Studies On Heterotic Performances And Genetic Characteristics Of Improved-Line Maize Containing Subtropical Blood

It is an important way that can broaden genetic basis and resolve the narrow heredity of Chinese maize by means of foreign germplasms. Tropical subtropical maize germplasm can not be directly used in Chinese north regions because of the sensitive photoperiodicity .Improved-line maize containing subtropical blood( It was called subtropical improved line for short , the same below) had actual utilization value in Chinese breeding because of the dull photoperiodicity . Studies on the genetic characteristics of subtropical improved lines which can broaden genetic basis of temperate maize , structure new heterotic patterns , resolve the back and force situation of Chinese maize breeding and overcome the obstacle of high and super- high yield breeding in order to provide the technique guarantee for the sustainable development of Chinese maize production.The materials include improved-lines maize containing subtropical blood and basic maize inbred lines of the temperate four systems in my study. Three augmented NCⅡ designs and two generation mean analysis designs were adopted in this experiment. Studies on the heterotic performances and genetic characteristics of the important characters in subtropical improved lines , such as yield ,plant height ,growth period ,kernel length,100-grain weight ,etc. The result of my study is as follows:(l)The results of three incomplete diallel cross experiment showed that the grain weight per plant namely ear kernel weight was the highest in heterosis of all characters . The heterosis of three experiments was 106. 8%, 97. 7%, 121.6% respectively.(2) In aspect of combining ability and tester selection of subtropical improved inbred , in these subtropical improved lines , H63, H76, H85 had higher general combining ability in yielding character , other subtropical improved lines had lower GCA . Many subtropical improved lines had higher GCA in ear length and grain number per row of subtropical improved lines .The inbred that coming from Lvdahonggu and Tangsipingtou is the first selection tester in breeding. (3)In aspect of heterotic pattern , we regard subtropical improved inbred line group (It was called subtropical improved group for short, the same below)×Lvdahonggu group, subtropical improved groupXTangsipingtou as two heteroticpatterns. In breeding it is even more practicality and according with thebreeding fact.(4)In aspect of genetic relationships , according to the result of three groupincomplete dial lei cross experiment and former studies and breeding practicethat we judged the subtropical improved group has far genetic relationships withLvdahonggu group and Tangsipingtou group.(5) In aspect of utilization and breeding inbred line , we advise using subtropicalimproved lines to improve inbred lines of Reid and Lancaster groups then crossingwith inbred lines of Lvdahonggu or Tangsipingtou group . It did had very highvalue in maize breeding.(6)In aspect of heritability , the results of three incomplete diallel crossexperiment showed that the narrow heritabilitiy of ear row number were over70%, and the narrow heritabilities of plant height ,ear height ,earwidth, 100-grain weight were over 50%, Which indicated that it was feasible onselection in the earlier generations . The narrow heritabilities of ear kernelweight and ear length were higher in two experiment but lower in another , whichindicated that it can not be select in the earlier generations . The narrowheritabilities of seeding ratio and kernel length were lower , so we should selectthem in late generation.(7)Results of tested genetic model:The results of three augmented NCII design and two generation mean analysis experiment showed : The heredity of ear-kernel weight and 100-grain weight conformed to additive-dominance-epistatic genetic model. Additive effects was negative, and many dominance effects was positive for heredity of ear-kernel weight. The 100-grain weight was mainly controlled by additive and epistatic gene effects ,but the additive effect was predominant . The ear length was controlled by additive effect , which the additive effect was negative. Dominance effect also existed in the heredity of ear length, many of them was positive . Additive effect was predominant in the heredity of ear width .We deemed that the additive-dominance-epistatic genetic model were in line with kernel length and kernel number per row . Three kinds gene effect existed in heredity of kernellength ,but the additive effect was the most important. The kernel number per row was affected mainly by additive effect.The results of two generation means analysis trial showed that the additive-dominance-epistatic genetic model was in line with plant height. Dominance gene effects was positive and dominant position. Additive gene effects was negative for plant height . Additive gene effects was dominant position for the heredity of days to pollen and days to silk.