Analysis Of The Genetic Traits Of F1 Hybrids Between Pomelo And Poncirus Trifoliate And Identification Of Their Cold Resistance Property

There are abundant local characteristic pomelo cultivars in China,such as ‘shatian pomelo’ and ‘Guanxi Mi You’ pomelo.These varieties are mainly bred with Trifoliate orange,lime and tangerine as rootstocks.However,these rootstocks have some defects,such as the poor grafting compatibility between pomelo and citrus stock,which affects the performance of comprehensive characters of pomelo.The lime anvil is not resistant to low temperature and susceptible to decline;The common ‘Trifoliate orange’ is a hybrid of sweet orange and pomelo,and the hybrid of grapefruit and immature orange is not compatible with pomelo.Because of pomelo is mainly characterized by arborization,so many measures should be taken to control plant height in production and dwarf rootstock is one of the most effective methods.At present,the citrus stock widely used has not only the obvious dwarf characteristic,but also the cold resistance,drought resistance,anti-fading disease,multiple embryo and so on,which is the ideal citrus stock germplasm.Therefore,the germplasm of citrus stock with traits such as dwarf,cold resistance,drought resistance,decline resistance and good affinity of grafting can be obtained by hybridization between citrus and pomelo,which provides an effective way to solve the problems in pomelo breeding at present.In this study,single embryo ‘shatian pomelo’ was used as the female parent and immature‘Trifoliate orange’ was used as the male parent.70 hybrid fruits were obtained by cross pollination.Through the quality analysis of hybrid fruits,genetic analysis of biological traits of hybrid plants,and evaluation and analysis of cold resistance and other traits,the following main research results were obtained:1.Hybrid fruits and hybrid seeds had obvious differences with their parents.There were significant differences in the fruit weight,transverse diameter,longitudinal diameter,Vc content and parents between ‘shatian pomelo’ and hybrid fruit of ‘Trifoliate orange’.The fruit weight,transverse diameter length and longitudinal diameter of hybrid fruit were significantly higher than those of Poncirus Trifoliate but significantly lower than those of shatian pomelo,and the Vc content was significantly lower than that of ‘shatian pomelo’The seed abortion rate of single fruit of hybrid fruit was(28.4%),which was significantly lower than that of ‘shatian pomelo’(41.12%).The germination rate is lower than that of parer.2.The hybrid traits of the same hybrid fruit were different.Among the 70 fruits obtained in this study,32 of the fruit-bred plant populations showed triple compound leaves throughout the growth and development period.The 19 fruit breeding groups showed single compound leaves in the seedling stage,but after 4 months of growth and development,4 plants with secondary compound leaves or tertiary compound leaves appeared in each fruit breeding group on average.The leaves of the 19 fruit breeding groups were similar to those of the parent ‘shatian pomelo’,and were always single compound leaves.Using molecular marker technology to a single hybrid blades are all present single compound leaf,fruit,and a single fruit all hybrids in addition to the late seedling stage blades for single compound grow two or three groups of compound identification.the results showed that as long as the same hybrid fruit seed breeding of hybrid population containing one or more hybrid rendering leaf traits of male parent,we can confirmthe fruit of seed breeding groups are based on hybrid seedlings.3.Genetic separation was observed between the biological characters of ‘shatian pomelo’ and the F1 hybrid.In the hybrid population,there were some genetic variations in the leaves,such as two-leafed compound leaf,four-leafed compound leaf and five-leafed compound leaf.The plants with two-leaf or more compound leaf accounted for 46%,and the plants with single leaf accounted for 54%.Of hybrid seedlings complete leaf wings leaf length,leaf wings width,leaf length,leaf width and the degree of plant height,stem thick,long thorn traits,such as separation,the dwarf mutant plant height,branch number show less variation,morphological properties such as petiole,leaf wings width,leaf length are small variations,however,long thorn,leaf length and leaf width are light,the trunk roughness and first thorn ate a large variation.4.There was a significant difference in cold resistance between ‘shatian pomelo’ and hybrid ‘Trifoliate orange’ seedlings,and there was a correlation between cold resistance and biological characters.The results showed that the electrical conductivity of 165 hybrids was significantly higher than that of ‘shatian pomelo’,accounting for 91% of the total 181 hybrids.The electric conductivity of 12 hybrids was lower than that of Faust,indicating that the cold resistance might be stronger than that of Faust.The electrical conductivity of 4hybrids was higher than that of ‘shatian pomelo’,indicating that they were sensitive to low temperature.The results showed that the cold resistance of hybrid seedlings was negatively correlated with plant height and positively correlated with stem diameter,total root length and average root diameter,but there was no significant correlation between them.Cold resistance was positively correlated with total root tip number and total root volume and positively correlated with total root surface area.