Location of the recessive gene ym (yellow margin) on chromosome 12 of diploid Solatium tuberosum by means of trisomic analysis

Summary Ten out of twelve primary trisomics of dip-loid S. tuberosum were crossed as females with a recessive mutant for yellow margin (ym ym) obtained from S. phureja. All primary trisomics used proved to be homozygous dominant. Trisomic plants from all ten F₁'s were backcrossed with the mutant and trisomics from eight F₁'s were crossed also with a disomic heterozygous f₁ plant from triple 10 X mutant.In both BC₁ and half sib progeny of each trisomic type the mutant plants were easily identified because of their typical small roundish leaflets with yellow or reddish margins. The observed segregation ratios for normal to mutant were tested against the expected non-critical ratios and against various expected critical ratios.From the results of these tests it is concluded that the gene ym is located on chromosome 12 of the potato. A hypothesis of linkage between ym and a gene l _x for lethality is put forward. It is concluded that l _x is not identical with a previously detected recessive gene l ₂ which is responsible for yellow cotyledons and lethality.     

Inheritance of heat-stable resistance to Meloidogyne incognita in Lycopersicon peruvianum and its relationship to the Mi gene

Summary The inheritance of heat-stable resistance to the root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, was studied in crosses between different accessions and clones of Lycopersicon peruvianum L. F₁, F₂ and BC₁ generations were evaluated for their index of resistance based on numbers of eggs and infective second-stage juveniles (J₂) per gram of root, and the segregation ratios were determined in experiments carried out at constant soil temperatures of 25 °C and 30 °C. L. peruvianum P.I. 270435 clones 3 MH and 2R2 and P.I. 126443 clone 1 MH, all heatstable resistant, were crossed with L. peruvianum P.I. 126440 clone 9 MH, which is susceptible at both 25 °C and 30 °C. All F₁ progeny were resistant at 25 °C and 30 °C; F₂ and BC₁ generations at 25 °C gave resistant: susceptible (RS) ratios of 151 and 31, respectively, which suggests that resistance is conditioned by two independently assorting genes. However, at 30 °C, RS ratios of 31 and 11 were observed for the F₂ and BC₁ generations, respectively. These results indicate that heat-stable resistance is conferred by a single dominant gene expressed at 30 °C, while the second resistance gene is heat unstable and not expressed at 30 °C. P.I. 270435 clones 2R2 and 3 MH and P.I. 126443 clone 1 MH were crossed with P.I. 128657 clone 3 R4 (source of gene Mi), which is resistant at 25 °C but susceptible at 30 °C. All of the F₁ progeny were resistant at 25 °C and 30 °C.TC₁ progeny of 270435-2 R2 x 128657-3 R4, 270435-3 MH x 128657-3 R4 and 126443-1 MH x 128657-3 R4 crossed with susceptible 126440-9 MH were all resistant at 25 °C and segregated in a 11 ratio at 30 °C. These results also suggest that the heat-stable resistance is monogenic and that it is non-allelic to gene Mi. The non-segregation of TC₁ progenies at 25 °C, suggests that the heat-unstable resistance factor in L. peruvianum P.I. 270435 clones 2 R2 and 3 MH and in P.I. 126443 clone 1 MH is allelic to or the same as gene Mi. We propose the symbol Mi-2 for the gene in P.I. 270435 that confers heat-stable resistance to M. incognita.     

Genetics of self incompatibility in diploid Ageratum houstonianum mill

Summary Diallels and backcrosses among self-incompatible (SI) clones and progeny of Ageratum houstonianum Mill. could be organized into intra-incompatible classes. Four of 5 progenies segregated in expected ratios of S genotypes. Ageratum expressed a one-locus incompatibility system of the sporophytic type with a linear dominance series of multiple alleles and complete allelic dominance in both pollen and stigma. In the second part of the study, a high percentage of self-seed set was observed during the first flowering of a progeny from a pseudo-self compatible (PSC) seed source. Six progenies were derived from the PSC seed source. Five of the 6 segregated PSC SI plants, 4 of which fit a 3 1 ratio of PSC SI plants. All plants of the sixth progeny were SI. Two F₁ progenies with the same PSC pollen parent produced significantly different segregations of PSC SI plants. It appeared that PSC acted as a major gene when the most recessive S allele was also present, but PSC was not expressed when the most dominant S allele was present. Clones propagated from PSC plants were SI and cross incompatible with a related S-allele tester. Thus, PSC was transient in that it was apparent in seed-propagated plants but not in plants clonally propagated from the PSC individuals.Scientific Journal Series Paper Number 12,299 of the Minnesota Agricultural Experiment Station     

