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Induced Mutations for Improvement of Fruit Trees
and Ornamental Plants in China

Wang Jing Liu Luxiang Zhao Shirong
Institute for Application of Atomic Energy,
Chinese Academy of Agricultural Sciences

Compared with other kinds of crops and other breeding methods, mutation breeding of vegetatively propagated plants showed unique advantages because of its higher variation frequency, wider variation spectrum, more useful variations and much quicker stabilization of mutations due to the vegetative propagation characteristic. After decades of research and practice, China has made significant achievements in using the induced mutations for improvement of fruit trees and ornamental plants. According to the data released by FAO/IAEA, by 2000 China has developed 11 new mutant cultivars in three kinds of fruit trees and 67 new mutant cultivars in six species of ornamental plants through Y-rays radiation. Techniques of mutation induction have been improving too. Besides the vegetative organs, in vitro cultured materials are more and more often used as radiation materials to acquire induced mutations. New mutagens have been exploited and put into practice. In vitro culture techniques are playing a more and more important role in separating and selecting target mutations. Conclusions were made that China has a great potential in the field of using mutation induction techniques to further improve fruit trees and ornamental plants. Combination of mutation induction techniques and other techniques, such as crossing and in vitro culture is full of good prospects in breeding new cultivars of fruit trees and ornamental plants.
1. Introduction
Research and practice have proved that mutation induction techniques can greatly increase the gene mutation frequency and create new germplasm, new materials and new cultivars meeting the breeding targets in a relatively short period. Compared with other kinds of crops and other breeding methods, mutation breeding of vegetatively propagated plants has its unique advantages. Firstly, the variation frequency increases greatly, which can be hundreds or a thousand times higher than natural mutation frequency. The variation spectrum is wide and various, among them useful variations increase significantly. It can even induce some rare mutations that are not easy to get in nature and by crossing method. Secondly, once the target mutation appears, it can be rapidly stabilized by vegetative propagation methods to speed up the selection process.
There are many kinds of vegetatively propagated plants. Fruit trees and ornamental plants are two important kinds among them. With the continuous development of economy and day by day rise of people's living standard in China in recent years, developing and spreading good and new cultivars of fruit trees and ornamental plants has become an important measure of strategic adjustment in China's industrial structure of agriculture. Because most fruit trees are perennial woody plants with high genetic heterozygosity, having long juvenile stage and taking up large scale of land, conventional breeding method of sexual hybridization is restricted to a great extent. Although China has rich resources of ornamental germplasm and long history of cultivation, the systematic breeding started much later and developed slowly and many cultivars depended on importing from other countries. So giving full play to the advantages of mutation induction techniques to develop new cultivars of good quality fruit trees and ornamental plants to meet the market demand seemed very important. This paper briefly reviewed the advances and achievements of radiation breeding of fruit trees and ornamental plants in China and forecast the prospects of the future development.
2. General situation of radiation breeding of fruit trees and ornamental plants
2.1 Fruit trees
China began the studies on radiation breeding of fruit trees in 1960’s. Officially released data showed that 11 new mutant cultivars of three kinds of fruit trees have been developed by 2000. Five of them are few-seeded or seedless orange cultivars, one is apple cultivar and five are pear cultivars.

Good fruit quality is the most important target of fruit production and breeding. Other desired variations in the obtained fine mutants were short-shoot form (or compact form) variation, early maturing variation, resistance variation and seedless variation.

The character of short-shoot form (or compact form) is very important in fruit dwarfing and close planting. Radiation breeding was proved to be an effective method to acquire cultivars of short-shoot form (or compact form). In breeding practice some short-shoot (or compact) mutants were obtained in apple, chestnut and hawthorn through this technique.

Early maturing variation not only can enrich the fruit types but also can extent the supplying time of fruits in the market. By use of the radiation-induced mutation technique, early maturing lines of Hawthorn, chestnut, pear and apple were obtained. Their mature periods were half to one and a half months earlier than their parent materials.

