小麦TaDRO与根系形态的关联分析及在中国和全球品种中的地理分布与演变

TaDRO, A Gene Associated with Wheat Root Architectures, Its Global Distribution and Evolution in Breeding

【目的】根系改良是提高小麦抗逆性和产量的关键因素之一。通过克隆不同根系类型小麦品种的根系相关基因TaDRO,分析其与小麦重要农艺性状的关系,开发标记,为品种改良提供理论依据和技术支撑。【方法】以根系性状多态性较高的21份普通小麦为材料,测序分析TaDRO-5A、TaDRO-5B和TaDRO-5D的序列多态性;利用"中国春"-缺体四体材料对其进行染色体定位,并用最新版的中国春基因组序列对其进行精细物理定位,根据TaDRO-5A和TaDRO-5B序列多态性开发分子标记;以323份普通小麦构成的自然群体为材料进行TaDRO单元型与表型性状的关联分析。【结果】克隆了小麦TaDRO的A、B、D基因组序列,利用最新版的中国春基因组序列分别将TaDRO-5A、TaDRO-5B和TaDRO-5D定位于小麦染色体5A、5B和5D上,分别位于426.15、381.00和327.60 Mb处;在TaDRO-5A全长序列中共检测到3个SNP,形成Hap-5A-A和Hap-5A-C 2种单元型,根据启动子区-2 271bp的序列差异,开发出分子标记TaDRO-5A-KASP。在TaDRO-5B全长序列中共检测到17个SNP和1个In Del,形成Hap-5B-Ⅰ和Hap-5B-Ⅱ2种单元型,根据-300 bp的In Del开发了分子标记TaDRO-5B-In Del。关联分析表明,TaDRO-5A与株高、千粒重和根系生长角度显著相关,Hap-5A-A是增大根系生长角度、降低株高、增加千粒重的浅根型单元型,而Hap-5A-C是减小根系生长角度、增加株高、降低千粒重的深根型单元型。TaDRO-5B与株高显著相关,Hap-5B-Ⅰ是增加株高和降低千粒重的深根型单元型,Hap-5B-Ⅱ是降低株高和增加千粒重的浅根型单元型。在地方品种中,Hap-5A-C和Hap-5B-Ⅰ为优势单元型,在育成品种中,Hap-5A-A和Hap-5B-Ⅱ为优势单元型;深根型单元型Hap-5A-C和Hap-5B-Ⅰ在干旱、半干旱麦区品种中的分布频率高于湿润麦区;在全球地理分布中,干旱麦区品种中Hap-5A-C为优势单元型,但Hap-5B-I优势不明显。随着育种年代推进,小麦品种中浅根型单元型Hap-5A-A和Hap-5B-Ⅱ的频率增加。【结论】小麦根系相关基因TaDRO的Hap-5A-C和Hap-5B-Ⅰ是增加株高和降低千粒重的深根型单元型,Hap-5A-A和Hap-5B-Ⅱ是降低株高和增加千粒重的浅根型单元型;随着灌溉和化肥用量的增加,中国小麦品种逐步由深根、高秆类型转变为浅根、矮秆类型;利用分子标记选择矮秆、深根类型,可能提高品种水肥利用效率。

[Objective] Root improvement is one of the key factors to improve stress resistance and yield of wheat. Root architecture related genes, homoeologous TaDRO, are cloned from cultivars with different root phenotypes. Molecular markers are developed to detect its relationship with important agronomic traits of wheat, which could provide technical support for wheat improvement. [Method] Polymorphic sites of TaDRO-A, -B and -D were detected in 21 common wheat accessions with high diversity. Physical locations of three homoeologues were determined based on the newest genome sequence of Chinese Spring. Molecular markers were developed according to the polymorphic sites at TaDRO-5A and -5B. Association analysis between genotypes and phenotypic traits were carried out in a natural population of 323 accessions. [Result] The three homoeologous genes of TaDRO-A, -B and -D were cloned. TaDRO-A, -B and -D were located on chromosomes 5A （426.15 Mb）, 5B （381.00 Mb） and 5D （327.60 Mb）, respectively. Three SNPs were detected at TaDRO-A among 21 accessions and two haplotypes were formed, Hap-5A-A and Hap-5A-C. A molecular marker, TaDRO-5A-KASP, was developed based on the SNP located at position of -2271 bp in the promoter region. Thirteen SNPs and one InDel in the promoter region, four SNPs in the coding region were detected at TaDRO-5B, formed two haplotypes, Hap-5B- Ⅰ and Hap-5B- Ⅱ. The marker TaDRO-5B-InDel was developed based on the Indel at position of -300 bp, Association analysis showed that haplotypes of TaDRO-5A were significantly correlated with plant height （PH）, thousand kernel weight （TKW） and root growth angle （RGA）. The genetic effects on Hap-5A-A showed RGA and TKW increasing, and root depth and PH decreasing, while those on Hap-5A-C exhibited the opposite effect. The effects of Hap-5B-Ⅰ exhibited root depth and PH increasing, and TKW decreasing, while those of Hap-5B- Ⅱ were the opposite. Hap-5A-C and Hap-5B-Ⅰ were favored haplotypes in landraces while they were non-favored ones in modern cultivars. The frequencies of Hap-5A-C and Hap-5B- Ⅰ in arid and semi-arid areas were higher than those in wet areas in China. Hap-5A-C was favored haplotype in dry regions worldwide. Frequencies of Hap-5A-A and Hap-5B- Ⅱ were increasing in breeding process, respectively. [ Conclusion] Hap-5A-C and Hap-5B- Ⅰ are associated with deeper root, higher PH and lower TKW, whereas Hap-5A-A and Hap-5B- Ⅱ behave the opposite. Wheat cultivars showed root depth and plant height decreasing in breeding process due to development of irrigation system and nitrogen industries. The developed molecular markers might be used to select the ideotypes of cultivars for higher efficiency use of water and nitrogen.