Variation of the crossability of durum wheat with maize

With the aim of examining crossability of durum wheat with maize, two sets of durum wheat genotypes and a set of D-genome chromosome substitution lines of the durum wheat variety ‘Langdon’ were crossed with maize, and followed by 2,4-dichlorophenoxyacetic acid (2,4-D) treatment in detached-tiller culture. In crosses of 25 durum wheat genotypes (breeding lines) with maize, percent frequencies of embryo formation increased from 1.4% to 2.8% by adding silver nitrate to the detached-tiller culture solution. In crosses of 32 durum wheat genotypes (advanced lines and varieties) with maize using the silver nitrate addition, frequencies of embryo formation ranged from 0.0% to 15.8%; seven genotypes showing more than 6.0% embryo formation frequency were related in their pedigrees. In crosses of a set of chromosome substitution lines with maize, higher frequencies of embryo formation were obtained in substitution lines with chromosomes 1D, 3D, 4D and 7D. These results suggest that 1) adding silver nitrate to the 2,4-D treatment increases overall frequency of embryo formation but is not effective enough to induce the development of seeds and embryos from all durum wheat genotypes, and 2) some D-genome chromosomes substituted in a durum wheat genetic background may enhance crossability with maize in combination with homoeologous chromosomes of durum wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of haploids in bread wheat, durum wheat and hexaploid triticale crossed with pearl millet

Pearl millet is an efficient alternative to maize as a pollen source for haploid production in bread wheat. To compare haploid production frequencies in other Triticeae species, the crossabilities of two genotypes each of bread wheat, durum wheat and hexaploid triticale with four pearl millet genotypes and a maize control were examined. Embryos were obtained from crosses of all three species with both pearl millet and maize. However, significant differences in crossability were found among the three species (10.5–79.8% seed development and 1.4–15.8% embryo formation), as well as among genotypes of durum wheat (7.2–23.7% and 2.1–6.4%) and hexaploid triticale (0.3–20.6% and 0.1–2.7%). Crossability of bread wheat with pearl millet was relatively high. Haploid plants were regenerated from crosses of all three species with pearl millet. As in the case of maize crosses, low crossabilities of durum wheat and hexaploid triticale with pearl millet can be attributed to the absence of D-genome chromosomes.     

Production of Doubled Haploids by Anther Culture and Wheat X Maize Method in a Wheat Breeding Programme

Utilization of the doubled haploid method of breeding usually shortens the time to cultivar release, and methods of haploid production need evaluation in a breeding programme. Thirty-eight different three-way crosses were tested for anther culture response. On average 5.8 percent of the anthers cultured produced calli. Three crosses were found recalcitrant for callus induction. Overall, the anther culture method produced 0.6 plantlet per 100 anthers cultured. Five crosses with an average of 5.8 and 2.8 percent of anthers producing calli and plantlets, respectively, were compared using anther culture and wheat × maize crosses. Non-responsive genotypes for callus induction and plantlet formation in the anther culture method proved to be good parental material in wheat × maize crosses. The average percentages of embryo formation and plantlet production in wheat × maize crosses were 10.3 and 4.7, respectively. Anther-derived plants were cytologically unstable, whereas all the plants regenerated from wheat × maize crosses were haploids (n = 21 chromosomes). The chromosome numbers of the polyhaploids were doubled with a colchicine treatment. Improvement of the two haploid production methods to facilitate their efficient use in a breeding programme is discussed.     

Nitrogen and phosphorus uptake and utilization efficiency in D(R) substitution lines of hexaploid triticale

Two sets of disomic substitution lines, derived from the cultivars ‘Presto’ and ‘Rhino’ of triticale, with rye chromosome pairs replaced by their wheat D‐genome homoeologues, were tested in hydroponic culture for nitrogen and phosphorus uptake and utilization efficiency. The effect of a substitution on the amount of absorbed nutrients was predominantly negative and proportional to the effect on plant dry matter. Significant decreases were found for the substitutions 5D(5R), 6D(6R) of both cultivars, 2D(2R), 4D(4R) of ‘Presto’ and 3D(3R) of ‘Rhino’. On the other hand, the nitrogen utilization efficiency was significantly increased in all substitution lines, with the exception of the 1D(1R) ones. The differences in phosphorus utilization were generally positive, but less pronounced, and significant only in the lines 2D(2R) and 6D(6R). The data suggest that presence of both rye and D‐genome chromosomes is conducive for the best effect of the applied N and P fertilizers.     

