Genetic Analysis Of Hypocotyl Length In Brassica Napus L

Lodging would reduce the yield and quality of rapeseed,because of the high incidence of sclerotinia and great trouble in harvesting.The hypocotyl length(HL)is of great influence on the lodging of rape.Breeding short hypocotyl varieties can effectively improve the lodging resistance of plants.Preliminary research,Long hypocotyl male ‘ZS11' was crossed with two short hypocotyl females,‘352' and ‘264-1' to build RIL1(352 x ZS11),and RIL2(264-1 x ZS11),respectively.To study the genetic basis of hypocotyl length in Brassica napus,we investigated the hypocotyl length of two RILs(RIL1-RIL2)in F6 and F7,and mapped the hypocotyl length QTL.We also analyzed the correlation between hypocotyl length and plant height(PH)of RIL1 and RIL2 in F6 to verify whether they are closely related,which preparing for breeding short hypocotyl length and moderate plant height varieties.And then,we compared the physical confidence interval of HL-QTLs and PH-QTLs.There is a significant difference between the three parents' hypocotyl length.The females,352 and 264-1 has a 11.87 mm and a 16.37 mm lower hypocotyl length average values of three tests than that of ZS11.And both the difference among 352 and 264-1 with ZS11 reached a more significant level.Then,we carried out the germination experiments with the seeds of two RILs in F6 and F7,and investigated the hypocotyl length of RIL1 and RIL2 for four times respectively.The total of eight germination experiments showed that hypocotyl length varies widely within two RILs and be normal distribution.The result of two-factors variance analysis showed that both the hypocotyl length of RIL1 and RIL2 are mainly influenced by genotype effect and environment,and the broad heritability of two RILs are 0.92 and 0.83,respectively.Correlation analysis results of each RIL showed that the hypocotyls length in different tests was extremely positively correlated in a very significant level.We also analyzed the different of the two RILs' plant height in five environments(PH1-PH5),the result showed that both in PH1 and PH5,the plant heights of two RILs are higher while the coefficient of variation are smaller.And the result of two-factors variance analysis showed that both the plant height of RIL1 and RIL2 are influenced by genotype effect and environment effect,and reaches a highly significant effect.The broad heritability of the two RILs are 0.87 and 0.94 respectively.Besides,correlation analysis results of each RIL showed that the plant height in different tests was extremely positively correlated in a very significant level.And the plant height of RIL1 and RIL2 in F6 significantly positively correlates with their hypocotyl length,which inferred that the selection of short hypocotyl may effectively reduce the plant height.Based on the above results,we did the QTL-mapping with the two population' hypocotyl length and plant height,a total of thirty-eight HL-QTLs whose R2 are between 4.90%-19.52% were detected on the remaining fourteen linkage groups except A01?A02?A04?A05?C02 linkage group.We also found eleven PH-QTLs distributing in A03?A06?A09?A10?C08 and C09 linkage group,and whose R2 are between 5.51%-46.04%.After integrated,we got twenty-seven independent HL-QTLs and eleven independent PH-QTLs which including seven consensus HL-QTLs within two RILs,and no HL-QTL cluster and PH-QTL cluster among the two RILs.After that,the integrated HL-QTLs and PH-QTLs of the two RILs were aligned,three groups of interval-overlapping QTLs were detected in A10 linkage group and all of them are in positive additive effect which means their enhancing alleles come from male parent ZS11.And one pair of overlapping QTLs in C09 linkage group which showed positive additive effect in hypocotyl length while negative additive effect in plant height.