Current breeding programs to increase oil content in oilseed rape, which are mainly focused on canola-quality, are seeking new resources. As discussed previously (section 3.5 and 4.5) individual loci controlling oil content identified in this study represent promising candidates and might be of use for marker assisted selection. Of highest interest in this case are genotypes combining as many positive alleles influencing oil content as possible. Phenotypic analyses of the SGEDH population in Europe and in China both identified DH lines exceeding the oil content of both parental genotypes. In the group of erucic acid free lines, which are of highest interest for practical breeding, SGEDH172 was identified with highest oil content in both environments. In addition, the application of a regression correction of oil content to eliminate the effect of erucic acid on oil content enabled the comparison of oil contents between erucic acid free and erucic acid containing genotypes in the SGEDH population. This correction identified SGEDH175 and SGEDH13 in European experiments, and SGEDH210 and SGEDH145 in Chinese experiments, with highest oil contents of all lines.
To confirm the potential of the lines with highest oil content as basic material for further increasing oil content in their respective environment, the marker genotypes of these lines were investigated at the positions of oil-QTL (Table 5.1 and Table 5.2). In Europe SGEDH175 exhibited five (71%) favourable marker alleles out of seven, while SGEDH13 and SGEDH172 included four (57%) out of the seven (Table 5.1). As expected, at the two oil-QTL positions linked to erucic acid content on A08 and C03, SGEDH172 exhibited no favourable marker allele, since it does not contain erucic acid, while SGEDH13 and SGEDH175 both showed the favourable marker allele for the oil-QTL on C03. At the remaining five positions which did not show linkage to erucic acid, SGEDH172 exhibited a non-favourable marker allele at the oil-locus on C07, and SGEDH175 lacked a favourable allele at the oil-locus on A10, indicating that the higher oil content of SGEDH175 was mainly caused by its favourable allele on C03. Whereas SGEDH13 missed two favourable alleles of the remaining five oil-QTL positions, explaining the lower oil content compared to SGEDH175. However, none of the top oil genotypes incorporated all favourable marker alleles of the five oil-loci not related to erucic acid content. These results show the potential to further increasing the oil content in these lines incorporating the missing favourable alleles. Additionally, Sollux and Gaoyou, the parental lines of SGDH14, were genotyped together with the SGEDH population. Comparing the favourable marker allele constitution of the oil-QTL loci identified in the SGEDH population to the marker alleles occurring in Sollux and Gaoyou, indicated that none of the favourable alleles identified for oil-QTL in the SGEDH population in European experiments was due to an allele contributed by Gaoyou, although most of the favourable marker alleles were contributed by SGDH14. Instead, Sollux was identified as the original contributor of the favourable marker allele of the oil-locus at C04, and showed the favourable allele of A10 in common with Express617, which was not present in SGDH14 and Gaoyou.
In Chinese trials comparable results were found (Table 5.2). Regarding the two oil-QTL loci associated with erucic acid, SGEDH172 carried no favourable allele, but SGEDH210 and SGEDH145 did. But SGEDH172 and SGEDH210 both showed the favourable marker genotypes at all four remaining oil-loci independent of erucic acid content. Nevertheless, due to the relatively small effect of these QTL, in SGEDH145 the favourable allele of the oil-locus on C03 compensated the absence of two minor favourable alleles, leading to a higher total oil content of this line compared to SGEDH172.