Effect of D-Genome Chromosome Substitutions on Hybrid Seed Development and Viability in T. turgidum var. durum X S. cereale Crosses

Triticum turgidum var. durum cv. ‘Langdon’ and the set of D-genome disomicsubstitutions in ‘Langdon’, produced at Fargo, U.S.A., were grown in a temperature controlled greenhouse and crossed with diploid spring rye (Secale cereals), to determine the effect of each substitution on 1. the crossability with rye, and 2, the viability of the resulting hybrids kernels. None of the disomicsubstitutions lines, with the possible exception of the 5D (5Bj line, gave an appreciable improvement in hybrid kernel set, -development, and -viability over the control, ‘Langdon’ The post-zygotic barrier to endosperm and embryo development, which operates in crosses between durum wheat and rye, could therefore not be suppressed by any specific chromosome of the D-genome.     

Wheat Substitutions in Hexaploid Triticale*

Crosses between octoploid and hexaploid triticales have been made m breeding programs for several years, From an analysis of the progeny of such crosses where selections for an octoploid-like phenotype had been made, it was established that 149 out of 150 lines were hexaploid in chromosome number, C-banding and in situ hybridization demonstrated that all but five of the 62 lines analyzed in detail contained visible chromosomes or segments from the D genome. Only four lines had D-genome chromosome replacing rye chromosomes. All of the remaining 53 D-genome substitutions involved the replacing of wheat chromosomes from either the A or B genomes. This establishes the ease with which D-genome genes can be placed into triticale without the loss of rye chromosomes.     

Identification of Rye Chromosomes Involved in Tolerance to Barley Yellow Dwarf Virus Disease in Wheat × Triticale Hybrids

Common wheat × hexaploid triticale hybrids were produced and evaluated for tolerance to barley yellow dwarf virus disease (BYD). The BYD tolerance expression varied with wheat × triticale combination. The selection for BYD tolerance increased the recovery of tolerant genotypes in the next generations. Homozygous tolerant and susceptible lines were obtained in advanced generations. The rye chromosomes 1R, 2R, and 4R with 7R were transmitted as disomic or monosomic, disomic, and double disomic substitution to the late generations of ‘Musala’ (common wheat) בMuskox 658’ (triticale), ‘Encruzilhada’ (common wheat) בNord Kivu’ (triticale) and ‘Encruzilhada’× 12th. International Triticale Screening Nursery 267 (12ITSN267) (triticale), respectively. A clear association was established between the 1R chromosome of the ‘Muskox 658’ triticale line and the tolerance to BYDV. Results suggest that the 2R chromosome may be involved in BYD tolerance of ‘Nord Kivu’ triticale line.     

The effect of introgressions of wheat D-genome chromosomes into 'Presto' triticale

Hexaploid triticale (X Triticosecale Wittmack) (2n= 6x= 42, AABBRR) and wheat (Triticum aestivum L.) (2n= 6x= 42, AABBDD) differ in their R and D-genomes. This produces differences in both agronomic and end-use quality characteristics. Our objective was to determine how introgressions of individual chromosomes from the D-genome of wheat affect these characteristics of a winter triticale 'Presto'. We studied the effects of 18 D-genome chromosome substitution lines, 15 sib-lines as controls, and five check cultivars at Lincoln, NE in 1996, using a randomized complete block design with two replications. The experiment was repeated at Lincoln and Mead, NE in 1997 and 1998 with 15 substitution lines that survived the first winter in Lincoln, along with their 12 control sibs and five check cultivars. Few D-genome chromosomes had positive effects. Chromosomes 2D, 4D, and 6D significantly reduced plant height when substituted for 2R, 4B, and 6R, respectively. No grain yield increases were associated with any of the D-genome chromosomes tested, but three substitutions decreased the grain yield. Depending on the allele of the hardness gene present, chromosome 5D increased or decreased kernel hardness when substituted for 5R or 5A, respectively. Introgressions of chromosomes 1D and 6D improved end-use quality characteristics of Presto. These results suggest that apart from beneficial effects of individual loci located on the D-genome chromosomes, no major benefit can be expected from D-genome chromosome substitutions.     

