Analysis Of Genetic Diversity And Heterosis Of Parents For RGMS In Brassica Napus

The recessive genic male sterility (RGMS) is one of the main ways of rapeseed heterosis utilization. It has plenty of superiority that are wide recovery source, easy to option high yield combinations, sterility genes easily transform, and sterility stable. Due to sterility gene mainly derived from the S45A and117A, we had adopted some method that hybridization-backcross-offspring separation to transfer sterility gene into good rapeseed varieties. For these reasons, analogous genetic background and small genetic differences existed between new RGMS and some restorer lines. In cross breeding, parents should have excellent complementary traits and higher combining ability, and certain genetic differences. The greater of genetic differences two parents have, the farther genetic relationship will be, and meaning that we can easily compound strong advantages hybrid. Therefore we fully understand the genetic differences between materials and dividing them into different genetic groups. This will help to guiding super hybrid crosses so as to quickly and efficiently utilization of heterosis.This thesis researched kinship and genetic differences between the RGMS lines and the restorer lines in Brassica napus by used SSR markers. Then analyzed combining ability and heterosis performance of15parents including six RGMS lines and nine restorer lines, and genetic distance of the parents was estimated. At last the author discussed the relationship between genetic distance and heterosis of hybrid.1. Genetic diversity analysis of parents for RGMS (Brassica napus L.) Based on SSR markersThe75pairs of SSR primers were used to analyze the genetic diversity of96materials including37RGMS lines and59restorer lines. The62polymorphism primers were selected which accounting for82.6%, and51primer pairs had been targeted to the19linkage groups of Brassica napus. These primers had detected313amplified bands. There had177polymorphism and the rate was56.5%. Each pair of primers got1to6 polymorphic bands and the average was2.9%. All lines of genetic similarity coefficient were ranged from0.57to0.93. We set0.62as the threshold and all of the materials were divided into7groups.35RGMS lines were classified into Group II-III except2365AB and2149AB which genetic background from the European winter oilseed rape. The restorer lines were distributed into all Groups except Group III. The genetic differences of the restorer lines were better than the RGMS lines, and genetic background of the restorer lines were wider. Although the RGMS lines of genetic differences were not as well as the restorer lines,14RGMS lines were found which the genetic distance were more than0.70. These results will help to cross breeding.2. GGE biplot analysis of incomplete diallel crossThis paper reports analysised combining ability of6X9incomplete diallel cross using GGE biplot. The GCA of six RGMS lines in descending was2127AB,98-116AB,2095AB,2225AB,2081AB and2133AB. The GCA of nine restore lines in descending was ZW004, ZY119, ZW3115,6-18C, DJ, DY18, HTY, CHY20and Y9. The hybrid crosses with high SCA included98-116A×DY18,98-116A×ZY119,2127A×6-18C,2095A×ZW3115,2225A×ZW004and2133A×ZW004.Among traits of the RGMS lines, the GCA of primary branches and seeds per pod were positively correlated with the GCA of yield, and the other traits were negatively correlated. Among trait of the restorer lines, the GCA of length of main raceme,1000-seed weight, pods per plant, seeds per pod and plant height were positively correlated with the GCA of yield, whereas branch height was negatively correlated.3. The mid-parent heterosis and high parent heterosis analysis of hybrid crossesThe results showed that pods of main raceme of54hybrid crosses had the highest MPH which ranged from -0.97% to56.89% with average value of23.86%, and the MPH of28crosses were more than20%. The second was the yield traits which ranged from-6.77% to48.25% with average value of23.11%, and the MPH of34crosses were more than20%. The third was seeds per pod which ranged from-12.32% to34.91%with average value of13.03%, and MPH of seven crosses were more than20%. The HPH of yield traits was the maximum which ranged from-12.91% to45.19% with average value of15.48%. The next was pods of main raceme which ranged from-20.77% to39.02% with average value of9.72%. The third was seeds per pod which ranged from-18.49% to31.75% with average value of6.4%. The pods per plant had the lowest HPH. These results showed that yield heterosis of Brassica napus were mainly determined by the pods of main raceme and seeds per pod in high-density planting conditions.4. The correlation analysis of genetic distance and yield heterosisThe genetic distance between six RGMS lines and nine restorer lines was estimated with SSR markers. The correlation analysis results showed that coefficient between genetic distance of parents and yield heterosis was0.33. The coefficient between genetic distance and MPH of yield trait was0.17. whereas coefficient between genetic distance and HPH of yield trait was0.08. These coefficients were not significant at0.05levels. This explained that SSR marker could not accurately predict yield heterosis of hybrid in Brassica napus.