Pleiotropic effects of the elongated glume gene P1 on grain and spikelet shape-related traits in tetraploid wheat

Wheat grain size and shape are associated not only with yield but also with product and milling quality. A subspecies of cultivated tetraploid wheat, Triticum turgidum ssp. polonicum, is characterized by elongated glumes. To elucidate morphological effects of the subspecies differentiation-related gene, we conducted QTL analysis for grain and spikelet shape using a mapping population between two tetraploid wheat subspecies, polonicum and durum. P1, the gene controlling the elongated glumes, was located on chromosome 7A, and the polonicum-type allele acted in an incomplete dominance manner to express the elongated glume phenotype. The polonicum allele of the P1 locus significantly affected not only glume length but also grain shape, spike shape, awn length and seed fertility in tetraploid wheat. The elongated glume phenotype was correlated with an increase in spike length, grain length and grain weight, and with a decrease in fertility, grain number and awn length. Thus, the subspecies differentiation-related gene in subspecies polonicum dramatically affects grain shape accompanied by alteration of spikelet shape in tetraploid wheat.     

Near-isogenic lines of durum wheat: their development and plant characteristics

Summary The effect of specific plant characteristics on the grain and biomass yield of durum wheat can be accurately determined by using isogenic lines, which, however, were not usually available. This study reported the effects of long glume, glaucousness, glume pubescence, black glume and purple culm on the yield and its associated characteristics in near-isogenic lines of durum wheat cv. LD222, which were developed by continuous backcrossing. The long glume trait which resulted in a large photosynthetic area did not enhance yield. Increased glume size associated with the P gene tended to increase the main culm dominance, characterized such as vigorous main culm and weak tillers, and plant height, but to reduce tillering and spike number. Consequently, grain yield and harvest index declined. Under the adequate water supplying condition of the present study, the glaucous trait was beneficial for grain yield. The trait of glume pubescence did not excert any significant effect on the yield related characteristics in the LD222 background. The traits of black glume and purple culm reduced the number of spikes per unit area and the number of kernels per unit area.     

Variation in developmental patterns of wild barley (Hordeum spontaneum L.) and cultivated barley (H. vulgare L.)

Summary Six wild barley (Hordeum spontaneum) accessions, from a diverse range of habitats, and two spring-cultivated barleys, were examined for variation in durations of development phases. The durations of the leaf initiation and spikelet initiation phases were longer and spikelet growth phases shorter, in wild than in cultivated barley. Across all wild and cultivated barleys the rate and duration of spikelet initiation were negatively correlated, but neither was related to the number of spikelets per spike. The number of spikelets was positively correlated with the number of leaves and the ratio of the number of spikelets to the number of leaves declined with increasing time to anthesis, indicating that each successive leaf was associated with a diminishing increase in the number of spikelets. The duration of culm elongation and final culm length were shorter in accessions of cultivated barley compared with wild barley. This paper also discusses the feasibility for increasing the number of spikelets per spike through breeding for genetic changes in lengths of pre-anthesis phases of development.Abbreviations ANOVA Analysis of variance - HV Hordeum vulgare - CE Culm elongation - DR Double ridge - HS Hordeum spontaneu - ° Cd Degree days     

Genetic mapping of loci determining long glumes in the genus Triticum

Elongated glumes are present in thetetraploid wheat species T.polonicum, T. turanicum, T.durum convar. falcatum and in thehexaploid species T. petropavlovskyi.Inheritance of glume length was studiedwith the aim to map the respective lociusing wheat microsatellite markers. In T. polonicum and T. petropavlovskyiloci conferring long glume were mapped nearthe centromere on chromosome 7A. These twoloci are designated P-A ^pol 1 andP-A ^pet 1, respectively. It isshown that both are probably homoeoallelicto each other and to the P gene ofT. ispahanicum on chromosome 7B. The loci determining elongated glumes in T. turanicum and T. durum conv. falcatum are not homoeologous to the P loci in the centromeric region of thegroup 7 chromosomes.     

