论文部分内容阅读
Abstract ［Objectives］ This study was conducted to investigate the mutagenic effects of space radiation mutagenesis on sugarcane hybrid seeds.
［Methods］ Sugarcane hybrid spikes were subjected to space radiation mutagenesis treatment to identify the effects on the germination, seedling growth and plant growth and development of sugarcane hybrid seeds.
［Results］ The space radiation treatment had a great impact on the germination and growth of sugarcane hybrid seeds, especially on the germination of sugarcane seeds. The germination number per gram of seeds increased significantly, and the survival rate of seedlings increased significantly. The effect on the growth status was relatively small. The average number of tillers decreased slightly, the percentage of available stems increased, and the plants became higher, which resulted in a greater effect on sugarcane yield. Sugarcane sucrose was increased. The seed germination and late growth status indicated that space radiation promoted the germination and growth of sugarcane hybrid seeds.
［Conclusions］ This study provides a basis for the space radiation mutagenesis breeding of sugarcane hybrid seeds and the promotion of sugarcane breeding process.
Key words Space radiation; Sugarcane; Mutation breeding; Seed germination
Received: May 27, 2019Accepted: September 18, 2019
Supported by General Project of Hainan Provincial Natural Science Foundation (No. 317257); The Fundamental Research Funds for Central Public Welfare Research Institutes (1630052019005); China Agricultural Research SystemSugar crop (CARS170716).
Yimei GAN (1982-), female, associate researcher, PhD, devoted to research about Crop genetic breeding.
*Corresponding author. Email: yangbenpeng@itbb.org.cn.
Sugarcane (Saccharum officinarum) is Chinas main sugar crop. More than 90% of Chinas sugar comes from sugarcane. In addition to being used mainly for sugar extraction, sugarcane can also be used to produce bioenergy such as ethanol. In addition, sugarcane processing byproduct bagasse can also be used as an edible fungi raw material［1］ and an improved soil［2］, or for improving environment［3］. Sexual hybridization is the most commonly used method for the selection of new sugarcane varieties. However, due to the lack of germplasm resources, the blood is monotonously poor, and it is difficult to obtain superior mutant materials for hybridization to obtain groundbreaking new varieties. Studies have shown that hybrid progeny seeds obtained through radiation mutagenesis can increase mutations by enhancing the accumulation of gene segregation and by inducing mutations, thereby increasing the mutation rate and thus effectively increasing the mutagenic effect［4］. Space radiation mutagenesis breeding refers to the new breeding technology for new varieties in which science researchers induce crop propagating materials by special radiation in outer space to produce mutations. The main advantages of spaceflight mutagenesis breeding are high mutation frequency, large mutation amplitude, rich type and easy stabilization of mutated materials, so it thus shortens the breeding cycle when causing light damage to plants and is easy to obtain mutations. Under natural conditions, the variation rate of rice is one in 200 000, and the mutagenic rate of ground radiation treatment is 0.12%, while the variation rate of space radiation mutagenesis is 12.5%, which is 100 times higher than the ground radiation mutagenesis. For example, the Brassica napus obtained some strong mutations such as dwarf and large grains after space radiation mutagenesis［5］, and mung beans after space radiation mutagenesis grew a single plant with a pod length of about 16 cm and a seed number of 15-19 per pod［6］. It indicates that space radiation is easier to obtain favorable materials for breeding of new varieties than other physical and chemical mutagenesis.
The mechanism of space radiation mutagenesis is complex, and the causes of genetic variation of plant traits caused by space environment such as high vacuum, microgravity, highenergy particle radiation, space radiation, intense ultraviolet radiation and alternating magnetic fields are not fully understood. Variations from space radiation mutagenesis mainly include plant height variation, leaf variation, yield variation, quality variation and resistance variation［7-8］. After space mutagenesis, most plants are more likely to become taller or shorter. For example, rice, corn, tomato, wheat, pepper and sorghum all showed plant height variation. The leaf variation mainly revolves around shape, color, size and quantity［9-10］. The variation in yield mainly lies in the variation of various factors affecting yield［11-12］. The quality variation mainly manifests in the variation of amino acid content, soluble sugar content and tannin content. The resistance variation is mainly in disease resistance, such as wheat stripe rust, cauliflower black rot and rice blast［13-15］.