Table 5.1: Marker genotypes of the parental lines of the SGEDH population, SGE DH lines with highest oil content (SGEDH172) and highest regression corrected oil content (SGEDH175, SGEDH13) in European trials, and the parental lines of SGDH14, Sollux and Gaoyou, for oil-QTL of European trials (environment-stable QTL are presented in bold; grey label indicates oil-QTL linked to erucic acid; favourable marker alleles are represented as capital letters) LGA08 A10C03C04C05C05C07 QTL E_Oil-1E_Oil- E_Oil-2E_Oil- E_Oil-3 E_Oil- E_Oil-4 reg_corr-1reg_corr-2reg_corr-3 Additive 1.12-0.270.630.230.60.64-0.39 effect R2 50.511.231.23.213.834.610 QTL 24.517.8190.451.49.339.749.5 position [cM] Marker 25.117.5195.847.47.3 39.950.2 position [cM] Genotype Oil
reg_corr SGDH1448.745.1Aa AAAAa Express617 45.145bBbbbbB Favourable marker alleles ABAAAAB SGEDH17246.546.4bBbAAAa SGEDH17548.546.9ba AAAAB SGEDH1348.746.7 ba AbAAB Sollux 48.644.9ABAAAAa Gaoyou4642.8 Aa AbAAa
Table 5.2: Marker genotypes of the parental lines of the SGEDH population, SGE DH lines with highest oil content (SGEDH172) and highest regression corrected oil content (SGEDH210, SGEDH145) in Chinese trials, and the parental lines of SGDH14, Sollux and Gaoyou, for oil-QTL of Chinese trials (environment-stable QTL are represented in bold; grey label indicates oil-QTL linked to erucic acid; favourable marker alleles are represented as capital letters) LGA06A07A08 A10C03C05 QTL C_Oil-1C_Oil-2C_Oil-3 C_Oil-4C_Oil-5C_Oil-6 Additive effect 0.330.391.06-0.340.730.41 R2 83.346.55.329.411.4 QTL position [cM] 60.395.224.528.6190.49.3 Marker position [cM]62.294.925.133.5195.8 7.3 Genotype OilOil- reg_corrMarker locus
SGDH1447.844.4AAAa AA Express61742.542.6bbbBbb Favourable marker alleles AAABAA SGEDH17245.445.5AAbBbA SGEDH21047.945.9AAABbA SGEDH14548.145.8 AAAa bb Sollux 46.443.1AbAa AA Gaoyou43.842.1 AAAa AA
Additionally, the lines identified with highest oil content in European and Chinese experiments were compared to a set of established and well-known cultivars mainly of European origin, but also including the Chinese cultivar Gaoyou. This comparison showed that the oil content of SGEDH172 not only exceeded the oil content of its parental line Express617 in Europe and in China, but also the oil content of most of the simultaneously tested cultivars. Only Oase showed 0.3% higher oil content in European trials, and NKBeauty showed 0.1% higher oil content in Chinese trials. Protein content and protein content in defatted meal were comparable to those of tested cultivars, but glucosinolate content was higher. While cultivars showed glucosinolate contents ranging from 15.9 to 26µmol/g in Europe and from 12.9 to 20.6µmol/g in China, SGEDH172 showed more than 60µmol/g in both environments. And also the thousand kernel weight of SGEDH172 was 0.4 to 1.4g lower compared to the cultivars. Whereas, the lines with highest corrected oil content exceeded the oil contents of all cultivars in their respective environment, and not only showed comparable contents of protein and protein in defatted meal, but also showed equal thousand kernel weights. Even more convincing except of SGEDH145 with 58µmol/g, the lines of highest corrected oil contents showed substantially lower glucosinolate contents. While SGEDH175 showed around 45µmol/g and SGEDH210 40µmol/g, SGEDH13 even reached a comparable amount of only 24µmol/g. However, due to the production of erucic acid in these lines their oleic acid content is drastically reduced. In further attempts towards increasing oil content in oilseed rape at the Department of Crop Sciences at the University of Göttingen line SGEDH13, due to its relatively high corrected oil content and low glucosinolate content, was used as parent in a cross with the high oil double low cultivar Adriana. From this cross a new DH population was developed which is currently characterized in field experiments.
In parallel to the development and investigation of the SGEDH population in Europe, a sister DH population was developed and is currently analysed in China, derived from a cross of a sister line of SGDH14 which performed best under Chinese conditions, and a Chinese high oil cultivar (Prof. Jianyi Zhao, Zhejiang Academy of Agricultural Sciences, Hangzhou, PR China, personal communication). Comparison of the SGEDH population and its sister population might confirm the present results, and allow further insights into the control and regulation of oil content.