Mechanisms and diversity of resistance to sorghum midge, Stenodiplosis sorghicola in Sorghum bicolor

Sorghum midge, Stenodiplosis sorghicola (Coquillett) is the most important pest of grain sorghum worldwide, and plant resistance is an important component for the control of this pest. To identify sorghum genotypes with diverse mechanisms of resistance to sorghum midge, we studied oviposition, larval survival, and midge damage in 27 sorghum midge-resistant genotypes, and a susceptible check under greenhouse conditions. Observations were also recorded on floral characteristics and compensation in grain mass. Of the 28 sorghum genotypes tested, 19 showed high levels of antixenosis to oviposition as a component of resistance, and had <20% spikelets with eggs when infested with 10 or 25 sorghum midge females per panicle under no-choice conditions in the headcage. Genotypes IS 8887, IS 10712, IS 21873, IS 21881, ICSV745, and QL 39 showed antibiosis as one of the components of resistance. Lines IS 7005, IS 10712, IS 18563, IS 21873, IS 21881, PM 15936-2,ICSV 197, and ICSV 745 showed <20% spikelets with eggs, larvae,or, midge damaged chaffy spikelets across infestation levels, compared with >80% midge damaged spikelets in QL 12 - the susceptible check. Genotypes showing resistance to sorghum midge have smaller glumes than the susceptible check, QL 12. However, IS 7005, IS 18653, and ICSV745 have relatively large sized glumes, but suffered <20% midge damage suggesting that factors other than glume size also contribute to midge resistance in sorghum. Fourteen genotypes showed >20% compensation in grain mass when the panicles were reduced to 250 spikelets and infested with 10 or 25 midges per panicle. There is considerable diversity in sorghum genotypes showing resistance to sorghum midge. Genotypes with diverse combination of characteristics associated with resistance to sorghum midge can be used in breeding programs to broaden the genetic base and increase the levels of resistance to this insect. This revised version was published online in August 2006 with corrections to the Cover Date.     

Morphology, Cytology and Fertility of Avena sativa L. ×A. magna Murph. et Terrell Amphiploids

The genotypes of Avena sativa were crossed to A. magna Murph. et Terrell, from the sterile pentapliod F₁ amphiploids were successfully developed after colchicine treatment. The C₁ plants were observed for their morphology, cytology and fertility. These plants were characterized by longer and broader glumes, swollen pedicel attachment, pubescent lemmas, bold seeds and persistent spikelets. Other characters, viz., final plant height, rachis length, peduncle length and spikelets per panicle were intermediate. All plants hail the chromosome number 2n = 70 or close to. 7C. Due to stickiness of chromosomes, meiosis of only two decaploid plants could be studied in detail. The average chromosome Association was 1.3 I + 28.56 II + 1.4 III + 1.77 IV + 0.07 VI and 0.13 I + 28.7 II + 0.14 III + 2.09 IV + 0.59 VI; but in some cells up to 35 bivalents were observed. Seed set as well as pollen fertility and size exhibited great variation.     

The genetics of rachis fragility and glume tenacity in semi-wild wheat

The inheritance of rachis fragility and glume tenacity in semi-wild wheat was studied in an attempt to help establish the taxonomic status and genetic origin of semi-wild wheat. Progenies of crosses and backcrosses of semi-wild wheat with the cultivar Columbus (common wheat) indicated that the fragile rachis and non-free-threshing character of semi-wild wheat were dominant to the tough rachis and free-threshing character of common wheat. F₂ and backcross data indicated that the rachis fragility and glume tenacity of semi-wild wheat were each controlled by a single gene in the cross of semi-wild wheat with Columbus. In the cross of semi-wild wheat with Triticum aestivum spp. spelta, the F₂ and F₃ population did not segregate for glume tenacity, but did segregate for rachis fragility. The F₂ and backcross data suggest that three genes interact to control three types of rachis fragility, i.e. semi-wild wheat-type, spelta-type and the tough rachis of common wheat. Semi-wild wheat differs from common wheat in rachis fragility and glume tenacity. This wheat also differs from other wheats with fragile rachis and tenacious glumes (T. aestivum ssp. spelta, macha and vavilovii) in the pattern and degree of rachis disarticulation. We conclude that semi-wild wheat is likely a subspecies within T. aestivum at the same taxonomic level as spp. spelta, macha and vavilovii. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic control of long glume phenotype in tetraploid wheat derived from Triticum petropavlovskyi Udacz. et Migusch.

The Chinese wheat landrace, Xinjiang rice wheat (T. petropavlovskyi Udacz. et Migusch., 2n = 42), known as ‘Daosuimai’ or rice-head wheat is characterized by long glumes, and was found in the agricultural areas in the west part of Talimu basin, Xinjiang, China in 1948. The gene for long glume from T. petropavlovskyi was introduced into a line of spring durum wheat, LD222. The gene for long glume is located approximately46.8 cm from the cn-A1 locus, which controls the chlorinatrait. Significant deviation from a 3:1 in the F₂ of LDN7D(7A)/ANW5C confirmed that the long glume of T. petropavlovskyi can be controlled by a gene located on chromosome 7A. The gene locates approximately 12.4 ± 0.5 cM from the centromere on the long arm of 7A. It is considered that the gene for long glume from T. petropavlovskyi is an allele on the P ₁ locus, and it should be designated as P _1a. It is suggested that T. petropavlovskyi originated from either the natural hybrid between T. aestivum that has an awn-like appendage on the glume and T. polonicum or a natural point mutation of T. aestivum. This revised version was published online in August 2006 with corrections to the Cover Date.     

