Mapping QTL/Segments Related To Cotton Worm Resistance And Leaf Pubescence Density In A Wild Soybean Chromosome Segment Substitution Line Population And Cloning GmTTG1Genes Related To Pubescence

Cultivated soybean （Glycine max （L.） Merr.）, originated from China, is one of the world’s most important cash crop. It is rich in vegetable protein and edible oil, and it is closely linked to human being’s life. Cotton worm （Spodoptera litura Fabricius） is one of the major soybean pests in our country. Recently, the outbreak frequency of cotton worm and its hazard area kept rising. So to carry out the control work to cotton worm and to breed new soybean variety have become a top priority. Researches showed that the pubescence traits on leaf of crops, like upright degree, density, length, colour et al., were closely connected with their residence to some pests. As indicative characters, some pubescence traits were widely used in screening resources of insect residence and molecular marker assisant selection.In this study, we used chromosome segment substitution lines population SojaCSSLPl as experimental material to mapping QTLs/segments realated to cotton worm resistance and pubescence density, length on leaf. And we analyzed the correlation between cotton worm resistance and pubescence density, length on leaf. Meanwhile, in this study, we used cultivated soybean NN1138-2as experimental material to clone GmTTG1which plays a vital role in pubescence growth. And to lay the foundation for further study, we built the plant over expression vector pMDC83-GwTTG1by Gateway technology and made detailed bioinformatics analysis. The main results as folloes:（1） Wild soybean has significant resistance to cottom worm.In this study, we used chromosome segment substitution lines population SojaCSSLP1as the experimental material and the experimental method was to feed the larva of cotton worm （Spodoptera litura Fabricius） with leaves of SojaCSSLPl indoors. The larva weight （LW） and the pupa weight （PW） were regarded as the indexes of resistance identification when QTL/segments related to cotton worm resistance were detected. When LW was used as the index, we detected3wild segments called Sat₃51, Satt126and Sat₁05related to the resistance to cotton worm in soybean. The corresponding additive QTLs were qLW-2-1, qLW-14-1and qLW-20-1, their PVE were8.7%,7.4%and4.8%, and they all showed decreasing effect. Meanwhile, this study also detected10pairs of epistatic QTLs/segments, their PVE were8.2%-15.7%.5pairs of them showed synergistic effect,and they were （Sat₃51, Sat₃56）,（Sat₃51, Sat₃36）,（Sat₃51, Satt160）,（Satt414, Sat₁05）,（Satt135, Sat₁05）; the other showed decreasing effect, and they were （Sat₃51, Sattl68）,（Sat₃51, SattO66）,（Sat₃51, Satt063）,（Sat₃51, Sat₄24）,（Sat₃51, Satt135）.The results above related to12locus, by means of the analysis of the genetype of parents and differential CSSLs on above-mentioned locus, we preliminary judged that the reason of the susceptible to cotton worm in SojaCSSLP1was related to the combined action between additive effect and interaction of epistasis effect. When LW was used as the index, we detected1wild segment called Satt491related to the resistance to cotton worm in soybean. The corresponding additive QTL was qPW-15-1, its PVE was4.2%, and it also showed decreasing effect. Thus it can be seen, under the indoor conditions, the resistance to cotton worm in soybean is a complex trait.（2） In this study, we used SojaCSSLP1as the experimental material as before. One of the purposes in this part was to mapping QTL/segments related to pubescence density and length on leaf, the other was to analysis whether these two traits were associated with the resistance to cotton worm in soybean. In this part, we detected5wild segments called Sct₁95, GMABAB, Sct₁90, Sat₄11and Satt434related to density of leaf pubescence in soybean. The corresponding additive QTLs were qPD-3-1, qPD-3-2, qPD-9-1, qPD-11-1and qPD-12-1, their PVE were2.6%,6.2%,4.4%,4.8%and3.4%, and they all showed synergistic effect; in this part, we did not detect QTL/segments related to length of leaf pubescence. Meanwhile, the experiment results showed that there was no significant correlation between the two traits of leaf pubescence and the resistance to cotton worm. So, the pubescence density and length on leaf can not be used as the indicative characters during screening soybean resources associated to the residence to cotton worm or molecular marker assisant selection.（3） In this study, we got the amino acid sequence of AtTTG1by searching in NCBI at first. Regarding the sequence as reference, we got four high homologous genes by doing BLASTP to whole genome of soybean in Phytozome. The four genes were named GmTTG1a, GmTTG1b, GmTTG1c and GmTTG1d. They were in four different chromosomes. We cloned the full length cDNA of GmTTG1a by homology-based cloning from NN1138-2and built the plant over expression vector pMDC83-GmTTGl by Gateway technology. In this study, we made predicted analysis to gene structure, homology and phyletic evolution, protein structure to these four GmTTG1s by bioinformatics method. The results showed that GmTTGl genes may have the similar function to AtTTG1. The predicted analysis to protein structure showed that GmTTGls have similar physicochemical property; they are hydrophilic proteins; they have no transmembrane domain or signal peptide; they do not belong to secreted protein; they are rich in phosphorylation sites; they are most possibly located in cytoplasmic or nucleus; they have very little coiled-coils; their secondary structure and tertiary structure are very similar. Meanwhile the results of bioinformatics analysis also showed that two branches appeared in GmTTGls. Among them, GmTTG1a was close to GmTTG1b, GmTTG1c was close to GmTTG1d. We conjectured this result was due to that during the evolution of soybean, at least two copies appeared in its genome. The two copies in soybean made the genome become highly repetitive, and led to the redundancies and loss of genes. During this process, the divergent evolution appeared in GmTTG1s, and led to the differences in each copy.