Durum wheat × maize crosses for haploid wheat production: Influence of parental genotypes and various experimental factors

To improve haploid plant production in durum wheat, the haplomethod involving intergeneric crossing with maize followed by embryo rescue was used. The influence of parental genotypes and various experimental factors were studied. Ten cultivars of Triticum turgidum ssp. durum (female parent) were crossed with eight genotypes of Zea mays. After pollination, plant stems were either maintained in situ or cut near the base and kept in a 2,4‐dichlorophenoxyacetic acid (2,4‐D)‐sucrose solution. Ten to 18 days after pollination, embryos were excised from developed ovaries and cultured on one of MS, MS/2, or B5 media. Haploid embryos and plants were obtained (78 green haploid plants regenerated in 0 year). The wheat genotype was significant for ovary development, embryo and plant formation, whereas the maize genotype was significant only for embryo formation. Detailed results of all crosses showed the best crossing partner for each wheat genotype. Cutting the plant stems after pollination gave better results than maintaining them in situ. The optimal stage for embryo rescue was 14 days and B5 and MS/2 media were more efficient than MS for embryo culture.     

Production of doubled haploids in triticale (×Triticosecale Wittm.) by means of crosses with maize (Zea mays L.) using picloram and dicamba

The aim of the present study of triticale × maize crosses was to find an appropriate growth regulator treatment to improve the yield of triticale haploids and the subsequent production of doubled haploids. The growth effect in unpollinated ovaries of triticale was examined after treatment with 1000 mg/1 indole-3-acetic acid (IAA) or 100 mg/1 solutions of the following auxin analogues: 2,4-dichlorophenoxyacetic acid (2,4-D), 3,6-dichloro-o-anisic acid (dicamba), 4-chloro-o-tolyloxyacetic acid (MCPA), phenylacetic acid (PAA), 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2,4,5-trichlorophenoxyacetic acid (2,4,5- T), respectively. Dicamba stimulated growth of the ovaries significantly more than picloram and both stimulated more growth than the other growth regulators tested. Neither dicamba nor picloram induced embryo development in unpollinated pistils. Dicamba and picloram solutions, at concentrations of 25, 50, 75 and 100 mg/1, were subsequently applied to pistils of triticale pollinated with maize. On average, between 17.1 and 21.5 embryos/100 fiorets were excised after treatment with 75 or 100 mg/1 solutions of picloram or dicamba but the concentrations of 20 and 50 mg were less effective. The frequencies of excised embryos did not differ between genotypes. Seventy-six green haploids were obtained from 100 embryos rescued in vitro on the 190–2 and modified B5 media, the first medium being superior. The plants were subjected to colchicine treatment at the 3–4 tiller stage. Out of 68 plants brought to maturity, 25 exhibited fertile sectors. In comparison with previous studies, picloram and dicamba significantly improved the efficiency of the triticale × maize crossing. The low dependence on the mother germplasm makes triticale × maize crossing an efficient alternative to the androgenetic methods of doubled haploid production in triticale.     

