青海育成小麦5个主效矮秆基因的分子检测

为系统了解青海小麦矮秆基因的分布特点,并进一步为青海高原小麦的株高育种提供优异种质资源。本研究利用5个矮秆基因的特异性分子标记对82份青海小麦品种资源中的矮秆基因进行了检测,并对不同矮秆基因的降秆效应进行了分析。结果表明:82份青海育成小麦品种中有49份材料至少含有一个矮秆基因,其中Rht-B1b的分布频率最高,约占参试材料的28.0%,其次是分布频率为23.2%的Rht8基因,而矮秆基因Rht-D1b、Rht5以及Rht12的分布频率分别为9.8%、13.4%、9.8%。在49份含有不同种类矮秆基因的材料中,其中16份材料同时含有2种及以上的矮秆基因,即RhtB1b和Rht8、Rht-D1b和Rht8、Rht-B1b和Rht5、Rht-D1b和Rht5、Rht8和Rht5、Rht-B1b和Rht12、Rht5和Rht12,并未发现同时含有矮秆基因Rht-B1b和Rht-D1b的品种;2份材料分别含有3种矮秆基因,即Rht-B1b、Rht8、Rht12和Rht-B1b、Rht5、Rht8;其余31份材料仅含有1种矮秆基因。82份青海育成小麦材料中仅含有Rht-B1b的材料11份,平均株高为86.2 cm,其降秆效应为5.7%;只含有Rht-D1b的材料有5份,平均株高为84.9 cm,其降秆效应为7.1%;仅含有Rht8的材料有9份,平均株高为88.6 cm,其降秆效应为3.1%。因此,在青海育成小麦品种中,矮秆基因的降秆效应为Rht-D1bRht-B1bRht8。     

Distribution of alleles of the WMS261 locus, marking the gene for the dwarf gene Rht8, in common wheat cultivars in southern Ukraine

The use of codominant microsatellite molecular markers allows one to study the inheritance and distribution of alleles linked to important agronomic characters. A microsatellite locus WMS261 tightly linked to a dwarfing gene Rht8 was analyzed in wheat cultivars and selection material of the Institute of Plant Breeding and Genetics. PCR screening of common wheat cultivars produced in the southern Ukraine showed the prevalence of a 192-bp allele at locus WMS261 that indicates adaptive significance of a corresponding allele of the Rht8 gene in the southern regions.     

Allele Distribution at Locus WMS261Marking the Dwarfing Gene Rht8in Common Wheat Cultivars of Southern Ukraine

The use of codominant microsatellite molecular markers allows one to study the inheritance and distribution of alleles linked to important agronomic characters. A microsatellite locus WMS261tightly linked to a dwarfing geneRht8was analyzed in wheat cultivars and selection material of the Institute of Plant Breeding and Genetics. PCR screening of common wheat cultivars produced in the southern Ukraine showed the prevalence of a 192-bp allele at locus WMS261that indicates adaptive significance of a corresponding allele of the Rht8gene in the southern regions.     

A new reduced height gene found in the tetraploid semi-dwarf wheat landrace Aiganfanmai

Aiganfanmai is a dwarf tetraploid wheat landrace (Triticum turgidum var. turgidum) that stably produces the semi-dwarf trait. Plant height varies from 80-105 cm under cultivation. Compared with tall durum wheat (T. turgidum var. durum) variety Langdon, we found it to have short spikes and seeds, besides a semi-dwarf character. We crossed Aiganfanmai with Langdon to analyze the genetic basis of the semi-dwarf trait. The F(2) population segregated at a 1:3 ratio for the short trait to the normal, which demonstrates that Aiganfanmai carries a recessive reduced height (Rht) gene. This gene was found to be located between the molecular markers Xgwm471 and Xgwm350 on chromosome arm 7AS by microsatellite analysis. No Rht gene had been reported from this chromosome; we designated it as Rht22. Rht 22, unlike other previously reported Rht genes, does not reduce internodal cell length. Reduced cell numbers might explain the short stem trait.     

