Creation And Identification Of Citrus New Germplasm

Polyembryony is a pervasive phenomenon in most citrus cultivars. Compared with nucellar, zygotic embryo is in the dry tree in the competition, resulting in serious degradation or abortion of zygotic embryos in hybrid breeding, which was a big obstacle for sexual hybridization. This led to the proportion of citrus varieties selected by cross breeding registered in recent decades less than 4.2%. Therefore, it was an effective way for citrus hybrid seedlings cultivation and of great practical significance to explore efficient separation technique of zygotic embryos, including isolating and culturing the zygotic embryo before they degenerated, overcoming the interference of nucellar and saving the zygotic embryos before abortion, in order to get mixed seeds and increase hybrid rate.The result of this study by embryo rescue are as follows:1. Creating new germplasm by hybrid:Statistics of fruit set indicated that the cross of W.murcott×Early Gold showed the highest fruit set and greater seeds. The reciprocal crosses of diploid Delta Valencia Orange×tetraploid Valencia Orange discovered that the cross tetraploid Valencia Orange×diploid Delta Valencia Orange showed higher fruit setting rate than that of diploid Delta Valencia Orange×tetraploid Valencia Orange. Fruit set of each crosses from high to low were:W.murcott×early gold, diploid Delta Valencia Orange×tetraploid Valencia Orange, early gold×grapefruit, Cara Cara×early gold.Statistics of transplanting found that there were 1218 plants after transplantation, the number of each crosses were as follows:early payment×grapefruit hybrids were 60; W.murcott×early gold crosses were 829; Cara Cara navel orange×early gold crosses were 2; diploid Delta Valencia Orange×tetraploid Valencia Orange hybrids were 136; Shatian pummelo×Early Gold crosses were 116; HB×Early Gold were 75. Statistics transplant survival rate of some crosses we discovered that Early Gold×grapefruit was 61.22%, W.murcott×Early Gold was 79.86%, Cara Cara navel orange×early gold crosses was 100%; diploid Delta Valencia Orange xtetraploid Valencia Orange hybrids was 88.89%.Analyses of crosses between diploid and tetraploid by flow cytometry, we discovered that there are one triploid and two tetraploid and 133 diploid plants in total 136 plant.2. Preliminary observation of early abortion embryos for offspring: In order to study the best time for embryo rescue, the experiment used the cross of W.murcott×tetraploid Paper rind as the research material, using the method of paraffin section, to observe the development of embryo in anatomy.By this method, we inferred that 70 days after pollination was the best time to isolate zygotic embryo to culture for individual, and found:the cross of W. Murcott as female parent and tetraploid Paper Rind as the male parent,45 days after pollination was not found zygote.50 days after pollination the fertilized egg continued cell division.60 days after pollination, the zygoric embryo became globose-shaped.70 days after pollination, the zygoric embryo was in globose-shaped state. This was the best time to isolate zygotic embryo and culture for individua1.75 days after pollination, in addition to zygotic embryo, there were a large number of nucellar embryos in embryo sac.80 days after pollination, the number of nucellar embryo jumped, the number of nucellar embryo was up to more than 10 and had been unable to distinguish zygotic embryos.