Because sugarcane is heavier in stems and lighter in spikes, the cost for space mutagenesis using spikes is lower. Therefore, in this study, sugarcane parents were selected and combined to obtain hybrid spike seeds, which were used as a material for space radiation mutagenesis, and then, the effects of space radiation on the germination and growth of sugarcane hybrid seeds were investigated. This study will provide a basis for early selection in space radiation mutagenesis breeding of sugarcane seeds. Materials and Methods
Materials
The sugarcane variety Guitang 02901, which is matured especially early with high sugar and high yield, was the female parent, and the foreign resistant variety Ke 5 was the male parent. The sugarcane spike seeds were obtained after sexual hybridization of the two parents in Hainan sugarcane breeding farm. The hybrid spike seeds of sugarcane were weighed and packed in kraft paper bags, and divided into two parts, one for control (CK) and the other for space radiation mutagenesis (SP). After the irradiation, the seeds were divided into three parts according to the weight, which were then sown according to the method of Gan et al.［16］, while the unirradiated seeds were seeded as the CK (also divided into three parts).
Seed germination and statistics before transplanting
The germination number per gram of seeds and seedling survival rate during seed germination were investigated according to the method of Gan et al.［16］. After one and a half months, the seedlings were planted to pots, grown in the pots for 1 month and then transplanted to the field.
Field investigation
The average number of tillers was investigated in SP and CK treatments after tillering of the seedlings. After jointing, the initial plant height of sugarcane was measured, and the plant height and sugar content of sugarcane were measured in the mature period.
Data processing
Test data were processed using EXCEL and SPSS.
Results and Analysis
Effects of space radiation treatment on germination and survival of sugarcane hybrid seeds
Sugarcane hybrid seeds have a large number and a low germination rate, and is generally quantified using the germination number per gram of seeds. The average germination number per gram was 167 and 100 in the space radiation treatment (SP, Sugarcane space radiation) and the unirradiated control treatment (CK, control), respectively, that is, after the space radiation treatment, the germination number per gram of sugarcane hybrid seeds was larger than that of the CK. The value of the SP treatment increased significantly, by 67%, compared with the CK, and there was a significant difference between SP and CK (Table 1). It showed that the space radiation treatment had a great influence on the germination of these sugarcane hybrid seeds and promoted seed germination.
The seedling survival rates of SP and CK were 54.78% and 20.26%, respectively. There was a significant difference between the space radiation treatment and the CK. After space radiation, the survival rate of seedlings from sugarcane hybrid seeds was higher than that of the unirradiated control seeds. There was a very significant difference between the treatment and the CK (Table 2). It indicated that the space radiation treatment had a great influence on the growth of these sugarcane hybrid seedlings and improved the survival rate of seedlings. Effect of space radiation on the tiller number and percentage of available tillers of sugarcane seedlings
The living sugarcane seedlings were transplanted to the field after temporary planting. After tillering, the tiller number and percentage of available tillers was investigated in the SP treatment and the CK, respectively. The average tillers of SP and CK were 7.06 and 8.77, respectively. The average tillers of sugarcane seedlings after the space radiation treatment were reduced compared with the unirradiated control seedlings, and the difference reached a very significant level (Table 3). It showed that the space radiation treatment had a strong influence on the tillering of these sugarcane hybrid seedlings, and significantly reduced tillers. The percentage of available tillers was 60.47% and 55.81% in SP and CK, respectively, that is, the percentage of available tillers of sugarcane seedlings subjected to space radiation treatment was higher than that of unirradiated control seedlings, and the difference reached a significant level (Table 4). It indicated that the space radiation treatment had a significant effect on the tillering of these sugarcane hybrid seedlings.
Effect of space radiation on plant height of sugarcane
After the sugarcane entered the jointing stage, the initial plant heights of the plants in SP and CK were measured. The initial plant heights of SP and CK were all around 150 cm, but the difference was extremely significant (Table 5), indicating that the radiation treatment had a greater impact on sugarcane plant height. At the maturity stage, the plant height of SP was higher than that of the CK, and the difference was extremely significant (Table 6), indicating that the plant height of the sugarcane hybrid progeny increased significantly after the space radiation mutagenesis treatment.
