Long-term optimized embryogenic cultures in durum wheat (Triticum durum Desf.)

Five varieties of durum wheat: Appulo, Ofanto, Latino, Creso, and Castello (Triticum durum Desf.) adapted to the semi-arid mediterranean environment have been tested for their in vitro response. Compact, embryogenic, highly regenerable calli originated from primary callus derived through proliferation of the scutellum of immature embryos explanted in the presence of 2,4 dichlorophenoxyacetic acid. Selective subculture of the white, compact, embryogenic sectors led to the establishment of long-term cultures. Regeneration occurred on hormone-free medium either via germination of somatic embryos, or via multiple-shoot formation probably due to precocious germination of somatic embryos. The three varieties, Ofanto, Creso and Appulo, were the best responding genotypes. Callus fragmentation and two subsequent transfers onto fresh medium at 7-day intervals yielded a frequency of plant regeneration of some 25–40 plantlets per gram fresh weight callus in 21 days on Murashige and Skoog's hormone-free medium. Plantlets could be efficiently established in soil, thus confirming the possibility of biotechnological approaches with varieties of this crop species.Abbreviations E embryogenic - NE non embryogenic - MS Murashige and Skoog's (1962) medium - 2,4-D 2,4 dichlorophenoxyacetic acid - DAA days after anthesis - FWT fresh weight tissue     

EST-SSR DNA polymorphism in durum wheat (Triticum durum L.) collections

SSRs derived from EST were molecular markers belonging to the transcribed region of the genome. Therefore, any polymorphism detected using EST-SSRs might reflect the better relationship among species or varieties. Using wheat EST-SSR markers, 60 durum wheat (Triticum durum L.) accessions from seven countries were investigated. Twenty-five primer pairs could amplify successfully in the 60 durum wheat accessions, of which tri-nucleotide repeats were the dominant type, and revealed 26 loci on all seven wheat homologous chromosome groups. A total of 87 eSSR alleles were detected, and the number of alleles detected by a single pair of primers ranged from 1 to 11, with an average of 3.3 alleles per locus. Higher numbers of alleles and PIC were identified on the B genome than those on the A genome.     

Radiation induced asynaptic mutations in durum wheat (Triticum durum DESF.)

The cytological behaviour and the inheritance of two asynaptic mutations independently obtained by neutron treatment of durum wheat seeds of var. Cappelli and Aziziah are considered. Mutant individuals of both lines have normal morphology, but are completely sterile. Analysis of chromosome behaviour at the several stages of PMC meiosis has been thoroughly accomplished in mutant progenies of both varieties during two subsequent generations. A completely random chromosome disjunction was found at anaphase I, together with multipolar spindles, laggard chromosomes etc. At meiotic second division a large amount of abnormalities were found, as a consequence of previous asynapsis and irregular polarization. Some differences in cytological behaviour were found between the asynaptic mutants of Cappelli and the asynaptics of Aziziah. - Genetic analysis demonstrated that both mutations behave as monogenic recessives.Contribution No. 139 from the Laboratory for the Application of nuclear energy to Agriculture, Casaccia Nuclear Studies Centre, Roma, Italy. - Part of the investigation was supported by Consiglio Nazionale delle Ricerche (Gruppo di lavoro per il miglioramento genetico delle piante erbacee e cultivate, Sottogruppo per il grano duro).     

Global diversity of durum wheat Triticum durum Desf. for alleles of gliadin-coding loci

Genetic diversity for the alleles of gliadin-coding loci was studied with 465 durum wheat accessions from 42 countries. A total of 108 alleles were identified for four loci; 60 alleles were described for the first time. Broad diversity of rare gliadin-coding alleles was observed. The highest genetic diversity was characteristic of durum wheat accessions from the Middle East, Trans-Caucasia, the Pyrenean Peninsula, and the Balkans. Two genetically isolated ancient branches of durum wheat were isolated. A “southern” branch included mostly accessions from the Mediterranean region, the Middle East, and Trans-Caucasia. A “northern” branch included Russian and Ukrainian durum wheat accessions and varieties obtained on their basis. An additional group included durum wheat accessions that had been obtained in several past decades on the basis of the material of international breeding centers (CIMMYT and ICARDA) and had low genetic diversity.     

