Primary Study On Matroclinal Inheritance Phenomenon And Mechanism Of The Intergeneric Hybrids Between Litchi And Longan

Longan(Dimocarpus longana Lour.)and Litchi(Litchi chinensis Sonn.)are both important fruit trees in south tropical Asian.They belong to Dimocarpus Genus and Litchi Genus respectively of Sapindaceae family.In this study,‘Shixia' longan,‘Ziniangxi' litchi and their reciprocal-crossing hybrid populations were used as materials.Through observing the phenotypic characteristics and the number of chromosomes,analyzing the genome in situ hybridization and the difference of gene expression,the matroclinal inheritance characteristics of intergeneric hybrids of the longan and litchi were analyzed from various levels.The main results were list as follows: 1.According to the phenotypic characteristics observation found that the pseudo-qualitative characteristics of leaves,flowers and fruits in the ‘SZ' population showed matroclinal inheritance.The pseudo-qualitative characteristics of leaves showed patroclinal inheritance and of flowers and fruits showed matroclinal inheritance in the ‘ZS' population.2.Hybrid index(HI)analysis of quantitative characteristics resulted,the average HI of leaves,flowers and fruits quantitative characteristics of ‘SZ' population were-7.20,0.29 and-1.19,respectively.The average HI of leaves,flowers and fruits of ‘ZS' population were 70.65,36.54 and 29.24,respectively.Cluster analysis revealed that ‘SX',‘SZ' population and ‘ZS' population were clustered into one group firstly;‘SZ' and ‘ZS' population were clustered into one group with their respective female parent in the comprehensive characters of flowers and fruits.The hybrid index and cluster analysis consistently showed that: the ‘SZ' population showed matroclinal inheritance and the ‘ZS' population showed paternal inheritance in the leaf characters;the ‘SZ' population and ‘ZS' population all showed matroclinal inheritance in the flowers and fruits characters.3.Through optimization different conditions of pretreatment,enzymes and their concentration,enzymatic time improved method of chromosome making of longan and litchi.The materials were pretreated at room temperature for 3h with 0.2mM 8-hydroxyquinoline solution.The best treatment of leaves were disposing 3~3.5h in mixed liquor of cellulose(5%): pectinase(5%)= 10:1,root tip and shoot tip were disposing 3~3.5h in mixed liquor of cellulose(6%): pectinase(0.6%)= 1:1.Highly dispersed and clearly distinguishable chromosomes were obtained from root tips,shoot tips and young leaves.4.Through optimization probe preparation,proteinase K treatment time,denaturation temperature and time,probe concentration,establishment of GISH system of longan and litchi.Chromosome pretreatment: incubation 10 min with 0.01% proteinase K at 37?.The hybridization mixture consisted of 5ng/?l probe in 20?l system.The mixture was denatured for 10 min in metal bath at 95? and chilled on ice for 10 min.Chromosomal DNA on the slide was denatured at 80? for 3min in the 70% deionized formamide solution.5.The chromosome numbers of the 20 interspecific hybrids between longan and litchi were 30(2n=2x=30),which were consistent with their parents'.There have not missing or increase or double chromosome numbers in the intergeneric hybrids.The GISH results showed that paternal DNA probes were observed only on a few chromosomes of intergeneric hybrids.It is speculated that the hybrids may not be inherited into the whole paternal chromosome.Instead,it was infiltrated and integrated into the maternal chromosome in the form of DNA fragments,resulting in the phenomenon of maternal inheritance.The results confirmed the authenticity of interspecific hybrids at the cytological level for the first time,which was more convincing than morphological and molecular markers.6.Transcriptome analysis of reciprocally-crossed intergeneric hybrids and their parents showed that the gene expression level of hybrids was more similar to the female parent.According to the double standard of expression quantity and hybrids index,87.57% of the genes screened out were of maternal inheritance.These genes were mainly involved in the interaction of plant pathogen interaction,starch and sucrose metabolism,plant hormone signal transduction,glycolysis,terpenoid backbone biosynthesis,flavonoid biosynthesis,carbon metabolism and other metabolic pathways,indicating that matroclinal hereditary genes were spread across multiple gene networks.7.Fruit characters were very important and the maternal inheritance was the most serious.The results of transcriptional analysis showed that there were many key genes in the pathway of flavonoid biosynthesis,terpenoid biosynthesis and plant hormone signal transduction.It is speculated that because the expression of genes related to the pericarp color and the fruit size showed matroclinal inheritance,it might be results in matroclinal inheritance of fruit phenotype in the intergeneric hybrids.