Researches On Radiation Breeding Of Korla Fragrant Pear And Variety Characteristics Of Its Bud Sport Sha01

This research applied radiation breeding selection and bud mutation to explore new germplasm resources of Korla Fragrant Pear. On one hand, the research applied radiation mutation test which set different dose groups to irradiate its one-year old dormant branches and chasteness branches, studying the mutagenic effects of radiation on phenotypic expression; on the other hand, the research made multi-angle comparative identification from the point of morphology, fruit quality, cytology, tissue anatomy, palynology and so on to study the variation source of its new bud mutation sha01. The research The main conclusions are as follows:1. Branches of Korla Fragrant Pear were quite sensitive to irradiation, low dosage radiation could promote grafting survival rate, shoot growth, while high dosage radiation exhibited inhibitory effects. The research presented that half lethal dose of dormant branches was100Gy, but practice proved that irradiation dose that was adaptable for dormant branches ranged from30Gy to50Gy, and irradiation dose that was adaptable for chasteness branches ranged from20Gy to40Gy.2. Irradiation inhibited germination stage and leaf opening stage of new branches, the phenological period of two type branches with same dosage treatment were basically consistent. Variation types of branch morphology mainly displayed crossed branches, platyclade and stanza shorten branches, leaves mainly took on incised leaves, wave leaf margin and linear leaves. Besides, phyllotaxis changed from opposite phyllotaxis to alternate phyllotaxis or whorled phyllotaxis.3. Compared to dormant branches, chasteness branches were more sensitive to irradiation.20Gy treatment could stimulate the growth of shoot length and diameter, dosage higher than30Gy could lead to obvious dwarfing effect;30Gy and40Gy treatment of dormant branches were easily to occur big leaves of which40Gy was the transition dosage,50Gy and60Gy treatment of dormant branches and40Gy treatment of chasteness branches were more inclined to form linear leaves.4. Irradiation affected leaf tissue structure of two type branches at different degrees and differences among those treatments were significant. Variation trends of the thickness of palisade tissue and spongy tissue were contrary between two type branches, but they all reached extreme values at20Gy.5. Irradiation had no significant effects on chlorophyll indices except that chlorophyll a/b of dormant branches changed greatly. Photosynthetic characteristics of chasteness branches were all inferior to CK, of which adaptability for light intensity of40Gy treatment was relatively weak;20Gy treatment of dormant branches had better adaptability for light intensity while30Gy treatment had poor adaptability.6. Tree characteristics, growth and fruit characteristics of Sha01were superior to that of Korla Fragrant Pear. Branches of Sha01tended to become stocky and compact, leaves became narrower and smaller, while corollas and fruits were relatively bigger, especially fruit transverse diameter was significantly overstriking; Fruit setting ratio of inflorescence and flower were higher; fruit maturation period was25days earlier than Korla Fragrant Pear. However, Sha01was easy to run water sprouts, which had negative effects on nutrient uptake and light distribution, besides, its cold resistance and disease resistance awaited to be improved.7. Sha01was excellent in integrated economic characters with bigger single fruit, uniform fruit shape, higher calyx dropping rate and edible rate, abundant water and Vc content, less stone cells, richer juice and crisper pulp; simultaneously, shortcomings such as bigger fruit dots and zonal aula on peel influenced its external finish, and sweetness deficiency also went against the taste, which could be improved by integrating fertilizer and water and enhancing training and pruning.8. The size, shape and exine ornamentation of the pollen from Sha01all had occurred variation. Owing to remarkable overstriking of equatorial axis, its pollens were more inclined to be ovoid and few took on irregular shape, while pollens of Korla Fragrant Pear were all long-bulboid types, simultaneously, polar view of pollens of Sha01occurred four colporated types, and pollens of Korla Fragrant Pear were three colporated types. Pole diameter, pole frequency, ridge width and ridge distance of Sha01had significant differences with that of Korla Fragrant Pear. According to the theory of histogenesis layers, the second layer of histogenic layer had occurred variation. Pollen viability of Sha01was low in initial stage of cultivating, then gradually increased, finally, it had no significant difference with Korla Fragrant Pear.9. The composition of leaf structure of Sha01was similar to Korla Fragrant Pear, but there were differences in specific indices. The thickness of upper and lower epidermis were both lower than Korla Fragrant Pear, while the thickness of palisade tissue, spongy tissue and leaf thickness were all higher than Korla Fragrant Pear, especially the indices of CTR and P/S of Sha01were superior to that of Korla Fragrant Pear, and palisade tissue occurred the variation types which had three layers. The result also proved that the second layer of histogenic layer had occurred variation. Simultaneously, leaf stomatal became smaller and stomatal density became larger, indicating that the first layer of histogenic layer had occurred variation.10. Chromosome doubling of Sha01led to the essential variation of genetic material, and further caused the variation of phenotype, from which we can conclude the third layer of histogenic layer had occurred variation.11. Chlorophyll content of Sha01was significantly higher than that of Korla Fragrant Pear, however, there was little difference in photosynthetic rate. From analysis on stomatal conductance, transpiration rate and water use efficiency, Sha01had great advantage on water using and could well adaptable for arid environment.