Yimei GAN et al. Effects of Space Radiation Mutation on Germination and Growth of Sugarcane Hybrid Seeds
Effect of space radiation on sugarcane sucrose
Sucrose is the main factor affecting the quality of sugarcane. It can be expressed by measuring the Brix, which is positively proportional to sucrose content. The average Brix of the sugarcane material after space radiation mutagenesis was higher than that of the CK. The average Brix reached its highest level in December and then decreased (Table 6). Both the induced material and the control material showed midearly maturity characteristic, and no changes in maturity were observed after mutagenesis. Conclusions and Discussion
The introduction of new variants by irradiation has become an important means of modern plant improvement and an access to new germplasms. Through the induction by space radiation, the mutation spectrum is easily broadened and the mutation rate is also increased, which makes the selection of favorable mutants easier, and therefore, space radiation becomes a means of obtaining new germplasms［17］. In space radiation breeding, it is necessary to supply enough amount of radiation to obtain the variation. In production, sugarcane is vegetatively propagated by the buds of the stem segments. If the buds of the stem segments are used as space radiation materials, they will produce a particularly heavy weight and volume, resulting in expensive costs.However, the seeds of sugarcane are small, and only a part of the seeds is required to obtain a large number of mutated sugarcane seedlings. Moreover, and it is easier to carry out the sugarcane space radiation mutagenesis test using sugarcane seeds without much cost.
The strength of seed vigor can directly affect the seed germination and emergence rate, affect the growth potential of seedlings, and affect the plants resistance to pests and diseases, and seed germination requires appropriate water, temperature and air to activate the original genes in the genome or the initiation and expression of new genes, to thereby restore metabolism and growth［18］. The seeds of sugarcane are small and light, and also have fluff, and the germination rate is extremely low. The hybrid spikes obtained after hybridization of some parents cannot be used due to the low germination rate, which greatly affects the innovation of sugarcane germplasms and the breeding of varieties. Studies have shown that 0.7 mmol/L salicylic acid treatment of corn seeds can improve its germination rate, germination potential, etc., but the treatment with higher concentrations of salicylic acid on corn seeds had a role in inhibiting its germination rate［19］, indicating that different treatments can increase or inhibit seed germination. Previous studies have shown that nuclear genetic variation in plant cells under irradiation conditions［20］ indicates that radiation affects the nuclear genes of seeds and thus affects seed germination and even seedling growth. In this study, the germination ability of sugarcane seeds after the space radiation treatment was enhanced, and the viability of seedlings was also enhanced, indicating that the material subjected to space radiation mutagenesis treatment obtained positive mutagenesis. Most of the literatures report that plants will become shorter after space mutagenesis. In fact, the variation of height is generally bidirectional. In this study, the height of sugarcane plants subjected to space radiation was positive in sugarcane production, which will significantly increase sugarcane yield. After sorghum seeds were loaded into spaceships for space mutagenesis treatment, and the heights of their multigeneration plants were analyzed. It was concluded that mutations will occur in the very generation undergone mutagenesis, will be inherited to the next generation, and then will segregate in the third generation, and the mutations inherited by the third generation will be stable［21］. Later, in the second generation of the space radiationinduced sugarcane in this study, the average plant height was still higher than that of the CK, indicating that the variation of the plant height of the mutagenized sugarcane was very promising.
This study shows that the space radiation mutagenesis of sugarcane seeds has obtained more positive mutations, such as seed activity, seedling survival rate, plant height, etc., which provide good materials for space radiation mutagenesis breeding of sugarcane.
