Assessment On Potential Of Tropical & Temperate Maize Populations And Index Analysis Of Photoperiod Sensitivity

Maize is the second large crop in China.The planting area reaches 27 million hectares.Maize is the main feed,industrial materials,food and economic crop in China.It not only takes the important position in national economy,but also is a model crop in genetic research,the discovery of jumping gene and molecular mechanism of heterosis was just found in maize.Maize germplasm enhancement is one of the important ways to new germplasm creation.Evaluation and usage of exotic germplasm is the applicable basic research on maize variety improvement.The development of modern genetics and statistics promote the researches on genetics and breeding constantly to progress,and also provides new methods and technologies for finding the genetic reasons of maize yield formation,Understanding the relationship between heterosis and genetic distance, predicting heterosis of crosses,and evaluating breeding potential of basic materials. Detailed evaluation,improvement and usage of landraces,populations and inbred lines from the original center of maize are significant for discovering favorable and rare allele in exotic germplasm.In this research,9 populations from tropics and temperate zone,two widely used hybrids and its 4 parents inbred lines were used as the research materials.Two mating designs were performed:(1) Using the 9 populations,the 36 crosses were formed based on the design of diallel cross,then field tests were performed using the method of completely random design in two locations in two years.For understanding the genetic reasons of yield formation,genetic variance components,heritability,additive and dominance effects and G×E interaction effects of yield component factors were analyzed using mixed linear models.For investigate the relationship between heterosis and genetic distance,the heterosis performance among 9 populations were further analyzed,the heterosis performances were divided into major effects and G×E interaction effects.In order to understand the inbreeding depression,generations of crossed offspring which could maintain＞5%heterosis were predicted,and this provided scientific evidence for choosing basic breeding materials.(2) Using 9 populations and 4 inbred lines,36 crosses were produced according to the design of NCâ…¡,and field tests were also made using the completely random design in two locations in two years.The breeding potential of 9 populations were evaluated using Dudley's gene transfer theory,Some genetic parameters were estimated,and obtain some useful information on choosing best donors for improving the two superior single crosses and pointing out the direction of improvement and forms of improvement.In order to find out the indices of photoperiod sensitivity,two parents,Huangzao4 and HZ32,with different sensitivity of photoperiod were used to construct a F_2:3 segregation population about photoperiod sensitive,and F_2:3 segregation population was evaluated in two different photoperiod conditions using the completely random design, and this offers a basis for adaptability improvement of exotic germplasm. Here are the main conclusions of our research:1.The major genetic reason for maize yield formation is dominant effects and effects of dominance×environment interaction,and scored 35.16%,29.73%,respectively,the total is 64.89%.While the additive effect and effects of additive×environment interaction only scored 0.18%,4.33%,respectively,the total is 4.51%.2.Based on the narrow heritability,yield component factors could be sorted like this RPE＞KPR＞EL＞1000KW＞PKW,and scored 26.38,16.44,11.36,9.13 and 0.18 respectively;Among them,RPE possessed the first rank of narrow heritability,and PKW possessed the last rank of smallest narrow heritability.So,in early selected generations of a breeding program,selection based on RPE must be more effective than PKW.3.There was not significant linear correlation between heterosis and genetic distance.It must be a complex non- linear correlation.There is significant linear correlation between Pre(F₁)(G) and HPM(F₁)(G),HPB(F₁)(G),the value is 0.86,0.80, respectively.4.Suwan 1×BSSS C₉ and Stay green C₄×BSSS C₉ are two heterotic patterns containing tropical germplasm.They probably can be used as substitute pattern in temperate zone of our country for maize breeding utilization,and further more,They could be extending the two major heterotic patterns,Reid×Sipingtou and Reid×Lvda Honggu.In Huanghuaihai summer maize growing region,Suwan 1 can be used to improve Singpingtou heterotic groups,and in northern,northeast and a part of southwest of China's spring maize growing region,Stay green C₄ can be used to improve Lvda Honggu heterotic groups.5.By analyzed the generations of crossed offspring which could maintain＞5% heterosis and heterosis performance,we found that Suwanl and Stay green C₄ could be recombined and improved mutually,after several cycle selections,it must be to form an elite heterotic group,and to unite with Sipingtou heterotic group,and then to form a extended heterotic pattern;The more generations(＞5%) are maintenance,the less inbred depressions are made.the meaning is the cross must contain more favored gene;In order to get elite lines that contain more favored genes,the breeding must be based on the large populations and long selection period.6.There are significant interaction effect between heterosis and environment.Heterosis performances could be divided into major heterotic effects and effects of G×E interaction.The degree of interaction effects depend on difference crosses;There are no any disciplinarian among locations and years;1×2,1×3 and 3×6 crosses have good adaptions,but 4×5 and 1×6 crosses.7.Based on Dudley's gene transfer theory,for improving elite single hybrids Ye478×Dan340 and HZ111×Mei22,The rank of best donors populations is:for Ye478×Dan340,population 1＞population 5＞population 8＞population,the improvement direction is Ye478 and the improvement form is backcross first;for HZ111×Mei22, population7＞population 8＞population 4,.the improvement direction is Mei22 and the improvement form selfcross directly.8.The main problem for using tropical germplasm in temperate zone is sensitive to photoperiod.In this research,231 families of F_2:3 were used as material,then the traits related to photoperiod reaction,such as PSD,SD,ASI,LN1,LN2 and LN1/LN2,were analyzed in two different conditions.It demonstrated that SD was more sensitive to photoperiod than that of DPS;LN1/LN2 can be used as the simplest indices for photoperiod.9.Bi-dierectional Group was pointed out for maize breeding:breed specific male group and female group,then limited traits of them were improved and selected.According to the heterosis model,firstly,accumulates and maintains the characteristic advantages of each group,then overcomes their disadvantage.Through this way,two parents will possess as much useful alleles as possible,and avoid having common disadvantage alleles.By full utilization of the useful alleles in male group and female group to reach the aim of mutually complementary in superior character,and finally exhibit the yield potential of hybrids.