Proceedings Volume 2010 (format .pdf) - SimpBTH

IMPACT OF PHOTOPERIOD ON SPINACH REGENERATIONCAPACITYJELENA MILOJEVIĆ 1 , LJILJANA TUBIĆ, SNEŽANA ZDRAVKOVIĆ-KORAĆ,DUŠICA ĆALIĆ-DRAGOSAVAC, BRANKA VINTERHALTER1 University of Belgrade, Institute for Biological Research "Siniša Stanković", Despot Stefan Blvd. 142, 11 060Belgrade, Republic of Serbia. E-mail: jelenamilojevic@ibiss.bg.ac.rsABSTRACTHigh variation in regeneration capacity of spinach at individual level masked the differences betweenregeneration responses in long days (LD) and short days (SD) in previous studies. In this study, weexposed explants isolated from the same individuals to both SD (8/16h light/dark period) and LD(16/8h light/dark period). Apical sections (1 cm) of seedling's lateral roots were used for theexperiment. Root sections were placed on solid medium with Murashige and Skoog's mineralsolution, 20 µM α-naphthaleneacetic acid and 5 µM gibberellic acid. A half of root sections isolatedfrom a single seedling has been exposed to SD, and the other half of root sections has been exposedto LD. In all of thirty seedlings used for the experiment, somatic embryos were noted in LD a fewweeks earlier than in SD. Both the frequency of regeneration and the mean number of somaticembryos were significantly higher in LD than in SD. Some of genotypes regenerated in LD only. Weassume that the process of somatic embryogenesis in spinach is triggered and controlled byphotoperiod.Keywords: Chenopodiaceae, photoperiod, somatic embryogenesis, Spinacea oleracea, tissueculture1. INTRODUCTIONSpinach is a vegetable crop used for human consumption, grown for leaves,which are rich in vitamins and other essential nutrients. At short days (SD) spinachplants force growth of vegetative organs, forming rosette, while in long days (LD)spinach plants bolt and flower. Eight continuous cycles of at least 12h of light arerequired for the induction of flowering (Ćulafić 1973), but spinach plants could beinduce to flower in SD conditions in response to different environmental stimuli,such as high temperature and egzogenously supplied GA 3 (Ćulafić and Nešković1980).In spite of this, almost all researches dealing with spinach tissue culture choseLD photoperiod for culture growth. In a preliminary study, we intended to cultivatespinich in SD, to prevent precocious flowering, but the induction of regenerationwas lower in SD than in LD, although the differences seemed statisticallyinsignificant. However, variations in regeneration response were observed amongdifferent spinach cultivars (Al-Khayri et al. 1991a; Komai et al. 1996; Knoll et al.1997), and even within population variations were reported for cultivars Nippon(Ishizaki et al. 2001) and Matador (Milojević et al. 2009). So, we assumed thathigh individual variations in regeneration response masked the differences causedby photoperiod. In this study, we assesed regeneration response of root sections of55