A somaclonal variant of wheat with additional β-amylase isozymes

Summary The progeny of 149 plants regenerated from tissue culture of immature wheat (Triticum aestivum) embryos were screened for variation in their grain -amylase isozyme pattern. One regenerant was found which was heterozygous for a variant pattern characterized by the presence of at least five new isozyme bands, as well as an increased intensity in existing bands in two more positions. The F₂ of a homozygous variant crossed back to the parent segregated in an approximate 31 ratio but resolution of the gels was not sufficient to distinguish whether this represents a dominant or co-dominant single mutant gene. No chromosome abnormalities were evident in mitosis or meiosis of the homozygous variant or in the F₁ of the variant crossed back to the parent. No recombination has been seen between the variant bands and production of multiple bands from a single locus is consistent with the nature of the known -amylase loci. However, the variant bands were not evident in a survey of 111 diverse genotypes, nor were they present in developing grain of the parent cultivar. Therefore, this variant could represent a rare mutation leading to expression of a currently unexpressed locus.     

Transformation of cultivated tomato by a binary vector in Agrobacterium rhizogenes: transgenic plants with normal phenotypes harbor binary vector T-DNA,but no Ri-plasmid T-DNA

Summary Cultivated tomato was genetically transformed using two procedures. In the first procedure, punctured cotyledons were infected with disarmed Agrobacterium tumefaciens strain LBA4404 or with A. rhizogenes strain A4, each containing the binary vector pARC8. The chimeric neomycin phosphotransferase (NPT II) gene on pARC8 conferred on transformed plant cells the ability to grow on medium containing kanamycin. Transformation reproducible yielded kanamycin-resistant transformants in different tomato genotypes. NPT II activity was detected in transformed calli and in transgenic plants. All of these plants were phenotypically normal, fertile and set seeds. Using the second procedure, inverted cotyledons, we recovered transformed tomato plants from A. rhizogenes-induced hairy roots. In this case, all of the transgenic plants exhibited phenotypes similar to hairy root-derived plants reported for other species. Southern blot analysis on these plants revealed that the plant DNA hybridized with both probes representing pARC8-T-DNA, and the T-DNAs of the A4 Ri-plasmid. However, southern analysis on those phenotypically normal transgenic plants from the first procedure revealed that only the pARC8-T-DNA was present in the plant genome, thus indicating that the pARC8-T-DNA integrated into the plant genome independently of the pRi A4-T-DNA. Genetic analysis of these phenotypically normal transgenic plants for the kanamycin-resistance trait showed Mendelian ratios, 31 and 11, for selfed (R1) and in crossed progeny, respectively.     

Interspecific hybrids between Brassica napus L. and B. oleracea L. developed by embryo culture

Summary Interspecific hybrids between Brassica napus and B. oleracea are difficult to produce, and previous attempts to transfer economic characters from one species to the other have largely been unsuccessful. In these studies, oilseed rape cv. Tower (2n38) (B. napus) was crossed with broccoli and kale (2n18) (B. oleracea), and hybrid plants were developed from embryos in culture by either organogenesis or somatic embryogenesis. In rape × broccoli, F₁ plants were regenerated from hybrid embryos and the plants produced viable selfed seeds. F₅ plants (2n38) homozygous for white flower colour were selected for high oil content (47%) and Line 15; a selection from these plants produced fertile hybrids with rape, broccoli and kale without embryo culture. In reciprocal crosses between oilseed rape cv. Tower and an aphid resistant diploid kale, 28 and 56 chromosome F₁ hybrid plants were regenerated from somatic embryos. The 56 chromosome plants were self-fertile and it was concluded from F₂ segregation ratios that a single dominant gene controls resistance to cabbage aphid in kale. The 28 chromosome F₁'s were self-sterile, but these and the 56 chromosome F₁'s could be backcrossed to rape and kale. A cross between the F₁ (2n56) and a forage rape resulted in the selection of a cabbage aphid (Brevicoryne brassicae L.) resistant line (Line 3). Both Line 15 and Line 3 can serve as bridges for gene interchange between B. campestris, B. napus and B. oleracea, which has not been possible hitherto. Hybridisations between rape and tetraploid kale produced F₁ plants with 37 chromosomes. One F₂ plant possessed coronal scales and the inheritance was shown to be controlled by a single recessive gene unlinked to petal colour.This paper is dedicated to Mr. T. P. Palmer, a colleague and close friend who retired from the DSIR as Assistant Director of the Crop Research Division in September 1984     

