Progress through evolution? An inquiry into the thought of C.H. Waddington

It was C.H. Waddington's contention that the Neo-Darwinian Theory of Evolution ought to be amended by imbedding it in a broader theoretical framework which takes the role of the phenotype into account. Waddington's theory alleges the existence of two interlocking feedback circuits between environment and phenotype on the one hand and genotype and phenotype on the other. The resulting dynamical model of evolutionary change gives new meaning to the notion of progress in evolution. In this model natural selection acts directly on the phenotype, thereby influencing the feedback relationships. Better tuning of the feedback relations, however, leads to progress in adaptability which in Waddington's theory replaces the cumbersome concept of progress in adaptation.This paper expounds Waddington's theory and places it into a broader philosophical perspective.     

RAPD analysis of somaclonal variants derived from embryo callus cultures of peach

Peach [Prunus persica (L.) Batsch] regenerants from cv Sunhigh embryo no. 156, regenerants obtained from cv Redhaven embryo no. 30, and two peach cultivars Sunhigh and Redhaven, were screened for polymorphic RAPD (Random Amplified Polymorphic DNA) markers with up to 60 10-mer primers. Although 35 primers produced results with scoreable bands, only 10 of the primers revealed polymorphism for regenerants of embryo no. 156 and cv Sunhigh, and 1 revealed a low level of polymorphism for regenerants of embryo no. 30 and cv Redhaven. This study demonstrates the feasibility of using RAPD markers to identify somaclonal variants of peach and provides evidence for the existence of genetic differences among these variants.Abbreviations PCR Polymerase chain reaction - RAPD random amplified polymorphic DNA - RFLP Restriction fragment length polymorphism - CTAB cetyltrimethyl ammonium bromide - PVP polyvinyl pyrolidone - dNTP deoxy-ribonucleotide triphosphate Communicated by R. N. Trigiano     

Exploiting selective genotyping to study genetic diversity of resistance to Fusarium head blight in barley

Numerous barley cultivars from around the world have been identified as potential sources of Fusarium head blight (FHB) resistance genes. All of these cultivars exhibit partial resistance, and several mapping studies have shown that resistance to FHB is controlled by multiple genes. Successful development of barley cultivars with high levels of FHB resistance will require combining genes from multiple sources. We characterized five potential new sources of FHB resistance (AC Oxbow, Atahualpa, HOR211, PFC88209, and Zhedar#1) to determine if they contain new FHB resistance genes. Cluster analysis, using a set of 80 SSR markers distributed throughout the genome, showed that most of the new sources of resistance were not similar to three cultivars that have been used in previous FHB mapping studies (Chevron, Frederickson, and Gobernadora), with Atahualpa and HOR211 being the most dissimilar. By selective genotyping, we determined whether markers linked to six known FHB resistance quantitative trait loci (QTLs), discovered in other genotypes, explained variation for resistance in advanced breeding populations created from the new sources of resistance. Markers linked to four of the six known QTLs were associated with FHB severity in at least one of the populations. However, none of the six QTL regions were associated with variation for FHB severity in populations derived from crosses that utilized sources of resistance HOR211 or PFC88209. Selective genotyping is an efficient method for breeders to utilize current QTL information about disease resistance to search for new resistance genes.     

High-level Expression of Maize <Emphasis Type="Italic">γ</Emphasis>-zein Protein in Transgenic Soybean (<Emphasis Type="Italic">Glycine max</Emphasis>)