Table 5.3: Mean values of EU trials for contents of seed oil (%), regression corrected seed oil (%), protein (%), protein in defatted meal (Prot.idM in %), glucosinolates (GSL in μmol/g), fatty acids (%) and for thousand kernel weight (TKW in g), begin of flowering (BOF), end of flowering (EOF), flowering period (FP in days) and plant height at end of flowering (PH_EOF in cm) of SGE DH lines with highest oil content (SGEDH172) and highest regression corrected oil content (SGEDH175, SGEDH13), SGEDH parental lines and cultivars Genotype OilOil- reg_corrProteinProt. idMGSL 16:018:118:218:320:122:1TKWBOFEOFFTPH_ EOF SGEDH17246.546.417.232.161.75.060.119.710.91.30.34.6116.7144.928.1134.6 Express 61745.145.017.832.426.04.961.218.39.81.81.05.4114.7143.629.3130.0 Oase46.846.816.230.319.54.364.218.38.51.50.25.5113.8143.930.9130.6 NKBeauty46.446.416.731.115.94.562.319.79.51.20.15.0114.9144.329.4136.5 Adriana 46.346.316.330.217.94.763.819.29.01.40.06.0113.9139.525.7135.2 Billy45.745.717.432.019.74.663.018.98.91.50.35.6114.0144.130.6126.5 Komando45.745.716.530.419.64.663.918.99.21.40.05.8115.1142.627.9131.9 Express45.145.117.832.323.84.961.519.39.81.50.25.3113.7143.530.2127.7 Krypton45.145.017.231.121.74.661.719.89.91.40.15.7115.9144.429.1131.2 Favorite43.843.818.232.417.24.861.319.110.11.60.45.6114.7142.828.6130.8 SGEDH17548.546.917.433.745.54.429.416.89.118.818.75.1117.6146.328.6148.9 SGEDH1348.746.717.634.224.14.825.314.810.018.823.75.0118.3146.528.6143.9 SG DH1448.745.118.135.165.83.614.714.09.411.743.35.3116.1144.529.0138.9 Sollux 48.644.918.235.477.83.614.014.68.811.344.55.3119.7145.425.9143.5 Gaoyou46.042.817.732.660.83.619.713.29.113.037.75.5113.7143.630.1139.6 withou
t 2
2:1 2:1 with 2
Table 5.4: Mean values of Chinese trials for contents of seed oil (%), regression corrected seed oil (%), protein (%), protein in defatted meal (Prot.idM in %), glucosinolates (GSL in μmol/g), erucic acid (%) and begin of flowering (BOF), end of flowering (EOF), flowering period (FP in days) and plant height at end of flowering (PH_EOF in cm) of SGE DH lines with highest oil content (SGEDH172) and highest regression corrected oil content (SGEDH210, SGEDH145), SGEDH parental lines and cultivars Genotype OilOil- reg_corrProteinProt.idMGSL NIRS22:1BOFEOFFPPH_EOF SGEDH17245.445.518.433.760.3-1.6142.8165.823.0173.3 Express 61742.542.620.335.320.6-0.5141.9167.525.6166.3 NKBeauty44.545.018.132.512.9-4.7140.0165.325.3166.0 Krypton43.844.318.633.117.1-5.0143.0167.324.3166.5 Billy43.843.918.032.013.6-1.1140.8165.324.5164.0 Komando43.243.618.632.717.6-3.4142.8168.325.5170.3 Oase42.743.218.832.816.5-4.7140.8167.326.5154.8 Adriana 42.643.118.331.915.5-4.6141.3165.023.8161.0 Favorite42.743.019.534.013.6-2.8141.8166.524.8155.8 Express42.542.519.834.417.9-0.3140.3166.325.9158.6 SGEDH21047.945.918.134.840.220.3144.0168.824.8175.3 SGEDH14548.145.818.235.158.023.2138.3164.326.0153.5 SGDH1447.844.417.934.461.934.7142.1165.323.1177.8 Sollux 46.443.119.636.669.633.6148.3170.322.0158.0 Gaoyou43.842.117.931.956.417.6140.6166.325.6165.4 withou
t 2
2:1 2:1 with 2