Regeneration ability of embryogenic callus derived nucellus of siam tangerine and phenotipic variation of its regenerants

Abstract

Wulansari A, Purwito A, Husni A, Sudarmonowati E. 2015. Regeneration ability of embryogenic callus derived from nucellus of siam tangerine and phenotypic variation of its regenerants. Pros Sem Nas Masy Biodiv Indon 1 (1): 97-104. Tangerine cv. siam is one favorite type of citrus fruit in Indonesia. Tangerine cv. siam dominates 80 % of the total citrus plantations in Indonesia. The fruit has a sweet flavor, easily peeled skin, soft, and juicy flesh. However, it has relatively many seeds (15-20 seeds per fruit) and dull-colored skin, making it less competitive in the market. Fruit quality improvement has been the subject of the citrus breeding program. The first step of the program is to increase variability for the efficient selection process. The improvement of genetic variability in tangerine was constrained by a long period of juvenile stage. One of strategy to accelerate genetic improvement is by in vitro culture techniques or somaclonal variation. The aim of this study was to determine the phenotypic variation of regenerant shoots from embryogenic callus. Callus was derived from nucellus of immature seeds 30-90 days after anthesis. Observation on the ability of callus proliferation in MW medium (Murashige & Wetmore) indicated that long period of callus and repeated subculture did not reduce the proliferation ability. A 4-week callus could grow almost twice bigger than its initial size. Callus weight increased 1.78 g. The color and structure of callus did not change. It was yellowish white and the structure was friable. Each callus (+ 0.5 g) has 8-12 proembryos. The percentage of somatic embryo formation in MW medium containing 0.5 mgL-1 ABA was 55.2%. At embryonic maturation stage, 100% somatic embryos could germinate in MW medium containing 0.5 mgL-1 GA3. There were 10 phenotypic variants of regenerant shoots. After grafting with JC as rootstocks, 100% regenerant shoots grew. Extended period of callus of Tangerine cv. siam did not reduce its regeneration ability and 10 phenotypic variations can be obtained for further molecular and agronomics analysis.