Obtaining And Identification Interspecific Hybrid Of Oryza Australiensis And Oryza Sativa

Wild rice,as the primitive ancestor of cultivated rice,underwent a long evolutionary process in order to adapt to various ecological conditions and geographical environment.Through long-term survival competition and natural selection,wild rice has accumulated a large number of excellent properties and has an extremely rich genetic diversity.As a natural gene pool,it contains many genes that are not available or have disappeared in cultivated rice.Therefore,it is of great significance to enhance the research and utilization of wild rice in the breeding process and to improve rice yield and quality.Oryza australiensis,which originated in Australia,and Oryza sativa are both diploid and belong to the AA and EE genomes of Oryza,respectively.In this study,by using embryo rescue technology,interspecific hybrid F1 was obtained from the distant hybridization between japonica rice varieties Nipponbare,Haifeng 1,Zhonghua 11 as female parents and Oryza australiensis as male parent.Subsequently,we identified the hybrids of O.sativa and O.australiensis by using the morphological observation,cytological identification,and molecular marker identification.The main results are as follows:1.Interspecific hybridization and immature embryo rescue techniques were applied to obtain interspecific hybrids between japonica rice cultivar Nipponbare,Haifeng 1 and Zhonghua 11 and Oryza australiensis,with the mating ratios of 2.22%,2.07%and 0.89%,respectively.2.The grown habit and some morphological traits between the hybrids F1 and wild rice parent O.australiensis are similar,such as plant height,flag length,flag width,last second leaf length,last second leaf width,panicle type,panicle length,long awned spikelets,grain shattering,sensitivity to photo-period and ability of tillering.Among them,obvious heterosis advantages of hybrid F1 were observed in flag leaf width,last second leaf length and last second leaf width,while the plant height resembles that of Nipponbare and the panicle type tends to like the O.australiensis.3.Based on sequence comparison between indica and japonica,we developped 660 SSR molecular markers.There were 115 polymorphism markers between parents and the frequency of polymorphism was 17.42%.In the genome regions with relatively sparse marker coverage density,we designed 155 specific Indel markers containing 123 polymorphism markers between parents.The frequency of polymorphism was 79.35%.Therein,the polymorphism frequency of specific Indel markers is significantly higher than that of SSR markers.4.Using digoxigenin-labeled genomic DNA from O.australiensis as a probe,GISH analysis of the metaphase chromosomes of hybrid F1 showed that the hybrids were allodiploid and the karyotype was AE.Meanwhile,chromosome GISH analysis of metaphase I in meiosis of hybrid pollen mother cells showed that most chromosomes existed as monovalent forms,and few chromosomes could be paired,which was the main reason of male sterility in hybrids.