Factors affecting field-scale production of seed of F1 hybrid Brussels sprouts

The two main factors involved in field-scale production of seed of F₁ hybrid Brussels sprouts are pollen availability and honeybee behaviour. Pollen availability depends upon the extent of winter survival of the parent inbreds, their flowering times, plant size and on the number of flowers per plant. Plant losses varied between inbreds and between sites and seasons. Differences in the commencement of flowering time in pairs of inbreds varied from 7 to 21 days, and plant size affected flower number. In hybrid seed-production there was a direct relationship between the number of mature flowers on each inbred and the percentage of non-hybrid seed produced from that inbred. Bees were highly selective in their visits to inbreds, and a mean selfing-to crossing-movement ratio of 30:1 was observed. This behaviour, together with pollen availability, greatly influenced the production of ‘sibs’. Radioactive experiments showed that the amount of cross-pollen carried by a bee decreased by about 30% at each flower visited but radioactive pollen grains were detected on the tenth flower visited. Of a number of factors investigated as possibly influencing bee behaviour, differences in flower colour and plant height were associated with discrimination between inbred lines.     

The feasibility of producing inbred rather than F1 hybrid cultivars in Brussels sprouts: predictions from early generations

Predicting the performance of recombinant inbred lines derived by single seed descent (SSD) following crosses between inbred lines is most reliable for traits in which epistasis and genotype environment interaction are absent. The analysis of two field trials of Brussels sprouts indicated the presence of such effects in seven quantitative characters. These effects could be minimised by transforming the scale on which each character was measured. Predictions were made of the likely performance of the recombinant inbred lines currently being produced by SSD at the Institute of Horticultural Research, Wellesbourne, compared with that of current F₁ hybrid varieties. The predictions from the first trial of F₂ material were encouraging for harvest date, stem length and waste weight, but low for sprout number, quality, marketable yield and total yield. Predictions from F₃ material in the second trial were good for sprout number and total yield (in addition to harvest date, stem length and waste weight as before), but still low for marketable yield and quality, with less than 0 01% of lines expected to perform better than the F₁. Model fitting to variances suggested the presence of linkage disequilibrium in dispersion for waste weight, but no information could be obtained about linkage disequilibrium for the two most important characters, marketable yield and quality. The broad heritability of each character except stem length was lower than 0 5 (0 3 or lower for total yield, waste weight and quality), suggesting that advanced generation selection, as used in SSD, might be more successful than selection in the early generations.     

The feasibility of producing inbred rather than F1 hybrid cultivars in Brussels sprouts (Brassica oleracea var. gemmifera): an assessment of recombinant inbred lines

Results are presented for the performance of improved inbred lines of Brussels sprouts grown in replicated and fully guarded plots. Some lines were identified which out-performed the reference F₁ hybrid, Gower, for the yield of marketable sprouts and for sprout quality. No lines were found which were superior for both of these traits. These results support earlier contentions that inbred line performance in Brussels sprouts could be improved to levels comparable with those of commercial F₁ hybrids. The genetic gains required to achieve commercial parity with hybrids for all agronomically important traits continue to be large. Therefore, the use of inbred lines as commercial cultivars can only be viewed as a long term objective. Previous studies have identified additive x additive epistasis and the segregation of many loci as important factors limiting the genetic gains to be expected from a single cycle of crossing and inbreeding. In addition to these factors the current study identifies areas of difficulty encountered when attempting to screen and select large numbers of inbred lines, produced either by single seed descent or by anther culture, in a single season. Evidence is presented which suggests that imperfect visual selection and/or genotype × seasonal interactions may substantially reduce the efficiency of selections based upon a single trial of very many unreplicated lines.     

The feasibility of producing inbred rather than F1 hybrid cultivars in Brussels sprouts: a preliminary genetical analysis and choice of material for inbreeding

The feasibility of producing commercially acceptable inbred lines of Brussels sprouts is investigated. Two experiments are described which examined the nature and extent of heterosis in this crop using the techniques of biometrical genetics. They indicate incomplete dominance for several production traits, lower F₁ uniformity and the presence of inbreds that outyield some F₁'s. These results strongly suggest that recombinant inbred lines, possibly outyielding the better F₁'s could be produced. Five crosses were identified for inbreeding by SSD and 1000 lines are being produced from each. The principles upon which these crosses were identified are described.     

