Chromosomal Behavior Of The Meiosis In F₁ Hybrids Between Saccharum Officinarum And Erianthus Arundinaceus

Erianthus arundinaceus is a closely related genus of sugarcane,which has high ratooning ability,vigor,resistance to barrenness,and resistance to pests and disease,etc.It is an excellent germplasm resource for sugarcane breeding.The utilization of E.arundinaceus is an important approach for the sugarcane germplasm innovation.However,during the development and utilization of E.arundinaceus,the pollen infertility of F1 hindered the progress of hybrid breeding between sugarcane and E.arundinaceus.In this study,conventional cytological observations and GISH were used to study on meiotic behavior of pollen mother cells.Chromosomal behavior of the meiosis in F1 between sugarcane and E.arundinaceus was studied through 45S rDNA-FISH and 5S rDNA-FISH mapping.The main results are as follows:1)Cytological analysis showed that Hainan 92-77,a fertile parent of E.arundinaceus,had normal meiosis.However,abnormalities occurred in the meiotic process of highly male sterile F1 hybrids,In F1 pollen meiosis process,there are a large number of abnormal phenomena such as univalent body,lagging chromosome,chromosome bridge,micronucleus and inequality.The abnormal ratios of YCE 96-40,YCE 96-66,and YCE 9541 were 47.48%,48.11%,and 45.26%,respectively.2)Based on analysis of the genomic in situ hybridization,we found that the lagging chromosomes were mostly from E.arundinaceus in the meiosis of F1 between sugarcane and E.arundinaceus.Furthermore,there were occurred cell segregation and unequal separation in this process.The abnormal meiosis of Fi pollen mother cells in the distant hybridization between sugarcane and E.arundinaceus is one of the reasons for the complete abortion of Fi pollen.The phenomenon of lagging chromosomes and inhomogeneous separation on the Fi chromosome may be due to the distant relationship between sugarcane and E.arundinaceus,and the chromosomes of E.arundinaceus interfere the normal pairing of sugarcane homologous chromosomes.3)The 45S rDNA-FISH of three F1 meristem mitotic metaphase cells showed that there are seven 45S rDNA,four 45S rDNA site on S.officinarum chromosomes,and three 45S rDNA site on E.arundinaceus chromosomes.But only six 45S rDNA sites were found during pollen mother cell meiosis.Four 45S rDNA site were located on S.officinarum chromosomes,and two 45S rDNA site on E.arundinaceus chromosomes.The number and distribution of 5S rDNA in F1 pollen mother cells are the same as those of somatic cells.There are six sites in the 5S rDNA pollen mother cell,four of 5S rDNA sites on S.officinarum chromosomes,tow of 5S rDNA site on E.arundinaceus chromosomes.According to the number of 45S rDNA and 5S rDNA site,it can be clearly seen that chromosome loss and uneven division occurred during the process of F1 meiosis.4)According to cytological and in situ hybridization studies,F1 meiosis behaviors can be divided into 12 kinds of situations.According to the behavior of the metaphase behavior,they are divided into two categories:The first,metaphase division is normal and there are six types.Among them,A is normal meiosis,B～F is the splitting pathway leading to polynuclear or chromosomal loss resulting in pollen sterility;The other,the first meiotic metaphase division is abnormal and chromosomes were found hysteresis,resulting in chromosome loss and separation unequal phenomena make pollen sterility,a total of six types.These 12 types of meiosis can explain the phenomenon in F1 meiosis.