| As garlic is an asexual crop with a low propagation coefficient, it is difficult to breed new varieties by g conventional method. As one of the most important methods for elite germplasm creation, chemical mutagenesis breeding is commonly used to produce traits in crops. In this study, garlic cultivars Zheng Yue Zao from Sichuan, Xin Jiang Zi Pi from Xinjiang, Cang Shan Pu Ke and Jin Xiang Zi Pi from Shandong were used as materials for chemical mutagenesis experiments, and in vitro plantlet regeneration system of garlic was established. Mutagenic effects of chemical mutagens such as colchicine to shoot tip plantlets in garlic were investigated. Several strains of tetraploid garlic were obtained successfully. The traits related to plant growth and development were analyzed and comparative study were performed between tetraploid and diploid garlic.The results are listed as follows:1. Technical systems of in vitro garlic regeneration from shoot tips and bulblets induction in garlic were established. The differences in plantlet regeneration rate, plant height and proliferation rate among four garlic varieties were significant. In detail, the variety such as ?Cang Shan Pu Ke‘ was relatively higher, while ?Xin Jiang Zi Pi‘ was lower than the others. The optimal schemes of hormone formula in the garlic shoot-tips initial culture and subculture medium(B5) were( 6-BA 0.328~0.494 mg/L+ NAA 0.105~0.162 mg/L) and(6-BA 2.088~3.596 mg/L+NAA0.104~0.179 mg/L) respectively. In the stage of rooting and bulblets induction, 6-BA was the main factor influencing the root numbers of ?Cang Shan Pu Ke‘, ?Jin Xiang Zi Pi ‘and ?Xin Jiang Zi Pi‘,while sucrose was the main factor influencing the root numers of ?Zheng Yue Zao ?and the bulblets formation rate of ?Cang Shan Pu Ke‘ and ?Jin Xiang Zi Pi‘.2. Systems of callus induction and plant regeneration in garlic were well established. The differences in callus induction rate among four varieties were significant. The callus induction rate of ?Cang Shan Pu Ke‘ ranks the highest, then ?Jin Xiang Zi Pi‘ and ?Xin Jiang Zi Pi‘ earned second place,the lowest was ?Zheng Yue Zao‘. The optimal formula of regulator which has more than 90% callus induction rate in the culture medium(B5) was(6-BA0.46~0.694 mg/L+2,4-D1.544~1.842 mg/). There is significant distinction in callus differentiation rate among different varieties. Distinguished from other varieties, ?Jin Xiang Zi Pi‘ had the highest adventitious bud rate therefor produced the most bud in quantity, while having the lowest differentiation rate of adventitious root. As for ?Xin Jiang Zi Pi‘ and ?Zheng Yue Zao‘, they had lower adventitious bud rate and produce less bud. The culture medium containing 6-BA1.5 mg/L+ZT0.75 mg/L induced the most bud from callus, having the highest induction rate at the same time.3. The mutagenic effects were clearly determined regarding the colchicine concentration and treatment duration on garlic. After treated with colchicine, the rate of garlic plantlet regeneration from shoot tips was decreased gradually along with the colchicine concentration get higher and the treatment duration get longer, among all the varieties, the differences were significant. After analyzed by software, The optimal scheme for concentration and treatment time of colchicine were 0.531%-0.580% and 79.8 h-112.2 h respectively, under the conditions of which the rate of plantlets regenerated and survived was more than 50% and the rate for tetraploid was more than 5%.4. The effects of different treatment with colchicine on the rate of plantlets and tetraploid for garlic shoot tips were found out. Significant differences were found between different colchicine treatments. The plantlet regeneration rate of shoot tips was the highest treated with solid culture, and then drip treatment, the plantlet regeneration rate with liquid culture was the lowest. The tetraploid rate with liquid culture was the highest, with solid culture was the lowest. The optimal schemes for concentration and treatment time of colchicine by liquid culture, drip treatment and solid culture were 0.387~0.694% + 67.92 ~ 114.432 h, 0.417 ~ 0.852% + 71.136 ~ 118.032 h, 0.387 ~ 0.819% + 69.72 ~ 114.432 h respectively.5. The mutagenic effects of oryzalin, pendimethalin and colchicine on garlic were definited. The optimal schemes for their concentration and treatment time were 4.170~8.52 mg/L + 71.136 ~ 118.032 h, 4.68~8.9 mg/L + 72.96 ~ 106.176 h and 3865 ~ 6940 mg/L + 67.92~114.432 h, respectively. The plantlet regeneration and tetraploid rates were higher treated with oryzalin and pendimethalin than with colchicine. So oryzalin and pendimethalin could be used as an effective mutagen for the getting of tetraploid garlic.6. The plant traits(plant height, width of pseudostem, leaf length, leaf width), garlic bolts traits(length, diameter, single weight) and bulb traits(transverse diameter, vertical diameter, single bulb weight) of tetraploids garlic in the four cultivars was significantly better than that of the control diploids. The plant height of the tetraploids ?Cang Shan Pu Ke‘, ?Jin Xiang Zi Pi‘, ?Xin Jiang Zi Pi‘ and ?’Zheng Yue Zao‘ were 34 cm, 26 cm, 16.4 cm and 16.4 cm higher than that of control diploids about,respectively. The single garlic bolt weight of the above four tetraploids were 9.9 g, 11.1 g and 11.1 g and 12.7 g higher than that of the control diploids,, respectively. The single bulb weight of the above four tetraploids were 46.1 g, 47.4 g and 44.5 g and 26.1 g higher than that of the control diploids, respectively.7. In the four garlic varieties, nutrient contents in garlic bolt and bulb of tetraploids were significantly higher than that of diploids. The soluble protein content in garlic bolt and bulb of tetraploid ?Xin Jiang Zi Pi‘ was higher than that of the control diploid, increased by 36.2% and 35% respectively. For ?Cang Shan Pu Ke‘, ?Jin Xiang Zi Pi‘, ?Xin Jiang Zi Pi‘ and ?Zheng Yue Zao‘, the alliin contents of tetraploids garlic bolt were 2.06 mg/g, 2.33 mg/g, 1.16 mg/g and 1.99 mg/g more than that of diploids, respectively. And the alliin contents of tetraploids bulb were 90.1 mg/g, 62.86 mg/g, 125.0 mg/g and 85 mg/g more than that of diploids, respectively. |
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