Production of polyhaploids of hexaploid wheat using stored pearl millet pollen

The effects of drying and freezing on viability of pearl millet pollen were examined with the aim of using stored pollen in polyhaploid production of hexaploid wheat. Freshly collected pollen of pearl millet line NEC 7006 with 55% water content, germinated at a frequency of 80%. Pollen that was dried for two hours to 6% water content showed 50% germination frequency and maintained similar frequencies after the freezing process. In crosses of hexaploid wheat variety Norin 61 with fresh pearl millet pollen, embryos were obtained at a frequency of 27.6%. In crosses with pollen stored at -196 °C, -80 °C and -20 °C for one month, embryo formation frequencies ranged from 27.5 to 17.4%. After five and twelve months of storage, the frequencies ranged from 29.7 to 14.6% at storage temperatures of -196 °C and -80 °C, and from 8.0 to 3.2% at -20 °C, indicating significant differences among storage temperatures. However, no significant frequency difference was found among pollen water contents at the time of collection. All plants regenerated from crosses with pearl millet pollen stored for five months were wheat polyhaploids. These results suggest that stored pearl millet pollen is an efficient medium for producing polyhaploids in hexaploid wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hexaploid triticales from hybrids of 'Langdon' durum D-genome substitutions with 'Gazelle' rye

The formation of unreduced gametes in some hybrids between disomic D‐genome substitutions (DS) of durum wheat cv.‘Langdon’ and rye provides a convenient approach for the rapid introduction of D‐genome chromosomes into hexaploid triticale. Meiotic pairing at metaphase I and seed fertility in spontaneous and colchicine‐induced amphidiploids derived from F₁ hybrids between a set of ‘Langdon’ DS and ‘Gazelle’ rye were analysed. The purpose was to determine the effects of the substitution of D‐genome chromosomes for their A‐ and B‐genome homoeologues on hexaploid triticale and to select stable disomic D‐genome substitutions of hexaploid triticale. The results showed that the disomic substitutions with D‐genome slightly increased the frequency of univalents (1.0‐3.13) compared with the ‘Langdon’ control primary hexaploid triticale (0.76). Substitutions 2D(2A) and 3D(3B) were partly desynaptic. The substitutions 1D(1A), 1D(1B) and 7D(7B) exhibited high seed fertility but the others had decreased fertility. Except for 2D(2A), 5D(5A), 3D(3B) and 5D(5B), 10 of the 14 possible hexaploid triticale D‐genome disomic substitutions have been obtained. The results suggest that the poor compensation ability of some D‐genome chromosomes for their homoeologous A‐ and B‐genome chromosomes is a major factor affecting meiotic stability and fertility in the hexaploid triticale D‐genome substitutions.     

Doubled haploid production in Turkish durum wheats using crosses with maize

Durum wheats cultivated in the Middle Anatolia region of Turkey (Triticum durum cvs ‘Kunduru’, ‘Berkmen’ and ‘Cakmak’) were crossed with maize to evaluate their capacity for haploid embryo and doubled haploid (DH) plant production. A total of 2960 florets were crossed with maize and 13.7% of the florets produced haploid embryos across the three varieties. Haploid embryo and plant regeneration frequencies were highest in ‘Kunduru’, but colchicine doubling was less successful with this genotype. There were statistically significant differences between ‘Cakmak’ and other genotypes for embryo yield (P < 0.01). Overall, 52.3% of all embryos differentiated, but there were no geno-typic differences in differentiation frequencies.     

Regeneration potential of CIMMYT durum wheat and triticale varieties from immature embryos

Twenty‐five durum wheat elite advanced lines and released varieties, and five triticale varieties were evaluated for their ability to produce embryogenic callus using three different media. For callus initiation and maintenance there were basal Murashige and Skoog (MS) medium containing double strains of macroelements and 2.5 mg/l 2,4D (DW1), basal MS medium containing 2.0 mg/l 2,4D (DW2), or basal MS medium supplemented with 1.0 mg/l 2,4 D and coconut milk (DW3). Plant regeneration was achieved on basal MS medium with indoleacetic acid and 6‐benzylaminopurine, and plants rooted on MS with 1‐naphthale‐neacetic acid. DW3 medium proved better than the other media tested for embryogenic callus initiation and maintenance. Regeneration rates varied widely with both genotype and initiation medium, with values ranging from no regeneration to 100% regeneration; the plantlets produced per embryo ranged from five to 20. Fourteen of the durum wheat genotypes showed 63–100% regeneration from DW3 callus formation medium, four lines from DW1 medium, and two lines from DW2. Four of the triticale varieties had regeneration of 48–100% from DW3 medium. After six subcultures, over a 6‐month period, genotypes lost their ability to regenerate plants. Only 10 lines retained some plant regeneration potential but regeneration was at reduced levels. Successful regeneration of durum wheat and triticale varieties will be used as an integral part of the transformation process.     