The inheritance and chromosomal location of a gene for long glume in durum wheat

Summary Several near-isogenic lines of durum wheat cv. LD222 have been developed. These include a near-isogenic line carrying gene P and designated P-LD222. The P gene from Triticum polonicum determines a long empty outer glume. The objective of this study was to determine the inheritance and chromosomal location of the P gene. To determine the inheritance, P-LD222 was crossed to two chlorina mutants and to a near-isogenic line for the purple culm trait, Pc-LD222. Linkage of the P gene with the mutated gene in chlorina mutant CDd6 indicated that the P gene was located on chromosome 7A. P-LD222 was also crossed with durum cultivar Langdon (LDN) and the LDN D genome substitution lines, LDN 7D(7A) and LDN 7D(7B). Segregation for the long glume trait in the F₂ of LDN/P-LD222 and LDN 7D(7B)/P-LD222 was normal (3:1) and indicated P gene was not on chromosome 7B. Significant deviation from a 3:1 in the F₂ of LDN 7D(7A)/P-LD222 confirmed the location of P on chromosome 7A, as indicated by the linkage analysis.     

Genetic mapping of the genes for glaucous leaf and tough rachis in Aegilops tauschii, the D-genome progenitor of wheat

Glaucous leaf and tough rachis phenotypes are rare in Aegilops tauschii, the D genome donor to common wheat (Triticum aestivum). The genes for glaucous leaf and tough rachis were mapped using microsatellite probes in A. tauschii. The glaucous phenotype was suppressed by the inhibitor W2^I located on chromosome 2DS. The gene W2^I was mapped to the distal part of 2DS, and was unlinked to the centromere. This suggests that the distance of the W2^I locus from the centromere was maintained during the evolution of hexaploid wheat from its diploid progenitors as the inhibitor gene is at the same position in A. tauschii and bread wheat. The Br^t (Brittle rachis of A. tauschii) locus was located on the short arm of chromosome 3D, and was 19.7 cM from the centromeric marker, Xgdm72.3D. Br^t causes breakage of the spike at the nodes, thus creating barrel-shaped spikelets, while Br₁ in hexaploid wheat causes breakage above the junction of the rachilla with the rachis such that a fragment of rachis is attached below each spikelet.     

Genome‐wide association analysis reveals flowering‐related genes regulating rachis length in rice

Rachis length is correlated with panicle size in rice. Unveiling the genetic basis of rachis length is important for understanding the genetic regulation of panicle size. In this study, we performed a genomewide association study of rachis length using 529 rice accessions from two environments. In total, 20 loci were identified for rachis length and distributed across the 12 chromosomes except for chromosomes 2 and 5. Thirteen of the 20 loci were not linked to the cloned panicle size genes. Six flowering‐related genes, including the CCT domain‐containing genes Ghd7, Ghd7.1, Hd1, OsCCT1 and OsCO3 as well as Ehd1, were associated with rachis length in this study. These findings suggest that the network of these flowering‐related genes probably participates in the regulation of rachis length and thus affects panicle length and yield. Interestingly, haplotype analysis showed that OsCCT1 is a putative candidate gene which plays a key role in the variation of rachis length. Together, the genetic loci identified in this study could be used for rice breeding by marker‐assisted selection to improve grain yield.     

Telosomic mapping of the homoeologous genes for the long glume phenotype in tetraploid wheat

Triticum turgidum ssp. polonicum and T. ispahanicum were characterized by the long glume phenotype. P ₁ gene determines the long glume phenotype of T. polonicum, and locates on chromosome 7A. T. ispahanicum has shorter glume than T. polonicum and the long glumephenotype is determined by P ₂ gene located on chromosome 7B. In the present study, aneuploid stocks of `Langdon' durum wheat were used to map the genes, P ₁ and P ₂. P ₁ located on the long arms of chromosome 7A and its map distances from the centromere was 14.5 cM. On chromosome 7B, four loci located as cc (chocolate black chaff) – Pc (purple culm) – centromere – P ₂ – cn-BI (chlorina). P ₂ located on the long arms of chromosome 7B and its map distances from the centromere was 11.7 cM. It was suggested that a paralogous gene set conditions long glume phenotype in the homoeologous group 7 chromosomes. The P ₁ and P ₂ genes may be useful as genetic markers in tetraploid wheat.     