The effects of gene Rht8 alleles in agronomic traits of winter bread wheat in the conditions of South Steppe of the Ukraine

Resistance to frost, winterhardiness, yield and its components were investigated in recombinant-inbred lines F5 Odesskaya 16/Bezostaya 1 and 61 winter wheat varieties differing on the alleles of Rht8 gene. The absence of influence of gene Rht8 different alleles on the tested traits was shown. The high frequency of distribution of alleles Rht8c in modern wheat varieties developed in Plant Breeding and Genetics Institute is a result of high frequency of use of this allele in genetic pool after 1959.     

Identification of 1AL/1RS translocation in winter common wheat varieties of Ukrainian selection

Analysis of alcohol-soluble protein (gliadin) patterns of a group of winter common wheat varieties from different breeding centers of Ukraine resulted in identification of six varieties with the rye 1AL/1RS translocation. The line 7086 AR also carries this translocation. The identified 1AL/1RS translocation is similar to that of the variety Amigo in the secalin pattern. The appearance of this translocation in varieties developed in different breeding centers of the forest-steppe of Ukraine indicates its involvement in coadaptive gene associations.     

矮秆基因对小麦部分农艺性状的效应

以中国主要麦区的124份小麦品种为材料,利用分子标记和系谱分析相结合,对其按照所含的矮秆基因Rht-B1b、Rht-D1b和Rht8进行分类,结合田间株高、旗叶长、小穗数和穗粒数以及室内苗期根系长度等农艺形状的调查,分析不同矮秆基因对小麦农艺性状的效应.结果显示:(1)参试的124份小麦品种(系)中23份含有Rht-B1b,7份含有Rht-D1b,22份含有Rht8基因,34份同时含有Rht-B1b和Rht8,16份同时含有Rht-D1b和Rht8,可分为6组.(2)Rht-B1b和Rht-D1b在降低株高的同时也缩短了旗叶的长度和苗期叶长,Rht8对株高的影响较弱,对旗叶和苗期叶长的影响也较小;3个矮秆基因对苗期根系长度、小穗数没有显著影响;Rht-D1b和Rht8显著增加穗粒数.研究表明,矮秆基因Rht8对小麦株高以及其他农艺性状的影响均较小,但能够显著增加穗粒数,是小麦矮化育种中比较理想的矮秆基因.     

Characterization of a Putative New Semi-Dominant Reduced Height Gene,Rht_NM9, in Wheat(Triticum aestivum L.)

Plant height is an important agronomic trait in cereal crops, and can affect both plant architecture and grain yield. New dwarfing genes are required for improving the genetic diversity of wheat. In this study, a novel dwarf mutant, NM9, was created by treating seeds of the wheat variety NAU9918 with ethyl methanesulfonate(EMS). NM9 showed obvious phenotypic changes, which were distinct from those caused by other dwarfing genes, especially the reduced plant height, increased effective tiller number, and elongated spike and grain length. The reduced plant height in NM9 was attributable to a semi-dominant dwarfing gene Rht_NM9, which was flanked by two closely linked SNP markers, SNP34 and SNP41, covering an 8.86-Mb region on the chromosome arm 2AS. The results of gibberellic acid(GA) sensitivity evaluation, comparative genomics analysis and allelism test indicated that Rht_NM9 was neither allelic to Rht7 and Rht21 nor homoeoallelic to Rht8, so Rht_NM9 was proposed to be a new dwarfing locus on the homoeologous group 2 chromosomes of wheat. Rht_NM9has a negative effect on plant height and positive effects on effective tiller number and grain size, thus, Rht_NM9 could be used for elucidating the mechanisms underlying plant architecture and grain development.     

