Study On Intergeneric Hybrid F₁ And BC₁ Between Triticum Aestivum And Roegneria Kamoji

Fusarium head blight(FHB),caused by Fusarium graminearum,has become one of the most serious diseases of wheat in humid areas.However,the problems such as only limited resources of high resistance to scab in common wheat,narrow genetic background and complex inheritance of FHB resistance hinder development of cultivars highly resistance to FHB in common wheat.Therefore,there is an urgent need to exploit novel resources of FHB resistance and introduce them into common wheat.Roegneria kamoji has been a demand for resistance breeding because of its high resistance to FHB.In order to transfer FHB resistance from Roegneria kamoji to common wheat,the cross of wheat with Roegneria kamoji was done in 2006,and the reciprocal intergeneric hybrids between Roegneria kamoji and wheat were successfully obtained by means of embryo culture,which was proved by the morphology and molecular cytogenetics study.It was found that the seed set in R.kamoji×T.aestivum cv.Chinese Spring was higher than that in T.aestivum cv.Chinese Spring×R.kamoji.To find out the reasons,the pollen grain germination and pollen tube growth were investigated in both cross combination.The results indicated that the abnormality of pollen germination and pollen tube growth, fertilization postponed in T.aestivum cv.Chinese Spring×R.kamoji might be the reasons of the phenomenon.The chromosome configuration of(R.kamoji×T.aestivum cv.Chinese Spring) F₁ and(T.aestivum cv.Chinese Spring×R.kamoji) F₁ was 40.40â… +0.79â…¡and 40.33â… +0.78â…¡+0.03â…¢,respectively,indicating very low homology between Roegneria kamoji and common wheat.Because of remote relationship between the parental species, the hybrid F₁ showed complete male sterility.Seeds of BC₁ could be obtained by backcrossing with Chinese Spring pollens.The somatic chromosome numbers of(R.kamoji×T.aestivum cv.Chinese Spring) F₁×T.aestivum cv.Chinese Spring BC₁ plants ranged from 55 to 63,and many univalents were observed at metaphase I of pollen mother cells after FISH.It resulted in the sterility of BC₁ plants;similarly,the chromosome numbers of (T.aestivum cv.Chinese Spring×R.kamoji) F₁×T.aestivum cv.Chinese Spring BC₁ plants also ranged from 55 to 63,however,many bivalents of PMC at MI and fertile pollens could be observed that caused partial fruitfulness in some BC₁ plants by self-crossing.All hybrid F₁ and BC₁ plants in reciprocal crosses between common wheat and R.kamoji showed high resistance to F.graminearum.In order to understand the difference between the resistant and susceptible materials during the infection,Chinese Spring, Roegneria kamoji and BC₁ were inoculated by the conidiospore of F.graminearum carring GFP gene and the process infected spikes were observed.It was found that all of the three materials could be infected,while there were differences in some aspects such as the speed of infection and whether the mycelium could enter into the rachis node.It was interested in that a plant(2n=63) with 42 wheat chromosomes and 21 R.kamoji chromosomes was obtained in the hybrid F₁ of R.kamoji×T.aestivum cv.Chinese Spring. The chromosome configuration of this plant at MI of PMC was 26.4â… +18.3â…¡.Because of many univalents existence,the hybrid plant showed complete male sterility,and BC₁ could be obtained by back-crossing with Chinese Spring pollens.The chromosome numbers of BC₁ ranged from 40 to 59,in which there were less alien chromosomes.Although the morphology of the spike in BC₁ was similar to that of Chinese Spring,these plants in BC₁ were still sterile.This hybrid F₁(2n=63) and most of its BC₁ plants showed high resistance to F.graminearum.