High-density genetic linkage map construction and QTL mapping of grain shape and size in the wheat population Yanda1817 × Beinong6.

High-density genetic linkage maps are necessary for precisely mapping quantitative trait loci (QTLs) controlling grain shape and size in wheat. By applying the Infinium iSelect 9K SNP assay, we have constructed a high-density genetic linkage map with 269 F 8 recombinant inbred lines (RILs) developed between a Chinese cornerstone wheat breeding parental line Yanda1817 and a high-yielding line Beinong6. The map contains 2431 SNPs and 128 SSR & EST-SSR markers in a total coverage of 3213.2 cM with an average interval of 1.26 cM per marker. Eighty-eight QTLs for thousand-grain weight (TGW), grain length (GL), grain width (GW) and grain thickness (GT) were detected in nine ecological environments (Beijing, Shijiazhuang and Kaifeng) during five years between 2010-2014 by inclusive composite interval mapping (ICIM) (LOD ≥ 2.5). Among which, 17 QTLs for TGW were mapped on chromosomes 1A, 1B, 2A, 2B, 3A, 3B, 3D, 4A, 4D, 5A, 5B and 6B with phenotypic variations ranging from 2.62% to 12.08%. Four stable QTLs for TGW could be detected in five and seven environments, respectively. Thirty-two QTLs for GL were mapped on chromosomes 1B, 1D, 2A, 2B, 2D, 3B, 3D, 4A, 4B, 4D, 5A, 5B, 6B, 7A and 7B, with phenotypic variations ranging from 2.62% to 44.39%. QGl.cau-2A.2 can be detected in all the environments with the largest phenotypic variations, indicating that it is a major and stable QTL. For GW, 12 QTLs were identified with phenotypic variations range from 3.69% to 12.30%. We found 27 QTLs for GT with phenotypic variations ranged from 2.55% to 36.42%. In particular, QTL QGt.cau-5A.1 with phenotypic variations of 6.82-23.59% was detected in all the nine environments. Moreover, pleiotropic effects were detected for several QTL loci responsible for grain shape and size that could serve as target regions for fine mapping and marker assisted selection in wheat breeding programs.

[The effect of first premolar extraction on third molar angulation and eruption space].

PURPOSE: To study the influence of the first premolar extraction on the angulation and eruption space of third molar. METHODS: One hundred and twenty patients cases of Class I malocclusions were divided into 2 groups by age, who were treated with extraction and non-extraction respectively. The following values was measured: angle of cusp line between the second and third molar(alpha angle),impact state and depth, distance from Rickett's Xi to distal cusp of third mandibular molar along the occlusal plane(Xi-LTM), anterior border of ramus to the third mandibular molar(R-LTM), distance from projection of distal contact point of maxillary third molar to intersection of pterygoid vertical on occlusal plane (PTV-UTM). The change between pre- and post-treatment was calculated and analyzed with SPSS10.0 software package. alpha angle, Xi-LTM, R-LTM, R-LTM were tested with independent-sample t test, impact state and depth was tested with Chi-square test. Influence of age on the values was also evaluated. RESULTS: In younger group, changes of mandibular alpha angle and Xi-LTM in extraction group was 7.16 degrees and 3.22mm, but in elder group, these changes was 2.42 degrees and 2.10mm, all values were significantly larger than non-extraction group (P<0.05). Impact state and depth of third mandibular molar improved in extraction group, while there was no significant changes in the maxilla. CONCLUSIONS: The third mandibular molar becomes upright and distal movement after first premolar extraction. The possibility of the third mandibular molar impaction is decreased, but the effect on the maxilla is not significant.

[Clinical observation on reimplanting the upper inversely impacted incisor after extraction].

In order to determine the feasibility of reimplantation of upper inversely impacted incisor, we enlarged the interdental distance by orthodontic appliance, then replanted the impacted incisor after extraction. 13 of 15 cases had good results. It was a good method to replant inverse impacted incisor after extraction which avoid extracting the tooth simply.