Genetic analysis of the dwarfing gene Rht8 in wheat. Part II. The distribution and adaptive significance of allelic variants at the Rht8 locus of wheat as revealed by microsatellite screening

 Wheat microsatellite WMS 261 whose 192-bp allele has been shown to be diagnostic for the commercially important dwarfing gene Rht8 was used to screen over 100 wheat varieties to determine the worldwide spread of Rht8. The results showed Rht8 to be widespread in southern European wheats and to be present in many central European wheats including the Russian varieties ‘Avrora’, ‘Bezostaya’ and ‘Kavkaz’. Rht8 appears to be of importance to South European wheats as alternative giberellic acid (GA)-insensitive dwarfing genes do not appear to be adapted to this environment. The very successful semi-dwarf varieties bred by CIMMYT, Mexico, for distribution worldwide have been thought to carry Rht8 combined with GA-insensitive dwarfing genes. Additional height reduction would have been obtained from pleiotropic effects of the photoperiod-response gene Ppd1 that is essential to the adaptability of varieties bred for growing under short-winter days in tropical and sub-tropical areas. The microsatellite analysis showed that CIMMYT wheats lack Rht8 and carry a WMS 261 allelic variant of 165 bp that has been associated with promoting height. This presumably has adaptive significance in partly counteracting the effects of other dwarfing genes and preventing the plants being too short. Most UK, German and French wheats carry an allelic variant at the WMS 261 locus with 174 bp. This could be selected because of linkage with the recessive photoperiod-sensitive ppd1 allele that is thought to offer adaptive significance northern European wheats. Received: 17 October 1997 / Accepted: 12 November 1997     

Clarification of the Rht8-Ppd-D1 gene linkage on the 2D chromosome of winter bread wheat

In the south part of Ukraine the haplotype of Rht8c and Ppd-D1 genes is widely distributed among modern bread wheat varieties. During the time of scientific breeding program it has been selected as one of the most important adaptive complexes for plants of this region. The genetic distance between the Rht8 and Ppd-D1 genes was clarified.     

A modern Green Revolution gene for reduced height in wheat

Increases in the yield of wheat during the Green Revolution of the late 20^th century were achieved through the introduction of Reduced height (Rht) dwarfing genes. The Rht‐B1 and Rht‐D1 loci ensured short stature by limiting the response to the growth‐promoting hormone gibberellin, and are now widespread through international breeding programs. Despite this advantage, interference with the plant's response to gibberellin also triggers adverse effects for a range of important agronomic traits, and consequently modern Green Revolution genes are urgently required. In this study, we revisited the genetic control of wheat height using an association mapping approach and a large panel of 1110 worldwide winter wheat cultivars. This led to the identification of a major Rht locus on chromosome 6A, Rht24, which substantially reduces plant height alone as well as in combination with Rht‐1b alleles. Remarkably, behind Rht‐D1, Rht24 was the second most important locus for reduced height, explaining 15.0% of the genotypic variance and exerting an allele substitution effect of –8.8 cm. Unlike the two Rht‐1b alleles, plants carrying Rht24 remain sensitive to gibberellic acid treatment. Rht24 appears in breeding programs from all countries of origin investigated, with increased frequency over the last decades, indicating that wheat breeders have actively selected for this locus. Taken together, this study reveals Rht24 as an important Rht gene of commercial relevance in worldwide wheat breeding.     

Genetic analysis of the dwarfing gene (Rht8) in wheat. Part I. Molecular mapping of Rht8 on the short arm of chromosome 2D of bread wheat (Triticum aestivum L.)

 Two sets of single chromosome recombinant lines comparing 2D chromosomes from the wheat varieties ‘Ciano 67’ and ‘Mara’ with the common 2D chromosome of ‘Cappelle-Desprez’ in a ‘Cappelle-Desprez’ background were used to detect a diagnostic wheat microsatellite marker for the dwarfing gene Rht8. The genetic linkage maps place the wheat microsatellite marker WMS 261 0.6 cM distal to Rht8 on the short arm of chromosome 2D. By PCR analysis the WMS 261 alleles of ‘Mara’, ‘Cappelle-Desprez’ and ‘Ciano 67’ could be distinguished by different fragment sizes of 192 bp, 174 bp and 165 bp, respectively. A screen of over 100 international varieties of wheat showed that the three allelic variants were all widespread. It also demonstrated that a limited number of varieties carried novel WMS 261 variants of over 200 bp. Following classification of the individual recombinant lines for allelic variants at the WMS 261 locus it was possible to attribute a 7- to 8-cm reduction in plant height with the WMS 261-192-bp allele compared to the WMS 261-174-bp allele in the set of recombinant lines comparing 2D chromosomes of ‘Mara’ and ‘Cappelle-Desprez’. A height reduction of around 3 cm was detected between the WMS 261-174-bp allele and the WMS 261-165-bp allele in the recombinant lines comparing 2D chromosomes of ‘Cappelle-Desprez’ and ‘Ciano 67’. Received: 17 October 1997 / Accepted: 12 November 1997     