Resistance variation can help enhance the resistance of fruit trees and improve the quality of fruits. Apple cultiva ‘Dongyuanhong ’ is the mutant of ‘Golden Delicious’. ‘Dongyuanhong’ is stronger in overwintering ability than ‘Golden Delicious’ and is resistant to early defoliating and powdery mildew. Using Fast neutron to irradiate dormant bud sticks of chestnut, three fine mutant lines resistant to fruit mildew and rot were obtained.

Induction and selection of seedless variation was concentrated on orange. So far some few-seeded or seedless orange cultivars or lines have been obtained by radiation-induced mutation technique. In order to reveal the causes of few seeds or no seed, meiosis of chromosome was studied. It showed that chromosome translocation and inversion caused by radiation were the basic reasons of few seeds or no seed in fruits.

In addition, skin color variation and store-tolerance variation of apple, and large-fruit variation of hawthorn were also found in the radiation-induced mutants.

2.2 Ornamental plants
Radiation breeding of ornamental plants in China started in 1980's. After almost 20 years' development, 67 new mutant cultivars have been developed and approved in 6 ornamental species by 2000. The new cultivars focused on rose and chrysanthemum, counting 35 and 21 cultivars respectively. Others are 4 cultivars of canna, 3 of lotus, 2 of bougainvillea and 2 of dahlia. The purpose of radiation breeding of ornamental plants was mainly to enhance the ornamental characters, such as flower color, flower type, flower size, petal type, petal number and plant form, etc.. Mutant cultivar ‘Ziyuntuoyue’ of chrysanthemum is a good example of flower color change by mutation induction technique. It was developed by Institute of Isotopes, Henan Academy of Sciences in 1991. 25Gy of Y-rays was used to irradiate the plant of parent cultivar ‘Shuangmantian’ whose color was pure white. Variations in flower color, flower type and petal type were found in the mutant cultivar, especially the flower color changed from white to purple. Besides the ornamental characters, the useful mutations in flowering time and stress-resistance were paid attention to at the same time.
3. Advances in techniques in radiation breeding of fruit trees and ornamental plants
Decades of research and practice showed that choosing proper materials to be irradiated, determining the radiation dose and separating the mutations were three basic technical links in radiation breeding of fruit trees and ornamental plants.
3.1. Plant materials used in radiation breeding
According to breeding targets, three principles were followed to choose the plant materials in radiation breeding: (1) chose materials with comprehensive good characters and only one or two defects; (2) chose materials with high genetic heterozygosity; (3) chose materials having genotypes which were easy to induce gene mutations. Only by doing so, mutant characters could be seen more easily and separated more efficiently in later generations.

As for plant organs used in irradiation, it depended on the propagation characteristics of plants. Based on the past work on vegetatively propagated plants in China, bud sticks, pollens, calli and seeds were often used in fruit trees.

Organs used in chrysanthemum radiation breeding were rooted plants, shoots, calli and in vitro plants. Stem sections, 1- or 2-year plants and F1 seeds were used in rose. Organs used in other ornamental species were dormant root-tubers, dormant rhizomas, bulbs, cuttings, potted plants and seeds.

Overall, the most frequently used plant organs in radiation breeding of woody fruit trees and ornamental plants were bud sticks for grafting and cuttings. On the other hand, growing plants and other vegetative organs were used more often in herbaceous plants.

Seeds of some vegetatively propagated plants were used in radiation breeding too. The great advantage of using seeds was that it was very convenient to treat a large amount of seeds at the same time. So it could provide a large population for selection of useful mutants. The disadvantages were that mutations from irradiated seeds were mostly chimeras and the time from sowing to fruiting was long, especially for woody plants. But seeds were still good materials in the combined project of long-term and short-term breeding or in herbaceous plant breeding.

