DNA Content Variation Of Calli, Somatic Embryogenesis And Induction Of Autotetraploid In Citrus

Callus conservation is an important way to preserve germ plasm resources of citrus. Its merits are saving resources and avoiding natural disasters, plant diseases and insect pests. But comprehensive genetic variation occurred in citrus callus. So callus needs to be identified to ensure the genetic stability. The squash technique was used in the past, but the technique wastes time and identifies few cells. The use of flow cytometry provides a convenient, fast and precise way to identify genetic stability of callus.Breeding of seedless triploid is the objective of citrus breeders. Hybridization of diploid and tetraploid is an effective way to breed seedless triploid citrus. But no autotetraploid variety occurs in nature. Creating autotetraploid provides bridge materials to breed seedless triploid. The main results were as follows:1. The cell DNA content of thirty-five citrus calli of different genotypes were measured for 3 times by flow cytometry during 4 years. The results showed that the percentages of DNA content variation of citrus calli progressively increased except Page tangelo, Shamouti sweet orange, Russ navel and Cleopatra. The data suggested that 71.4% out of thirty-five citrus calli had increasing polyploids.There existed significant difference in the variation among genotypes.2. A study carried out on the induction of somatic embryogenesis revealed that 9 citrus calli had competence for somatic embryogenesis and 26 did not. Correlation analyses suggested that the effect of DNA content variation on competence for somatic embryogenesis of citrus calli was not significant and the coefficient of correlation was minus 0.1008 (P<0.01) ; The effect of subculture duration on competence for somatic embryogenesis was also not significant. There existed correlation between growth speed and competence for somatic embryogenesis of citrus calli and their coefficient of correlation was minus 0.3683. Heat shock and low temperature had minor influence to competence for somatic embryogenesis. Different carbon source had different influence to citrus calli which had competence for somatic embryogenesis, but different carbon source had little influence on citrus calli which lost competence for somatic embryogenesis.3. Cell cycle analysis can provide reference for studying the physical and chemical mutagenesis and regeneration to Citrus calli. Cell cycle phase distribution percentages of four citrus calli (Anliucheng sweet orange, Changsha mandarin, Microcitrus,...