Determine the effect of gamma irradiation towards the growth of two local garlic genotypes

Garlic is a diploid plant that is propagated clonal or vegetatively so that the variability is low. Garlic breeding is limited to the selection of genetic varieties. Genetic diversity in garlic can be increased through mutation breeding. The study used Randomized Complete Block Design [RCBD] with the first factor being the two levels of genotypes [Tawangmangu Baru and Lumbu Kuning] and the second-factor is gamma-ray irradiation dose consisting of 7 level doses [0,1, 2, 3, 4, 6,8, and 10 Gy]. 14 treatments were groups 4 times and each experimental unit was planted 20 cloves. The cloves were irradiated according to the dosage of gamma rays in PAIR BATAN. The results showed there was a difference in the growth response of each genotype to gamma rays irradiation treatment. The greater the gamma rays irradiation applied the more it suppresses the growth of plant height, plant weight, bulb diameter, bulbil formation and decreases the living percentage of two local garlic genotypes. Gamma rays irradiation dose up to 2 Gy could increase bulb diameter in the 2 local garlic genotypes. Lumbu Kuning was significantly better growth response than Tawangmangu Baru at the same irradiation dose. The radiosensitivity of garlic genotype to gamma rays irradiation was different. Tawangmangu Baru was more sensitive than Lumbu Kuning. LD50 genotype Tawangmangu Baru was obtained at a dose of 7.5 Gy, LD50 Lumbu Kuning at a dose of 10 Gy.


Introduction
Garlic is the second most important spice in Indonesia after shallots. Garlic is recognized as a spice for food [1,7,13]. Garlic contains an amino acid commonly called "Allin" which is the main chemical element in garlic that is antiseptic [21,7]. Garlic is believed to be a cure for various diseases [16,7]. In addition to medicine and food seasonings, garlic extract can be used as an insecticide, fungicide, and bactericide [4,17,24,7].
Garlic is a diploid plant [2n = 2x = 16] which is cloned or vegetatively propagated so that the variability is low. Garlic breeding is limited to the selection of preexisting genetic variability [2,8,10]. Genetic diversity in garlic can be increased through mutation breeding [18,20]. The improvement of garlic varieties using artificial mutation techniques was suggested by [14,20].
The use of gamma rays is reported to have a positive effect on plants. As reported by [9]. Gamma rays are used to improve biotic stresses, abiotic stresses, and characters both in plants produced from seeds and those propagated vegetatively. Besides, gamma-ray mutations can also improve the character of plant growth and production [23,25,15]. The purpose of this study was to determine the effect of two local Indonesia garlic genotypes growth on gamma-rays in MV1 generation.

Results and Discussion
The irradiation treatment had influenced the growth of garlic. The greater the dose presented, the more pressed plant growth and reduced the percentage of life garlic plants. Exposure to plants with high doses of gamma-ray irradiation would kill mutated or sterilized material. Whereas the application of gamma-ray irradiation at low doses was able to maintain the viability of plants [5,3,19].

Plant Height
The genotype treatment and irradiation dose gave a very significant effect on plant height parameter. The highest average plant height was found in the control treatment [0 Gy] and the lowest average plant height was found at a dose of 10 Gy [ Figure 1]. The influence of genotypes showed that Lumbu Kuning had a higher plant height average than the Tawangmangu Baru genotype. These results indicated that the radiosensitivity of each genotype was different from gamma-ray irradiation. Tawangmangu Baru was more sensitive to exposure to gamma-ray irradiation so that plant height was more inhibited than Lumbu Kuning.
The highest plants were in control plants. This showed that the higher the irradiation dose, the plant height would decrease. This happened because the plant metabolism is disturbed. Irradiation could disrupt protein synthesis that played a role in plant growth [6].
The results section should highlight the crucial foundation of the research and its significance in the context of other previously published works. Results should be written in the past tense and directly. The discussion section should elaborate on the justification of the results by comparing the results obtained from the manuscript and results from previous works. The discussion should not repeat or reexpress the mentioned results in the form of sentences.