References
［1］ MA HX, MA ZL, MA GY, et al. Optimizing culture formula for cultivating Auricularia cornea by using bagasse［J］. Edible fungi of China, 2018, 37(3): 25-29. (in Chinese)
［2］ NIU G, LIAO L, SHI JF. Adsorption characteristics of modified bagasse ash to sulfate in the wastewater［ J］. Industrial Safety and Environmental Protection, 2018, 44(9): 20-24. (in Chinese)
［3］ LIU XM, MA C, WU F, et al. Adsorption of Cr (Ⅵ) in waste water by bagasse carbon［J］. Applied Chemical Industry, 2019, 48(1): 72-76. (in Chinese)
［4］ ZHANG ZQ. Notable problems in the sexualhybridization radiation mutagenesis breeding of sugarcane［J］. Sugarcane and Canesugar, 1995(5): 7-8. (in Chinese)
［5］ WANG WR, SUN CC, JIANG MY, et al. Analysis of progeny characteristics of Brassica napus L. subjected to space mutagenesis［J］. Journal of Nuclear Agricultural Sciences, 2015, 29(2): 215-220. (in Chinese)
［6］ QIU F, LI JG, WEN ML, et al. Molecular biological analysis of mung bean longpod mutants from spatial mutagenesis［J］. Scientia Agricultura Sinica, 1998, 31(6): 1-5. (in Chinese)
［7］ LI XF, ZHU HF, ZHU YY, et al. Development of a new latebolting germplasm and breeding a new cultivar Yanchun of pakchoi by using space mutation［J］. Journal of Nuclear Agricultural Sciences, 2018, 32(7): 1249-1255. (in Chinese) ［8］ FU XJ, YANG QH, YUAN FJ, et al. Breeding of Zhexian No.9 by space mutation and variation analysis of its characters［J］. Journal of Nuclear Agricultural Sciences, 2019, 33(5): 0841-0847. (in Chinese)
［9］ TRIPATHY BC, BROWN CS, LEVINE HG, et al. Growth and photosynthetic responses of wheat plants crown in space［J］. Plant Physiol, 1996, 110(3): 801-806
［10］ YANG HS. Breeding of Spaceinduced New multifoliaolate alfafa Varieties［D］. Lanzhou: Lanzhou University, 2018. (in Chinese)
［11］ PEI XB, GU XJ, CHEN CH, et al. Characters of tomato and pepper bred by space mutation in glasshouse［J］. Journal of Nuclear Agricultural Sciences, 2004, 18(4): 321-322. (in Chinese)
［12］ PENG L, RU M, WANG KR, et al. Spaceflight environmentinduced variation in root yield and active constituents of salvia miltiorrhiza, Planta Med., 2014(80): 1029-1035
［13］ CHENG ZL, LIU M, ZHANG M, et al. Transcriptomic analyses of spaceinduced rice mutants with enhanced susceptibility to rice blast, Advances in Space Research, 2007, 40(4): 540-549
［14］ DU JY, BAI B, JIN MA, et al. Study on variation and selection effect of stripe rust resistance in wheat space mutagenesis progeny［J］. Journal of Triticeae Crops, 2012, 32(4): 767-77. (in Chinese)
［15］ WU H, HUANG CL, ZHANG KP, et al. Mutations in cauliflower and sprout broccoli grown from seeds flown in space［J］. Advances in Space Research, 2010, 46(10): 1245-1248
［16］ GAN YM, WU YL, CAO ZY, et al. Preliminary study on effects of the sugarcane seed germination and seedling growth under 60Coγ irradiation［J］. Seed, 2018, 37(4):71-73.
［17］ SUN DY, ZHANG JX, CHEN GZ, et al. Advances and prospects of breeding rice varieties resistant to rice blast by space mutation［J］. Journal of Nuclear Agricultural Sciences, 2017, 31(2): 271-279. (in Chinese)
［18］ CONGER BV, KENZAK CF. The influence of temperature on radiationinduced oxygendependent and independent damage in barley seeds［J］.Radiat. Res., 1971, 46(3): 601-602.
［19］ WANG QJ, YAN B, HU HJ, et al. Effect of exogenous salicylic acid on germination characteristics of maize seeds under low temperature stress［J］. Guizhou Agricultural Sciences, 2018, 46(9): 23-25. (in Chinese)
［20］ HU LF, SU LS, ZHU CL, et al. Genetic and cytological analysis of radiationinduced male sterile mutant tda in rice［J］. Journal of Nuclear Agricultural Sciences, 2015, 29(12): 2253-2258. (in Chinese)
［21］ YANG W, WANG CX, WANG LJ, et al. Analysis of effect and combining ability of space mutagenesis on main genetic traits of sorghum［J］. Gansu Agricultural Science and Technology, 2012(8): 7-10. (in Chinese)
［Methods］ Sugarcane hybrid spikes were subjected to space radiation mutagenesis treatment to identify the effects on the germination, seedling growth and plant growth and development of sugarcane hybrid seeds.
