Breeding and Characteristics of a New Wheat Variety Jike 33

Siyou XU Kai DING Dahu SHANG Shansan NIU Shilong XIE Tongfu MA

AbstractIn this study, two indica varieties with different dormancy characteristics ［4K58 (II 32B dormant), 4K59 (II32B)］ and their F2 seeds (C178, C179) obtained through hybridization with sterile line (II32A) were used as materials. Different aged seeds (0, 3, 6 and 9 d) of these four varieties were acquired by artificial accelerated aging method. Effects of artificial aging on malondialdehyde (MDA) content and catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) activity were investigated. The results showed that with the prolongation of aging time, MDA contents of these four rice varieties increased significantly, while the activity of antioxidant enzymes decreased dramatically. Besides, MDA contents and SOD, CAT and APX activity of the two inbred lines were significantly lower than those of the hybrid varieties. In addition, the activity of antioxidant enzymes in 4K58 and C178 was significantly lower than that in 4K59 and C179, respectively. This study indicated that artificial aging treatment significantly inhibited the activity of antioxidant system in seeds, improved membrane lipid peroxidation degree, and thus aggravated the deterioration of seeds. In addition, it also suggested that rice seeds with dormant property were more intolerant to storage.

Key wordsArtificial accelerated aging; Rice; Seed; Physiological characteristics; Dormancy



Received: August 22, 2018Accepted: November 9, 2018

Supported by National Key Research and Development Project (2018YFD 0101000).

Dongdong CAO (1983-), male, P. R. China, PhD, research assistant, devoted to research and extension of seed science and engineering technology.

*Corresponding author. Email: ruangh@zaas.org.

Food reserve is an important part of food security［1］, while the deterioration of rice quality and the decline of germination rate during rice storage have always been problems that are difficult to overcome in production, storage, transportation and operation parts［2］, resulting in an annual loss of stored grains up to 3.5×1010 kg in China. The storability of seeds affects food reserve, so it is particularly important to study the storability of rice seeds. The research methods of seed storability mainly include natural aging and artificial accelerated aging. Seed aging is the irreversible natural decline of seed vigor after it reaches its maximum at physiological maturity stage［3］. Seed aging can cause the decline of storage substances［4］, accumulation of toxic substances［5］, cell structure destruction and disorder of physiological metabolism in seeds, thereby seriously affecting seed storability and seed vigor［6］. Dong et al.［7］ believe that natural aging is very slow, so it is difficult to measure seed vigor in a short period of time, and it is difficult to apply it in screening for resistant germplasm in variety improvement［8］. Ellis et al.［8］ believe that when treating seeds at -13-80 ℃, the aging laws of the seeds are consistent. Therefore, the use of artificial accelerated aging method to simulate natural aging has become a common method for studying the storability of seeds.

In the process of hybrid rice seed production, the breeding of maintainer and sterile lines with strong dormancy can solve the problem of seed germination during seed production and prolong the storage time of seeds. Hou［9］ believes that dormant seeds can maintain vitality through longterm storage and have strong adaptability. However, some scholars believe that dormant seeds may affect seed germination and are not necessarily more resistant to storage［10］. There have been few studies on the relation between seed dormancy and storability, which is still unclear. In this study, two rice cultivars and their hybrid F2 seeds with different dormancy characteristics were aged by the artificial accelerated aging method through high temperature and high humidity, and the effects of aging on the physiological characteristics of rice seeds with different dormancy characteristics were investigated, with an attempt to reveal the relation between seed dormancy and storability. This study will provide a theoretical reference for the selection of storageresistant rice varieties.

Materials and Methods

Experimental materials

The test materials were seeds of indica varieties 4K58 (II32B, dormant), 4K59 (II32B), F2 C178 and C179. Seeds of 4K58 were dormant; and C178 and C179 were the F2 generations obtained through hybridization of 4K58 and 4K59 with the sterile line (II32A), respectively.

The tested materials were treated by the artificial accelerated aging method at 100% RH and 40 ℃ for 3, 6 and 9 d, respectively. After aging, the seeds were allowed to dry at room temperature for 24 h, packaged in paper bags, and stored at 4 ℃ for later use. Seeds free of aging served as the control (CK).

