摘要
小麦叶片颜色与植株光合效率和籽粒产量密切相关。人工合成小麦Y223表现为生理性黄叶,与正常绿叶品种晋作82的杂种F1植株叶色表现为中间型,在Y223旗叶抽出17 d后,杂种F2群体中绿叶、中间和黄叶类型植株数目的分离比例符合1∶2∶1,表明Y223的黄叶表现不完全显性。采用混合分离群体分析法,利用杂种F2植株构建绿叶池和黄叶池,从分布于小麦21条染色体的569个SSR标记中筛选出12个在亲本间和绿叶/黄叶池间表现多态性的标记。利用9个位于2B染色体的多态性标记扩增F2群体,最终用5个标记定位了黄叶位点,暂命名为YL-2B,其侧翼标记为Xbarc200和Xbarc55,与YL-2B的遗传距离分别为2.3 cM和3.8 cM。通过比较显隐性、黄叶表型和标记连锁程度,证明YL-2B与2B染色体上已报道黄叶位点均不相同,是1个新的黄叶位点。本研究初步明确了Y223黄叶位点的遗传规律和染色体位置,为下一步基因克隆以及叶片衰老机制解析奠定了基础。
作为世界上三大主粮作物之一,小麦稳产、高产对保障粮食安全具有重要意义。叶片是小麦光合作用的主要器官,叶片颜色、叶面积以及叶夹角的变化均能显著改变植株光合效率,进而影响籽粒产
小麦第二部分同源群包含多个小麦黄叶早衰位点。例如,Agarwal
控制叶片衰老进程的重要基因可通过正向或反向遗传学手段加以验证,例如,NAC转录因子NAM-B1
Y223是一个人工合成六倍体小麦,由硬粒小麦MV TD14-00与粗山羊草Y168杂交、幼胚拯救获得单倍体,经秋水仙素人工加倍获得双二倍体创制而成。Y223植株叶片在拔节期出现黄色斑点,后期变为典型黄叶。为了分析黄叶表型的遗传规律和控制位点,本研究利用Y223与正常叶色品种杂交构建了作图群体进行分子定位,以期为黄叶基因克隆和叶片衰老机制解析奠定基础。
黄叶品系Y223、正常叶色品种晋作82、晋作82×Y223杂种F1植株(共18株)和F2群体(由9个杂种F1植株收获的所有种子种植而来,共包含245个F2单株),用于黄叶表型的遗传分析和基因定位。试验于2021-2023年度在山西农业大学东阳试验基地温室进行。
2022年10月下旬在温室播种F2群体及其亲本,行长1.5 m,行宽0.2 m,每行等距种植10粒种子。次年4月在亲本Y223植株旗叶完全展开3 d、10 d和17 d后,分别鉴定遗传群体的旗叶表型。参考Liu
采用SDS法提取三叶期F2群体单株及其亲本的叶片基因组DNA。根据后期旗叶表型鉴定结果,采用混合分离群体分析法(BSA, bulked segregant analysis)在F2群体中随机选取1级单株(正常绿色)和5级单株(完全黄叶)各10株,分别将其DNA等量混合建立绿叶池和黄叶池。采用分布于小麦21条染色体的569个SSR标
标记名称 Marker name | 上游引物 (5'-3') Forward sequence(5'-3') | 下游引物 (5'-3') Reverse sequence(5'-3') | 产物长度(bp) Product size | 退火温度(℃) Tm |
---|---|---|---|---|
Xwmc314 | ACACGGGGTCTGATTGCTTTAC | ATCGCTTTTTGACAAGTGAGGC | 188 | 61 |
Xbarc200 | GCGATATGATTTGGAGCTGATTG | GCGATGACGTTAGATGCGGAATTGT | 168 | 52 |
Xbarc55 | GCGGTCAACACACTCCACTCCTCTCTC | CGCTGCTCCCATTGCTCGCCGTTA | 131 | 55 |
Xgwm374 | ATAGTGTGTTGCATGCTGTGTG | TCTAATTAGCGTTGGCTGCC | 184 | 60 |
Xbarc91 | TTCCCATAACGCCGATAGTA | GCGTTTAATATTAGCTTCAAGATCAT | 129 | 50 |
Y223幼苗植株叶片保持正常绿色,从拔节期开始,叶片开始出现黄色斑点,从下往上逐渐变为黄叶,至旗叶完全抽出第10天后,旗叶完全变黄,整株呈现黄叶表型;此时期与正常绿叶品种晋作82相比,Y223旗叶差异明显,整个叶片呈黄色,原先黄色斑点变为红棕色斑点(

图1 Y223、晋作82以及晋作82×Y223杂种后代的旗叶表型
Fig. 1 Flag leaf phenotypes of Y223, Jinzuo 82, and progenies of cross Jinzuo 82×Y223
A:Y223 (左)和晋作82 (右)植株表型;B:Y223 (左)和晋作82 (右)旗叶表型;C:杂种F1植株表型;D:杂种F2群体旗叶表型分离,从左到右依次为1~5级