Relative efficiency of different Gramineae genera for haploid induction in triticale and triticale x wheat hybrids through the chromosome elimination technique

The study was undertaken to evaluate the relative efficiency of different Gramineae genera for haploid induction in triticale (x Triticosecale) and triticale × wheat (Triticum aestivum) hybrids through the chromosome elimination (wheat × maize, Zea mays) system. Eight intergenotypic triticale and 15 triticale x wheat crosses were subjected to hybridization with nine different Gramineae genera viz., Z. mays, Sorghum bicolor, Pennisetum americanum, Setaria italica, Festuca arundinacea, Imperata cylindrica, Cynodon dactylon, Lolium temulentum and Phalaris minor in two separate experiments. This was followed by in vivo auxin treatment of the crossed spikes and subsequent rescue of the haploid embryos to regenerate green haploid plantlets. All the triticale and triticale x wheat crosses resulted in seed set in variable frequencies when hybridized with maize, I. cylindrica, pearl millet and sorghum. Seed set was also obtained with S. italica, F. arundinacea and P. minor in a few crosses in both groups. In general, all the triticale x wheat crosses, except for one in each case, resulted in embryo formation and green haploid plantlet regeneration when hybridizations were carried out with maize and I. cylindrica. However, the latter outperformed the former in embryo formation (25.48% vs. 20.0%) and regeneration (34.17% vs. 15.10%) frequencies, the differences being significant for regeneration frequencies. In the case of triticale hybrids, no significant differences between maize and I. cylindrica were observed for the three parameters of haploid induction. Embryo formation and regeneration were also observed in some of the triticale as well as triticale × wheat F₁ hybrids when hybridized with sorghum and pearl millet.     

Production and Cytogenetical Analysis of a Rye-Cytoplasmic Tetraploid Triticale

A rye-cytoplasmic tetraploid triticale was found in F_s progenies of crosses between tetraploid rye‘No 1323’and hexaploid triticale‘KT 77′. In the tetraploid triticale, two complete rye genomes and two mixed wheat genomes, consisting of the chromosomes 1A. 2A, 4A, 7A, 3B, 5B, and 6B are present. The rye cytoplasm did not affect stability of rye chromosome pairing during metaphase 1, since rye chromosomes participated in pairing irregularities just as did wheat chramosomes, even on a larger scale. The fertility of F₀, plants ranged from 0 to 75.6 %, always associated with high grain shrivelling. The analyzed pairing behaviour of induced triploid hybrids from crosses between the tetraploid triticale and diploid rye indicates the presence of at least one wheat-rye translocation in one of the investigated triploid plants.     

An improved protocol for androgenesis in cauliflowers (Brassica oleracea var. botrytis)

The genotypic responsiveness to androgenesis and the effect of two exposure times of cultured anthers to auxins (12 days and the entire period of culture) were studied in three lines of cauliflower (one spring - and two winter-types). The anthers of all genotypes responded to the protocol by producing embryos (0.2 -25.3%), 44.2% of which regenerated plantlets through organogenesis on a regulator-free B5 medium containing 40 g/l of sucrose and 800mg/l of L-glutamine. Embryo yield improvement, recently achieved on solid medium with the addition of 125mg/l silver nitrate, was not observed in liquid cultures. Mean frequencies of androgenic embryos, as affected by the duration of auxin supply to the culture, were always significantly higher (6.6- and 8.1-fold.) in the‘12 days of exposure’treatment than in the‘entire period of culture’treatment. The resolution of the parameter‘embryo percentage’into its two components (% of responsive anthers and number of embryos per responsive anther) gave evidence of a highly significant increase in the percentage of responsive anthers, whereas the number of embryos per responsive anther did not change statistically. The percentage of embryos regenerating plants was not influenced by the duration of auxin supply during anther culture. Chromosome count analysis revealed a haploid/diploid/polyploid plant ratio of 6:79:15. Of the 78 androgenic plants (RO generation) grown in the field, only 14 were fertile and produced seeds. RAPD analysis showed that none of the seven polymorphic loci out of 23 analysed expressed polymorphism within the RI progenies of 11 anther culture-derived lines.     