The Spatial Distribution of Growth in the Extension Zone of Seedling Wheat Leaves

Two models of the distribution of relative elemental rates ofelongation (RELEL) were tested for the extension zone (EZ) ofthe first foliage leaf of seedling wheat plants, by comparisonto patterns of separation of rings and gyres in the walls ofprotoxylem vessels. One model, containing a defined growth maximumin the basal half of the EZ, is favoured in the literature andwas derived from data published for perennial ryegrass. Theother, containing a flat, broad maximum throughout the regionof the EZ with stomates, was constructed from regressions ofinterstomatal distance against distance along the EZ in thefirst foliage leaf of wheat seedlings. The test strongly favouredthe model with the flat maximum. Although the gibberellic acid(GA) insensitivity alleles Rht1 and Rht2 reduce length of extensionzone (LEZ), leaf extension rate (LER) and final cell and leaflengths, they had no effect on maximum RELEL. Results with aninhibitor of GA synthesis indicated that control of leaf elongationby the control of LEZ may be generalizable as a mechanism bywhich GA controls LER in the grass leaf. Extension zone, elongation, gibberellic acid, Rht, wheat, Triticum aestvum L.     

Effects of dwarfing genes on the genetic background of wheat varieties in southern Ukraine

The effects of the Rht8c, Rht-B1b, Rht-B1e, and Rht-D1b genes on wheat height have been investigated. Variations in these effects are significantly modified by the genetic background and year conditions. A combination of the Rht8c, Rht-B1a, Rht-D1b, and Ppd-D1a alleles is the most advantageous for the conditions of southern Ukraine, since it is associated with optimal plant height under contrasting conditions within different years. The genotypes of some varieties were shown to include gene(s) that were unidentifiable by the molecular markers and significantly decreased plant height.     

Modification by gibberellin of the growth-temperature relationship in mutant and normal genotypes of several cereals

High-resolution growth measurements were conducted using a linear variable displacement transformer in conjunction with a temperature-programmed meristem-cooling collar. Chilling and rewarming profiles were determined for a range of Gramineae, in the presence and absence of varying concentrations of gibberellic acid (GA₃). In wheat (Triticum aestivum L.) seedlings, the growth-constraining temperature (P_e) was progressively lowered by increasing GA₃ concentration, with a difference of-4.8°C between controls and material treated with 10^–4 M GA₃. Dwarf-5 maize (Zea mays L.) seedlings had a higher P_e than tall segregates and the difference was markedly reduced by exposure to a saturating concentration of GA₃. A similar effect was observed with Tanginbozu dwarf rice (Oryza sativa L.). The growth ratetemperature responses of Rht3 gibberellin-insensitive dwarf wheat seedlings were unaffected by GA₃ and the P_e values for these segregates were around 5° C higher than for normals. Slender (s1) barley (Hordeum vulgare L.) genotypes had P_e values of-7° C, compared with +4° C for wild-type material, and did not show positive hysteresis for growth rate during the rewarming phase. These studies indicate that GA₃ modifies the thermal sensitivity of meristem function in Gramineae in a manner which enhances low-temperature growth.Abbreviations GA gibberellin - GA₃ gibberellic acid - LVDT linear variable displacement transducer     

The effects of temperature and the Rht3 dwarfing gene on growth, cell extension, and gibberellin content and responsiveness in the wheat leaf