A: Phenotypes of Y223 (left) and Jinzuo 82 (right) plants;B: Phenotypes of Y223 (left) and Jinzuo 82 (right) flag leaves;C: Phenotype of F1 plants;D: Phenotypic separation of flag leaves in the F2 population, from left to right, leaves with grade 1 to 5
Y223黄叶表型多年来表现稳定,将Y223与晋作82杂交,杂种F1植株叶片上分布大量黄色斑点,叶片大部分呈淡黄色(
亲本或世代 Parent or generation | 数目 Number | 1级 Grade 1 | 中间型 Intermediate type | 5级 Grade 5 | P | ||||
---|---|---|---|---|---|---|---|---|---|
2级 Grade 2 | 3级 Grade 3 | 4级 Grade 4 | 合计 Total | ||||||
晋作82 Jinzuo 82 | 10 | 10 | 0 | 0 | 0 | 0 | 0 | ||
Y223 | 10 | 0 | 0 | 0 | 0 | 0 | 10 | ||
F1 | 18 | 0 | 0 | 0 | 18 | 18 | 0 | ||
F2 (3 d) | 245 | 85 | 67 | 41 | 29 | 137 | 23 | 34.81 |
2.8×1 |
F2 (10 d) | 245 | 66 | 45 | 57 | 32 | 134 | 45 | 5.76 | 0.06 |
F2 (17 d) | 245 | 59 | 41 | 43 | 37 | 121 | 65 | 0.33 | 0.85 |
统计分析结果显示,F2群体第一次旗叶表型鉴定结果中的绿叶类型、中间类型和黄叶类型单株数目比例不符合1∶2∶1 (P < 0.05),而第二次鉴定结果大致符合(P = 0.06)、第三次鉴定结果最为符合(P = 0.85) (

图 2 晋作82×Y223 F2群体黄叶表型3次鉴定结果相关性分析
Fig. 2 Correlation analysis among three investigation results of yellow leaf phenotype in the Jinzuo 82×Y223 F2 population
通过BSA从569个SSR标记中选出191个(33.57%)在晋作82和Y223间存在多态性的标记,进一步筛选出12个在亲本间多态性和绿叶/黄叶表型池间多态性一致的标记。这12个SSR标记中,Xgpw2204和Xgwm30位于2A染色体、Xgwm515位于2D染色体,其余9个均位于2B染色体,包括Xgwm47、Xgwm374、Xgwm382、Xwmc314、Xwmc474、Xbarc200、Xbarc55、Xbarc91和Xbarc101。使用位于2B染色体的9个标记扩增F2群体,所有标记均为共显性标记(
SSR标记 SSR markers | Y223带型数目 No. of Y233-type | 杂合带型数目 No. of heterozygous type | 晋作82带型数目 No. of Jinzuo82-type | 总计 Total | (d=2) | P |
---|---|---|---|---|---|---|
Xgwm47 | 49 | 114 | 82 | 245 | 10.07 | 0.006 |
Xgwm374 | 69 | 119 | 57 | 245 | 1.38 | 0.50 |
Xgwm382 | 42 | 91 | 112 | 245 | 56.20 |
6.3×1 |
Xwmc314 | 68 | 122 | 55 | 245 | 1.38 | 0.50 |
Xwmc474 | 33 | 104 | 108 | 245 | 51.51 |
6.5×1 |
Xbarc55 | 66 | 121 | 58 | 245 | 0.56 | 0.76 |
Xbarc91 | 73 | 113 | 59 | 245 | 3.07 | 0.22 |
Xbarc101 | 53 | 101 | 91 | 245 | 19.33 |
6.3×1 |
Xbarc200 | 59 | 120 | 66 | 245 | 0.50 | 0.78 |

图 3 YL-2B连锁标记在Y223、晋作82及其F2单株中的扩增带型