Experimental methods

Determination of MDA content in seeds

The seeds aged for different days were uniformly placed on wet filter paper for 24 h［11］, and the content of malondialdehyde (MDA) was determined by the method of Cao et al.［12］. A certain amount of imbibed sample (0.15 g) was weighed, ground with 4 ml of 0.05 mol/L phosphate buffer (pH 7.8), and then centrifuged at 10 000×g for 15 min. Then, 1.5 ml of the supernatant was added with 2.5 ml of 5% (w/v) thiobarbituric acidtrichloroacetic acid solution. The mixed solution was boiled at 100 ℃ for 15 min and then rapidly cooled. After centrifugation at 1 800×g for 10 min, the absorbance values of the supernatant were measured at 532 and 600 nm. The MDA content was calculated using an extinction coefficient of 155 mM-1 cm-1.

Table 1Comparison of MDA contents in seeds of different rice varieties after accelerated aging treatment

VarietyCK

Aging days∥d

369

4K58C 7.4±0.31 bBC 8.5±0.36 bcB 9.7±0.57 abA 11.7±0.64 c

4K59C 6.2±0.52 bBC 8.0±0.46 cB 9.1±0.48 bA 11.8±0.87 c

C178B 9.8±0.45 aB 10.1±0.36 aB 10.8±0.31 aA 16.7±0.89 a

C179B 8.9±0.46 aB 9.7±0.26 abB 9.7±0.34 abA 14.3±0.11 b

CK refers to seeds free of aging. Different lowercase letters following the values indicate a significant difference in MDA content between different rice varieties treated with the same aging days; and different numerical capital letters indicate a significant difference in MDA content between treatments of the same rice variety treated with different aging days (LSD, α=0.05).

Determination of antioxidant enzyme activity in seeds

The seeds aged for different days were uniformly placed on wet filter paper for 24 h, and 0.15 g of the swollen seed sample was weighed, ground with 4 ml of 0.05 mol/L phosphate buffer (pH 7.8), and then centrifuged at 10 000×g for 15 min, obtaining the supernatant as the crude enzyme extract for measuring enzyme activity［13］. The activity of catalase (CAT) was determined by monitoring the decrease in the absorbance value of H2O2 at 240 nm according to the method of Hu et al.［13］. The reaction liquid included 2.8 ml of 25 mmol/L phosphate buffer (pH 7.0, containing 2 mmol/L EDTANa2), 100 μl of 300 mmol/L H2O2 and 100 μl of crude enzyme extract. The activity of ascorbate peroxidase (APX) was measured by monitoring the decrease in absorbance of the reaction liquid at 290 nm according to the method of Nakano and Asada［14］, and 3 ml of the determined mixture contained 2.7 ml of 25 mmol/L phosphate buffer (pH 7.0, containing 2 mmol/L EDTANa2), 100 μl of 300 mmol/L H2O2 and 100 μl of crude enzyme extract. The activity of peroxidase (POD) was determined by measuring the increase in absorbance of the reaction liquid at 470 nm within 1 min according to the method of Guan et al.［15］. The reaction liquid contained 2.7 ml of 25 mmol/L phosphate buffer (pH 7.0, containing 2 mmol/L EDTANa2), 100 μl of 1.5% guaiacol, 100 μl of 300 mmol/L H2O2, and 100 μl of crude enzyme extract. The activity of superoxide dismutase (SOD) was measured according to the method of Xu et al.［16］. The total SOD activity was calculated with the amount of enzyme inhibiting 50% of the NBT photoreduction reaction as an enzyme activity unit at 560 nm.

Statistical analysis

The data were statistically analyzed by SAS, and multiple comparisons were performed by the least significant difference method (LSD), α=0.05. The percentage data were subjected to an inverse sine transformation before analysis (y=arcsin［sqrt (x/l00)］).

Results and Analysis

Effect of aging days on MDA content in seeds

In the unaged seeds (CK), the MDA contents of C178 and C179 were significantly higher than those of 4K58 and 4K59, and there were no significant differences between C178 and C179 and between 4K58 and 4K59. After 3 d of seed aging, the MDA content in C178 seeds was significantly higher than those in 4K58 and 4K59, and there was no significant difference between the latter two. There was also no significant difference between C178 and C179. After 6 d of seed aging, the MDA content of 4K59 seeds was significantly lower than those of other three varieties, and there were no significant differences between the three varieties. After 9 d of seed aging, the MDA content of C178 seeds was significantly higher than other three varieties; and the MDA content of C179 seeds was significantly higher than those of 4K58 and 4K59, and there was no significant difference between 4K58 and 4K59.