Location of genes for high grain protein percentage and other quantitative traits in wild wheat Triticum turgidum var. dicoccoides

Summary The genetic control of grain protein percentage (GPP) in the wild tetraploid wheat, Triticum turgidum var. dicoccoides, was determined by crossing four accessions of this taxonomic variety with durum cultivar Inbar, and analyzing the parents, F₁ and F₂ populations. Reciprocal crosses indicated no cytoplasmic effect on GPP. The F₂ variation was continuous in all crosses, showing no transgressive segregation. However, crosses between different accessions of var. dicoccoides showed transgressive segregation indicating the presence of different genes for high GPP in these accessions. Grain protein percentage was mostly codominant with high GPP, showing either no dominance, or a weak dominance. Heritability coefficients (broad sense) ranged from 0.30 to 0.53. Correlation coefficients between GPP and yield components were usually significantly negative, with the exception of the number of spikelets per spike, and in some crosses, grain weight.The number and chromosomal location of genes coding for high GPP were determined by the association between GPP and 27 markers (23 morphological and 4 biochemical markers). For this purpose, the genetic control of these markers, their linkage groups and chromosomal location were studied. At least four loci for high GPP that segregated in the F₂ populations are suggested: one on chromosome arm 1AS, marked by the black glume gene (Bg); one on 1BS, marked by the HMW gliadin locus Gli-B1; one on group 5, marked by the genes for beaked glume (Bkg) and toothed palea (Tp); and one on group 7, marked by the kinky neck gene (Kn). The relationship between GPP and several yield components was studied in a similar manner. In general, loci of markers that correlated positively with high GPP were not correlated with a decrease in yield components. Moreover, several loci of var. dicoccoides were associated with an increase in yield components.The utilization of markers for chromosomal location of genes coding for quantitative traits is compared to the technique of aneuploid analysis, commonly used in wheat. The significance of the above findings for breeding is discussed.     

不同供水条件下小麦不同绿色器官的气孔特性研究

为了考察小麦叶片与非叶器官气孔结构特性的差异及其对供水条件的反应，本研究设置不同灌水处理，利用电镜观察小麦灌浆期不同绿色器官的气孔分布和结构特征，并分析其与气孔特性指标间的关系。结果表明，在不同灌水处理下看到各非叶器官（穗、旗叶鞘和穗下节间）均分布着气孔，但其数目少于旗叶叶片。护颖仅在远轴面存在气孔；外稃在多水条件下（4水处理）近轴面出现较多气孔，而远轴面看不到气孔，但在水分胁迫（无水处理）条件下，气孔却出现在远轴面而不在近轴面；在不同水分处理下均观察到芒上明显的气孔分布。从气孔大小看，穗各部分（护颖、外稃、内稃和芒）略小于其他器官。随着灌水次数的减少，各器官气孔密度呈增大趋势，气孔器及气孔孔径表现出长度增加、宽度减小的特征。限水灌溉下非叶器官（穗、旗叶鞘和穗下节间）在籽粒灌浆期气孔导度、蒸腾速率和光合速率的稳定性高于叶片。相关分析表明，不同器官的气孔导度与蒸腾速率均呈显著正相关，非叶器官气孔导度与光合速率的相关程度明显低于叶片。说明在干旱少水条件下，叶与非叶器官蒸腾作用均会减弱，叶片光合速率亦相应降低，而非叶器官光合速率可能保持相对稳定，可相对提高其水分利用效率。     

Enhanced pollen grain embryogenesis and plant regeneration in anther cultures of Brassica juncea cv. PR-45

Summary Pollen grain embryogenesis in anther cultures of Brassica juncea cv. PR-45 was considerably enhanced by treating the donor plants with 4 mll^-1 (v/v) of ethrel or delayed sowing of the donor plants, the latter treatment being superior. The anthers derived from plants sown about two months after the normal sowing period showed 18% androgenesis as compared to 3.5% in the control.Pollen grain embryos normally showed very poor germination (10%) on B₅ or B₅ containing GA₃. However, ABA or cold treatment promoted normal germination of these embryos. Exposure of the embryos to 4°C for 6 days, which proved to be the best treatment, induced 66% germination of the embryos.     

Relationship between Quality, Colour of Glume and Gliadin Electrophoregrams in Durum Wheat

Gliadin electrophoregrams, protein content and SDS-sedimentation values from the modified SDS-sedimentation test were obtained from six Greek cultivars of Triticum durum and 98 biotypes (78 with white glumes, 20 with red glumes). Our results provide wheat breeders with the tool TO predict the cooking quality of durum wheat from early generation breeding lines, since we were able to correlate the colour of the glume with the presence or absence of gliadin bands 42/45. All red glume biotypes lacked gliadin band 45 and possessed gliadin band 42. Furthermore, their SDS sedimentation values were around 27 (weak gluten), indicating poor cooking quality. Yet, the electrophoregrams of the gliadin proteins allowed an identification of the wheat cultivars examined, since for each cultivars the pattern was different. No correlation was found between the colour of the glume and the amount of total gram protein.     

