Germplasm Diversity And Exploration For Stress Tolerance Genes In Eruca Vesicaria

Eruca vesicaria var.sativa is an important cruciferae oil crop germplasm with high tolerance to salt,drought and barreness.In this study correlation,regression and path analyses were carried out in 11Eruca lines.Partial correlation,stepwise regression and path analyses indicated that the contributions of siliqua number per plant(X7),seeds per siliqua(X8),1000-seed weight(X9)and siliqua number of main raceme(X6)to seed yield per plant(Y)were highly significant and positive,and the contribution of number of secondary branches(X4)and plant height(X1)was significant and positive,but the contribution of branching height(X2)was significant and negative(P<0.05).The regression formula was Y=-2.134 + 0.010X1-0.011X2+ 0.049X4+ 0.028X6 +0.019X7+ 0.056X8+ 0.465X9.Siliqua number per plant showed the greatest direct contribution to seed yield per plant,followed seeds per siliqua,siliqua number of main raceme,1000-seed weight,number of secondary branches,and plant height.Number of secondary branches showed the greatest indirect effect to seed yield per plant via siliqua number per plant,followed by plant height,siliqua number of main raceme,seeds per siliqua.Branching height and 1000-seed weight showed a minor negative effect on seed yield per plant via siliqua number per plant.Eruca vesicaria was reported to be one of the most drought-tolerant species in Cruciferae.In this study PEG-simulated drought tolerancewas evaluated in one line of Brassica carinata,one line of B.napus and 249 Eruca lines based on principal component and UPGMA cluster analyses.Principal component analysis based on eight drought tolerance indices indicated that the first three components accounted for 85.46%of the total variation with PC1 accounting for 43.89%,PC2 for 27.85%and PC3 for 13.73%of the total variation.The loadings for the components yielded from PCA are given in the following Equations:Z1= 0.46RSG+ 0.22RRL+ 0.08RSL+0.03RFSW+0.32RSV-0.34RMGT+0.51RGV+ 0.51 RGDRI;Z2=-0.12RSG+0.50RRL+ 0.47RSL +0.42 RFSW+0.47 RSV+0.21 RMGT-0.18 RGV-0.17 RGDRI;Z3= 0.22 RSG + 0.35 RRL-0.43RSL-0.53 RFSW + 0.32 RSV + 0.48 RMGT-0.09RGV-0.06 RGDRI.UPGMA cluster analysis indicated that B.napus cv.Zhongshuang 9 and the Eruca lines could be clustered into five major group,with group 1 being in general drought sensitive,group 2 slightly-medium drought tolerant,group 3 drought tolerant,group 4 highly drought sensitive and group 5 highly drought tolerant.Eruca seedlings 5 days after seed germination were treated with liquid MS/20%PEG and then subjected for trancriptomic sequencing.KEGGenrichment analysis indicated that in the drought-tolerant Eruca line but not in the sensitive line,genes involved in pathways like alpha-Linolenic acid metabolism,Tyrosine metabolism,Phenylalanine,tyrosine and tryptophan biosynthesis,Galactose metabolism,Isoquinoline alkaloid biosynthesis,Tropane,piperidine and pyridine alkaloid biosynthesis,Mineral absorption,were all up-regulated;while genes involved in ribosome,ribosome biogenesis,Pyrimidine metabolism,RNA degradation,Glyoxylate and dicarboxylate metabolism,Aminoacyl-tRNA biosynthesis,Citrate cycle,Two-component system,Methane metabolism,Carbon fixation in photosynthetic organisms,ECM-receptor interaction,were all down-regulated.BLAST analysis indicated that among the 2946 DEGs in drought-tolerant Eruca line but not in the sensitive line47 DEGs were most significantly up-regulated(log2 ratio?8),including genes for 3 DEGs for trehalose-phosphate phosphatase,2 for allene oxide cyclase,2 for ethylene-responsive transcription factor,2 for low-temperature-induced 65 kDa protein-like;275 unigenes were most significantly down-regulated(log2Fold Ratio<-8),including genes for 38 DEGs for ribosomal protein,4 disease resistance protein,2 carboxypeptidase,2 for cytochrome b5,4 for serinethreonine-protein kinase,4 for heat shock protein,3 for glutamate dehydrogenase,2 for lysine--tRNA ligase,2 for nucleoside diphosphate kinase,2 for peroxidase,2 for pyrophosphate-energized vacuolar membrane proton pump.Genes for nicotianamine synthase and DREB2A were cloned from E.vesicaria subs,sativa and over-expression vectors were constructed.Efficient regeneration and genetic transformation systems were established in E.vesicaria subs.sativa.These findings and results will be important and valuable for germplasmutilization,drought tolerance mechanism illustration and exloration of drought tolerance genes in Eruca.