Genetic Analysis Of Boron Nutrition And Ionome In Brassica Napus

The growth of crops often occur various disorders because of the lack or excessive of elements in the soil.Middle and lower reaches of the Yangtze River in China's is main producing areas of rapeseed.In the past,a large number of rapeseed and cotton decreased production or total destruction for more serious lack of boron(B) in the region.Although fertilizer in the process of cultivation could guarantee the normal growth of crop,but the application of fertilizers to farmers undoubtedly added economic burden;and the loss of fertilizer from farmland by rain,resulted in not only waste of fertilizer,also caused serious water pollution.The development of green crops,and cultivating the efficient use of fertilizer varieties,in maintaining high and stable yield at the same time reducing the amount of fertilizer is an important subject in agricultural research.A lot of studies were concerning about the physiological basis of B efficient for oilseed.Although a lot of assumptions were proposed,but there still were not fundamentally explains for the mechanism of B efficient.Detection of B efficent loci in rapeseed genome is our research objection by investigating characters of mature stage traits combining with TN genetic resourses.A further inquiry was firstly performed about preliminary ionomics exploration in the seedling stage.1.Genetic analysis of rapeseed B efficiency in field experimentsTN population of 202 lines was planted for two years in B deficiency soil,Qichun of Hubei.1.5 kg/ha of boron and 15 kg/ha of boron were fertilized to design two levels of controlled experiment.The experiment included three repeats,each repeat of random block design of 202 lines with the parents as control.In vegetative growth stage,rapeseed under low B environment grew significantly weaker than under normal B environment.In low B environment,efficient parent(Ningyou7) and efficient DH lines grew normally, but inefficient parent(Tapidor) and inefficient DH lines appeared with typical symptoms of B deficiency:purplish leaf edge,cracked stem,the SAM necrosis,many-branch.In bolting stage,rapeseed is most sensitive of the lack of B.Flowering time was significantly delayed for B deficiency with pod lost.It's the typical symptoms with "flowering not seeding".Two traits(the seed production under the low B environment and B efficient coefficient) were tested.Ten QTL and ten interaction pairs were detected.The two QTL on A2 and A6 lingkage groups could be validated by two years results.The major QTL on A2 linkage group of TN pupulation could be identical with QTL in LG9 of BQ population,The result found that a stable production-related QTL under low B conditions exist across two genetic populations.At the same time,we found the QTL on A2 linkage group interacted with other genetic locus in genome.It suggest complicated epistatic effect exists in the major B QTL.2.Concentrations of seven mineral elements of rapeseed seedling in the two B conditionsTwo B levels of hydroponical culture were low B levels for 0.25μM,B normal level for 50μM,respectively.The concentrations of seven mineral elements in shoots and roots were measured.B concentration has been most intensely decreased because of the stress, followed increased with concentrations of Cu,Fe and Zn.But fluctuation of elements concentrations in roots is comparative with elements in shoots.3.Genetic analysis for the concentrations of mineral elementsIn the two B conditions,total 107 QTL and 154 interation pairs were detected for the concentrations of 7 mineral elements.In shoots,wefound three overlapping QTL for Ca/Mg and the biggest effect P-QTL across two B conditions.In roots,QTL for cations (Ca,Mg,Cu,Fe and Zn) has 7 overlapping QTL intervals.It means the cations may exist the common non-selective absorption mechanism.4.Small regions of the Arabidopsis genome have already been targeted by comparative mapping between B.napus and Arabidopsis.The genes that were related to mineral absorption and allocation in each syntenic block of Arabidopsis were located according to their physical positions in the genome of Arabidopsis.The positions of putative genes were then aligned with the TN linkage map according to the position of close anchor marker(s) in the same syntenic block.If the position of an aligned gene(s) was located in the confidence interval of a QTL,the orthologous gene(s) was considered to be associated with the target QTL.By the method of in silico mapping,hundreds of mineral transporting genes in Arabidopsis have been aligned with the linkage map of B.napus.In our study,alignment results were used to construct blocks of syntenic or insertion fragment islands between the Arabidopsis chromosomes and TN linkage groups. According to homologue relationship between Arabidopsis and rapeseed,the genetic map of TN population with Arabidopsis thaliana section,used to support the position of QTL and there may be some candidate genes.We have found in the various ion transporter gene through this comparative genomic methods to determine their genes in the genome, to pave the way for map-based cloning of these genes.5.According to the sequence of the transporter genes of NIP5;1,BORl family in Arabidopsis,the primers were designed and amplified in TN population.Five single-strand conformation polymorphism(SSCP) markers were got and single marker was located in QTL intervcal for root length in low B condition.By using target region polymorphism(TRAP) and bulked segregate analysis(BSA), we identified 2 TRAP markers linked to the B efficient locus on A2 lingkage group.The markers will be useful for marker-assisted selection(MAS) in breeding programs and provide the bases for map-based cloning of this gene.6.AFLP markers were used to densify the target QTL interval on A2 linkage group. The original interval covers 30 cM with sparse markers.By BSA method,9 AFLP markers were added in the QTL interval.