With the prolongation of the aging treatment time, the MDA contents in seeds of the four varieties showed a gradually increasing trend. After 9 d of aging, the MDA contents in seeds of the four varieties were significantly higher than those in seeds aged for 6 d. After 6 d of aging, the MDA contents of the four varieties were not significantly different from the values of seeds aged for 3 d, but the MDA contents in the seeds of 4K58 and 4K59 were significantly higher than that of the CK. After 3 d of aging, there were no significant differences in MDA content between seeds of the four varieties and those of the CK (Table 1).

Effects of aging days on activity of antioxidant enzymes in seeds

Effect of aging days on CAT activity in seeds

In the untreated seed (CK), the CAT activity of 4K58 was not significantly different from that of 4K59, and the CAT activity of both of them was significantly lower than C178; and the CAT activity of C178 was significantly lower than that of C179. After 3 d of seed aging, the CAT activity of 4K58 seeds was significantly lower than that of 4K59, which was significantly lower than the CAT activity of C178, which was significantly lower than that of C179 in turn. After 6 d of seed aging, the CAT activity of 4K58 seeds was significantly lower than that of 4K59, and there was no significant difference between 4K59 and C178, both of which had CAT activity significantly lower than C179. After 9 d of seed aging, the CAT activity in seeds of the four varieties of seeds was consistent with that in seeds aged for 3 d (Fig. 1).

With the prolongation of aging time, the CAT activity in seeds of the four varieties showed a decreasing trend. After 3 d of aging, the CAT activity in seeds of the four varieties was significantly lower than that in the CK. After 6 d of aging, the CAT activity in 4K58 and 4K59 seeds was not significantly different from that in the seeds aged for 3 d, and the CAT activity of C178 and C179 was significantly lower than that of the seeds aged for 3 d. After 9 d of aging, the CAT activity of 4K58 and 4K59 seeds were significantly lower than that of the seeds aged for 6 d; and the CAT activity of C178 and C179 was not significantly different from that of the seeds aged for 6 d.



CK refers to seeds free of aging. Different lowercase letters above the columns indicate a significant difference in CAT activity between different rice varieties treated with the same aging days; and different numerical capital letters indicate a significant difference in CAT activity between treatments of the same rice variety treated with different aging days (LSD, α=0.05).

Fig. 1CAT activity in accelerated aging seeds of four rice varieties

Effect of aging days on APX activity in seeds

The APX activity in unaged 4K58 seeds was significantly lower than that in 4K59 seeds, which was significantly lower than that of C178, and the APX activity of C178 was significantly lower than that of C179 in turn. After the seeds were aged for 3 and 6 d, changes of APX activity in the four varieties were consistent with the unaged treatment. After 9 d of seed aging, the APX activity of 4K58 seeds was significantly lower than that of 4K59, and there was no significant difference between 4K59 and C178, both of which were significantly lower than C179 in APX activity.

With the prolongation of aging time, the APX activity in seeds of the four varieties showed a decreasing trend. Except C179, the APX activity in unaged seeds of the remaining three varieties was significantly higher than that in the seeds aged for 3 d. After 6 d of aging, the APX activity of 4K58 and 4K59 seeds was not significantly different from that of the seeds aged for 3 d, and the APX activity of C178 and C179 was significantly lower than that of the seeds aged for 3 d. After 9 d of aging, except 4K59, the APX activity of other three varieties was significantly lower than that of the seeds aged or 6 d. After 6 d of aging, the APX activity of 4K58 and 4K59 seeds was not significantly different from that of the seeds aged for 3 d, and the APX activity of C178 and C179 was significantly lower than that of the seeds aged for 3 d. After 9 d of aging, except 4K59, the APX activity of other three varieties was significantly lower than that of the seeds aged for 6 d (Fig. 2).



CK refers to seeds free of aging. Different lowercase letters above the columns indicate a significant difference in APX activity between different rice varieties treated with the same aging days; and different numerical capital letters indicate a significant difference in APX activity between treatments of the same rice variety treated with different aging days (LSD, α=0.05).

