| Fruit firmness is considered as essential trait for tomato fruit quality and ranks as second importance of the tomato evaluation index after fruits flavor.This study treated tomato fruit of Solanum pennelliiLA716as research materials and focused on red fruit firmness.The research objects were to deeply study the principal component and cluster analysis of fruit traits,QTLs identification for red fruit firmness,genetic effect of the QTLs for tomato red fruit firmness increasing,candidate genes screening of red fruit firmness increasing major QTL,and the difference of fruit pericarp tissue from special fruit firmness lines.The results could preliminarily illustrated the inheritance and regulation mechanism of the tomato fruit firmness.Furthermore,the results could also provide theoretical basis for tomato fruit firmness improvement.The main results were as follows:1.The introgression line population,which was generated via processing tomato parent S.Lycopersicum M82 and a wild species S.PennelliiLA716,was employed in this paper to evaluate seven fruit’s traits using principal component and cluster analysis.The results showed that these seven fruit traits were mainly composed of three independent principal components,including fruit weight factor,fruit shape factor and fruit quality factor,that the cumulative contribution of these three factors was 85.44%.Furthermore,77 introgression lines could be divided into three groups by euclidean distance UPGMA method.The first group include 70 lines which could be further divided in to two sub-groups at D=20.65level.The second group include one lines,and the third group included six lines.The experimental result showed that the 70 lines with excellent fruit traits mostly belong to group one.2.According to the results from four independent trials,nine QTLs for red fruit firmness increasing were successfully identified by employing the S.Pennellii introgression lines(ILs).These QTLs were designed as Crf1、Crf2a,Crf2b,Crf3,Crf5,Crf8,Crf10,Crf12a and Crf12b,respectively.Compared to M82,the red fruit firmness of these QTLs increased 8.76%to 21.00%.Furthermore,the nine QTLs were located on chromosome 1,2,3,5,8,10 and 12 respectively.3.16 QTLs for red fruit firmness reducing were identified and designed as Crf-R-1,Crf-R-2,Crf-R-3,Crf-R-4a,Crf-R-5,Crf-R-6b,Crf-R-7b,Crf-R-8a,Crf-R-8b,Crf-R-9a,Crf-R-9b,Crf-R-9c,Crf-R-10,Crf-R-11a,Crf-R-11band Crf-R-12,respectively.Compared to M82,the red fruit firmness of these QTLs reduced8.27%to 30.80%.Furthermore,the 16 QTLs were located on chromosome 1,2,3,4,5,6,7,8,9,10,11 and 12 respectively.4.The results from Dunnett test from ANOVA analysis showed that the QTL for tomato red fruit firmness increasing expressed over-dominant,dominant and additive genetic effect,moreover the QTL interaction was over-dominant,dominant and additive effect either.Meanwhile,when the firmness of red fruit at 45N,139 individual plants from F2 group showed high compression resistance and 61 individual plants showed poor compression resistance.The result from X~2test showed that high compression resistance:poor compression resistance=2.773:1 which coincided with 3:1 of the Mendelian separation ratio(X~2=2.773,P=0.096>0.05)and the Crf12a could be considered as a dominant monogenic.5.Totally,1137865 SNPs were found by BSA and whole genome re-sequence technology.Four candidate genes were identified and they were Solyc12g017560.1,Solyc12g011050.1,Solyc12g011300.1and Solyc12g017840.1 respectively.These genes involved in different biological process.6.The breeding line WT-75 had special firmness.The content of soluble pectic of WT-75 was significantly better than wild line ZH-10.In the range of 200μm from scanning electron microscope observation,the cell size of fruit pericarp tissue from WT-75 was significantly smaller than wild lines ZH-10 and cells arranged closely.After 35 days later under room temperature,the fruits of WT-75 easily happened to rotted in via of the number of the lenticel on fruit pericarp skin,supposedly. |
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