Primers were developed for 118 microsatellites isolated from grape (Vitis vinifera) genomic libraries enriched for (AC)n repeats. Only one microsatellite sequence matched other grape SSR-sequences in the GeneBank database. Genotyping was carried out in the parental lines and four offspring of two pseudo-test-cross populations, Cabernet Sauvignon x Seyval and Chardonnay x Bianca, and a further six other grape genotypes (V. vinifera Sultanina, Merlot, Syrah, Müller-Thurgau, Vitis Regent and V. riparia Gloire de Montpellier). A total of 108 microsatellites showed easily scorable alleles and 100 of them segregated according to a configuration suitable for mapping in either cross. A further 8 SSRs, although unsuitable for mapping in those crosses, showed polymorphism in the other genotypes tested. This set of markers was used, along with 75 microsatellites of other repeat-types, to fingerprint 46 offspring of the cross Chardonnay x Bianca. For each full-sib, individual heterozygosity and distance in repeat units between pairs of alleles at each locus (mean d²) were calculated as a tool for predicting highly outbred recombinant individuals. Six microsatellites with segregation ratios significantly distorted towards the lack of homozygous sibs were identified and mapped to linkage groups LG 3 and LG 5. Estimation of heterozygosity at genome-wide level and genotyping at loci for which homozygous sibs are discriminated against are discussed for marker-assisted background selection in outcrossing grapevines.     

Predominance and tissue specificity of adenine methylation in rice

Summary Using A and C methylation-specific restriction enzymes, namely, MboI, Sau3AI, DpnI, MspI, and HpaII, total rice cv Basmati 370 DNA, repetitive DNAs, and a specific repeat sequence indicated an abundance of adenine methylation. Although cytosine methylation in 5-CCGG-3 sequences suggested more CpC methylation than CpG, the C methylation in sequence 5-GATC-3 was comparatively less than A methylation. Furthermore, the presence of adenine methylation was tissue specific; it was predominant in rice shoot DNA as compared to embryo DNA. This pattern was also observed in two other cultivars of rice, i.e., R-24 and Sona, and was again confirmed using a cloned probe of a specific repeat sequence. Besides the changes in adenine methylation, there was also a qualitative change in 5mC from CpG to CpC dinucleotides in these two tissue systems.     

Triple hybridization with cultivated barley (Hordeum vulgare L.)

Summary A crossing programme for trispecific hybridization including cultivated barley (Hordeum vulgare L.) as the third parent was carried out. The primary hybrids comprised 11 interspecific combinations, each of which had either H. jubatum or H. lechleri as one of the parents. The second parent represented species closely or distantly related to H. jubatum and H. lechleri. In trispecific crosses with diploid barley, the seed set was 5.7%. Crosses with tetraploid barley were highly unsuccessful (0.2% seed set). Three lines of diploid barley were used in the crosses, i.e. Gull, Golden Promise and Vada. Generally, cv Gull had high crossability in crosses with related species in the primary hybrid. It is suggested that Gull has a genetic factor for crossability not present in cv Vada and cv Golden Promise. One accession of H. brachyantherum used in the primary hybrid had a very high crossability (seed set 54.7%) in combination with cv Vada but no viable offspring was produced. In all, two trispecific hybrids were raised, viz. (H. lechleri x H. brevisubulatum) x Gull (2n=7–30) and (H. jubatum x H. lechleri) x Gull (2n=20–22). The first combination invariably had a full complement of seven barley chromosomes plus an additional chromosome no. 7, but a varying number of chromosomes (19–22) of the wild-species hybrid. The second combination had a full set of barley chromosomes. The meiotic pairing was low in both combinations.     

Patterns of direct and indirect embryogenesis from mesophyll protoplasts of Medicago sativa

Clones of three cultivars of Medicago sativa (Rambler, Regen S and Rangelander) were used as sources of mesophyll protoplasts. Although all three clones readily produced protoplasts, the subsequent development patterns in culture varied greatly among genotypes, with protoplasts from Regen S and Rambler forming calli which could be induced to form embryos, and protoplasts from Rangelander undergoing direct embryogenesis. Protoplasts of Regen S exhibited high rates of division while those of Rangelander tended to aggregate with only a few cells per aggregate surviving. The surviving cells gave rise to proembryos within the aggregates; these proembryos developed into differentiated embryos after 5–7 weeks of culture. Based on the initial protoplast population, the efficiency of embryo formation averaged 0.13% and ranged from 0.001–0.4%. Observations during the early stages of culture indicated that cell aggregation was a prerequisite for direct embryogenesis.     