Catalogue of alleles of gliadin-coding loci in durum wheat (Triticum durum Desf.)

Gliadins are seed storage proteins which are characterized by high intervarietal polymorphism and can be used as genetic markers. As a result of our work, a considerably extended catalogue of allelic variants of gliadin component blocks was compiled for durum wheat; 74 allelic variants for four gliadin-coding loci were identified for the first time. The extended catalogue includes a total of 131 allelic variants: 16 for locus Gli-A1(d), 19 for locus Gli-B1(d), 41 for locus Gli-A2(d), and 55 for locus Gli-B2(d). The electrophoretic pattern of the standard cultivar and a diagram are provided for every block identified. The number of alleles per family is quite small for loci Gli-A1(d) and Gli-B1(d) of durum wheat, as contrasted to loci Gli-A2(d) and Gli-B2(d) that are characterized by large families including many alleles. The presence of large block families determines a higher diversity of durum wheat for loci Gli-A2(d) and Gli-B2(d) as compared to Gli-A1(d) and Gli-B1(d). The catalogue of allelic variants of gliadin component blocks can be used by seed farmers to identify durum wheat cultivars and evaluate their purity; by breeders, to obtain homogenous cultivars and control the initial stages of selection; by gene bank experts, to preserve native varieties and the original biotypic composition of cultivars.     

High molecular weight glutenin subunit in durum wheat (T. durum)

Summary The diversity of high molecular weight (HMW) glutenin subunits of 502 varieties of durum wheat (Triticum durum) from 23 countries was studied using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Twenty-nine types of patterns were observed with 18 mobility bands. A total of 18 alleles were identified by comparing the mobilities of their subunits to those previously found in hexaploid wheat (T. aestivum) and in Triticum turgidum var. dicoccum. Five new alleles were detected: two on the Glu A1 and three on the Glu B1 locus. Comparison of the frequency of alleles in the three species T. aestivum, T. dicoccum and T. durum was investigated. Significant differences exist between each of these species on the basis of the frequency distributions of their three and four common alleles at the Glu A1 and Glu B1 locus, respectively. The Glu B1c allele occuring very frequently in hexaploid wheats was not found in the two tetraploid species. More than 83% of the T. durum analysed were found to have the Glu A1c (null) allele.     

Stability parameters and performance of interregional crosses in durum wheat (Triticum durum Desf.)

Summary Twelve durum wheat varieties originating from 3 ecologically diverse regions and their 48 intergroup crosses were evaluated for stability of performance with respect to grain yield and certain component traits. The linear component of the genotype-environment interaction was revealed for grain yield, 100-grain weight and plant height, non-linear for tiller number whereas for grains per spike both components were equally important. However, except for tiller number, the linear component appeared to be contributing to a large extent towards the prevalent interactions. NP 404, Bijaga Yellow and Giorgio VZ 331 depicted stable performance for grain yield. However, considering all the attributes, the parents NP 404, Bijaga Yellow, Anhinga s and Mexicali 75 and hybrids NP 401 x Mexicali 75, NP 404 x Anhinga s, NP 412 x Mexicali 75, NP 404 x Gerardo VZ 466 and Anhinga s x Capeiti appeared promising. The Mexican group as a whole exhibited a more stable performance than the other two evaluated groups. Compensating shift among the component characters was evident in the case of parents as well as hybrids and stability of performance appeared to be under genetic control. Effective utilization of these two aspects through introduction in otherwise desirable varieties has been advocated.Part of Ph.D. thesis of senior author submitted to the Punjab Agricultural University     

Occurrence of moniliformin,deoxynivalenol, and zearalenone in durum wheat (Triticum durum Desf.)

Forty-eight durum wheat samples from 5 locations in Austria were examined forFusarium infection andFusarium toxin content.F.gramlnearum andF.avenaceum were by far the prevailingFusarium species In durum wheat kernels, followed byEpoae, F.culmorum, andF.equlsetl. Ion-paired HPLC analyses of the samples showed moniliformin contents of kernels up to 0.88 mg/kg. All moniliformin contaminated samples also contained high levels of deoxynivalenol (up to 8.2 mg/kg) and lower levels of zearalenone (<0.33 mg/kg). The levels of zearalenone in naturally contaminated durum wheat samples did not correspond to the high yields of zearalenone found in cultures of the fusaria isolated from the durum wheat kernels. These conflicting results as well as some toxicologlcal aspects of the carry over ofFusarium toxins from durum wheat kernels into pasta are discussed.     

