Detection Of QTL For Photooxidation-related Traits, Dynamic Chlorophyll Content And Resistance To Bean Pyralid(Lamprosema Indicata Fabricius) In Soybean(Glycine Max L. Merrill)

Photosynthesis is the most important chemical reaction on the earth and very closely related to agricultural production. Improving photosynthetic efficiency is an important way to increase crop yield and to select the cultivar with high photosynthetic efficiency, because net photosynthetic rate is significantly related to the number of photosynthetic units per area. However, a number of studies have suggested that the photosynthetic apparatus is hurt and photo-oxidation phenomenon often happens under the situation of strong or middle strong light in plants. Therefore, more and more attention was paid to the effect of this physiological disease on photosynthetic production.The F2, F2:3and F2:4populations derived from the soybean cross of Lishuizhongzi-huang and Nannong493-1at Jiangpu experimental station of Nanjing Agricultural University or/and at Linyi experimental station of Linyi Agricultural Academy were used to study the inheritance of quantitative traits related to photooxidation. First, genetic linkage maps in soybean were constructed. Then, mapping quantitative trait loci （QTL） responsible for the above traits was carried out in order to obtain stable QTL across various populations and mapping approaches, based on the genetic linkage maps above. The results presented will provide some useful information for molecular design breeding and high photosynthetic efficiency in soybean.1. Construction of genetic linkage maps in soybeanThe genetic linkage map of soybean using244F2plants derived from the soybean cross above was constructed in this paper. Before the construction of a linkage map, the two parents were screened for polymorphism with972SSR primer combinations. In total,150of972primers （15.4%） could produce polymorphic loci. All these polymorphic markers were performed in the F2population. In the construction of a genetic linkage map, there are three steps. The first step is to cluster markers into linkage groups. Ninety-one molecular markers were assigned to28linkage groups with Mapmaker3.0software. The second step is to estimate genetic distances in each of the linkage groups. The results show that the length of each linkage group ranges from6.9to108.3cM and all these molecular markers covered1356.42cM for the whole genome. The minimum, maximum and average of marker spacing are6.9（linkage group L）,51.3（linkage group1-2） and14.91cM, respectively. Number of markers included in each linkage group varies from2to9. There are twenty-eight marker intervals with marker spacing longer than20cM. Fifty-nine markers are not placed on any linkage groups. The last step is to optimize the orders of all mapped markers in all linkage groups. The presented maps were the optimized linkage groups. Among ninety-one markers, the linkage gropup and order for eighty-six marker are consistent with the public genetic maps in soybean while different order between satt077and sat₁10, and between satt266and sat₂542, and different linkage group for satt669are found in this paper.2. Mapping QTL for photooxidation-related traits in soybeanTwo-hundred and forty-four F2:3families derived from the soybean cross above at Jiangpu experimental station in2007and the corresponding F2:4families at the Jiangpu experimental station and at Linyi experimental station in2008were measured for four photooxidation-related traits, including normal chlorophyll concentration before photo-oxidation （NCC）, chlorophyll concentration after photo-oxidation （PCC）, photo-oxidation rate （POR） and yellow leaf rate （YLR）. Its purposes is to perform the inheritance analysis of the above traits by using the CIM, MIM and multi-marker joint analysis （MJA）. Each dataset was analyzed respectively by the first two approaches and all data was jointly analyzed by the MJA. The results showed that181main-effect QTL along37epistatic QTL,4environmental effects and29QTL-by-environment interactions were detected in the seven genetic analyses. Of52QTL for PCC,10QTL were identified repeatedly2to5times. Of41QTL for NCC,8QTL were mapped repeatedly2to3times. Of29QTL for POR,5QTL were identified repeatedly2to4times. Of59QTL for YLR,7QTL were found repeatedly2to4times. The phenomenon of QTL cluster was present in our results. Several QTL that influence multiple traits were detected in the same genomic regions. A total of six intervals were found to be involved in the control of two or more traits and located on marker intervals satt640-satt42, sat₁60-satt147, satt413-satt256, satt263-satt045, sat₄18-sat₄19and sat₃91-satt150in the linkage groups C2, Dlb, D2, E, G and M, respectively. We deduce that there are some genes responsible for the traits related to photooxidation in these regions above. In addition, results showed that there are high consistency between the CIM and the MIM, between different places in the same year, and between different years in the same place, and low replication between different years. Results from QTL mapping may explain the correlation between photooxidation-related traits.3. Mapping QTL for dynamic chlorophyll content in soybeanTwo-hundred and forty-four F2:3families derived from the soybean cross above at Jiangpu experimental station in2007and the corresponding F2:4families at the Jiangpu experimental station and at Linyi experimental station in2008were measured for chlorophyll content at eight, one and four different developmental stages, respectively. Therefore, the average for each family across different developmental stages could be calculated at fixed year or experimental station. The average data was analyzed by using the MJA while the data at different developmental stages was analyzed by using the CIM and MIM. The results showed that45QTL were detected.At the measured times1to8at Jiangpu experimental station in2007,3,2,2,3,3,2,3and0QTL for chlorophyll content were detected, respectively. Of these QTL, one QTL located on the marker interval satt234-satt022in the linkage group N, with maximum percentage57.0%of the total phenotypic variance explained, was repeatedly identified across four times, some QTL placed on the linkage groups D1a, D1b, D2and F were repeatedly confirmed across2to3times, and there were11QTL with more than10.0%of the total phenotypic variance explained.At the measured stages1to4at Linyi experimental station in2008,2,3,4and2QTL for chlorophyll content were detected, respectively. Of these QTL, the QTL located on different positions of the linkage groups D2and D1a were identified across two times, there were2QTL with more than10.0%of the total phenotypic variance explained, and maximum percentage of the total phenotypic variance explained was14.0%.One common QTL, qchl-D1a-1, located on the marker interval sat₁60-sattl47in the linkage group Dla, was mapped across different years at Jiangpu experimental station. Three common QTL, qchl-D1a-1, qchl-D2-1and qchl-K, located on the linkage groups D1a, D2and K, respectively, was mapped between Jiangpu and Linyi experimental stations.Using the multi-marker joint analysis for the average data above,7main-effect QTL,4environmental interactions QTL and1environmental effect were identified on nine linkage groups. Five common QTL placed on the linkage groups D1a, D2, M and N were detected between the CIM and MJA approaches. Significant environmental effect indicates that environment have a large effect on chlorophyll synthesis. In addition,6new QTL and four environmental interactions were found by the MJA.4. Genetic analyses for resistance of soybean to bean pyralid（Lamprosema indicata Fabricius）Two-hundred and forty-four F2plants derived from the soybean cross between Lishui-zhongzihuang （resistance） and Nannong493-1（susceptible） were measured for resistance in soybean to natural population of bean pyralid in the field according to its defoliation percentage in2006. QTL detection for the resistance was carried out using the F2population. The results showed that two QTL were mapped on the linkage groups Dlb and K using composite interval mapping （CIM）. Four QTLs along with six interactions were identified in the linkage groups A2, Dlb, K and N using multiple intervals mapping （MIM）. Among these QTL, there were two common QTL with more than19.2%of total phenotypic variance explained.