Effect of photoperiod on in vitro tuberization of potato (Solanum tuberosum L.)

Single-node cuttings of potato cultivars Jemseg, Katahdin, Russet Burbank and Superior were cultured on a multiplication medium containing MS salts and no growth regulators. Cultures were exposed to 8 h (SD) and 16 h (LD) photoperiodic regimes. The subsequent plantlets were excised and single node cuttings from each photoperiodic regime were placed under SD or LD on a second medium containing growth regulators which promoted tuberization. Production of microtubers was strongly influenced by genotype and by photoperiodic treatments. Superior produced stunted plantlets and some microtubers under SD conditions in the multiplication medium. The number of microtubers formed by Jemseg was not influenced by photoperiod. However, Katahdin and Russet Burbank formed fewer microtubers under LD-LD conditions compared to LD-SD, SD-SD and SD-LD regimes. Compared with the other regimes, LD-SD photoperiod generally promoted microtuber formation with larger diameters and significantly (p<0.05) greater fresh weight. The intensity of the tuberization stimulus was affected by daylength, and this was characterized by microtubers with secondary tubers, the growth of more than one axillary microtuber, and microtubers subtended by stolons. The maturity group of the potato cultivars and photoperiodic regime in vitro strongly influenced the production of microtubers. These results can be employed to adapt light regimes for multiplication and tuberization to the specific requirements for cultivars from different maturity groups, and thus increase the efficiency of potato multiplication protocols.     

Nuclear and cytoplasmic gene control of resistance to loose smut (Ustilago tritici (Pers.) Rostr.) in wheat (Triticum aestivum L.)

Summary Using disomic chromosome substitution lines based on the susceptible wheat cultivar Chinese Spring, loose smut resistance of wheat cultivars Hope and Thatcher was shown to be conferred in each case by a single dominant major gene carried on chromosome 7 A (Hope) or 7 B (Thatcher). Partial resistance was determined by genes on an additional eight Hope or seven Thatcher chromosomes, and similarities were evident between the partial resistance genotypes ofHope and Thatcher. Chinese Spring exhibited a mean infection value of approximately 50%, indicating a significant level of partial resistance, which was found to be due, in part, to genes on the homoeologous chromosome arms 1 As, 1 Es and 1 Ds, and to cytoplasmic genes. Substitution of the Chinese Spring nucleus into the cytoplasm of Aegilops squarrosa, Ae. variabilis or Ae. mutica resulted in increased susceptibility to Ustilago tritici. Several alloplasmic lines of the resistant wheat cultivars Selkirk and Chris exhibited race-specific susceptibility to U. tritici.     

Immature embryo rescue,culture and seedling development of acid citrus fruit derived from interploid hybridization

Interploid sexual hybridizations were completed in 2001 and 2002 between seven lemon (Citrus limon(L.) Burm. f.) varieties, Key lime (C. aurantifolia (Cristm.) Swing), Palestine sweet lime (C. imettioides Tan.), Lakeland limequat (C. aurantifolia x Fortunella japonica (Thumb.) Swing.), and Etrog citron (C. medica L.) as diploid progenitors and four allotetraploid somatic hybrids (Key lime + Valencia orange, Hamlin orange + Femminello lemon, Valencia orange + Rough lemon, and Valencia orange+ Femminello lemon) in efforts to generate improved seedless triploid acid fruit hybrids. Efficient recovery of triploid progeny from such crosses requires embryo rescue to avoid embryo abortion due to endosperm failure. Germination of rescued genetically diverse immature embryos was induced on two culture media (EME and Gamborgs B5), with two sucrose concentrations (50 or 70 g l^–1). All media contained 0.5 g l^–1 malt extract and 4.50 M GA₃. Germination of globular, heart and torpedo shaped embryos (defined as small embryos) was significantly (p < 0.05) affected by medium and genotype. Gamborgs medium induced 82.89% germination. Of germinated embryos, 11–65% developed into normal plants with differences among crosses. Cotyledonary embryos (defined as immature embryos with fully developed cotyledons) germinated and developed into normal plants at higher rates than less-developed embryos. In efforts to improve the efficiency of plant recovery, small embryos from Todo el año × HF and Lisbon × HF crosses conducted during 2002 were rescued and cultured on three media (MS, Gamborgs, and RMA) for comparison. Media did not significantly affect the proportion of normal plant recovery.     