Yield, Grain Weight and Height Relationships in Two Random Samples of Early Semi-Dwarf Genotypes of Spring Wheat (Triticum aestivum L.)

The objective of this work is to study the association between the genotypic differences in mean grain weight and grain yield, the relationship of yield and grain weight with culm length, and the differences between the effects of the Rht1 and Rht2 dwarfing alleles on these characters. Yield, grain weight, grains m^-2 and culm length were evaluated in two random samples of 19 semi-dwarf early lines, selected in F₅ and tested in F₂, from two different crosses between cultivars differing in the Rht allele controlling their semi-dwarf ness. The lines of each cross were tested in 4-replicated field trials at two different sites. Phenotypic, genotypic, partial and multiple correlations as well as hertability estimates were computed. In each cross the lines differed significantly in their mean values of all the characters tested. In both crosses there was no apparent association between grain weight and grain yield. It therefore seems that in wheat of the type investigated in this study, grain yield and grain weight are independent controlled and that high grain yield is not restricted to any particular range of mean grain weight. A rather high positive correlation between culm length and grain weight was found in one cross but not in the other indicating the dependence of this relationship on the genetic background. In both crosses no significant differences were found between the performance of the lines carrying the Rht1 dwarfing allele and those carrying the Rht2 allele.     

Genetic Analysis of Chromosome 2D of Wheat

The Yugoslavian varieties ‘Novosadska Rana 1’ and ‘Sava’ are shown by monosomic comparisons to carry weak height promoters on chromosome 2D characteristic of the ‘Akakomugi’ gene for reduced height, Rht8. Reciprocal monosomic crosses between ‘Bersee’ and ‘Sava’ demonstrate ‘Sava’ chromosome 2D reduces height by about 16 cms, accelerates ear emergence by about 9 days and increases yield through increased grain number and grain size. Recombinant lines developed for chromosome 2D suggest that this chromosome in Mediterranean wheats carries three genes, Rht8, Ppd1 and Yr16, important to their adaptation. Rht8 and Ppd1, a gene for day length insensitivity together reduce height. Ppd1 and, to a minor degree, either yr16, the susceptible allele of a gene for adult plant resistance to yellow rust or a closely linked gene, accelerate time to flowering and thereby avoid desiccating Yugoslavian summer conditions. The same genes reduce spikelets numbers but this is offset by increased floret fertility producing an overall increase in the number of grains per ear. Ppd1 also by avoiding desiccating conditions increases gram size and together with either yr16 or the closely linked fertility gene increases ear and plant yields.     

Genetic analysis of the response to day length in rice

Summary Inheritance of time-to-flowering, plant height, tiller number, spikelet number and flag leaf area was studied under day lengths of 10 and 14 hours in a diallel cross of six rice varieties. Early flowering was dominant to late in both environments but the varieties flowering early in one environment were late flowering in the other. Analysis of F₁ and F₂ data from the cross of Heenati-310 x IR-8 suggested a digenic control of early flowering in short days with complementary interaction. It is considered that while relatively few genes control time-to-flowering in rice a previous proposal that separate genes for time-to-flowering and photoperiod sensitivity exist is unnecessary on present evidence. Whereas culm length, tiller number and flag leaf area were increased by longer days, the number of spikelets per panicle was reduced. The length of the panicle was little affected by changing environment, and throughout certain characters and varieties, such as tiller number in I-geo-tze, were more stable than others. Varietal crosses of Heenati-310 x IR-8 and Tainan x MI-273(m) appeared to give high yield potential.     

Seventh supplementary list of wheat varieties classified according to their genotype for hybrid necrosis and geographical distribution of Ne-genes

Summary The seventh supplement of the genotype hybrid necrosis in Triticum is presented. This list contains 414 Ne ₁-, 179 Ne ₂- and 662 non-carriers. The total number of varieties tested is 4629 viz. 1298 (28.0%) Ne-, 1031 (22.3%) Ne ₂- and 2300 (49.7%) non-carriers.The various aspects reported in literature and those studied by me are discussed.The geographical distribution of Ne-genes and their alleles indicates two Ne ₁ ^w -areas, one Ne ₁ ^m -area, probably two Ne ₂ ^ms.s -areas and four non-carrier-areas.