Germinal Excision and Reinsertion Frequencies of the Mobile Element Ds Transposed from Two Unlinked T-DNA Loci in Tomato

Acceptor sites of unlinked transposed Ds element from two T-DNA loci in tomato were mapped. Experimental data obtained from TC₁ progeny testing were employed for estimation of germinal excision frequency (GEF) of Ds element and frequency of its reinsertion (FR). The donor T-DNAs 1481J and 1601D, containing a 35S:NPT transformation marker, a 35S:BAR or nos:BAR excision marker conferring phosphinothricine resistance and a Ds element in the 5 untranslated leader of the nos (or 35S): BAR gene, were located on chromosome 7 and 8, respectively. Ds transposition was induced by 105121 T-DNA carrying stabilized Ac (sAc) which provides a source of transposase and 2:GUS marker conferring -glucuronidase activity. Tomato plants harbouring the Ds in 1481J or 1601D locus and sAc were crossed and F₁D, were crossed individually as seed parents to wild-type plants to generate TC₁ progenies. TC₁ seed was germinated on phosphinothricine (Basta)-containing medium, and individual seedlings carrying a transposed Ds and lacking sAc were identified by PCR (to detect the Ds) on phosphinothricine resistant individuals that lacked -glucuronidase activity. From segregation ratio in TC₁ the germinal excision and reinsertion frequencies of the Ds element were estimated for individual F₁ plants. A total of 14560 TC₁ seedlings of 1481J and 16195 TC₁ seedlings of 1601D was analyzed. We observed high variation between individual plants as regards both GEF and FR despite of donor locus (1481J or 1601D), however, the average germinal excision frequencies as well as average frequencies of reinsertion were very similar for both donor loci: GEF_1481J = 24 %, GEF_1501D = 25 %, FR_1481J = 42 %, FR_1601D = 46 %.     

Somatic hybridization in potato: use of γ-irradiated protoplasts of Solanum pinnatisectum in genetic reconstruction

Summary Leaf mesophyll protoplasts of Solanum pinnatisectum (2n=24) -irradiated at doses of 200 Gy and consequently unable to divide were fused with untreated protoplasts of genomic chlorophyll deficient mutant IvP 841-1 (2n=24) containing the germplasms of S. tuberosum and S. phureja. Two types of plants differing in their pigmentation characteristics were selected. The regenerants of one group were identified as true somatic hybrids by using isozyme analyses of esterase and aspartate aminotransferase. The anthocyanin marker of S. pinnatisectum was phenotypically expressed in these regenerants and could be used as an additional selection trait for hybrid screening in this species combination. The regenerants of the second group were corrected for the gene controlling chlorophyll deficiency but contained species-specific isozymes of the potato cultivar only. Restriction analysis of chloroplast DNA revealed chloroplasts of the S. pinnatisectum type in all but one of the plants tested. The fusion experiments involving -irradiated protoplasts show that this approach in potato reconstruction has the advantage of producing a wide range of genetically novel plants.Dedicated to Prof. H. F. Linskens on his 65th birthday     

Dominance and recessiveness at loci for virulence against potato and tomato in Phytophthora infestans

Summary In this study we investigated the genetic control of virulence in the diploid fungal pathogen, Phytophthora infestans, against host resistance genes R1, R2, R3, and R4 (potato) and Ph1 (tomato). For four of these virulence traits, the presence or absence of segregation indicated conclusively which phenotype was dominant. We observed a 31 (virulentavirulent) segregation on R2 in the progeny of parents which were both virulent, suggesting that virulence is dominant and both parents are heterozygous. In a cross in which one parent was virulent and the other avirulent on potato gene R3, all progeny tested were avirulent, so avirulence against R3 is dominant. The same virulent parent crossed with a different avirulent parent produced virulent and avirulent progeny in a 13 ratio, indicating that a second locus may be involved. The progeny of two parents virulent on R4 segregated for virulence and avirulence, so virulence against R4 is dominant. For Ph1, a 13 segregation in the progeny of two avirulent parents showed that the avirulent phenotype is dominant, and a 31 ration in a second cross suggested the involvement of a second locus. The segregations for virulence against R1 did not indicate which phenotype was dominant, but did suggest singlelocus control.     