Fig. 2APX activity in accelerated aging seeds of four rice varieties

Agricultural Biotechnology2019

Effect of aging days on POD activity in seeds

In the unaged seeds, the POD activity of 4K59 was significantly higher than that of other three varieties, among which 4K58 was significantly higher than C178 and C179, and there was no significant difference between the latter two. After 3 d of seed aging, the POD activity of 4K59 seeds was significantly higher than that of other three varieties, among which 4K58 was significantly higher than C179, which was significantly higher than C178 in turn. After 6 d of seed aging, changes of POD activity in seeds of the four varieties were consistent with those in seeds aged for 3 d. After 9 d of seed aging, changes of POD activity in seeds of the four varieties were consistent with the unaged treatment (CK).



CK refers to seeds free of aging. Different lowercase letters above the columns indicate a significant difference in APX activity between different rice varieties treated with the same aging days; and different numerical capital letters indicate a significant difference in APX activity between treatments of the same rice variety treated with different aging days (LSD, α=0.05).

Fig. 3POD activity in accelerated aging seeds of four rice varieties

With the prolongation of aging time, the POD activity in seeds of the four varieties showed a decreasing trend. After 3 d of seed aging, the seed POD activity of 4K58 and 4K59 was not significantly different from that of the unaged treatment (CK), and the POD activity of C178 and C179 seeds was significantly lower than that of the CK. After 6 d of seed aging, the POD activity of 4K59 and C178 was significantly lower than that of the seeds aged for 3 d, and the POD activity of 4K58 and C179 was not significantly different from the seeds aged for 3 d. After 9 d of seed aging, except 4K59 having no significant difference in POD activity from that after 6 d of aging, other three varieties had significantly lower POD activity than after 6 d of aging (Fig. 3).

Effect of aging days on SOD activity in seeds

The unaged seeds of 4K58 had SOD activity significantly lower than 4K59, which was significantly lower than C178 and C179, and there was no significant difference between C178 and C179. After 3 d of seed aging, the SOD activity of the four varieties was consistent with the CK. After 6 d of seed aging, the SOD activity of 4K58 was significantly lower than that of other three varieties, and there were no significant differences between the latter three. After 9 d of seed aging, the SOD activity of 4K58 was significantly lower than that of C178, which was significantly lower than 4K59, which was then significantly lower than C179 in turn.

With the prolongation of aging time, except 4K59 seeds having a nonsignificant change in SOD activity, the SOD activity of other three varieties showed a decreasing trend. After 3 d of seed aging, the SOD activity in seeds of the three varieties was not significantly different from that of the unaged treatment. After 6 d of seed aging, the SOD activity of C178 was significantly lower than that of the seeds aged for 3 d, and the SOD activity of other two varieties was not significantly different from that after 3 d of aging. After 9 d of seed aging, the SOD activity of 4K58 and C178 was significantly lower than that after 6 d of aging (Fig. 4).



CK refers to seeds free of aging. Different lowercase letters above the columns indicate a significant difference in SOD activity between different rice varieties treated with the same aging days; and different numerical capital letters indicate a significant difference in SOD activity between treatments of the same rice variety treated with different aging days (LSD, α=0.05).

Fig. 4SOD activity in accelerated aging seeds of four rice varieties

Discussion

Seed aging is a natural phenomenon that is common in the storage of crop seeds. During the aging process of seeds, a series of physiological and biochemical changes will occur in the interior, including destruction of membrane integrity and autooxidation of the membrane, changes in enzyme activity in seeds, accumulation of toxic substances and reduction of synthesis and repairing ability in seeds［17］. In this study, two indica rice varieties with different dormancy characteristics and their hybrid F2 seeds obtained through hybridization with the sterile line were aged by the artificial accelerated aging method. It was found that after aging treatment, the deterioration of all seeds was deepened, which was reflected by the significantly increased MDA content and decreased activity of antioxidant enzymes (SOD, POD, CAT and APX), and there were significant differences between different varieties.

MDA is usually used as an indicator of lipid peroxidation, and its content can reflect the level of membrane lipid peroxidation to some extent［18］. The results of this study showed that the MDA contents of the four rice cultivars increased significantly with the prolongation of aging time, indicating that aging caused lipid peroxidation, which is consistent with the research results of wheat［19］, waxy corn［20］ and sorghum seeds［21］. In addition, it was also found that among all treatments, the MDA contents of the two inbred lines (4K58 and 4K59) were significantly lower than those of the two hybrids (C178 and C179), which might be related to the fact that hybrid seeds are less resistant to storage than conventional rice (inbred line) seeds［22］. Due to the genetic characteristics of hybrid rice seeds, the grains are loose with poorer glume closure and declined protective performance, and are susceptible to external factors, which is not conducive to storage. Furthermore, the hybrid rice has strong physiological metabolism and larger respiratory intensity than conventional rice, which makes its storage stability poorer［23］. The difference in dormancy characteristic had a certain effect on the MDA content in aged seeds, but it was not significant, and only the MDA content in C178 seeds aged for 9 d was significantly higher than that of C179.

