Segregation Of Traits Research Articles

Genetic segregation of natural Saccharomyces cerevisiae strains derived from spontaneous fermentation of Aglianico wine.

Investigation of the meiotic segregation of karyotypes and physiological traits in indigenous Saccharomyces strains isolated from Aglianico (South Italy) red wine. Segregation was studied in F1 and F2 descendants. Tetrads were isolated from sporulating cultures by micromanipulation. The spore clones were subjected to karyotype analysis by pulse-field gel electrophoresis (Bio-Rad model CHEF-DR II) and to various physiological tests. Certain chromosomes of the isolates showed 2:2 segregation patterns in F1 but proved to be stable in F2. The ability of cells to utilize maltose also segregated in a 2 : 2 manner in F1 and did not segregate in F2. Resistance to CuSO4, SO2 tolerance, the fermentative power and the production of certain metabolites segregated in both F1 and F2 generations and showed patterns indicating the involvement of polygenic regulation. The analysis revealed a high degree of genetic instability and demonstrated that meiosis can improve chromosomal and genetic stability. Winemaking is critically dependent on the physiological properties and genetic stability of the fermenting Saccharomyces yeasts. Selection of clones from F2 or later generations can be a method of reduction of genetic instability.

Improvement in hydroxy fatty acid seed oil content and other traits from interspecific hybrids of three Lesquerella species: Lesquerella fendleri, L. pallida, and L. lindheimeri

Interspecific hybridization offers potential to improve the hydroxy fatty acid (HFA) content of lesquerella. Lesquerella fendleri is currently being developed for cultivation as a potential new industrial oilseed crop because of its seed productivity. However, it has lower HFA content compared to L. pallida and L. lindheimeri. The objectives of this research were to improve the HFA oil content of L. fenderi through interspecific hybridization and to characterize hybrids and successive generations for seed oil fatty acid profile, fertility, seed set and other morphological traits. In this work, three species were successfully hybridized, self-pollinated, and backcrossed. Ovule culture was used in some cases to produce progeny where interspecific hybrids did not produce viable embryos. The traits measured were petal length, ovules per silique, seeds per silique, and weight of 1000 seed. Patterns of leaf trichomes were used to distinguish between parents and hybrids. Seed per silique indicated that autofertility occurred in L. pallida but not in the other two species. HFA oil content of L. fendleri seed were 50.5% compared to 80 and 84% for L. pallida and L. lindheimeri, respectively. The HFA oil content of the hybrids ranged from 57 to 70% in A2 and A3 generations, and the range of values depended on the parents used in the crosses. These measurements will help predict the value of different interspecific crosses for breeding. Segregation for various yield related traits should allow selection for favorable improvements in the HFA trait and in seed yield.

Wild helianthus species and wild-sunflower hybridization in Argentina

Two wild Helianthus species native to North America have been naturalized in Argentina, H. annuus ssp. annuus and H. petiolaris. They grow as adventitious overlapping about 50% of the crop area. Hybridization and introgression between these wild species and sunflower have important biological and practical consequences, the former including homoploid hybrid species formation, and the latter including a possibility of transgene spreading from genetically modified (GM) sunflower cultivars to wild or weedy populations. Wild populations were screened for isozyme and morphological variation. Intermediate plants were found in several locations and subjected to progeny tests. Variability among progeny of each one was compared with the variability in wild accessions of both species. Segregation for phenotypic traits, intermediate phenology and low fertility levels were found in most progenies, accounting for the hybrid origin of their maternal plants. Attempts to quantify gene flow included screening of progenies from H. petiolaris populations growing near sunflower crops. Hybrid plants were recognized by morphological traits and reduced fertility. Overall hybridization was about 1%. Hybrid progeny on wild H. annuus plants were identified by a crop isozyme marker. A mean frequency of 7% hybridization was found. These results confirm that gene flow occurs among crop and wild Helianthus species, and it concerns crop management and environmental impact if release of GM sunflower cultivars is to be authorized in Argentina.

Metabolic diversity of Saccharomyces cerevisiae strains from spontaneously fermented grape musts

One hundred and fifteen Saccharomyces cerevisiae strains from Aglianico del Vulture, a red wine produced in Southern Italy, were characterized for the production of some secondary compounds involved in the aroma and taste of alcoholic beverages. The strains exhibited a uniform behaviour in the production levels of n-propanol, active amyl alcohol and ethyl acetate, whereas isobutanol, isoamyl alcohol and acetaldehyde were formed with a wide variability. Only five strains produced wines close to the reference Aglianico del Vulture wine for the traits considered. Of these, two strains were selected, underwent to tetrad analysis and the single spore cultures were tested in grape must fermentation. The progeny of one strain showed a significant metabolic variability, confirming the necessity to test starter cultures for the segregation of traits of technological interest. Our findings suggest the selection of specific strains for specific fermentations as a function of the vine variety characteristics in order to take the major advantage from the combination grape must/S. cerevisiae strain.