Sex determination in the genus Oreochromis

Summary Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 11, 35 and 13 (malefemale). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (13) and most sex-reversed females (10) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW superfemale, which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.     

Association of the yellow leaf (y10) mutant to soybean chromosome 3

At least 19 single recessive gene yellow leaf mutants and one duplicate recessive gene mutant have been described in soybean. This study was conducted to associate a yellow leaf mutant, y10, with a specific soybean chromosome by using primary trisomics (2n = 41). Seven soybean primary trisomics were hybridized as female parent with genetic stock strain, T161, carrying y10. F(1) disomic and primary trisomic plants were identified cytologically. One disomic (control) and all primary trisomic plants were allowed to self-pollinate and F(2) populations were classified for green versus yellow leaf mutant. The F(2) population of Triplo 3 segregated in a 17:1 ratio, while a disomic (3:1) ratio was observed with Triplo 8-, 17-, 18-, and 20-derived F(2) populations, suggesting that the y10 locus is on chromosome 3. The y10 locus was examined with four simple sequence repeat (SSR) markers (Satt584, Sat_033, Satt387, and Satt022) from molecular linkage group (MLG) N and y10 was found linked with Satt022. Therefore we confirmed the association of MLG N with chromosome 3. The possible association of y10 with Triplo 16 and Triplo 19 are discussed.     

A genetic model for the endosperm balance number (EBN) in the wild potato Solanum acaule Bitt. and two related diploid species

Solanum acaule Bitt. is a disomic tetraploid potato which has been assigned two endosperm balance numbers (EBN). It readily crosses with diploids but does not cross with other tetraploid species, although exceptions have been reported. The genetic basis of this behavior was studied in intra- and interspecific crosses involving plants of four introductions of this species and plants of one introduction of 2x S. commersonii Dun., one of 2x S. gourlayi Haw., and two of 4x S. gourlayi Haw., which have been assigned one EBN, two EBN, and four EBN respectively. Some of the pollinated pistils were used to analyze pollen-pistil compatibility reactions; the rest were left in the plants for seed production. At harvest, seeds were sorted according to size and plumpness, and the ploidy of the resulting plantlets determined from root tips. A model is proposed to explain the results of these crosses as well as the exceptions previously reported. It is based on the presence of two independent loci controlling the EBN, with two alleles in homozygosity: 1/2 and 0. This model, which is extended to cmm and grl, also explains the behavior of 3x (cmm x grl) hybrids in crosses with one-EBN, two-EBN, and four-EBN species reported in a previous work.     

Mutations conferring lincomycin, spectinomycin, and streptomycin resistance in Solanum nigrum are located in three different chloroplast genes

A number of Solanum nigrum mutants resistant to the antibiotics spectinomycin, streptomycin and lincomycin have been isolated from regenerating leaf strips after mutagenesis with nitroso-methylurea. Selection of streptomycin- and spectinomycin-resistant mutants has been described earlier. Lincomycin-resistant mutants show resistance to higher levels of the antibiotic than used in the initial selection, and in the most resistant mutant (Ll7A1) maternal inheritance of the trait was demonstrated. The lincomycin-resistant mutant L17A1 and a streptomycin plus spectinomycin resistant double mutant (StSpl) were chosen for detailed molecular characterisation. Regions of the plastid DNA, within the genes encoding 16S and 23S rRNA and rps12 (3) were sequenced. For spectinomycin and lincomycin resistance, base changes identical to those in similar Nicotiana mutants were identified. Streptomycin resistance is associated with an A C change at codon 87 of rps 12 (converting a lysine into a glutamine), three codons upstream from a mutation earlier reported for Nicotiana. This site has not previously been implicated in streptomycin resistance mutations of higher plants, but has been found in Escherichia coli. The value of these mutants for studies on plastid genetics is discussed.     

