| Tomato is an important horticultural crop.How to accelerate the breeding of tomato varieties with high yield and high resistance has been an important research direction of tomato breeding.Assuming that one generation is planted per year,it generally takes 6-8 years to cultivate new varieties by conventional methods.In order to improve the breeding efficiency and shorten the breeding cycle,immature embryos can be cultured in vitro through embryo rescue technology,thus accelerating the process of breeding.Peru tomato(Lycopersicon peruvianum)has a distant relationship with cultivated tomato(Lycopersicon esculentum Mill)and is considered to be the largest repository of genetic diversity of tomatoes.However,there are the hybrid incompatibility between Peru tomato and cultivated tomato,and embryo rescue technology could effectively overcome the barrier of distant hybridization,thereby introduce the excellent traits of Peru tomato into cultivated tomato.The purpose is to study the effects of embryo age,genotype,medium and phytohormone concentrante on zygote embryo germination,and to explore their effects on the shortening of tomato breeding time,to establish an in vitro culture method of immature embryos for rapid generation advancement(RGA)of tomatoes.The results showed that the embryo age of 7 DAP could not germinate in the heterotrophic stage,and the minimum embryo age that could germinate was 14 DAP with a germination rate of 34%.From 14 DAP to 30 DAP,the germination rate of immature embryo kept increasing,and the germination rate of 30-35 DAP reached a stable rate of about 70%.The genotype effect had little effect on the germination rate of young embryo,and the germination rate of tomato with different genotypes ranged from 45%to 53%,indicating that in vitro culture of immature embryo was universal to cultivated tomato.When 0.2mg/L IAA+0.6mg/L ZT+0.5mg/L GA3 was added to MS medium,the germination rate of immature embryo was the highest,reaching 54.8%.It usually takes about 75 days for normal flowering and pollination to harvest mature seeds for further sowing.However,in vitro culture of immature embryos after 15 days of pollination can shorten the breeding cycle by 60 days,so as to calculate the breeding cycle of 6 generations a year,so as to significantly improve the breeding efficiency.Therefore,the immature embryo in vitro culture method established in this study can significantly accelerate the process of tomato breeding and provide a reliable new method for the rapid generation renewal of tomato.In the hybridization between cultivated tomato and Peruvian tomato,this study observed that the pollen tube could extend to the ovary normally after 24 hours of pollination,but the seeds in the mature fruit were dried and without embryos,indicating that the incompatibility of distant hybridization was probably caused by the abortion of hybrid embryos during development.In order to overcome the barrier of distant hybridization,in vitro culture of hybrid embryos was conducted by using embryo rescue technique,and the effects of embryo age and hormone formula on the success rate of embryo rescue were explored.The test results show that:Early embryos of internal differentiation is not entirely germination ability,the late embryonic development happens abortive,finally this study use 30 DAP young embryo in add 0.1 mg/L IAA+0.5 mg/L ZT+0.5 mg/L GA3 on the MS culture medium of a successful interspecific hybridization seedlings,and combination of markers to verify the heterozygosity of the hybrid plants.In summary,the embryo rescue technique established in this study,as an auxiliary breeding method,can not only accelerate the seedling formation of seeds,but also overcome the incompatibility of distant hybridization,providing a reliable new method for the expansion and utilization of tomato germplasm resources. |
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