Fig. 3 Amplification banding patterns of markers linked to YL-2B in Y223, Jinzuo 82, and their F2 individuals
将9个2B染色体标记扩增F2群体的基因型数据与第3次叶色鉴定(Y223旗叶抽出17 d后)表型数据导入软件,选择Kosambi函数计算遗传距离,最终有5个标记Xgwm374、Xwmc314、Xbarc55、Xbarc91和Xbarc200与黄叶位点连锁。将定位的黄叶位点暂命名为YL-2B,其侧翼标记为Xbarc200和Xbarc55,与YL-2B的遗传距离分别为2.3 cM和3.8 cM (

图 4 YL-2B的遗传图谱
Fig. 4 Genetic map of YL-2B
目前,小麦2B染色体上报道的黄叶早衰位点有3个:els
位点 Loci | 显隐性 Dominance/ recessiveness | 黄叶表型 Phenotype | 来源 Source | 连锁标记 Linkage marker | ||
---|---|---|---|---|---|---|
名称 Name | 亲本多态性 Polymorphism between parents | 与表型连锁 Linked to phenotype | ||||
YL-2B | 不完全显性 |
拔节期起叶片现黄色斑点,抽穗期旗叶 完全变黄 | 人工合成小麦 | Xbarc200 | + | + |
Xbarc55 | + | + | ||||
els1 | 隐性 |
拔节期起叶片发黄失绿,抽穗期旗叶 出现变黄枯死表型 |
小麦杂交组合F3 突变家系 | WGGB306 | + | - |
WGGB307 | + | - | ||||
Els2 | 不完全显性 | 叶片在三叶期变黄,抽穗期旗叶完全变黄 | 小麦EMS突变体 | Xgpw4043 | - | - |
Xwmc149 | + | - | ||||
Y1718 | 不完全显性 | 叶片在苗期变为黄绿色,拔节期开始黄色加深,抽穗期旗叶完全变黄 | 小麦自然突变体 | Xwmc25 | - | - |
BE498358 | - | - |
+:存在多态性或连锁; -: 不存在多态性或连锁
+: Polymorphic or linked; -: Non-polymorphic or unlinked
黄叶是植物衰老的重要表征之一,受叶绿素合成、库-源诱导和内源激素信号转导等途径调控。这些调控途径中的基因如发生突变则会加速或延缓衰老,造成黄叶或滞绿表型。因此,小麦生理性黄叶被认为是由基因突变引起的叶片早衰。例如,小麦脱镁叶绿素酶基因TaPPH-7A突变导致叶绿素含量降低、叶片失
本研究中的黄叶品系Y223为一个由四倍体硬粒小麦与二倍体粗山羊草杂交人工合成六倍体小麦,不同倍性基因组的整合可能增加了基因突变的频率。Y223植株旗叶在抽出第10天后完全变黄,整株呈现黄叶表型,与正常叶色品种晋作82的杂种F1植株旗叶表现中间型。以Y223为参照,在Y223旗叶抽出3 d、10 d和17 d后,分别鉴定F2群体单株的旗叶颜色。结果显示,只有第3次鉴定结果(Y223旗叶抽出17 d)符合不完全显性黄叶基因的分离比例,而前两次的鉴定结果中,绿叶单株偏多。这可能是由于Y223抽穗较晚、晋作82抽穗较早,杂种F2群体植株旗叶抽出时期发生了偏分离,即在Y223抽出旗叶10 d后,仍有部分F2植株旗叶未抽出或未完全显示出黄叶,直至Y223抽出旗叶17 d后,F2群体的旗叶表型基本稳定,黄叶性状得以充分显示。利用SSR标记将Y223携带的黄叶位点YL-2B定位在小麦2B染色体上,通过比较显隐性、黄叶表型和标记连锁程度,发现YL-2B与2B染色体已报道黄叶位点均不相同,可能是1个新的黄叶位点。
YL-2B被定位在标记Xbarc200和Xbarc55之间约6.1 cM的遗传区段内。在小麦品种中国春参考基因组(IWGSC v1.0版)序列中,Xbarc200~Xbarc55对应Chr.2B: 47.64~133.52 Mb的物理距离,此区间共有744个高置信(High confidence)注释基因(详见https://doi.org/10.13430/j.cnki.jpgr. 20240318002,
此外,Y223植株在成株期还对白粉病表现为免疫,白粉菌孢子在其黄叶上不能生长,而相邻种植的正常叶色小麦品种晋作82则重度感病。这种叶片早衰植株的成株抗病性增强的现象已有许多报道,尤其是类病斑叶。例如,携带Qlr.pser.1BL的类病斑叶突变体成株期对叶锈病抗性增
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