The Arabidopsis nuclear DAL gene encodes a chloroplast protein which is required for the maturation of the plastid ribosomal RNAs and is essential for chloroplast differentiation

Altered pigmentation is an easily scored and sensitive monitor of plastid function. We analyzed in detail a yellow colored transposon-tagged mutant (dal1-2) that is allelic to the dal mutant previously identified (Babiychuk et al., 1997). Mesophyll cells of mutant plants possess abnormal nucleoids and more but smaller plastids than wild type cells. Plastid development in dal1-2 is not altered in the dark but is arrested at the early steps of thylakoid assembly. The amino acid sequence of the protein deduced from our cDNA clone is 21 amino acids longer than the previously published DAL sequence (Babiychuk et al., 1997) and allowed us to show that DAL codes for a chloroplast protein. The dal1-2 mutation has a global negative effect on plastid RNA accumulation and on expression of nuclear encoded photosynthetic genes. We show that the plastid RNA polymerases, the nuclear-encoded NEP and the plastid-encoded PEP, are functional in the mutant. Precursor 16S and 23S rRNA species specifically accumulate at a high level in the mutant but the 5-end and the long 3-end trailer are not modified. We suggest that the dal mutation is involved in plastid rRNA processing and consequently in translation and early chloroplast differentiation.     

Streptomycin resistance is inherited as a recessive Mendelian trait in a Nicotiana sylvestris line

Summary The SR180 cell line has been isolated in a callus culture derived from a haploid Nicotiana sylvestris (n = X = 12) plant by its ability to proliferate on a selective medium containing 2,000 g/ml streptomycin sulphate. From the cell line diploid plants have been regenerated. The SR180 selfs are resistant to streptomycin. Streptomycin sensitivity in F1, and a 31 (sensitive to resistant) segregation in F2 indicate that resistance in the SR180 mutant is the result of a recessive Mendelian mutation.     

Isozyme evidence and the origin ofSenecio vulgaris (Compositae)

An electrophoretic survey of isozyme variation was conducted to test the hypothesis thatSenecio vulgaris L. (2n = 40) is of autotetraploid origin fromS. vernalis Waldst. & Kit. (2n = 20). It was established thatS. vulgaris exhibited fixed heterozygosity at three loci examined, showed disomic inheritance at all polymorphic loci, and contained a gene (Est-1) and an allele (Aat-3b) which were not present in the single population ofS. vernalis surveyed. From this it is concluded thatS. vulgaris is not of autotetraploid origin. Instead, the genetic evidence is in keeping with an allopolyploid origin ofS. vulgaris with the possibility thatS. vernalis acted as one of its two parents.     

Inheritance of the fuzzless-lintless character in cotton (Gossypium hirsutum)

Summary A fuzzless-lintless mutant was identified in MCU.5 (Gossypium hirsutum) cotton in 1984. The inheritance of this character is reported in this paper. The fuzzless-lintless mutant was crossed with fuzzy-linted parents viz. MCU.5, MCU.7, Express Sindh (W), Piedmont Cleveland and Sindis Wild and the segregation pattern was studied in F₂ and BC₁F₁ generations. The segregation ratios for fuzzy-linted and fuzzless-lintless were 151 in the first cross, 631 in the second, third and fourth crosses and 2551 in the fifth cross. These ratios indicated that this character is controlled by 2–4 gene pairs, and the fuzzless-lintless character is a recessive to fuzzy-linted character. The chi-square test was significant only in the BC₁F₁ generation with MCU.7 and Express Sindh (W). The test revealed that the observed values deviated significantly from the expected ratio of 71, suggesting that this character is also influenced by modifier gene complex.     

Identification of resistance to Meloidogyne javanica in the Lycopersicon peruvianum complex