The F1 genes of the F1F0 ATP synthase from the acidophilic bacterium Thiobacillus ferrooxidans complement Escherichia coli F1unc mutants

Abstract Because of the allelic variations within the M protein gene ( emm gene) of group A streptococci, reliable typing of this important human pathogen can be accomplished by the use of emm gene-specific oligonucleotide probes. Two technical modifications (a reverse dot blot and a reverse line blot hybridization assay) of a novel approach for the type-specific identification of emm genes have been developed. Both procedures involved amplification of an emm gene by polymerase chain reaction. The non-radioactively labeled amplicon was subsequently hybridized to a membrane carrying an array of immobilized emm gene-specific oligonucleotide probes, thus allowing the simultaneous analysis of the gene polymorphism in a single hybridization reaction. The feasibility of these rapid and easy to perform methods was shown for the unequivocal identification of reference strains and clinical isolates belonging to 16 different M serotypes.     

Estimating sib percentages from small samples of F1 hybrid populations

Plant breeders raising F_x hybrid populations cannot usually grow more than about 300 plants from one seed lot. If not more than k sibs are observed in a random sample of size N, they then need to estimate the probability that the proportion of sibs in the population is at most p. For sample sizes of not more than 300 this note describes the required statistical procedure which, though not new, may be unfamiliar to plant breeders.     

The reactions of some Brussels sprout F1 hybrids and inbreds to cauliflower mosaic and turnip mosaic viruses

Virus infection of Brussels sprout crops was widespread in Britain in 1974–76. Infected plants contained mostly cauliflower mosaic (CaMV) and turnip mosaic (TuMV) viruses but occasionally broccoli necrotic yellows virus (BNYV) was also found. The most seriously affected cultivar was the F₁ hybrid cv. Fasolt. Other hybrids including cvs Achilles, Citadel and King Arthur were more tolerant of infection. A key was developed for assessing the reactions of various F₁ hybrids and their parent inbred lines to CaMV + TuMV. Tests showed that the mean symptom severity of hybrids was usually less than the mean symptom severity of the parent inbreds, indicating that resistance to infection is partially dominant. The reactions of infected inbreds grown in winter under glasshouse conditions (15–18°C) were closely correlated with those of plants grown in the field. Thus, rapid selection of virus-tolerant inbreds can be made under glasshouse conditions.     

Predictors of marker-informativeness for an outbred F2 design

Generalization of the polymorphism information content (PIC) index to represent marker informativeness (MI) for a three-generation F2 design requires that two additional sources of non-informativeness be added to the PIC formula: the probability of matings between like-heterozygous F1 individuals, of which one is non-informative; and that of matings between like-heterozygous F1 individuals, which are both fully informative but where line of origin of the same alleles is reciprocal. Given the dense marker-maps currently available for some species, this F2 informativeness parameter constitutes the natural criterion for marker selection in F2 designs, and two computer programs to predict MI from grandparental marker-genotypes were developed for an F2 population originating from two divergent selection lines of outbred mice (F approximately 0.2). A total of 403 markers had been genotyped for the F0 grandparents (n=31), and 14 markers had also been genotyped in the complete pedigree including 559 F2 individuals. One program was based on assumptions of random-mating (RM), while the other (PED) accounted for the pedigreed mating structure. For the 403 markers, the correlation between MI from RM and from PED was 0.95, and the average deviation between the two predictions was 0.005 MI units (MI ranged from 0 to 1). Correlations between predicted and realized MI for the 14 fully genotyped markers were 0.97 for PED and 0.94 for RM, while the corresponding average of deviations between predicted and actual values were 0.01 and 0.04, respectively. Absolute deviations from realized MI never exceeded 0.09 and 0.16 for PED and RM, respectively. Simulated optimization of the mating system to maximize average MI of 28 markers on one chromosome led to improvements in the range of 15-20% average MI (0.07-0.09 MI units). The degree of relative advantage conferred by the F2 generalization of the PIC index over the traditional index was found to be of minor significance.     

