| Oilseed rape is one of the important oil crops in China. It is a typical species in family of Cruciferae characterized with four petals. Apetalous rapeseed can significantly increase the efficiency of solar energy utilization and reduce the incidence of sclerotinia, owing to the micro-environment improved in the population level. Apetalous breeding has been regarded as directing to high yield and disease resistance in rapeseed. Results from former researches on the inheritance of apetalous in Brassica napus demonstrated that pctalous degree (PD) on 10% could be used as a critical value to recognize a plant with petalous or apctalous. But the distribution of PD was almost succession in segregating population. So it was unreasonable to divide petalous and apetalous rapeseed using a fixed PD. In fact apetalous trait in Brassica napus could be regarded as a quantitative trait. So it is necessary to further study its inheritance and QTL mapping.The aim of rapeseed production is to produce oil. So oil content in seed is a most important economic trait for rapeseed. The main fatty acid profile in oil includes palmetic acid, stcaric acid, oleic acid, linoleic acid, linolenic acid, eicosenoic acid and erucic acid. Economic value of the oil is affected by the composition of fatty acid either for edible use or for industrial use. Researches on oil content in rapeseed resulted from different authors were different, it might be that different materials and different methods they used in their researches. Although there were several papers about inheritance of enlcic and oleic acids published and genes were cloned, the othcr fatty acid in rapeseed had less research and got different results. It is necessary to study further on inheritance of major fatty acid in rapeseed oil with newly developed major gene plus polygene methodology, and mapping QTLs linked to them.In this paper, a six basic generations (P1, P2, F1, B1, B2 and F2) derived from crosses of APL01(apetalous)×M083 (petalous) and APL01 (apetalous)×NB6 (petalous) in rapeseed (Brassica napus L.) were used to analyze the inheritance of apetalous, oil content in seed and fatty acid in oil, applying the mixed model of major gene plus polygene. And the BC1F1 population derived from the cross of APL01×M083 was used to construct a genetic map in rapeseed (Brassica napus L.) based on RAPD, SSR and SRAP markers. QTLs linked to apetalous, oil content and fatty acid were identified in this population. Results were as follows:1 Inheritance of apetalous in rapeseedThe fitting model detected for apetalous in the two crosses was E-0 genetic model, which was two additive-dominance-epistasis major genes plus additive-dominance-epistasis polygene model. The additive effects of the two major genes were equality, but the value was different in two crosses and years. The range of the additive effect of the two major genes was -11.13～-20.08. The dominance effects of the two major genes estimated in cross of APL01×NB6 was different; one of the major genes was significantly larger than that of the other, while there was no difference found between the dominance effects of two major genes estimated in cross of APL01×M083. The epistasis effect was also different in the two crosses; there were mainly additive-additive and additive-dominance epistasis in cross of APL01×NB6, while in cross of APL01×M083, it was mainly dominance-dominance epistasis. The heritability of major gene was 76.29%-94.13%, which was significantly larger than that of the polygene, and the heriatbility of major gene estimated from B1 was larger than that of B2.2 Construction of genetic map in rapeseedUsing (APL01×M083)BC1F1 as mapping population, a genetic map in rapeseed (Brassica napus L.) was construct by 251 molecular markers, including 219 markers SRAP, 25 SSR and 7 RAPD markers. The genetic map contained 19 linkage groups, N1 - N19. And the genetic distance was totally 3095.85cM. The average distance between two markers was 12.33cM. This map was aligned with the ultradense genetic map in Brassica napus by using the same SRAP markers.3 QTLs linked to apetalous in rapeseedFour QTLs linked to apetalous trait in rapeseed were identified by Windows QTL Cartographer V2.0. qAP5 was located in the region of A0226Bb152 -m31e40b on N5, which could explain 3.71% of the petalous variation in the segregation population BC1F1. qAP6 was mapped in the region of m25e7 -OPY9 on N6, and accounted for 3.02% phenotypic variation, qAP8 was located between A0226Gb468 -m29e20 on linkage group N8 and explained 30.94% phenotypic variation, qAP15 was located in the region of m21e4b-A0225Bb201 on linkage group N15, and accounted for 21.96% phenotypic variation. Two main-effect QTLs of them (qAP8 and