium for microtuber production and determine microtuber mineral composition, especially Ca content. The response of cultivars ‘Bintje’ and ‘Russet Burbank’ to the Ca concentration in the media including 3 (control), 10, 15, 20, or 25 mM was differentfor most parameters measured. Ca at 10 mM concentration improved overall performance of ‘Bintje’ but not‘Russet Burbank’, compared to controls (3 mM Ca). Higher levels of Ca in the medium were somewhat toxic to both cultivars. Increased Ca concentration in the medium did not affect final shoot fresh weight (SFW) in ‘Bintje’ but reduced it in ‘Russet Burbank’ compared with control medium. Ten mM Ca increased microtuber number by 19% in both cultivars. It also increased microtuber fresh weight by 19.5% in ‘Bintje’ with no effect on ‘Russet Burbank’. Mean tuber weight was not affected in ‘Bintje’ but was decreased by 17% in ‘RussetBurbank’. Harvest index in both cultivars was slightly improved at 10 mM Ca but higher levels reduced this index significantly. Microtuber tissue Ca content was greatly increased by Ca treatment in both cultivars. Maximum increase was observed at 15 mM Ca (70%) and 10 mM Ca (61%) in ‘Bintje’ and ‘Russet Burbank’, respectively. Ten mM Ca also increased P (25%) and K (19%), in ‘Bintje’ whereas in ‘Russet Burbank’ only P was increased up to 20% at this level of Ca. Unlike Zn, accumulation of other microelements were affected rather differently in two cultivars. Ten mM Ca had no reducing effects on Fe, Mn and Cu accumulation in‘Bintje’ whereas it had significant reducing effects in ‘Russet Burbank’. It is concluded that the conventional concentration of Ca in MS medium (3 mM) is not high enough for optimum microtuberization. Hence, it appears that optimization of the Ca concentration is necessary for each cultivar.