The effects of gamma rays on morphology, biochemical, and genetic diversity of zingiber officinale roscoe / Nor Yusliza Kamaruddin

Ginger (Zingiber officinale Roscoe) is an important spice crop known for its medicinal properties. The lack of genetic variability among the genotypes is one of the bottlenecks in ginger genetic improvement. In this study, gamma radiation was applied to increase genetic variability in ginger. Two varieties of ginger; Bentong and Tanjung Sepat were exposed with different doses of gamma rays (5, 7, 9, 11, 13 and 15 Gy) at dose rate of 4.31 Gy per minutes using Caesium-137 source. The lethal dose (LD50) was obtained at 7.56 Gy for Bentong variety and 9.38 Gy for Tanjung Sepat variety. The parameters observed are plant survival, plant height, and number of leaves and shoots were significantly decreased with increased radiation doses. The stimulatory effect of gamma rays at low doses was also observed. The treatment at 5 Gy dose produced the highest ginger rhizome yield of 99.55g in Bentong variety and 187.0g in Tanjung Sepat variety after nine months cultivation. The crude fiber analysis was also varied in different doses of gamma rays and the effect was varietydependent. Bentong variety at 9 Gy recorded 8.53% while Tanjung Sepat variety at 5 Gy obtained 8.70% which gave the lowest crude fiber composition. Meanwhile, the highest moisture content in Bentong variety at 7 Gy (95.73%) compared with Tanjung Sepat variety at 9 Gy (94.74%). It was also noticed that high proportions of chromosomal aberrations have been attributed to clumping, laggards and stickiness of chromosomes. The PCR based RAPD analysis showed 97.62% of polymorphisms which indicated that there were high changes in genetic sequences in irradiated ginger genotypes. Therefore, the findings of this research provide guidance in mutation induction and selection of mutant in ginger.