[目的]探究不同氮素供应环境下与小麦苗期生物量及氮效率相关性状显著关联的SNP位点,预测相关候选基因,为小麦氮效率的基因克隆及其在育种中的应用提供参考.[方法]以134个小麦品种(系)组成的群体为供试群体,设置低氮、正常氮和高氮3个处理,各处理重复4次,并在2年(2013和2014年)进行了2次完全重复的营养液培养试验.试验对小麦苗期生物量及氮效率相关的14个性状进行了表型鉴定,采用MLM+K+Q混合线性模型,利用90K SNP芯片对小麦生物量及氮效率相关性状进行全基因组关联分析(genome-wide association study,GWAS),获得显著关联的SNP位点.[结果]与正常氮处理相比,低氮处理条件下,根系、地上部及植株氮含量和氮积累量均显著下降,而根生物量和根、植株氮效率均显著增加,高氮处理下,几乎所有鉴定性状均显著增加;14个性状的广义遗传力均在40％以上,其中,植株总干重的遗传力最高(95.73％).利用9329个SNP标记进行关联分析,共检测到838个SNP标记位点与供试材料的14个性状存在显著关联(P≤0.001),分布在21条染色体上.有435个(51.91％) SNP标记位点仅在一个关联分析环境中被检测到;有403个位点至少在2个处理环境(包含均值环境)中被检测到与同一性状显著关联(稳定关联标记).其中8个SNP标记位点至少在3个环境中被检测到.在4个环境下(包括均值环境)均检测到的稳定关联位点有2个:Kukri_c65481_121和tplb0025f09_1052,分别与植株总氮利用效率(total nitrogen use efficiency of plant,TNUE)和根系总氮利用效率(root nitrogen use efficiency,RNUE)显著关联;同时与至少6个性状(生物量及养分效率相关性状)显著关联的SNP标记位点共5个,分别位于1A、1B (3)和2A染色体上;根据小麦基因组注释及LD衰减水平,在同时定位了6个性状的5个SNP位点和2个多环境(4个环境)稳定关联的SNP位点的214 kb的基因组区域中共筛选候选基因84个,根据已知克隆氮效率基因的编码蛋白类型、候选基因功能注释信息及利用植物比较基因组学资源库蛋白序列同源比对分析,筛选到3个候选基因与生物量及氮效率相关.[结论]不同氮素处理显著影响小麦苗期生物量、氮效率相关性状及其相关QTL的表达,大多数SNP位点仅在1个氮素检测环境中被检测到,但也存在环境稳定性较强的位点.生物量及氮效率相关性状之间存在显著相关关系,并在一定程度上受到相同的QTL/基因控制.

小麦是我国重要的粮食作物,筛选养分高效小麦品种是品种推广应用的基础,也可以为养分高效育种提供种质.本试验以黄淮麦区135个品种/系为材料,设置正常氮磷钾(CK)、低氮(LN)、低磷(LP)和低钾(LK)4个处理,研究不同养分处理条件下小麦产量性状和氮磷钾养分效率的基因型差异,建立以产量及产量三要素为基础的养分效率指数评价指标.结果表明,减量施肥处理对小麦产量及氮磷钾养分效率均有显著影响,但是不同小麦品种/系存在显著基因型差异;氮磷钾养分效率指数与小麦籽粒产量和养分效率指标之间高度正相关,能够反映小麦在养分胁迫环境下的养分效率综合表现,可作为养分高效评价指标;根据养分效率指数分别筛选出氮、磷、钾高效种质27份、26份和30份,其中氮磷钾均高效的有LS4697、石新618、冀5265、山农18、烟农19和烟农21,为小麦养分高效育种提供了重要信息和材料.