Effect of salt and osmotic stresses on germination in durum wheat (Triticum durum Desf.)

In order to determine the relative importance of ionic toxicity versus the osmotic component of salt stress on germination in durum wheat (Triticum durum Desf.), seeds of three cultivars differing in their salt and drought resistance (Omrabi-5, drought-resistant; Belikh, salt-resistant and Cando, salt-sensitive) were incubated in various iso-osmotic solutions of NaCl, mannitol and polyethylene-glycol (PEG) (osmotic potential of –0.15 (control solution) –0.58, –1.05 or –1.57 MPa). Moderate stress intensities only delayed germination, whereas the highest concentration of NaCl and PEG reduced final germination percentages. PEG was the most detrimental solute, while mannitol had no effect on final germination percentages. All osmotica reduced endosperm starch and soluble sugars content as well as -amylase activities recorded after 48 h of treatment while -amylase activities were, in contrast, slightly stimulated in all cultivars. Deleterious effects of NaCl and PEG were higher on isolated embryos germinated onto an in vitro Linsmaier and Skoog (LS) medium comparatively to whole seeds. All PEG-treated embryos, however, recovered after the stress relief while NaCl-treated embryos exhibited a lower rate of recovery and some extent of abnormal germination after rinsing. It was concluded that stress inhibition of germination could not be attributed to an inhibition of mobilisation of reserves and that the main effect of PEG occurred via an inhibition of water uptake while detrimental effects of NaCl may be linked to long-term effects of accumulated toxic ions. The behaviour of the three cultivars during germination did not fully reflect their mean level of putative stress resistance in field conditions and germination is, therefore, not recommended as a reliable selection criterion for breeding purposes.     

Production of durum wheat substitution haploids from durum x maize crosses and their cytological characterization.

The objective of this study was to investigate the effect of individual durum wheat (Triticum turgidum L.) chromosomes on crossability with maize (Zea mays L.) and to cytologically characterize the haploids recovered. Fourteen 'Langdon' (LDN) D-genome disomic substitution lines, a LDN Ph mutant (Ph1b ph1b), and normal 'Langdon' were pollinated with maize pollen. After pollination, hormonal treatment was given daily for up to 14 days. Haploid embryos were obtained from all lines and were aseptically cultured. From a total of 55,358 pollinated florets, 895 embryos were obtained. Only 14 of the embryos germinated and developed into healthy plants. Different substitution lines showed varying degrees of success. The most successful was the substitution 5D(5B) for both embryo formation and haploid plantlet production. These results indicate that the substitution of 5D for 5B confers on durum wheat a greater ability to produce haploids. Fluorescent genomic in situ hybridization (GISH) showed that the substitution haploids consisted of 7 A-genome chromosomes, 6 B-genome chromosomes, and 1 D-genome chromosome. Triticum urartu Turn. genomic DNA was efficient in probing the 7 A-genome chromosomes, although the D-genome chromosome also showed intermediate hybridization. This shows a close affinity between the A genome and D genome. We also elucidated the evolutionary translocation involving the chromosomes 4A and 7B that occurred at the time of evolution of durum wheat. We found that the distal segment translocated from chromosome 7B constitutes about 24% of the long arm of 4A.     

Stay-green trait-antioxidant status interrelationship in durum wheat (Triticum durum) flag leaf during post-flowering

Three independent durum wheat mutant lines that show delayed leaf senescence or stay-green (SG) phenotype, SG196, SG310 and SG504, were compared to the parental genotype, cv. Trinakria, with respect to the photosynthetic parameters and the cellular redox state of the flag leaf in the period from flowering to senescence. The SG mutants maintained their chlorophyll content and net photosynthetic rate for longer than Trinakria, thus revealing a functional SG phenotype. They also showed a better redox state as demonstrated by: (1) a lower rate of superoxide anion production due to generally higher activity of the antioxidant enzymes superoxide dismutase and catalase in all of the SG mutants and also of the total peroxidase in SG196; (2) a higher thiol content that can be ascribed to a higher activity of the NADPH-providing enzyme glucose-6-phosphate dehydrogenase in all of the SG mutants and also of the NADP⁺-dependent malic enzyme in SG196; (3) a lower pro-oxidant activity of lipoxygenase that characterises SG196 and SG504 mutants close to leaf senescence. Overall, these results show a general relationship in durum wheat between the SG phenotype and a better redox state. This relationship differs across the different SG mutants, probably as a consequence of the different set of altered genes underlying the SG trait in these independent mutant lines.     