Another important reflection of seed aging is the decline in activity of antioxidant enzymes in seeds. Li et al.［4］ studied the seed vigor and physiological indexes of artificially aged corn seeds, and found that the correlation coefficients between seed vigor and POD, CAT and dehydrogenase activity reached significant or extremely significant level, and they can well predict seed vigor level. Therefore, studying the changes of antioxidant enzyme activity during seed aging has important reference value for understanding seed vigor and deterioration. The results of this study showed that with the prolongation of aging time, the activity of antioxidant enzymes in the four rice varieties, especially the three enzymes CAT, APX and POD, showed a decreasing trend. These results are consistent with the research results in previous studies of seeds such as corn［4］, platycodon［11］ and wheat［24］. Similarly, in almost all treatments, the SOD, CAT and APX activity of the two inbred lines was significantly lower than that of the two hybrids, which further verifies that hybrid rice seeds have stronger physiological metabolism and greater respiration rate than conventional rice［22-23］. However, it should be noted that the POD activity of the two inbred lines was significantly higher than the two hybrids, which might be related to the type of rice variety or antioxidant enzyme. The difference in dormancy characteristic of seeds significantly affected antioxidant enzyme activity: among all the treatments, the activity of antioxidant enzymes (SOD, CAT, APX and POD) in 4K58 seeds was significantly lower than that in 4K59; and similarly, the hybrid F2 seeds (C178) obtained through hybridization of 4K58 and the sterile line also had lower antioxidant enzyme activity than C179. In addition, it was also found that with the prolongation of aging time, 4K58 and C178 seeds had SOD, APX and POD activity shown a decrease higher than 4K59 and C179 seeds, respectively. Since the antioxidant enzyme activity of seeds is significantly positively correlated with the level of seed vigor［4,25］, these results seem to indicate that rice seeds with dormancy characteristic are also not resistant to storage.

In summary, after artificial accelerated aging treatment, the MDA content in seeds of the four rice varieties increased significantly with the prolongation of aging time, and the antioxidant enzyme activity decreased gradually. It indicates that the aging treatment significantly inhibited the activity of antioxidant system in seeds, deepened the degree of membrane lipid peroxidation, and caused or aggravated the deterioration of seeds. The MDA content and antioxidant enzyme activity of hybrid F2 seeds were significantly higher than those of inbred seeds, which proved that hybrid rice seeds were less resistant to storage than conventional rice seeds. In addition, because the antioxidant enzyme activity of 4K58 and C178 seeds was lower than that of 4K59 and C179, respectively, it was speculated that the dormant rice seeds were less tolerant to storage.

References

［1］ CAI QH, HU YY, ZHANG JF, et al. Preliminary study on physiological characteristics for rice seed after aging［J］. Fujian Journal of Agricultural Sciences, 2012, 27(10): 1061-1066. (in Chinese)

［2］ ZHANG Y, TENG B, WU JD, et al. Study on accelerated aging test of rice seeds with high temperature and humidity［J］. Journal of The Chinese Cereals and Oils Association, 2010, 25(10): 8-12. (in Chinese)

［3］ ZHANG CQ, YANG W, DAI ZL, et al. Physiological and biochemical characteristics of ‘Dongsheng' cabbage seeds during artificial aging［J］. Acta Botanica BorealiOccidentalia Sinica, 2012, 32(8): 1615-1620. (in Chinese)

［4］ LI CL, MA SJ, PENG B, et al. Effects of artificial aging on seed vigor indexes, embedded substance content and physiological indexes of maize［J］. Journal of Jilin Agricultural University, 2014, 36(5): 505-509, 514. (in Chinese)

［5］ FU YF, LI HY, HUANG F, et al. Effects of artificial aging on seed vigor, physiological and biochemical changes of Elymus sibiricus seeds［J］. Journal of Plant Genetic Resources, 2014, 15(6): 1360-1363. (in Chinese)

［6］ WANG F, LIAO L, HUA MY, et al. Effects of artificial aging on amylase and malt quality of beer barley grains［J］. Acta Agriculturae Nucleatae Sinica, 2017, 31(2): 0288-0297. (in Chinese)

［7］ DONG GJ, HU XM, GUANG DL, et al. Comparison between artificial ageing and natural ageing in rice［J］. Journal of Zhejiang Agricultural Sciences, 2004, 1: 27-29. (in Chinese)

［8］ ELLIS RH, HONG TD, ROBERTS EH. A lowpostirecontent limit to logarithmic relations between seed moisture content and longevity［J］. Annals of Botany, 1998, 61: 405-408.