The effects of low temperature and the Rht3 dwarfing gene onthe dynamics of cell extension in leaf 2 of wheat were examinedin relation to gibberellin (GA) content and GA-responsivenessof the extension zone. Leaf 2 of wild-type (rht3) wheat closelyresembled that of the Rht3 dwarf mutant when seedlings weregrown at 10C. The maximum relative elemental growth rate (REGR)within the extension zone in both genotypes was lower at 10Cthan at 20C, but the position with respect to the leaf basewas unaffected by temperature. The size of the extension zoneand epidermal cell lengths were similar in both genotypes at10C. Growth at 20C, instead of 10C, increased the lengthof the extension zone beyond the point of maximum REGR in thewild type, but not in the Rht3 mutant. Increasing temperatureresulted in longer epidermal cells in the wild type. Treatingwild-type plants at 10C with gibberellic acid (GA₃) also increasedthe length of the extension zone, but the Rht3 mutant was GA-non-responsive.However, the concentrations of endogenous GA₁ and GA₃ remainedsimilar across the extension zone of wild-type plants grownat both temperatures, despite large differences in leaf growthrates. The period of accelerating REGR as cells enter the extensionzone, and the maximum REGR attained, are apparently not affectedby GA. It is proposed that GA functions as a stimulus for continuedcell extension by preventing cell maturation in the region beyondmaximum REGR and that low temperature increases the sensitivitythreshold for GA action. Key words: Cell extension, gibberellin, Rht3 dwarfing gene, temperature, wheat leaf     

Comparison of endogenous gibberellins and response to applied gibberellin of some dwarf and tall wheat cultivars

Summary A number of dwarf wheat cultivars of the Norin 10 type were compared with several tall forms. Applied gibberellic acid markedly stimulated the growth of seedlings of the tall cultivars but not the growth of dwarf seedlings. Several other gibberellins were also inactive when tested with one dwarf cultivar. De-embryonated grains of all cultivars formed -amylase in response to gibberellic acid. Gibberellic acid caused an increase in soluble carbohydrates in the leaves of the tall cultivars but not in those of the dwarfs.Germinating grains, light-grown seedlings and developing stems of the dwarf cultivars contained more endogenous gibberellin-like activity than those of tall cultivars. It is suggested that the dwarf cultivars have a block to the utilisation of gibberellin in the shoot.     

In vitro expression of genes affecting whole plant phenotype — the effect of Rht/Gai alleles on the callus culture response of wheat (Triticum aestivum L. em. Thell)

Summary Calli were initiated from immature embryos of 12 lines of hexaploid wheat (Triticum aestivum L. em. Thell). The lines were from 3 varieties — April Bearded, Bersee and Maris Huntsman — isogenic for the reduced height/gibberellic acid insensitivity (Rht) genes — Rht1, Rht2 and Rht3 — and the tall (rht) allele. The dwarfing genes had significant effects on the growth and morphogenesis of calli. The genes interacted with the 2,4-D in the medium and the varietal background. Calli of each line were cultured in the presence and absence of 1 mg/l of gibberellic acid (GA), but there was no interaction of the Rht genes with GA in vitro. The effect of the Rht genes is discussed in relation to their effects on cellular hormone metabolism and their involvement in previously described chromosome 4B effects in culture.     

Genetic Diversity and Population Structure Analysis of European Hexaploid Bread Wheat (Triticum aestivum L.) Varieties

Progress in plant breeding is facilitated by accurate information about genetic structure and diversity. Here, Diversity Array Technology (DArT) was used to characterize a population of 94 bread wheat (Triticum aestivum L.) varieties of mainly European origin. In total, 1,849 of 7,000 tested markers were polymorphic and could be used for population structure analysis. Two major subgroups of wheat varieties, GrI and GrII, were identified using the program STRUCTURE, and confirmed by principal component analysis (PCA). These subgroups were largely separated according to origin; GrI comprised varieties from Southern and Eastern Europe, whereas GrII contained mostly modern varieties from Western and Northern Europe. A large proportion of the markers contributing most to the genetic separation of the subgroups were located on chromosome 2D near the Reduced height 8 (Rht8) locus, and PCR-based genotyping suggested that breeding for the Rht8 allele had a major impact on subgroup separation. Consistently, analysis of linkage disequilibrium (LD) suggested that different selective pressures had acted on chromosome 2D in the two subgroups. Our data provides an overview of the allele composition of bread wheat varieties anchored to DArT markers, which will facilitate targeted combination of alleles following DArT-based QTL studies. In addition, the genetic diversity and distance data combined with specific Rht8 genotypes can now be used by breeders to guide selection of crossing parents.