Breeding for increased grain protein and micronutrient content in wheat: Ten years of the GPC-B1 gene

To provide food and nutrition security for a growing world population, continued improvements in the yield and nutritional quality of agricultural crops will be required. Wheat is an important source of calories, protein and micronutrients and is thus a priority to breed for improvements in these traits. The GRAIN PROTEIN CONTENT-B1 (GPC-B1) gene is a positive regulator of nutrient translocation which increases protein, iron and zinc concentration in the wheat grain. In the ten years since it was cloned, the impacts of GPC-B1 allelic variation on quality and yield traits have been extensively analyzed in diverse genetic backgrounds in field studies spanning forty environments and seven countries. In this review, we compile data from twenty-five studies to summarize the impact of GPC-B1 allelic variation on fifty different traits. Taken together, the results demonstrate that the functional copy of the GPC-B1 gene is associated with consistent positive effects on grain protein, Fe and Zn content with only marginally negative impacts on yield. We conclude that the GPC-B1 gene has the potential to increase nutritional and end use quality in a wide range of modern cultivars and environments and discuss the possibilities for its application in wheat breeding.     

Mapping genes for grain protein concentration and grain yield on chromosome 5B of Triticum turgidum (L.) var. dicoccoides

Grain protein concentration (GPC) is an important quality factor in durum wheat [Triticum turgidum (L.) var. durum]. Due to the strong environmental influence on GPC, molecular markers linked to quantitative trait loci (QTL) affecting GPC have the potential to be valuable in wheat breeding programs. Various quantitative traits in a population of 133 recombinant inbred chromosome lines were studied in replicated trials at three locations in North Dakota. Segregation for GPC, 1000-kernel weight, gluten strength, heading date, and plant height was observed. By relating phenotypic data to a linkage map obtained from the same population, three QTL affecting GPC, and one affecting yield were identified. The genotypic coefficients of determination for both traits were high.     

Isoenzyme differences between the wild diploid and tetraploid wheats

Variability of acid phosphatase (ACP), esterase (EST), and superoxide dismutase (SOD) isoenzymes among 660 accessions of wild diploid wheats Triticum boeoticum (475) and T. urartu (185) and among 35 accessions of wild tetraploid wheats T. araraticum (21) and T. dicoccoides (14) was studied with the use of polyacrylamide gel electrophoresis. The wild diploids are differentiated by the electrophoretic variants of ACP-B, ACP-C, EST-A, EST-B, EST-C, EST-D, and SOD-B. Triticum urartu matches the A genome of wild tetraploid wheats T. araraticum and T. dicoccoides by allozymes of ACP-B, ACP-C and SOD-B, but differs distinctly by the monomorphic allozyme EST-A66. Triticum boeoticum fits the A genome of polyploid wheats by allozymes of EST-A and EST-B, but differs in allozymes of ACP-B and SOD-B. Thus, none of the two contemporary diploid wheats corresponds exactly to the A genome of wild tetraploid wheats by all diagnostic isoenzymes. Triticum boeoticum and T. arararicum share EST-C46 and EST-D71, whereas T. urartu and T. dicoccoides are fixed for silent EST-C0 and share EST-D73, suggesting independent origin of the two tetraploid wheats with a contribution from ancestral forms of both diploids.     

野生二粒小麦α-淀粉酶抑制因子编码基因序列分析

对3份野生二粒小麦(Triticum dicoccoides)材料的抗虫24 kDaα-淀粉酶抑制因子编码基因进行分离克隆,得到72个24 kDaα-淀粉酶抑制因子基因,并进行序列分析。结果发现,α-淀粉酶抑制因子在野生二粒小麦中以多拷贝形式存在,经卡方检验初步推断野生二粒小麦中的α-淀粉酶抑制因子成熟蛋白编码基因序列变异类型在供试材料间无显著差异。序列分析表明,24 kDaα-淀粉酶抑制因子成熟蛋白编码基因序列无论在野生二粒小麦种内还是与小麦属的其他物种之间,都具有很高的一致性,说明该基因在进化过程中十分保守。     

应用SSR检测导入普通小麦的野生二粒小麦遗传物质

以抗白粉病和条锈病的野生二粒小麦AS846为父本,与阿勃非整倍体植株进行杂交,在杂交后代中选育出抗白粉病的N9134a,N9134b和N9134c3个品系。采用66个SSR引物对AS846、阿勃和3个N9134姊妹系进行分析,结果发现,46个引物对(69.7%)在AS846和阿勃之间有多态性,其中34个引物对在AS846中扩增出特异性产物,13个引物对在N91343个系中扩增出AS846的特异性产物。表明野生二粒小麦AS846的遗传物质已经导入到普通小麦中。根据微卫星标记在小麦染色体的位置及SSR分析结果推断,N9134的5B染色体上含有野生二粒小麦AS846的遗传物质。     