Plant regeneration from protoplasts of durum wheat (Triticum durum Desf. cv. D6962)

Suspension cultures of durum wheat were established from embryogenic callus maintained in liquid medium for 30 months. Protoplasts were readily isolated from the suspension cultures with yields as high as 3 X 10⁷ protoplasts per g fresh weight suspension cells. When incubated in a modified MS medium containing half strength of the macroelements, 5 M 2,4-D (2,4-dichlorophenoxyacetic acid) and 0.6 M glucose, protoplast-derived cells divided at frequencies ranging from 1.4 to 10.0 %. After transfer to a solid subculture medium, the protoplast-derived colonies formed embryogenic protuberances, from which green plants have been regenerated.     

Ethylene production and involvement during the first steps of durum wheat (Triticum durum) anther culture

The role of ethylene in anther culture of durum wheat ( Triticum durum Desf. cv. Ardente) was analyzed by testing the effects of 2-chloroethylphosphonic acid (ethrel) silver thiosulfate (Ag⁺), a -aminooxyacetic acid (AOA) and 1-aminocyclopropane-l-carboxylic acid (ACC) on microspore division observed after 21 days of culture and on development of calli estimated at day 45. The use of ethrel and Ag⁺ indicated a positive effect of ethylene on microspore division, whereas the use of AOA, and to a lesser extent ACC, snowed a negative effect. In contrast, the addition of ethrel or Ag⁺ indicated that ethylene inhibits the development of microspore-derived calli. AOA gave contradictory results. Ethylene production by anthers was about 7 pl anther⁻¹h⁻¹ and decreased during culture. ACC content in the anthers was maximal at day 9, whereas malonyl ACC (MACC) increased sharply from day 0 to day 3 and then decreased. The addition of AOA or ACC to the culture medium decreased or increased, respectively, ethylene production of anthers and the ACC and/or MACC content, but at concentrations higher than those that modified the formation of calli. This formation seems to occur in two successive phases: induction and initiation of microspore division, which was promoted by ethylene, followed by callus development, which was inhibited by ethylene.     

A genetic linkage map of durum wheat

 A genetic linkage map of tetraploid wheat [Triticum turgidum (L.) Thell.] was constructed using segregation data from a population of 65 recombinant inbred lines (RILs) derived from a cross between the durum wheat cultivar Messapia and accession MG4343 of T. turgidum (L.) Thell. ssp dicoccoides (Korn.) Thell. A total of 259 loci were analysed, including 244 restriction fragment length polymorphisms (RFLPs), one PCR (polymerase chain reaction) marker (a sequence coding for a LMW (low-molecular-weight) glutenin subunit gene located at the Glu-B3 locus), seven biochemical (six seed-storage protein loci and one isozyme locus) and seven morphological markers. A total of 213 loci were mapped at a LOD≥3 on all 14 chromosomes of the A and B genomes. The total length of the map is 1352 cM and the average distance between adjacent markers is 6.3 cM. Forty six loci could not be mapped at a LOD≥3. A fraction (18.6%) of the markers deviated significantly from the expected Mendelian ratios; clusters of loci showing distorted segregation were found on chromosomes 1B, 3AL, 4AL, 6AL and 7AL. The durum wheat map was compared with the published maps of bread wheat using several common RFLP markers and general features are discussed. The markers detected the known structural rearrangements involving chromosomes 4A, 5A and 7B as well as the translocation between 2B-6B, but not the deletion on 2BS. This map provides a useful tool for analysing and breeding economically important quantitative traits and for marker-assisted selection, as well as for studies of genome organisation in small grain cereal species. Received: 5 January 1998 / Accepted: 31 March 1998     