［Results］ The space radiation treatment had a great impact on the germination and growth of sugarcane hybrid seeds, especially on the germination of sugarcane seeds. The germination number per gram of seeds increased significantly, and the survival rate of seedlings increased significantly. The effect on the growth status was relatively small. The average number of tillers decreased slightly, the percentage of available stems increased, and the plants became higher, which resulted in a greater effect on sugarcane yield. Sugarcane sucrose was increased. The seed germination and late growth status indicated that space radiation promoted the germination and growth of sugarcane hybrid seeds.
［Conclusions］ This study provides a basis for the space radiation mutagenesis breeding of sugarcane hybrid seeds and the promotion of sugarcane breeding process.
Key words Space radiation; Sugarcane; Mutation breeding; Seed germination
Received: May 27, 2019Accepted: September 18, 2019
Supported by General Project of Hainan Provincial Natural Science Foundation (No. 317257); The Fundamental Research Funds for Central Public Welfare Research Institutes (1630052019005); China Agricultural Research SystemSugar crop (CARS170716).
Yimei GAN (1982-), female, associate researcher, PhD, devoted to research about Crop genetic breeding.
*Corresponding author. Email: yangbenpeng@itbb.org.cn.
Sugarcane (Saccharum officinarum) is Chinas main sugar crop. More than 90% of Chinas sugar comes from sugarcane. In addition to being used mainly for sugar extraction, sugarcane can also be used to produce bioenergy such as ethanol. In addition, sugarcane processing byproduct bagasse can also be used as an edible fungi raw material［1］ and an improved soil［2］, or for improving environment［3］. Sexual hybridization is the most commonly used method for the selection of new sugarcane varieties. However, due to the lack of germplasm resources, the blood is monotonously poor, and it is difficult to obtain superior mutant materials for hybridization to obtain groundbreaking new varieties. Studies have shown that hybrid progeny seeds obtained through radiation mutagenesis can increase mutations by enhancing the accumulation of gene segregation and by inducing mutations, thereby increasing the mutation rate and thus effectively increasing the mutagenic effect［4］. Space radiation mutagenesis breeding refers to the new breeding technology for new varieties in which science researchers induce crop propagating materials by special radiation in outer space to produce mutations. The main advantages of spaceflight mutagenesis breeding are high mutation frequency, large mutation amplitude, rich type and easy stabilization of mutated materials, so it thus shortens the breeding cycle when causing light damage to plants and is easy to obtain mutations. Under natural conditions, the variation rate of rice is one in 200 000, and the mutagenic rate of ground radiation treatment is 0.12%, while the variation rate of space radiation mutagenesis is 12.5%, which is 100 times higher than the ground radiation mutagenesis. For example, the Brassica napus obtained some strong mutations such as dwarf and large grains after space radiation mutagenesis［5］, and mung beans after space radiation mutagenesis grew a single plant with a pod length of about 16 cm and a seed number of 15-19 per pod［6］. It indicates that space radiation is easier to obtain favorable materials for breeding of new varieties than other physical and chemical mutagenesis.
The mechanism of space radiation mutagenesis is complex, and the causes of genetic variation of plant traits caused by space environment such as high vacuum, microgravity, highenergy particle radiation, space radiation, intense ultraviolet radiation and alternating magnetic fields are not fully understood. Variations from space radiation mutagenesis mainly include plant height variation, leaf variation, yield variation, quality variation and resistance variation［7-8］. After space mutagenesis, most plants are more likely to become taller or shorter. For example, rice, corn, tomato, wheat, pepper and sorghum all showed plant height variation. The leaf variation mainly revolves around shape, color, size and quantity［9-10］. The variation in yield mainly lies in the variation of various factors affecting yield［11-12］. The quality variation mainly manifests in the variation of amino acid content, soluble sugar content and tannin content. The resistance variation is mainly in disease resistance, such as wheat stripe rust, cauliflower black rot and rice blast［13-15］.