qAP15) could be applied in marker-assisted selection for apetalous rapeseed breeding, and the other two QTLs (qAP5 and qAP6) were two modified genes.4 Inheritance of oil content and fatty acid in rapeseedSeed oil content in the cross of APL01×M083 was controlled by an additive-dominance major gene plus additive-dominanee-epistasis polygene. The heritabilities of major gene were 38.37%-47.16%, while that of the polygene was 24.29%-38.28%.Palmitic acid and eicosenoic acid content were controlled by two additive-dominance-epistasis major genes plus additive-dominance polygene. And the additive effect of major genes controlling palmitie acid content was larger than dominance effect, while the additive and dominate effects of major genes controlled eicosenoic acid were all lager. Stearic acid, oleic acid, linoleic acid and linolenic acid content were all controlled by two additive-dominance-epistasis major genes plus additive-dominance-epistasis polygene. The additive effect of major genes controlled stearic acid was larger, and the heritability of two major genes were 75.00%-92.45%. The additive effects of two major genes controlled oleic acid were 14.38 and 9.92, the dominance effects were -2.24 and -0.44, respectively. The heritability of two major genes were large, which were 81.93%-92.68%. The additive effect of major genes controlled linoleic acid was larger than dominance effect, which was the same as linolenic acid. Erucic acid was controlled by two additive-dominance major genes. The additive effects of these two major genes were-12.27 and -8.83, the dominance effects were 0.35 and 1.69, respectively. No epistasis and polygene effects existed in erucic acid content inheritance. The heritability of major gene was 92.54%- 96.72%.5 QTLs linked to oil content in rapeseedFive QTLs, qOC1, qOC8, qOC10, qOC13-1 and qOC13-2, related to seed oil content were identified, qOC1 was located in the region of m19e21c-A0214Ra142 on linkage group N1, which could explain 5.21% of the oil content variation in the population, qOC8 was located in the region of A0216Gb206-m5e42 on N8, and accounted for 6.34% phenotypic variation, qOC10 was located between m15e48-A0228Bb437 on linkage group N10 and explained 9.45% phenotypic variation, qOC13-1 was located in the region of A0224Rb157-A0301Gb399 on linkage group N13, and accounted for 18.12% phenotypic variation, qOC13-2 was located in the region of A0226Ba377-A0226Ba367 on linkage group N13, and accounted for 10.17% phenotypic variation. Among these five QTLs, qOC10 and qOC13-2 loci, APL01 expressed positive effects for the oil content, while qOC1, qOC8 and qOC13-1 loci, M083 expressed positive effects. The qOC13-1 with larger phenotypic effect could be regarded as major gene locus, the effects of other four QTLs, however, were relative smaller, and could be regarded as polygene loci.6 QTLs linked to fatty acid in rapeseedFive QTLs linked to palmitic acid content were identified, and the two major effective QTLs qPA8-1 and qPA13 were located in the region of m14e24a- mlle37b on linkage group N8 and A0224Rb157- A0301Gb399 on N13, which explained 11.31% and 14.47% of the palmitic acid content variation in thesegregation population BC1F1, respectively. Three QTLs linked to stearic acid content were identified, and the major effective QTL qST16 was located in the region of A0225Ba449-A0225Ga475 on N16, and accounted for 12.22% phenotypic variation. Two QTLs, qOL8 and qOL13, both were major effective QTLs linked to oleic acid content were located in the region of ml le37b-A0226Ba267 on linkage group N8 and m18e46-m20e25a on N13, and accounted for 11.73% and 27.14% phenotypic variation, respectively. Three QTLs linked to linoleic acid content were identified, and the major effective QTL qLI8-1 was located in the region of m14e24a-mlle37b on linkage group N8, and accounted for 13.25% phenotypic variation. Three QTLs, qLN1, qLN8 and qLN11, linked to linolenic acid content were identified, but they had a rather small effects, and could be regarded as minor QTLs. Four QTLs were identified linked to eicosenoic acid content, and three of the them, qEI8-1, qEI8-2 and qEI13, were major effective QTLs, which located in the region of mlle37b-A0226Ba267 on linkage group N8, m5e42-A0226Gb468 on N8 and m18e46-m20e25a on N13, and accounted for 12.20%, 10.22% and 11.14% phenotypic variation, respectively. Two QTLs, qER8 and qER13, both were major effective QTLs were located in the region ofml le37b-A0226Ba267 on linkage group N8 and A0301Bb398-m18e46 on N13, and accounted for 16.74% and 31.32% phenotypic variation, respectively. The major effective QTLs linked to fatty acid content could be used for marker assisted selection in fatty acid improvement in rapeseed. |