Genetic analysis of two wheat cultivars, ‘Sonalika’ and ‘WL 711’ for reaction to leaf rust (Puccinia recondita)

Summary Genetic analysis for leaf rust reaction of two widely adapted cultivars, Sonalika and WL 711, has been done using 21 near isogenic Lr lines and rust culture IL004 — avirulent on the two cultivars and all the Lr lines used. The segregation pattern in the F₂ generation indicated the presence of a recessive gene in Sonalika and of a dominant gene in WL 711. These genes in cultivars Sonalika and WL 711 have been identified as Lr 11 and Lr 13, respectively. Gene Lr 13 is no longer effective in WL 711 but it continues to give field resistance in the backgrounds of Chris, Prelude and Thatcher. There has been no significant change in the virulence spectrum of the leaf rust pathogen in India with the release of WL 711. High susceptibility of WL 711 seems to be due to the evolution of more aggressive forms of the pathogen to this cultivar. The gene Lr 11, which behaves as a recessive in Sonalika, was effective against leaf rust when this cultivar was released. The high susceptibility of Sonalika is probably due to an increase in the frequency of race 77 virulent on Lr 11. Lr 11 has shown a dominance reversal in the background of Sonalika. Present results suggest that interaction of resistance genes with the background genotype must be studied for their effective use in breeding programme.     

Immunofluorescence localization of the epidermolytic toxin target in mouse epidermal cells and tissue

Summary An epidermolytic toxin target was observed in keratohyalin granules of sectioned epidermis by a direct fluorescence procedure using FTC-toxin, but not by an indirect procedure using sequential reaction with toxin, anti-toxin and FTC-secondary antibody. The investigation of the two procedures was extended to keratinocytes. A dispase digestion procedure yielded three fractions which corresponded to basal, spinous and granular cells according to biochemical and morphological criteria. It was shown that the direct and indirect procedures both detected the toxin target in the keratohyalin granules of granular cells, but that the indirect procedure was very insensitive. In control experiments, the profilaggrin of keratohyalin granules was detected readily in cells by a direct procedure using FTC-antiprofilaggrin but only weakly by an indirect double antibody procedure. Insensitivity to indirect procedures thus appears to be a particular property of the keratohyalin granule site. It was shown that the toxin target was readily accessible in permeable (trypsin-isolated) granular cells but inaccessible in impermeable (dispase-isolated) cells.     

Organogenesis from ‘Passe Crassane’ and ‘Old Home’ pear (Pyrus communis L.) protoplasts and isoenzymatic trueness-to-type of the regenerated plants