Because sugarcane is heavier in stems and lighter in spikes, the cost for space mutagenesis using spikes is lower. Therefore, in this study, sugarcane parents were selected and combined to obtain hybrid spike seeds, which were used as a material for space radiation mutagenesis, and then, the effects of space radiation on the germination and growth of sugarcane hybrid seeds were investigated. This study will provide a basis for early selection in space radiation mutagenesis breeding of sugarcane seeds. Materials and Methods
Materials
The sugarcane variety Guitang 02901, which is matured especially early with high sugar and high yield, was the female parent, and the foreign resistant variety Ke 5 was the male parent. The sugarcane spike seeds were obtained after sexual hybridization of the two parents in Hainan sugarcane breeding farm. The hybrid spike seeds of sugarcane were weighed and packed in kraft paper bags, and divided into two parts, one for control (CK) and the other for space radiation mutagenesis (SP). After the irradiation, the seeds were divided into three parts according to the weight, which were then sown according to the method of Gan et al.［16］, while the unirradiated seeds were seeded as the CK (also divided into three parts).
Seed germination and statistics before transplanting
The germination number per gram of seeds and seedling survival rate during seed germination were investigated according to the method of Gan et al.［16］. After one and a half months, the seedlings were planted to pots, grown in the pots for 1 month and then transplanted to the field.
Field investigation
The average number of tillers was investigated in SP and CK treatments after tillering of the seedlings. After jointing, the initial plant height of sugarcane was measured, and the plant height and sugar content of sugarcane were measured in the mature period.
Data processing
Test data were processed using EXCEL and SPSS.
Results and Analysis
Effects of space radiation treatment on germination and survival of sugarcane hybrid seeds
Sugarcane hybrid seeds have a large number and a low germination rate, and is generally quantified using the germination number per gram of seeds. The average germination number per gram was 167 and 100 in the space radiation treatment (SP, Sugarcane space radiation) and the unirradiated control treatment (CK, control), respectively, that is, after the space radiation treatment, the germination number per gram of sugarcane hybrid seeds was larger than that of the CK. The value of the SP treatment increased significantly, by 67%, compared with the CK, and there was a significant difference between SP and CK (Table 1). It showed that the space radiation treatment had a great influence on the germination of these sugarcane hybrid seeds and promoted seed germination.
The seedling survival rates of SP and CK were 54.78% and 20.26%, respectively. There was a significant difference between the space radiation treatment and the CK. After space radiation, the survival rate of seedlings from sugarcane hybrid seeds was higher than that of the unirradiated control seeds. There was a very significant difference between the treatment and the CK (Table 2). It indicated that the space radiation treatment had a great influence on the growth of these sugarcane hybrid seedlings and improved the survival rate of seedlings. Effect of space radiation on the tiller number and percentage of available tillers of sugarcane seedlings
The living sugarcane seedlings were transplanted to the field after temporary planting. After tillering, the tiller number and percentage of available tillers was investigated in the SP treatment and the CK, respectively. The average tillers of SP and CK were 7.06 and 8.77, respectively. The average tillers of sugarcane seedlings after the space radiation treatment were reduced compared with the unirradiated control seedlings, and the difference reached a very significant level (Table 3). It showed that the space radiation treatment had a strong influence on the tillering of these sugarcane hybrid seedlings, and significantly reduced tillers. The percentage of available tillers was 60.47% and 55.81% in SP and CK, respectively, that is, the percentage of available tillers of sugarcane seedlings subjected to space radiation treatment was higher than that of unirradiated control seedlings, and the difference reached a significant level (Table 4). It indicated that the space radiation treatment had a significant effect on the tillering of these sugarcane hybrid seedlings.
Effect of space radiation on plant height of sugarcane
After the sugarcane entered the jointing stage, the initial plant heights of the plants in SP and CK were measured. The initial plant heights of SP and CK were all around 150 cm, but the difference was extremely significant (Table 5), indicating that the radiation treatment had a greater impact on sugarcane plant height. At the maturity stage, the plant height of SP was higher than that of the CK, and the difference was extremely significant (Table 6), indicating that the plant height of the sugarcane hybrid progeny increased significantly after the space radiation mutagenesis treatment.