从87（341）的培育成功分析硬粒小麦品质性状的选择研究

根据通心面的商品外观、加工品质和蒸煮品质对硬粒小麦原料提出的主要品质要求,在优质硬粒小麦８７（３４１）品系的选育过程中,品质性状的选择以蛋白质、面筋和黄色素为主。Ｆ３代面筋的质量、含量和黄色素含量的分离相当大,为不错失优质品系,应从Ｆ３代起就开始分析。Ｆ４代在农艺性状选择的基础上,为品质测试和品质上择优汰劣的关键世代。Ｆ５代及其后代的选择则继续兼顾产量和品质指标,以达到高产优质的选育目的。     

Inheritance of deeper root length and grain yield in half-diallel durum wheat (Triticum durum) crosses

Inheritance, heterosis and combining ability of deeper root length (DRL) and grain yield (GY) were investigated in durum wheat populations obtained from half‐diallel crossings among five parental lines differing in their DRL and GY. The study was conducted with the final objective of identifying parent lines to be used in a breeding programme to develop drought‐tolerant wheat varieties. General combining ability and specific combining ability effects were significant for both traits; however, additive gene effects were predominant over non‐additive effects. Partial dominance was ambidirectional for DRL and unidirectional for GY. Lines INRAT69 and Omrabia conferred DRL whereas Omrabia and Khiar transmitted high GY to their respective progenies. In the studied material, both characters were controlled mainly by dominant alleles, but they could also be attributed to recessive alleles although less frequently. Both broad‐sense and strict‐sense heritabilities were high for DRL, confirming the importance of additive gene effects, whereas strict‐sense heritability for GY was average, indicating the importance of interaction effects as compared with the additive effects; this could mean reduced selection efficiency for the latter trait. Thus, the expected genetic progress per cycle of selection will be lower for GY compared with DRL. Omrabia should be included in the breeding programme as a parent so that while maintaining high GY, resulting progeny should be better able to resist drought through DRL.     

Control of sodium transport in durum wheat

In many species, salt sensitivity is associated with the accumulation of sodium (Na(+)) in photosynthetic tissues. Na(+) uptake to leaves involves a series of transport steps and so far very few candidate genes have been implicated in the control of these processes. In this study, Na(+) transport was compared in two varieties of durum wheat (Triticum turgidum) L. subsp. durum known to differ in salt tolerance and Na(+) accumulation; the relatively salt tolerant landrace line 149 and the salt sensitive cultivar Tamaroi. Genetic studies indicated that these genotypes differed at two major loci controlling leaf blade Na(+) accumulation (R. Munns, G.J. Rebetzke, S. Husain, R.A. James, R.A. Hare [2003] Aust J Agric Res 54: 627-635). The physiological traits determined by these genetic differences were investigated using measurements of unidirectional (22)Na(+) transport and net Na(+) accumulation. The major differences in Na(+) transport between the genotypes were (1) the rate of transfer from the root to the shoot (xylem loading), which was much lower in the salt tolerant genotype, and (2) the capacity of the leaf sheath to extract and sequester Na(+) as it entered the leaf. The genotypes did not differ significantly in unidirectional root uptake of Na(+) and there was no evidence for recirculation of Na(+) from shoots to roots. It is likely that xylem loading and leaf sheath sequestration are separate genetic traits that interact to control leaf blade Na(+).     

The addition of Dasypyrum villosum (L.) Candargy chromosomes to durum wheat (Triticum durum Desf.)

Summary Six monosomic addition lines were produced in which different Dasypyrum villosum (L.) Candargy chromosomes were added to the chromosome complement of Triticum durum Desf. cv. Creso. Each added alien chromosome was found to have a specific effect on plant morphology and fertility. Transmission rate varied widely (from 7.5 to 27.7%) among the six univalent chromosomes. Different monotelosomic addition plants derived by a relatively high frequency of chromosome misdivision were isolated. The addition lines should be useful for studying Dasypyrum chromosome homoeology and the introduction of alien variation into durum and common wheats.Research supported by a grant from the Italian Research Council for Finalized Project IPRA. Sub-project Plant Breeding, Paper No. 1095