[目的]探明控制产量及氮效率相关性状的稳定基因关联位点,为高产和氮素高效小麦育种及养分管理提供参考.[方法]采用134个小麦品种(系)为试验材料,依据小麦产量水平600和400 kg/hm2的需氮量设置正常氮(T1)和低氮(T2)2个处理,进行了2年田间试验,共形成4个处理环境.对小麦成熟期与产量及氮效率相关的14个性状进行了表型鉴定,采用GLM+Q一般线性模型和MLM+K+Q混合线性模型相结合的方法,利用群体差异SNP分子标记(90K SNP芯片)对小麦产量和氮效率相关性状进行全基因组关联分析.[结果]与正常氮处理相比,低氮处理条件下小麦籽粒产量、秸秆产量显著下降;所有性状的遗传力均在75％ 以上,其中小穗数的遗传力最高(95.12％).利用9329个SNP标记进行关联分析,共检测到382个SNP标记位点与供试14个性状存在显著关联(P≤0.001),分布在21条染色体上.有305个(79.84％)SNP标记位点仅在一个关联分析环境中被检测到;有77个位点在至少两种处理环境(包含平均值环境)中被检测到与同一性状显著关联(稳定关联标记).其中9个SNP标记位点在至少3个环境中被检测到.在4个环境下(包括平均值环境)均检测到的稳定关联位点有4个:BobWhite_c47168_598、Kukri_c31599_1456、wsnp_CAP11_c1761_958064和Excalibur_c62826_254,分别与穗粒数、籽粒氮含量和小穗数显著关联;同时与至少3个性状显著关联的SNP标记位点共12个,分别位于2A、3A、4A、5B和7B染色体上,贡献率为11.14％～22.97％,其中,标记BobWhite_c47168_598和Kukri_c31599_1456还分别定位了两个多环境(4种环境)稳定位点.根据12个与多性状共同定位位点和4个多环境(4个环境)稳定位点关联的SNP标记位置获得稳定位点附近区域的基因(基于LD block等方式估算的区间大小),使用NCBI中CDD工具和EnsemblPlants网站对这些基因进行基因功能注释,根据功能注释,共得到10个与产量和氮效率性状相关的候选基因.[结论]氮供应水平对小麦成熟期产量和氮效率相关性状均有显著影响,氮素累积量与小麦产量显著正相关.本试验中检测到的与产量及氮效率相关性状显著关联的位点中,79.84％的SNP标记位点仅在一个氮处理环境中出现,环境稳定性较差;4个位点在4个环境条件下均被检测到,环境稳定性较好;12个SNP标记位点同时与至少3个性状显著关联,涉及性状均为产量及氮效率相关性状,反映了籽粒产量与氮素效率之间的显著相关关系,也可能是同时控制这些性状的遗传热点位点.根据这些热点位点和环境稳定性好的位点筛选到10个与产量及氮效率相关性状有关候选基因,值得深入探讨.

Wheat is one of the most important staple food crops in many parts of the world. Nitrogen (N) is often considered to be the most important mineral nutrient element for crop growth and development. Nitrogen use efficiency (NUE) comprises nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE). We constructed a high-density genetic map using a set of 184 recombinant inbred lines (RILs) derived from the cross ‘Tainong 18 × Linmai 6’ (TL-RILs). In this study, 14 seedling traits and 17 maturity traits related to NUE and agronomic traits of wheat were investigated using the TL-RILs under hydroponic culture trials with high N (HN), moderate N (MN) and low N (LN) levels in two time frames, and under field trials with HN and LN levels in two growing seasons. A total of 121 and 130 quantitative trait loci (QTLs) we detected at seedling and maturity stages, respectively. Of these, 47 relatively high-frequency QTLs (RHF-QTLs) and 16 QTL clusters were found. The most important cluster, C9, included morphological, biomass, yield, NUpE and NUtE traits at the same time. The contributions for most QTLs were high, with the highest contribution of 30.00%. Seventeen RHF-QTLs were detected in this cluster, and it showed a favorable relationship between the RHF-QTLs for breeding programs. The markers in the region of cluster C9 should be valuable in marker-assisted selection (MAS). The sequence of DArT marker D-3940950 in the C9 region was identified to the RhtB1 gene with the similarity of 100% by BLAST against the Chinese Spring genome (IWGSCv1.0). The correlation analysis suggested that the morphological/biomass traits and eight yield traits can be considered as the primary morphological indexes for the evaluation of NUE instead of using element determinations, and the outcomes make it easy to identify NUE on a large scale.