Yimei GAN et al. Effects of Space Radiation Mutation on Germination and Growth of Sugarcane Hybrid Seeds
Effect of space radiation on sugarcane sucrose
Sucrose is the main factor affecting the quality of sugarcane. It can be expressed by measuring the Brix, which is positively proportional to sucrose content. The average Brix of the sugarcane material after space radiation mutagenesis was higher than that of the CK. The average Brix reached its highest level in December and then decreased (Table 6). Both the induced material and the control material showed midearly maturity characteristic, and no changes in maturity were observed after mutagenesis. Conclusions and Discussion
The introduction of new variants by irradiation has become an important means of modern plant improvement and an access to new germplasms. Through the induction by space radiation, the mutation spectrum is easily broadened and the mutation rate is also increased, which makes the selection of favorable mutants easier, and therefore, space radiation becomes a means of obtaining new germplasms［17］. In space radiation breeding, it is necessary to supply enough amount of radiation to obtain the variation. In production, sugarcane is vegetatively propagated by the buds of the stem segments. If the buds of the stem segments are used as space radiation materials, they will produce a particularly heavy weight and volume, resulting in expensive costs.However, the seeds of sugarcane are small, and only a part of the seeds is required to obtain a large number of mutated sugarcane seedlings. Moreover, and it is easier to carry out the sugarcane space radiation mutagenesis test using sugarcane seeds without much cost.
The strength of seed vigor can directly affect the seed germination and emergence rate, affect the growth potential of seedlings, and affect the plants resistance to pests and diseases, and seed germination requires appropriate water, temperature and air to activate the original genes in the genome or the initiation and expression of new genes, to thereby restore metabolism and growth［18］. The seeds of sugarcane are small and light, and also have fluff, and the germination rate is extremely low. The hybrid spikes obtained after hybridization of some parents cannot be used due to the low germination rate, which greatly affects the innovation of sugarcane germplasms and the breeding of varieties. Studies have shown that 0.7 mmol/L salicylic acid treatment of corn seeds can improve its germination rate, germination potential, etc., but the treatment with higher concentrations of salicylic acid on corn seeds had a role in inhibiting its germination rate［19］, indicating that different treatments can increase or inhibit seed germination. Previous studies have shown that nuclear genetic variation in plant cells under irradiation conditions［20］ indicates that radiation affects the nuclear genes of seeds and thus affects seed germination and even seedling growth. In this study, the germination ability of sugarcane seeds after the space radiation treatment was enhanced, and the viability of seedlings was also enhanced, indicating that the material subjected to space radiation mutagenesis treatment obtained positive mutagenesis. Most of the literatures report that plants will become shorter after space mutagenesis. In fact, the variation of height is generally bidirectional. In this study, the height of sugarcane plants subjected to space radiation was positive in sugarcane production, which will significantly increase sugarcane yield. After sorghum seeds were loaded into spaceships for space mutagenesis treatment, and the heights of their multigeneration plants were analyzed. It was concluded that mutations will occur in the very generation undergone mutagenesis, will be inherited to the next generation, and then will segregate in the third generation, and the mutations inherited by the third generation will be stable［21］. Later, in the second generation of the space radiationinduced sugarcane in this study, the average plant height was still higher than that of the CK, indicating that the variation of the plant height of the mutagenized sugarcane was very promising.
This study shows that the space radiation mutagenesis of sugarcane seeds has obtained more positive mutations, such as seed activity, seedling survival rate, plant height, etc., which provide good materials for space radiation mutagenesis breeding of sugarcane.