以色列野生二粒小麦和光稃野燕麦杂交亲本与后代核型分析

 对以色列野生二粒小麦（母本）和光稃野燕麦（父本）远缘杂交亲本与后代的核型及进化关系进行了分析。结果表明：母本的染色体长度比为1626,核型公式为2n=4x=28=18m（2SAT）+10sm（2SAT）,核型为1A。父本的染色体长度比为2526,核型公式为2n=6x=42=20m（2SAT）+22sm（4SAT）,核型类型为2B。以色列野生二粒小麦和光稃野燕麦杂交后代0878株系的染色体数目为42,染色体长度比为1.802,核型公式为2n=6x=42=22m（2SAT）+20sm（2SAT）,核型为2A。 0878-1株系的染色体数目为42,染色体长度比为2.057,核型公式为2n=6x=42=38m+4sm（4SAT）,核型为2B。由于光稃野燕麦遗传物质渗入到该杂交后代,获得了进化程度高于其母本的普通小麦型小麦新种质。     

野生二粒小麦与野燕麦杂种核型研究

1989年用野生二粒小麦(Triticum dicoccoides Corn.2n=4x=28)与通北野燕麦(Avenafatua L.2n=6x=42)杂交成功,F_2分离出燕麦型、二粒小麦型、硬粒小麦型、斯卑尔脱型和普通小麦型。斯卑尔脱型F_4中的一个类型,与双亲野生二粒小麦和通北野燕麦的核型进行比较研究。杂种中有一对近端着丝点染色体,5对随体染色体。近端着丝点染色体来源于通北野燕麦,5对随体染体来源于双亲野生二粒小麦和通北野燕麦。证明野生二粒小麦与通北野燕麦杂种斯卑尔脱型是真杂种。     

野生二粒小麦HMW-GS特异性及其对小麦的可利用性研究

对来自以色列的133份野生二粒小麦进行SDS-PAGE检测发现,其高分子谷蛋白亚基具有较高的遗传多样性。在Glu-A1和Glu-B1两个位点共有18种可确定的亚基变异类型,其中,A位点上的亚基1、2和B位点上的亚基7+8与17+18品质评分为3分(出现频率分别为59.4%和12.78%)。同时,出现了在普通小麦中不表达的1Ay亚基和许多普通小麦所稀有或缺乏的特异亚基类型,如1、7+9、17+18、7+8、7+8、7+9、7+8等,而且在22份材料中出现了9种未命名的新亚基类型。比较研究表明,高分子谷蛋白亚基的表达与材料的来源地有关。用具有1Ay亚基的材料与栽培小麦“川农16”杂交,在分离世代F2中检测到了1Ay亚基的存在。据此认为,可望将野生二粒小麦中诸如1Ay的特异高分子量谷蛋白亚基导入栽培小麦,这对拓宽小麦品质遗传基础,改良小麦加工品质具有重要意义。     

野生二粒小麦与二倍体野燕麦远缘杂交后代的核型分析及进化关系

对野生二粒小麦与二倍体野燕麦远缘杂交后代进行染色体核型分析。结果表明：杂交后代084株系的核型公式为2n=6x=42=36m(4SAT)+6sm，核型为1A，为极对称核型，属于原始类型；野生二粒小麦、二倍体野燕麦及084株系的进化指数分别为1、4和1，表明084株系的进化程度与野生二粒小麦一致，低于二倍体野燕麦；084株系的染色体相对长度较亲本大，且其平均臂比、核型不对称系数及臂比大于1.7的染色体比例均在野生二粒小麦与二倍体野燕麦之间，说明远缘杂交在一定程度上对加速小麦属的进化有重要意义；084株系染色体臂比与母本的相近，且存在4对染色体与父本的相对长度和臂比极为相近，核型分析结果从一定程度上证明了野生二粒小麦与二倍体野燕麦杂交后代的真实性。     

Genetic Resources for Salt Tolerance in the Wild Progenitors of Wheat (Triticum dicoccoides) and Barley (Hordeum spontaneum) in Israel

Salt tolerance was tested in the progenitors of cultivated cereals, wild barley (Hordeum spontaneum) and wild emmer wheat (Triticum dicoccoides) from Israel. Plants from five selected populations of H. spontaneum from the Mediterranean Coastal Plain and northern Negev desert, were grown on 250 and 350 mM of NaCl. Likewise, five populations of T. dicoccoides from the eastern Samaria steppes, Mt. Hermon and Mt. Carmel, were grown on 175 and 250 mM of NaCl. Here we report on superior genotypes of H. spontaneum, ripening at 350 mM NaCl (= 60 % sea water), and of T. dicoccoides ripening at 250 mM (— 40 % sea water). We are proceeding now with both genetical and physiological studies aimed at chromosomally-locating salt tolerant genes and unravelling the mechanism(s) of salt resistance in these wild cereals.