Phosphorus (P) efficiency (PE), which comprises phosphorus uptake (PupE) and utilization efficiency (PutE), is considered as one of the most important factors for crop yield. In the present study, 11 seedling traits and 13 maturity traits related to wheat PE and morphology were investigated using a set of recombinant inbred lines (RILs) derived from the cross of “TN 18 × LM 6,” under hydroponic culture trials and field trials at low P (LP) and normal P (NP) levels in two different years, respectively. The LP input reduced of biomass, yield and PupE traits, but increased PutE traits. A total of 163 QTLs for seedling and maturity traits under different P levels and their AV, and 15 QTLs for relative traits were detected on 21 chromosomes. Of these, 49 and 63 QTLs for were detected specially in LP and NP treatments, respectively. We found 11 relatively high-frequency QTLs (RHF-QTLs) and four important QTL clusters, which may be the potential targets for marker-assisted selection (MAS) in wheat breeding programs for PE. Favorable relationships for breeding programs were found in the four important QTL clusters, which allow the possibility of improving the morphological traits and PutE simultaneously. A total of 29 markers which associated with 51 QTLs were found highly homologous with EST sequences, which suggested that they were potential functional loci. We suggested that the four biomass traits (SDW, RDW, TDW, and RSDW), five yield traits (SN, PH, TGW, GWP, and StWP) and two relative traits (Rstwp and Rgwp) can be considered as the primary indexes for the evaluation of PE for they are easy to identify on a large-scale.

[Objectives]The objective of this study was to detect quantitative trait locus (QTL) for N use efficiency related traits at the seedling stage of wheat under different levels of phosphorus (P) and potassium (K) treatments. The results will deepen our understanding of the relationship between N and P/K, and this knowledge could be applied for map-based cloning and marker assisted selection (MAS) in wheat breeding.[Methods]Population employed for QTL analysis was a set of 131 RILs derived from a Chuan 35050 × Shannong 483 cross. The 131 RILs and their parental lines were grown under hydroponic culture in greenhouse. Nine treatments were designed. The concentrations of the applied P and K treatments were as follows: moderate P and K (MPMK), high P (HP), low P1 (LP1), low P2 (LP2), low P3 (LP3), high K (HK), low K1 (LK1), low K2 (LK2) and low K3 (LK3). Combined with an enriched genetic map, we conducted research on the N use efficiency traits under different P and K treatments in order to map the QTLs (quantitative trait loci) related to N use efficiency of 10 traits at the wheat seedling stage and to conduct genetic analysis at the whole genome level.[Results] A total of 137 QTLs for the 10 seedling traits were detected on 20 chromosomes, with the exception of 3D. Of these QTLs, 122 (89.05%) were detected in only one treatment. Three relatively high-frequency QTLs (QRnue-1A.2, QSnue-1A.1 and QTnue-1A.1) were detected in four treatments at least. Five QTLs (QRnue-1A.1, QTnue-1A.1, QSnc-4A, QRnc-6A.3 and QSnue-6B) were detected in both the low P and low K treatments. Seventeen important QTL clusters (C1-C17) containing at least three or more traits which involved 66 out of 137 QTLs (48.18%) were mapped on chromosomes 1A, 1B, 2B, 2D, 3A, 3B, 4A, 4B, 5D, 6A, 6B, 6D and 7A. Most QTL clusters were detected in both P and K treatments, while five QTL clusters only associated with specific phosphorus or potassium treatments. Many QTL cluster sites in this study were also related to the biomass, yield and other nutrients in the predecessors’ investigation.[Conclusions] The supply of P and K significantly affects N efficiency of wheat at the seedling stage and the expression of related QTLs. Most N efficiency related QTLs were only detected in certain treatments, but many QTLs were located at the same hot sites and composed clusters (hot sites). Many of these sites were also co-located QTLs for biomass, yield and other nutrient traits in the previous study. The detection of these QTL/gene hot sites is valuable for further understanding about the genetic control of N efficiency related traits of wheat and their relationship with P and K environment.