References
［1］ MA HX, MA ZL, MA GY, et al. Optimizing culture formula for cultivating Auricularia cornea by using bagasse［J］. Edible fungi of China, 2018, 37(3): 25-29. (in Chinese)
［2］ NIU G, LIAO L, SHI JF. Adsorption characteristics of modified bagasse ash to sulfate in the wastewater［ J］. Industrial Safety and Environmental Protection, 2018, 44(9): 20-24. (in Chinese)
［3］ LIU XM, MA C, WU F, et al. Adsorption of Cr (Ⅵ) in waste water by bagasse carbon［J］. Applied Chemical Industry, 2019, 48(1): 72-76. (in Chinese)
［4］ ZHANG ZQ. Notable problems in the sexualhybridization radiation mutagenesis breeding of sugarcane［J］. Sugarcane and Canesugar, 1995(5): 7-8. (in Chinese)
［5］ WANG WR, SUN CC, JIANG MY, et al. Analysis of progeny characteristics of Brassica napus L. subjected to space mutagenesis［J］. Journal of Nuclear Agricultural Sciences, 2015, 29(2): 215-220. (in Chinese)
［6］ QIU F, LI JG, WEN ML, et al. Molecular biological analysis of mung bean longpod mutants from spatial mutagenesis［J］. Scientia Agricultura Sinica, 1998, 31(6): 1-5. (in Chinese)
［7］ LI XF, ZHU HF, ZHU YY, et al. Development of a new latebolting germplasm and breeding a new cultivar Yanchun of pakchoi by using space mutation［J］. Journal of Nuclear Agricultural Sciences, 2018, 32(7): 1249-1255. (in Chinese) ［8］ FU XJ, YANG QH, YUAN FJ, et al. Breeding of Zhexian No.9 by space mutation and variation analysis of its characters［J］. Journal of Nuclear Agricultural Sciences, 2019, 33(5): 0841-0847. (in Chinese)
［9］ TRIPATHY BC, BROWN CS, LEVINE HG, et al. Growth and photosynthetic responses of wheat plants crown in space［J］. Plant Physiol, 1996, 110(3): 801-806
［10］ YANG HS. Breeding of Spaceinduced New multifoliaolate alfafa Varieties［D］. Lanzhou: Lanzhou University, 2018. (in Chinese)
［11］ PEI XB, GU XJ, CHEN CH, et al. Characters of tomato and pepper bred by space mutation in glasshouse［J］. Journal of Nuclear Agricultural Sciences, 2004, 18(4): 321-322. (in Chinese)
［12］ PENG L, RU M, WANG KR, et al. Spaceflight environmentinduced variation in root yield and active constituents of salvia miltiorrhiza, Planta Med., 2014(80): 1029-1035
［13］ CHENG ZL, LIU M, ZHANG M, et al. Transcriptomic analyses of spaceinduced rice mutants with enhanced susceptibility to rice blast, Advances in Space Research, 2007, 40(4): 540-549
［14］ DU JY, BAI B, JIN MA, et al. Study on variation and selection effect of stripe rust resistance in wheat space mutagenesis progeny［J］. Journal of Triticeae Crops, 2012, 32(4): 767-77. (in Chinese)
［15］ WU H, HUANG CL, ZHANG KP, et al. Mutations in cauliflower and sprout broccoli grown from seeds flown in space［J］. Advances in Space Research, 2010, 46(10): 1245-1248
［16］ GAN YM, WU YL, CAO ZY, et al. Preliminary study on effects of the sugarcane seed germination and seedling growth under 60Coγ irradiation［J］. Seed, 2018, 37(4):71-73.
［17］ SUN DY, ZHANG JX, CHEN GZ, et al. Advances and prospects of breeding rice varieties resistant to rice blast by space mutation［J］. Journal of Nuclear Agricultural Sciences, 2017, 31(2): 271-279. (in Chinese)
［18］ CONGER BV, KENZAK CF. The influence of temperature on radiationinduced oxygendependent and independent damage in barley seeds［J］.Radiat. Res., 1971, 46(3): 601-602.
［19］ WANG QJ, YAN B, HU HJ, et al. Effect of exogenous salicylic acid on germination characteristics of maize seeds under low temperature stress［J］. Guizhou Agricultural Sciences, 2018, 46(9): 23-25. (in Chinese)
［20］ HU LF, SU LS, ZHU CL, et al. Genetic and cytological analysis of radiationinduced male sterile mutant tda in rice［J］. Journal of Nuclear Agricultural Sciences, 2015, 29(12): 2253-2258. (in Chinese)
［21］ YANG W, WANG CX, WANG LJ, et al. Analysis of effect and combining ability of space mutagenesis on main genetic traits of sorghum［J］. Gansu Agricultural Science and Technology, 2012(8): 7-10. (in Chinese)