The Effect of Photoperiod Insensitivity on the Salt Tolerance of Amphiploids between Bread Wheat (Triticum aestivum) and Sand Couch Grass (Thinopyrum bessarabicum)

From the crosses (6 × triticale ‘Lasko’× AARR) בLasko’ one plant with 56 chromosomes was obtained. The selfed progenies showed reduction of somatic chromosome number. A reciprocal cross of hyperploid introgressive plants with ‘Lasko’ indicated similar transmission rates of additional chromosomes through female and male gametes. The degree of initial reduction is of great importance for the number of succeeding generations needed to reach the hexaploid level. With regard to the output of introgressive lines of practical breeding importance, it is necessary to continue and to promote the recombination processes between donor and recipient genetic information for as long as possible. An interruption of recombination by beginning selection too early leads to the loss of genetic variability in the progenies.     

花生体细胞胚诱导及植株再生研究

为了建立花生体细胞胚诱导及植株再生体系,为花生分子育种提供技术支撑,以花生品种‘桂花30’和‘桂花771’为材料,采用预培养3天的种子胚小叶、下胚轴、子叶节为外植体,在添加外源激素的MS培养基中使体细胞脱分化形成体细胞胚,再分化成植株。结果表明,在所设定2,4-D浓度（3,5,10,15,20 mg/L）范围内,胚小叶最容易诱导形成体细胞胚,2,4-D的适宜浓度为10 mg/L,经过约30天培养,可产生大量体细胞胚,‘桂花30’和‘桂花771’的平均诱导率分别为55.37%和36.72%。平均每个外植体产胚量分别为5.68个和4.27个。将诱导形成的体细胞胚转接到6-BA浓度由5 mg/L逐渐降低到1.5 mg/L的MS培养基中,体细胞胚萌发再生成无根小苗,正常植株再生率‘桂花30’为32.6%,‘桂花771’为23.5%。将无根苗转接到生根培养基中可获得完整植株。花生是较难诱导体细胞胚形成的作物之一,筛选合适的基因型、外植体和激素浓度是获得较高体细胞胚发生率和植株再生率的关键技术。     

Molecular cytogenetic characterization and phenotypic evaluation of new wheat–rye lines derived from hexaploid triticale ‘Certa’ × common wheat hybrids

Hexaploid triticale contains valuable genes from both tetraploid wheat and rye and plays an important role in wheat breeding programmes. In order to explore the potential of hexaploid triticale ‘Certa’ in wheat improvement, two crosses were made using ‘Certa’ as female parent, and common wheat cultivars ‘Jinmai47’ (JM47) and ‘Xinong389’ (XN389) as male parents. The karyotyping of BCF_4:5 lines from Certa/JM47//JM47 and F_5:6 lines from Certa/XN389 was investigated using sequential fluorescence in situ hybridization (FISH). One 1B(1R) substitution line and five 1BL.1RS whole‐arm translocation lines were identified, one of which was found lacking ω‐secalin locus. Many structural alterations on wheat chromosomes were detected in the progeny. Great morphologic differences resulting from genetic variations were observed, among which the photosynthetic capability was increased while grain quality was slightly improved. Compared with both parents, the stripe rust resistance at adult stage was increased in lines derived from Certa/JM47//JM47, while it was decreased in lines derived from Certa/XN389. These newly developed lines might have the potential to be utilized in wheat improvement programmes.