In recent years, tissue-cultured materials, such as in vitro protoplasms, suspended-cultured cells, in vitro calli and explants have been used more and more often in studies of radiation breeding. The advantage of using tissue-cultured materials for radiation was to avoid or restrict the formation of chimera and therefore obtain homogeneous mutants directly. But it had higher demand in in vitro culture techniques, especially the techniques of organ generation, morphogenesis and plant regeneration under in vitro conditions.

3.2 Ray source and radiation dose
In the past decades of radiation breeding practice in China, Y-rays was the most commonly used mutagen to induce mutations in fruit trees and ornamental plants. So far, the released mutant cultivars of fruit trees and ornamental plants were all developed by use of Y-rays radiation. Besides Y-rays, fast neutron, laser, microwave were also used in fruit trees.

Exploiting and trying new radiation sources may play an active role in radiation breeding of fruit trees and ornamental plants. Research showed that the mutation frequency of ion radiation was between 6.8-12.0%, higher than that of Y-rays. Ion radiation could also induce several mutations to occur at the same time. Institute for Application of Atomic Energy of CAAS treated seeds of Echinacea purpurea by different doses of 7Li3+ ion beam, various variations in flowers were found in M1 generation, including the petal color, petal shape, petal number and flower size.

Radiation dose affected the mutation frequency directly. Because vegetative organs were the materials that usually used in the radiation breeding of vegetatively propagated plants, so the radiation dose that vegetatively propagated plants could tolerate was much lower than the dose seeds could tolerate. The dose of the former was only about 1/10 of the later. To determine the appropriate radiation dose, the plant species, cultivar, the developing phase and physiological status of organs and materials, and environment conditions should be taken into account. Usually LD50 was considered to be an index when deciding the radiation dose in seed propagated plants. But in radiation breeding of vegetatively propagated plants, medium radiation dose that made 60-70% plants survive (i.e. LD30-40) was proper.

3.3 Separation and selection of mutants
Mutations induced by radiation in fruit trees and ornamental plants were mostly chimeras. Making the mutations appear, separating and selecting useful mutations were the most important measures in radiation breeding. Effective methods to make mutants express on individual plant level were adventitious bud techniques, continuous pruning, grafting and cutting techniques and in vitro culture techniques. Stable mutants were usually not able to acquire until after several generations. Using in vitro culture techniques in the procedure of mutation breeding to help separate somatic mutation could effectively avoid the formation of chimera and diploid selection. It opened up a vast range of prospects for speeding up the process of mutation breeding.

In addition, some morphological and biochemical indexes could help identify and select mutations in early stage. Tang (1993) found that in the process of developing new lines of seedless ‘Hongjiangcheng’ orange, the deformity of the young plants could help separate and select mutants. Chen (1992) found that compared with the control, all the seedless mutant strains of citrus lacked one band on peroxidase zymogram in leaves. According to this, the number of the bands on peroxidase zymogram was suggested as a biochemical index to early identification and selection of mutants. With the development of molecular biology, people will be able to conduct early identification of mutants on molecular level.

4. Conclusions and Prospects
Crop mutation breeding was first conducted in China in 1960’s. According to the FAO/IAEA Database, China has developed 605 mutant cultivars of all kinds of crops by 2000, making up 26.8% of 2252 mutant cultivars developed all over the world. But among the 605 mutant cultivars, only 78 are fruit trees and ornamental plants, accounting for less than 13%. And also, species of fruit trees and ornamental plants involved in the radiation breeding were concentrated on just a few ones. So there leaves a great potential in using mutation induction techniques to improve fruit trees and ornamental plants in China.

In regard to the development of mutation induction techniques, it is worth exploiting and trying new mutagens in radiation breeding. Meanwhile, to enhance the efficiency of mutation breeding, combination use of mutation induction techniques and other techniques is a way full of good prospects. Combination of mutation breeding and cross breeding is still a wide used and very effective way to develop new cultivars. The theoretical bases of conventional cross breeding and mutation breeding are gene recombination and gene mutation respectively. So cross breeding has strong foresight while mutation breeding has great random, but the latter can create new materials and new germplasm. So the both methods can play a supporting role to each other, therefore to get better results in breeding. There have been quite a few successful examples in developing rose mutant cultivars by irradiating F1 seeds.