Clones of Lycopersicon peruvianum PI 2704352R2, PI 270435-3MH and PI 126443-1MH expressed novel resistance to three Mi-avirulent M. javanica isolates in greenhouse experiments. Clones from PI 126443-1MH were resistant to the three M. javanica isolates at 25°C. The three isolates were able to reproduce on one embryorescue hybrid of PI 126443-1MH, but not on three L. peruvianum-L. esculentum bridge-line hybrids of PI 1264431MH when screened at 25°C (Mi-expressed temperature). Clones of PI 270435-2R2 and all its hybrids with susceptible genotypes were resistant to the three M. javanica isolates at 25°C. The bridge-line hybrid EPP-2xPI 2704352R2 was susceptible to M. javanica isolate 811 at 32°C, whereas PI 270435-2R2 and all other hybrids of PI 27043 5-2R2 crossed with susceptible genotypes were resistant at 32°C. At 32°C, one F₂ progeny of PI 126443-IMHxEPP-1, and three test-cross progenies of PI 1264409MHx[PI 270435-3MHxPI 126443-1MH], and reciprocal test-cross progenies of [PI 270435-3MHxPI 2704352R2]xPI 126440-9MH, each segregated into resistant: susceptible (RS) ratios close to 31. The results from the F₂ progeny indicated that heat-stable resistance to Mi-avirulent M. javanica in PI 126443 -1MH is conferred by a single dominant gene. The results from the test-crosses indicated that this gene in PI 126443-1MH is different from the resistance gene in PI 270435-3MH. The resistance gene in PI 270435-3MH was also shown to differ from the resistance factor in PI 270435-2R2. The expression of differential susceptibility and resistance to M. javanica and M. incognita in individual plants of the bridge-line hybrid, embryo-rescue hybrid, F₂, and test-crosses indicated that at least some genes governing resistance to M. javanica differ from the genes conferring resistance to M. incognita. A new source of heat-stable resistance to M. javanica was identified in Lycopersicon chilense.     

Characterization of a novel cellulose synthesis inhibitor

The physiological effects of an experimental herbicide and cellulose synthesis inhibitor, N2-(1-ethyl-3-phenylpropyl)-6-(1-fluoro-1-methylethyl)-1,3,5-triazine-2,4-diamine, called AE F150944, are described. In the aminotriazine molecular class, AE F150944 is structurally distinct from other known cellulose synthesis inhibitors. It specifically inhibits crystalline cellulose synthesis in plants without affecting other processes that were tested. The effects of AE F150944 on dicotyledonous plants were tested on cultured mesophyll cells of Zinnia elegans L. cv. Envy, which can be selectively induced to expand via primary wall synthesis or to differentiate into tracheary elements via secondary wall synthesis. The IC₅₀ values during primary and secondary wall synthesis in Z. elegans were 3.91×10^–8 M and 3.67×10^–9 M, respectively. The IC₅₀ in suspension cultures of the monocot Sorghum halapense (L.) Pers., which were dividing and synthesizing primary walls, was 1.67×10^–10 M. At maximally inhibitory concentrations, 18–33% residual crystalline cellulose synthesis activity remained, with the most residual activity observed during primary wall synthesis in Z. elegans. Addition to Z. elegans cells of two other cellulose synthesis inhibitors, 1 M 2,6-dichlorobenzonitrile and isoxaben, along with AE F150944 did not eliminate the residual cellulose synthesis, indicating little synergy between the three inhibitors. In differentiating tracheary elements, AE F150944 inhibited the deposition of detectable cellulose into patterned secondary wall thickenings, which was correlated with delocalization of lignin as described previously for 2, 6-dichlorobenzonitrile. Freeze-fracture electron microscopy showed that the plasma membrane below the patterned thickenings of AE F150944-treated tracheary elements was depleted of cellulose-synthase-containing rosettes, which appeared to be inserted intact into the plasma membrane followed by their rapid disaggregation. AE F150944 also inhibited cellulose-dependent growth in the rosette-containing alga, Spirogyra pratensis, but it did not inhibit cellulose synthesis in Acetobacter xylinum or Dictyostelium discoideum, both of which synthesize cellulose via linear terminal complexes. Therefore, AE F150944 may inhibit crystalline cellulose synthesis by destabilizing plasma membrane rosettes.Abbreviations AE F150944 N2-(1-ethyl-3-phenylpropyl)-6-(1-fluoro-1-methylethyl)-1,3,5-triazine-2,4-diamine - CBI cellulose biosynthesis inhibiting - CGA CGA 325615, 1-cyclohexyl-5-(2,3,4,5,6-pentafluorophenoxy)-14,2,4,6-thiatriazin-3-amine - DCB 2,6-dichlorobenzonitrile - TE tracheary element     

Production and cytogenetic analysis of BC1, BC2, and BC3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F₁ hybrid with Chinese Spring resulted in 22 BC₁ seeds with an average seed set of 1.52%. Five BC₁ plants with 39–41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC₁ was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC₂ plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC₃ progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.