Chloroplast ultrastructure in two Crassulacean species and an F1 hybrid with differing biomass δ13C values

Abstract. The chloroplasts of two species of the Crassulaceae and their F₁ hybrid were compared by electron microscopy. The two species had contrasting leaf tissue δ¹³C values of −25°/_∞ ( Sedum greggii ) and −13°/_∞ ( Cremnophila linguifolia ), and the F₁ hybrid had a value of − 18°/_∞. S. greggii had a mean of 8.9 thylakoids per granum in contrast to C. linguifolia which had a mean of only 3.8 thylakoids per granum. The F₁ hybrid had a mean of 6.4 thylakoids per granum. Crystaloids were observed in S. greggii and the hybrid but not in C. linguifolia     

Inheritance of Pathogenicity of Progeny from an F1 Culture of Melampsora lini

Abstract Races 1 and 400 of Melampsosau bni the causal agent of flax [Lmum usitatissimum]), were crossed and the resulting F² progeny evaluated on near-isogcnic fiax lines. The infection type of the parental cultures, the F¹² and the segregating f² progeny were used to evaluate the inheritance of pathogenicity. Races 1 and 400 as well as the F² and all the F² progeny were avirulent on lines N and P⁴ genes. This indicated both races to be homozygous avirulent. The F² and all the F² progeny were virulent on lines containing L9, M1, M4, and P. This indicated the F to be homuzygous for virulence at these loci. Segregation ratios of the F² cultures fit monogenic ratios on lines with host genes K. L2, L5, L6, L7, L11, M, M2, M3, N1, P1, P2, and P3. Race 1 was avirulent, race 400 virulent and tht F, avirulent on these lines. Several linkage groups were indicated including close linkage at A^p1, A^p2 and A^p3. Segregation on lines L, L3, M5, M6 and cultivars Flor, Dufferin, Linott, and Wishek fit a digenic model. The infection tvpes of the parents, the F¹ and the F², segregations could usually be explained by classical gene-for-gene interactions. Possible exceptions were segregations on L4, L8 and N2 which did not fit a 3: 1 ratio but did fit a 9: 7 ratio. Segregation on L 10 fit a 7: 9 ratio but line L10 may be temperature sensitive. Segregation on L1 indicated a single dominant gene for pathogenicity.     

The restoration of male fertility in F1 wheat hybrids

The yield of F₁ wheat hybrids is often limited by reduced male fertility. Improvement depends upon selecting male and female parents capable of allowing good fertility ‘restoration’ in the F₁ hybrids. Assessment of restoring potential in growth rooms was difficult because fertility was much lower than in field grown plants. In the field, two experiments showed differences between parent lines but also that the fertilities of the F₁ hybrids were site-specific, and that this factor might be considered during further selection. Variation between reciprocal crosses, possibly due to cytoplasmic differences, rendered a proposed test for the early assessment of fertility restoration capacity amongst potential male-sterile lines to be of doubtful value with present stocks.     

Hybridisation in the genera Vulpia and Festuca: the production of artificial F1 plants

The results of hybridisation experiments involving 24 strains of diploid, tetraploid and hexaploid Vulpia , representing nine species in three sections, and 22 strains of hexaploid and octoploid Festuca rubra agg., are presented, and the taxonomic implications discussed. 7848 pollinations produced 741 hybrid caryopses, from which 137 mature hybrid plants were raised (1.75% success rate) by embryo culture. Festuca x Festuca crosses were relatively easily achieved, and Festuca x Vulpia crosses were as successful as Vulpia x Vulpia crosses, indicating a close relationship between these two genera. Hybrids with F. rubra agg. were raised from females of species from all three sections of Vulpia. Within Vulpia , the most successful crosses involved V. geniculata, V. ligustica, V. fasciculata and V. pyramidata , whereas V. alopecuros was the least successful parent of all, producing only one mature hybrid from 2595 pollinations.     

Assembly of the Escherichia coli F1F0 ATPase, a large multimeric membrane-bound enzyme

The F₁F₀ proton translocating ATPase of Escherichia coli is a large membrane-bound enzyme complex consisting of more than 20 polypeptides that are encoded by the unc operon. Besides being a system for analysing the enzymology of ATP synthesis and energy coupling, the ATPase is a model system for determining how large oligomeric membrane-bound proteins are synthesized and assembled. The assembly of the ATPase involves differential gene expression and assembly of the subunits within the membrane and with each other. This review discusses the influence of F₁ subunits on the assembly and proton permeability of the F₀ proton channel, and the possible advantages to assembly of the particular arrangement of genes in the unc operon.     