Combination of mutation induction techniques and biotechnologies, especially in vitro culture techniques has become more and more popular. Applying in vitro culture system to mutation breeding process has many advantages in material treatment, mutant separation, selection and stabilization, rapid propagation of good mutant cultivars or mutant lines, etc.. With the improving of both in vitro culture techniques and mutation induction techniques, the breeding method combining the two will open up a new way for improvement of fruit trees and ornamental plants.


Chen, S.C., et al. 1992. Studies on Genetics and Isozyme of Radiation-induced Seedless Lines of Orange. Acta Horticulturae Sinica. 19(2): 105-110. (In Chinese with English Abstract)
Feng, Y.L., et al. 1993. Studies on Radiation Breeding of Apple. J. Nucl. Agric. Sci. 14(2): 51-55. (In Chinese)
Guo, A.X., B.A. Yang, J.L. Fan, et al. 1991. Selection of Six Chrysanthemum Cultivars including ‘Jinguangsishe’ by Radiation-induced Mutation Technique. J. Nucl. Agric. Sci. 12(2): 73-75. (In Chinese)
Guo, A.X., J.L. Fan, B.A. Yang, et al. 1997. Study on the Technique of Inducing Mutation Breeding in Chrysanthemum. Acta Agriculturae Nucleatae Sinica. 11(2): 65-73. (In Chinese with English Abstract)
Huang, S.W., and Y.F. Chen. 1985. Studies on Mutation Breeding in Rose Cultivars. Application of Atomic Energy in Agriculture. (Suppl.): 176-177. (In Chinese with English Abstract)
Li Yazhi. 1996. Induction and Selection of Mutations in Vegetatively Propagated Plants. In: Xu, G.R. (Ed.). 1996. Plant Mutation Breeding. Beijing: China Agricultural Press. P.310-368. (In Chinese)
Li, Z.Y., L.T. Song, and Q.X. Jiang. 1990. Preliminary Report on Mutations Induced by 60Co Y-rays of Korean Pear (Pyrus communis). J. Nucl. Agric. Sci. 11(4): 168-170. (In Chinese)
Liu, J.H., C.G. Hu, and X.X. Deng. 1999. Advances of Studies on Radiation Breeding of Fruit Trees in China. China Fruits. (4): 48-50. (In Chinese)
Liu, Q.L., and J.Y. Chen. 1998. Inheritance and Improvement of Flower Traits in Ornamental Plants A Literature Review. Acta Horticulturae Sinica. 25(1): 81-86. (In Chinese with English Abstract)
Maluszynski, M., K. Nichterlein, L. Van Zanten, and B.S. Ahloowalia. 2000. Officially Released Mutant Varieties The FAO/IAEA Database. Mutation Breeding Review. 12: 1-12
Niu, C.T., and Y.Z. Li, 1988. The Radiation Induced Mutation of Canna (Canna, L.). Acta Agriculturae Nucleatae Sinica. 2(1): 33-39. (In Chinese with English Abstract)
Qi, M.W., and H.G. Wang. 1997. Advances and Analyses of Flower Radiation Breeding in China. J. Nucl. Agric. Sci. 18(6): 288-290. (In Chinese)
Tang, X.L, et al. 1993. Develop New Lines of Seedless ‘Hongjiangcheng’ Orange by Repetitive Radiation. China Orange. 22(4): 18-19.
Wang, C.Q., F. Liu, and Y.Z. Li, 2000. Advances in Induced Mutation Breeding for Fruit Plant. Acta Agriculturae Nucleatae Sinica. 14(1): 61-64. (In Chinese with English Abstract)

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