Inducing the Variability of Embryogenic Callus of Mandarin Citrus cv. Garut to Obtained Putative Mutants through Gamma Rays Irradiation.

Abstract

Mandarin Citrus cv. Garut is one of local citrus which has some several superiority such as easy to peel, fresh and sweet flavour, yellowish green skin and containt 12-15 seeds per fruit, but can it not compete with citrus from other countries. Quality improvement have been the subject of citrus breeding programme. The objective of this research is to increase genetic variability of Mandarin Citrus cv. Garut through gamma rays irradiation on embryogenic callus. Callus was irradiated at doses of 0, 20, 30, 40, 50, 60, 70, 80, 90 and 100 Gy and regenerated through somatic embryogenesis. The result of radiosensitivity dose for Growth Reduction (GR50) analyzed by Curve Expert 1.4 software was 75.31 Gy. Observation on the growth of callus showed variation on morphology and weight of callus. At doses 0–50 Gy callus growth was not inhibited, but at doses 60–100 Gy callus growth was inhibited. Gamma irradiation also affected the formations of somatic embryos. After six weeks on maturation medium produced the highest of embryo somatic at dose of 20 and 100 Gy and on germination medium produced planlet highest at dose of 20 and 40 Gy. Based on morphological characters selected 10 regenerants with variability of 0–58% and genetic variability with ISSR markers by 0–26%. The number of mutan putative produced were M30/2, M50/1, M80/3 and M100/1 comformed by ISSR. After four week grafting between putative mutan shoots as scion and Japansche Citroen as rootstock it was obtainted the growth percentage 37.5-50% on Ex Vitro Grafting and 75% on In Vitro Grafting.