Phloretin as an Antagonist of Prostaglandin F2α Receptor in Cultured Rat Astrocytes

Abstract: The effect of phloretin on prostaglandin (PG) F_2α-induced phosphoinositide hydrolysis and elevation of intracellular Ca²⁺ concentration was examined in cultured rat astrocytes. Phloretin inhibited PGF_2α (1 μ M )-induced phosphoinositide hydrolysis in a concentration-dependent manner with an IC₅₀ value of 16 μ M . The inhibitory action of phloretin was specific for PGs. The addition of increasing concentrations of phloretin caused progressive shifts of the dose-response curves of PGF_2α to the right. In digitoninpermeabilized astrocytes, phloretin (100 μ M ) inhibited the stimulation induced by PGF_2α (1 μ M ) plus GTPγS (50 μ M ) without affecting that induced by GTPγS alone. PGF_2α at 1 μ M transiently increased astrocytic intracellular Ca²⁺ concentration in 39% of the cells tested. The response was completely blocked by 100 μ M phloretin and the calcium response recovered again after washing out phloretin. These results suggest that phloretin is an antagonist of PGF_2α receptor linked to phospholipase C in astrocytes.     

Regional Distribution of Prostaglandins D2, E2, and F2α and Related Enzymes in Postmortem Human Brain

Abstract: The presence of prostaglandins D₂, E₂, and F_2α was demonstrated and their contents measured in various regions of postmortem human brain, pineal body, and pituitary by using specific radioimmunoassays and gas chromatography-mass spectrometry. The three prostaglandins were widely distributed in similar concentrations ranging from several hundred pg/g wet weight to about 40 ng/g wet weight. Prostaglandins D₂ and E₂ showed consistent and similar regional distributions in all six brains tested; amounts were high in pineal body, pituitary, olfactory bulb, and hypothalamus. On the other hand, prostaglandin F_2α was distributed more evenly. Prosta- glandin D synthetase and prostaglandin E synthetase activities were found in cerebrum homogenate from a single subject and were recovered from the 100,000 × g supernatant. The presence of 1 m M glutathione, reduced form, markedly stimulated the activity of prostaglandin E synthetase, but did not affect prostaglandin D synthetase activity. Activity of 15-hydroxyprostaglandin dehydrogenase was found in the cerebrum homogenate and was partially purified. This enzyme required NADP as a cofactor and copurified with prostaglandin E 9-ketoreductase.     

Environmental and genetic control of crassulacean acid metabolism in two crassulacean species and an F1 hybrid with differing biomass δ13C values

Abstract The growth, biomass δ¹³C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F₁ hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ¹³C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ¹³C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψ_leaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ¹³C values than did the plants watered only weekly.     

A Chemical Indicator for the Rapid Measurement of F0 Values

A new chemical indicator for monitoring steam sterilization processes has been calibrated in F ₀ units. The effective temperature range for F ₀ measurements using this device has been shown to lay between 115 and 123°C. The effective F ₀ range of the device has been shown to be 4–23 F ₀ units. Using the device, measurements can be made within 0.5 units of conventionally calculated F ₀ values.     

The F1FO ATP synthase genes in Methanosarcina acetivorans are dispensable for growth and ATP synthesis

There is a long-standing discussion in the literature, based on biochemical and genomic data, whether some archaeal species may have two structurally and functionally distinct ATP synthases in one cell: the archaeal A₁A_O together with the bacterial F₁F_O ATP synthase. To address a potential role of the bacterial F₁F_O ATP synthase, we have exchanged the F₁F_O ATPase gene cluster in Methanosarcina acetivorans against a puromycin resistance cassette. Interestingly, the mutant was able to grow with no difference in growth kinetics to the wild type, and cellular ATP contents were identical in the wild type and the mutant. These data demonstrate that the F₁F_O ATP synthase is dispensable for the growth of M. acetivorans .     

Reaction of Cotton Cultivars and an F2 Population to Stem Inoculation with Isolates Verticillium dahliae

Four Verticillium dahliae isolates (V76, TS‐2, PH, and V44) were used in screening four cotton cultivars (Pima S‐7, Acala Prema, M‐315 and Acala 44). Pima S‐7 and Acala Prema gave the highest resistance reactions and Acala 44 was the most susceptible. Isolate V76 of V. dahliae was the most virulent. An interspecific cross between the resistant cv Pima S‐7 (Gossypium barbadense) and the susceptible cv. Acala 44 (G. hirsutum) was made and the F₂ population phenotyped for Verticillium wilt effect. Phenotyping of plant reaction to the disease was quantified by using a set of six growth parameters (number of healthy leaves, number of nodes, leaf weight, stem weight, leaf to stem ratio, and total shoot weight) measured 3 weeks after inoculation. The F₂ phenotypic distribution of these parameters suggests that distribution is towards resistance and polygenic. Transgressive segregation also was observed. The number of healthy leaves and total shoot weight were found to be the best indicators of resistance. Results obtained in this study will be useful to quantify resistance to V. dahliae and identify the best parameters to phenotype in genetic studies.