［9］ HOU YJ. Analysis of the relationship between seed dormancy and resistance to storage［J］. Mod Agric Sci Technol, 2015, 23: 51. (in Chinese)

［10］ YU XJ, XU CL, WANG F, et al. Reasons for dormancy of Anemone rivularis seed and method of releasing dormancy［J］. Chinese Journal of Ecology, 2014, 33(1): 65-70. (in Chinese)

［11］ YAO XM, ZHANG RE, OU C, et al. Effects of artificial aging on physiological and biochemical characteristics of Platycodon grandiflorus seeds［J］. Journal of Northwest SciTech University of Agriculture and Forestry: Natural Science Edition, 2015, 43(2): 203-210. (in Chinese)

［12］ CAO DD, HU J, ZHU SJ, et al. Relationship between changes in endogenous polyamines and seed quality during development of sh2 sweet corn (Zea mays L.) seed［J］. Scientia Horticulturae, 2010, 123: 301-307.

［13］ HU J, XIE XJ, WANG ZF, et al. Sand priming improves alfalfa germination under highsalt concentration stress［J］. Seed Science Technology, 2006, 34: 199-204.

［14］ NAKANO Y, ASADA K. Hydrogen peroxide is scavenged by ascorbate specific peroxidase in spinach chloroplasts［J］. Plant and Cell Physiology, 1981, 22: 867-880.

［15］ GUAN YJ, HU J, WANG XJ, et al. Seed priming with chitosan improves maize germination and seedling growth in relation to physiological changes under low temperature stress［J］. Journal of Zhejiang University SCIENCEB, 2009, 10: 427-433.

［16］ XU SC, LING YP, HU J, et al. Responses of antioxidant enzymes to chilling stress in tobacco seedlings［J］. Agricultural Sciences in China, 2010, 9: 1594-1601.

［17］ YANG YP, JIANG XC, CHEN LB, et al. Study on physiological mechanism in aging of rice seeds［J］. Journal of Hunan Agricultural University: Social Sciences, 2008, 34(3): 265-269. (in Chinese)

［18］ ZHOU XM, WANG ZX, QIAO YX. Effects of artificial aging on physiological and biochemical characteristics of sesame seed［J］. Chinese Journal of Oil Crop Sciences, 2008, 30(4): 460-463. (in Chinese)

［19］ DING YR, LI WH, CAI YR, et al. Effects of artificial accelerated aging and repairing process on seed vigor and physiological characteristics of wheat seeds［J］. Seed, 2016, 35(4): 13-17. (in Chinese)

［20］ CHEN J, LI JP, LI R. Physiological and biochemical characteristics of waxy maize seeds during artificial aging［J］. Acta Agriculturae Borealioccidentalis Sinica, 2016, 25(6): 857-862. (in Chinese)

［21］ HAN Y, ZHOU YF, GAO MY, et al. Effect of artificial accelerated aging on germination and physiological and biochemical characteristics of sorghum seeds［J］. Seed, 2015, 34(5): 9-13. (in Chinese)

［22］ HU J, DAI XW, YE CF. Storage characteristics and physiological and biochemical changes of hybrid rice and its three lines［J］. Seed, 1989, 2: 1-5. (in Chinese)

［23］ HUANG XH, YANG YZ, JIANG YC. Studies on the formation of desiccation tolerance and the correlation with storage of Oryza Sativa L. seeds［J］. Seed, 2010, 29(7): 25-29. (in Chinese)

［24］ QIN P, KONG ZY, LIU YJ. Effect of artificial aging on physiological and biochemical characteristics of wheat seeds［J］. Journal of Triticeae Crops, 2010, 30(4): 656-659. (in Chinese)

［25］ QIAO YX, GAO PP, MA JH, et al. Study on physiological characteristics and seed activity changes of two maize inbreds in ageing course［J］. Acta Agronomica Sinica, 2003, 29(1): 123-127. (in Chinese)