Bulb Diameter
The genotype and irradiation dose gave a very significant effect on the diameter of the garlic bulb diameter. The largest bulb diameter was at a dose of 2 Gy and the smallest tuber diameter was at a dose of 10 Gy. A decrease in the size of the garlic bulb diameter occurs at doses of 4-10 Gy [ Table 1]. The Lumbu Kuning genotype had a larger diameter than the Tawangmangu Baru genotype [ Table 2]. Gamma-ray irradiation treatment affected the size of the garlic bulb diameter, 2 Gy irradiation dose was a dose that was able to stimulate the diameter of the bulbs of garlic. The formation of bulb and cloves in garlic plants required low temperatures and significant temperature differences day and night [13]. Based on the experiments carried out it was suspected that higher irradiation for garlic would inhibit the process of division and elongation of clove cells so that the bulbs did not enlarge.

Plant Fresh Weight
Garlic plant fresh weight did not affect by genotypes and irradiation dose. The heaviest plant weights found at an irradiation dose of 1 Gy and the lightest fresh weight was at a dose of 10 Gy [ Figure 2]. Plants with radiation treatment of 1 Gy had more bulbil [ Figure 3], so they could increase the fresh weight of the garlic plant.

Percentage Of Bulbil Formation
The highest percentage of bulbil formation in Tawangmangu Baru genotype was at 4 Gy and in Lumbu Kuning genotype there was at 1 Gy. Bulbil is a rounded organ that is part of the vegetative reproduction of plants. Bulbil contained food reserves resulted from plant photosynthesis translocation. Bulbil garlic would then turn into a segment commonly called cloves [21]. Bulbil or often referred to as air tubers was a failure of flower formation caused by temperature factors [11].
Bulbil in garlic cultivation was an unexpected organ. The formation and development of bulbil on the pseudostem of garlic would divert the assimilate that should be transported to the cloves so that it could result in a smaller bulb during harvest. Based on these results gamma rays irradiation provides an opportunity to suppress the formation of bulb whose dosage varies depending on the genotype of garlic.

Radiosensitivity and Lethal Dose
Based on observations on plant height parameters, fresh weight, bulb diameter, percentage of bulbil formation, it showed that the Tawangmangu Baru genotype was more sensitive than the Lumbu Kuning to exposure to gamma-ray irradiation. This showed that radiosensitivity also depends on the genotype used. It suggested with high radiosensitivity would increase the percentage of mutants formed, because with a low dose of irradiation has been able to reach more than 50% mortality. Based on the calculation of the live percentage of Tawangmangu Baru and Lumbu Kuning in the gamma-ray irradiation dose tested with, LD50 values were obtained for Tawangmnagu Baru at a dose of 7.5 Gy  Figure 5].
Different LD 50 values also indicated that the radiosensitivity of the Lumbu Kuning genotype was lower or less sensitive than Tawangmnagu Baru for exposure to gamma-ray irradiation. It was suggested that the Tawangmangu Baru genotype is a newly released garlic genotype that was not yet stable, had more water content in the cloves so that more sources of H + ions were irradiated, skin thickness of the clove was thinner, and the Lumbu Kuning could adapt to lower land heights so that it was more resistant to high-temperature stress [900 meters above sea level ].

Conclusion
Genotype and doses of gamma rays irradiation gave a significantly different response to bulb diameter, and plant height, but did not give significant effect to the number of leaves and plant fresh weight. Irradiation dose at 2 Gy could increase vegetative growth on the Lumbu Kuning garlic genotype and gave high bulb diameter and plant fresh weight. Lumbu Kuning genotype gave 100 percent normal bulb with cloves compared to Tawangmangu Baru 97 percent. Highest Bulbil formation in Lumbu Kuning obtained on dose 1 Gy while Tawangmangu Baru at dose 4 Gy. Tawangmangu Baru more sensitive to gamma rays irradiation compares to Lumbu Kuning. LD50 value Tawangmangu Baru genotype obtained at dose 7.5 Gy, and LD50 Lumbu Kuning at dose 10 Gy.