Summary Large numbers of highly viable mesophyll protoplasts were isolated from shoot cultures of the scion cv Passe Crassane and the rootstock genotype Old Home of common pear (Pyrus communis L.). Protoplasts were cultured for both genotypes either as liquid layers or as liquid-over-agar cultures, in ammonium-free MS medium with 0.5 M mannitol, 50 mg/l casein enzymatic hydrolysate (CEH), 2.0 mg/l NAA and 1.0 mg/l BAP, plus either 0.5 mg/l IAA (for Old Home) or 2.0 mg/l IAA (for Passe Crassane). Protoplast microcalli, obtained by day 60 (Passe Crassane) or day 80 (Old Home), were transferred for further growth to ammonium-free MS medium with 2.0 mg/l NAA and 1.0 mg/l BAP. Shoot bud regeneration from the protoplastderived callus was first attempted between 100 (Passe Crassane) and 120 (Old Home) days after protoplast isolation. For Passe Crassane, shoot buds were regenerated (day 130) on a half-strength MS medium with 0.1 mg/l IBA, 0.5 mg/l BAP, 50 mg/l CEH and 20 mg/l Ca-panthotenate. For Old Home, shoot but regeneration only occurred 30 days later and on the same medium as above, which was additionally supplemented with double the concentration of the group B vitamins found in the original MS formulation and 0.05 mg/l GA₃. Following micropropagation and in vitro rooting of shoots, the plants were transferred to soil following standard procedures. Trueness-to-type of the regenerated plants was assessed by analysing their leaf isozyme banding profiles (for EST, AP, PRX, SOD, ENP, LAP, PGI, AAT, ADH, MDH and PGM) and comparing them to those corresponding to the original shoots that provided the protoplasts. No differences between the mother shoots and the protoclones were observed for any one of the 11 isozyme systems studied.     

Viability and activity in readily culturable bacteria: a review and discussion of the practical issues

In microbiology the terms viability and culturability are often equated. However, in recent years the apparently self-contradictory expression viable-but-nonculturable (VBNC) has been applied to cells with various and often poorly defined physiological attributes but which, nonetheless, could not be cultured by methods normally appropriate to the organism concerned. These attributes include apparent cell integrity, the possession of some form of measurable cellular activity and the apparent capacity to regain culturability. We review the evidence relating to putative VBNC cells and stress our view that most of the reports claiming a return to culturability have failed to exclude the regrowth of a limited number of cells which had never lost culturability. We argue that failure to differentiate clearly between use of the terms viability and culturability in an operational versus a conceptual sense is fuelling the current debate, and conclude with a number of proposals that are designed to help clarify the major issues involved. In particular, we suggest an alternative operational terminology that replaces VBNC with expressions that are internally consistent.     

Selection for rate of development and pupal weight in ‘Cnephasia’ jactatana: A genetic tool for quality improvement

Selection for fast and slow rate of pupation over three successive generations in Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) produced a fast strain that pupated 2 days earlier than the slow strain. Selection for pupal weight was asymmetrical with the light selection having more effect than the heavy selection. The larval critical weight (L_CW), the larval maximum weight (L_MW) and the latent feeding period were not affected by any of the selections. Slow and light selections resulted in longer pre-pupal periods than fast, heavy or the laboratory population. Fecundity was reduced in females from slow and light selections. Selection in insects is discussed as a possible genetic tool for overall quality improvement.Résumé La sélection pour la rapidité d'apparition des chrysalides de C. jactatana Walker produit en 3 générations une lignée rapide qui se nymphose 2 jours avant la lente. La sélection pour le poids des chrysalides est asymétrique, ayant plus d'effet sur la sélection développement lent que sur la sélection développement rapide. Le poids critique larvaire (L_CW), le poids larvaire maximal (L_MW) et la période latente d'alimentation ne sont pas modifiés par ces sélections. Les lignées lente et légère ont des périodes prénymphales plus longues que les lignées rapide et lourde, ou la souche de laboratoire. Les fécondités des lignées lente et légère sont réduites. Les sélections associées des insectes sont examinées comme outil génétique potentiel permettant d'améliorer les performances globales.     

Microsatellite markers in the hexaploid Prunus domestica species and parentage lineage of three European plum cultivars using nuclear and chloroplast simple-sequence repeats

