分子标记辅助选育高饲用价值低硫苷油菜新品种

Development of High-feeding Value and Low-glucosinolate Content Rapeseed Cultivar by Marker-assist Selection

低硫苷育种是油菜(Brassica napus L.)遗传改良的重要方向之一,随着上世纪80年代低硫苷油菜种质‘Bronowski’的引进,中国油菜品种种子硫苷含量显著降低,从100μmol/g以上降低到30μmol/g以下。然而现有菜籽饼粕的硫苷含量(20~30μmol/g)还是影响了其在饲用饼粕(由大豆饼粕,菜籽饼粕等按比例混合而成)中的添加比例,利用新的低硫苷基因资源进一步降低现有油菜品种种子硫苷含量从而提高菜籽饼粕在饲用饼粕中的添加比例,对保障现阶段中国饲用蛋白安全具有重要意义。前人研究表明:BnaA3MYB28基因的自然变异并不是来源于‘Bronowski’,这一基因的低硫苷等位基因在现有双低品种中并未固定下来(Liu et al.,2020a)。为了利用这一基因的功能缺失等位变异进一步降低现有品种(硫苷含量为20~30μmol/g)的种子硫苷含量,本研究以长江中游已大面积推广的双低常规油菜品种‘中双11’(‘ZS11’)为轮回亲本,以‘6502B’为供体亲本,通过温室加代一年种植3~4季,并在温室和大田分别通过1次杂交、3次回交和2次自交得到BC3F3后代。在BC3F2代获得目标基因型纯合单株。在BC3F3代将目标基因基因型纯合的低硫苷株系及轮回亲本‘ZS11’进行重要农艺性状和品质性状(如含油量和油酸等)考察,同时用覆盖全基因组的1010个单核苷酸多态性(single nucleotide polymorphism,SNP)标记进行低硫苷株系的背景回复率检测。结果表明:本研究获得了与轮回亲本‘ZS11’综合农艺性状最接近的株系Z6-32,其种子硫苷含量为(11.46±0.31)μmol/g,可作为轮回亲本对应的低硫苷新品种。对获得的2个低硫苷株系的遗传背景进行SNP标记基因型检测,发现Z6-13、Z6-32株系的背景回复率分别为85.2%和86.1%。本研究为进一步提高现有油菜品种饼粕的饲用价值提供了科学依据。

Low-glucosinolate(GSL)content breeding is one of the important directions in rapeseed genetic improvement.Chinese breeders have dramatically reduced the level of seed GSL content(SGC)from>100μmol/g to<30μmol/g through the introgression of lower SGC alleles from the Polish cultivar’Bronowski’since 1980s.However,the GSL content in the existing rapeseed meal(20~30μmol/g)still affects its addition proportion in the feed meal(composed of soybean meal,rapeseed meal,etc.mixed in proportion).Using new low GSL gene resources that not derived from’Bronowski’to further reduce SGC in the existing rapeseed cultivars,so as to increase the addition proportion of rapeseed meal in the feed meal,is of great significance to ensure the safety of feed protein in China at present.Previous studies found that the natural variation of BnaA3MYB28 gene was not identified in’Bronowski’,and the low-GSL allele of BnaA3MYB28 has not been fixed in the existing double low(low GSL content and low erucic acid)rapeseed cultivars,therefore,utilization of the loss-function variation of BnaA3MY-B28 may further reduce the SGC of existing cultivars(the SGC is 20~30μmol/g).In present study,’ZS11’,which has been widely cultivated in the middle area of the Yangtze River,was used as recurrent parent(BnaA3MYB28 gene with normal function)and the inbre line’6502B’(an INDEL with 1356 bp occurs in the 2th exon of BnaA3-MYB28 gene,leading frameshift)as donor parent.The target gene genotypes of backcross and selfing progenies were detected by agarose gel electrophoresis.Via 1 cross,3 backcrosses and 2 self-crossing in greenhouse and field,BC3F2and BC3F3progenies were obtained.Two homozygous individuals with low GSL were obtained in BC3F2generation.In BC3F3generation,the low-GSL lines and their corresponding recurrent parent-’ZS11’were investigated for important agronomic(such as plant height,seed weight,etc.)and quality traits(such as oil content and oleic acid content),and the background recovery rate of low GSL lines was detected by 1010 SNP markers covering the whole genome.The results showed that a line’Z6-32’,which has the closest agronomic characters to the recurrent parent’ZS11’was obtained.Its SGC was(11.46±0.31)μmol/g,additionally,the recurrent rate of Z6-13 and Z6-32 were85.2%and 86.1%respectively.This study provided a scientific basis for further improve the feeding value of the existing popularized rapeseed cultivar.