In a previous study, cDNA microsatellite markers were described in apricot (Prunus armeniaca L.). Specific PCR primers were designed to amplify the microsatellite-containing regions from genomic DNA in different Prunus species. In the present work, cDNA microsatellite markers were developed in the hexaploid Prunus domestica L. species and polymorphism was ascertained in a segregating plum population. Co-dominant mendelian segregation of alleles was demonstrated and microsatellite polymorphism displayed up to 6 alleles per SSR locus per individual. Parentage lineage of three full-sib European plum cultivars (cv. Cacanska najbolja, Cacanska rana and Cacanska lepotica) was reconstructed by the analysis of the above nuclear SSR markers, completed by four chloroplastic microsatellite loci. The six most informative nuclear loci enabled discrimination between the three Cacak cultivars and unrelated individuals as well as the previously proposed parents, Wangenheim and Pozegaca. Data obtained support previous evidence that these cultivars originated from the Stanley cultivar. However, SSR analysis finally excluded Wangenheim as the other possible parent. Based on the results obtained with nuclear and chloroplast SSR loci, we propose the origin of those three Cacak cultivars in a cross between Stanley as the mother plant and Ruth gerstetter as the pollinator. Furthermore, we demonstrate the utility of these apricot SSR markers for genotype fingerprinting of the hexaploid plum cultivars.     

Inheritance of early elongation ability in floating rice revealed by diallel and QTL analyses

In floating rice, stem elongation begins much earlier than in non-floating rice, which is the major survival mechanism for flooding. Inheritance of this early elongation ability was studied using diallel and quantitative trait locus (QTL) analyses. The diallel analysis was undertaken using a set of 6×6 half-diallel crosses involving four floating (Goai, Habiganj Aman VIII, Badal 106, and Oryza rufipogon strain W120) and two non-floating (Latisail and Patnai 23) parents. The additive gene effects were higher than the dominant effects. The dominant alleles were concentrated in the cultivated floating parents (Goai, Habiganj Aman VIII, and Badal 106), whereas the recessive alleles were in the wild floating parent (W120). A QTL analysis using a Patnai 23 × Goai F₂ population detected two putative QTLs. Of these QTLs, the one on chromosome 12 behaved as a partially dominant major gene that explained more than half of the total genetic variation.Communicated by D.J. Mackill     

Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

Complementary binding of oligonucleotides with 16S RNA and ribosomal ribonucleoproteins

The accessibility of single-stranded sequences of 16S RNA in free state and in ribonucleoprotein particles (RNP) to complementary binding with isoplith fractions of oligonucleotides was studied. RNP had different protein composition and corresponded to intermediate stages of E. coli 30S subunit assembly in vitro. Gel-filtration was used to detect the most strong binding. It was found that S4 essentially inhibited the hexamer binding to RNA. Core proteins bound to 16S RNA strongly increased the shielding of single-stranded regions while split proteins insignificantly changed the hexamer binding. Nevertheless evidence is presented that split proteins might also interact directly with 16S RNA in the 30S subunit.     

Cytogenetic analysis of structural rearrangements in three varieties of common wheat,Triticum aestivum

Summary The winter wheat varieties Starke and Cappelle Desprez and the spring wheat Chinese Spring were analysed for structural chromosome rearrangements that resulted in the formation of multivalents in F₁ hybrids. The analyses were carried out using hybrids involving euploids, monosomic and ditelosomic stocks, and double-monotelodisomic constructs. The study confirmed that Cappelle Desprez differs from Chinese Spring in a reciprocal translocation between chromosomes 5B and 7B (Riley et al. 1967); a translocation involving chromosomes 3B and 3D could not be verified. Furthermore, the analysis showed that Starke differs from Chinese Spring in a reciprocal translocation between chromosomes 7A and 7D. Both translocations have a coefficient of multivalent realisation of about 0.84. Further multivalents in euploid Starke, in euploid and some aneuploid stocks of Cappelle Desprez, and in euploid as well as various types of aneuploid hybrids between all three varieties could nearly all be explained hypothesizing that chromosome 2B of both Starke and Cappelle Desprez is a duplication-deficiency chromosome. In the hypothesis a part of the long arm of 2B is missing and replaced by a duplicated part of the long arm of chromosome 2D. The multivalents of this rearrangement showed an average coefficient of realisation of about 0.09.Sven Ellerström died in December 1985