Segregation of DNA markers of potato (Solanum tuberosum ssp. tuberosum L.) resistance against Ro1 pathotype Globodera rostochiensis in selected F<sub>1</sub> progeny

Marker assisted selection is the fast and objective method for detection of resistance major genes. This method is practical for identification of some candidate genes of quantitative resistance. Genetic markers based on Polymerase Chain Reaction (PCR) were used for evaluation of F<sub>1</sub> progenies Ornella × Mira and Tábor × Mira. Cultivar Mira has resistance against Ro1 pathotype G. rostochiensis. Cultivars Ornela and Tábor are susceptible to Ro1. Seedlings of F<sub>1</sub> generations were used for analyses. Plants were cultivated in greenhouse. DNA was isolated from tissue discs by GenElute Plant Genomic DNA Kit (Sigma, SRN). PCR marker of major gene H1 was used for bulked analyses, according to (Niewöhner et al. 1995). Size of this marker was 760 bp. Standard infection tests with Ro1 pathotype G. rostochiensis according to Potoček (1987) in all of the analysed genotypes were made. Segregation ratios of F<sub>1</sub> progenies were determined. These ratios have described segregation of resistance markers and segregation of traits in the biological test. The both methods of evaluation of potato’s resistance were compared by correlation analyse. High correlations were found between occurrence of PCR marker for H1 and resistance to Ro1 in biological test. Coefficient of correlation r = 0.962 in F<sub>1</sub> progeny Ornella × Mira and r = 0.964 in hybrids Tábor × Mira. Statistical evaluation of real ratios of segregation by infection tests and DNA markers with theoretical ratios of segregation in simplex and duplex H1 gen qualitative determined resistance was made as well. Resistant cultivar Mira as donor of simplex determined resistance was confirmed.

Feeding behaviour and metabolic efficiency contribute to growth heterosis in Pacific oysters [ Crassostrea gigas (Thunberg)

Physiological measurements were made on Pacific oysters from controlled crosses between inbred lines. Hybrid individuals were expected to perform better than inbred oysters, for a variety of traits related to feeding behaviour. The oysters were offered a diet simulating natural suspended particulate matter. By quantifying the organic and inorganic fractions of food, faeces and pseudofaeces, various aspects of feeding were elucidated. The results agreed with expectation; on average, hybrid oysters had higher rates and efficiencies of feeding and growth than inbreds. In one experiment there were significant differences between hybrids and inbreds for seventeen out of twenty cases; in another experiment hybrids performed better than inbreds for eight out of sixteen cases. In both experiments, we find significant differences between the reciprocal hybrids, though heterosis for growth is evident for all hybrids. Our experiments therefore confirmed heterosis for growth and hybrid superiority for physiological traits, independent of ration level; emphasised the complexity of these relationships amongst genotypes; and demonstrated the segregation of physiological traits in the F 2 generation.

Genetic Analysis and Interrelationships between Traits for Cooking Time, Water Absorption, and Protein and Tannin Content of Andean Dry Beans

A knowledge of the relative proportion of additive and nonadditive genetic variances for complex traits in a population forms a basis for studying trait inheritance and can be used as a tool in plant breeding. A North Carolina Design II mating scheme was used to determine the inheritance of cooking time, protein and tannin content, and water absorption among 16 genotypes of dry bean (Phaseolus vulgaris L.) representative of the Andean Center of Domestication. Heritability and the degree of dominance for the traits were also calculated to provide guidelines for adopting breeding strategies for cultivar development. Thirty-two progeny resulted from the matings and these were assigned to two sets of 16 progeny each. Variances due to general combining ability (GCA) and specific combining ability (SCA) were significant for the traits. The GCA was larger in all cases. Narrow-sense heritability for protein, tannin, water absorption, and cooking time averaged 0.88, 0.91, 0.77, and 0.90, respectively. Degree of dominance estimates indicted that the traits were governed by genes with partial dominance except, in one case, tannin had a degree of dominance value of zero, indicating no dominance. The phenotypic correlation (-0.82) between water absorption and cooking time justifies using the water absorption trait as an indirect selection method for cooking time. With regard to parent selection in crosses, significant differences between GCA females and GCA males suggested cytoplasmic influences on trait expression. Hence, the way a parent is used in a cross (i.e., as female or male) will offset trait segregation. Using fast-cooking bean cultivars in conjunction with fuel-efficient cooking methods may be the best strategy to conserve fuelwood and help reduce the rate of deforestation in East and Central Africa.

Simple inheritance of key traits distinguishing maize and teosinte.

The segregation of key traits distinguishing maize and teosinte was analyzed in three F2 and three backcross populations derived from crosses of the modern maize inbred T232 with Zea mays ssp. parviglumis. These traits were (i) paired vs. single female spikelets; (ii) two-ranked vs. many-ranked ears; (iii) non-indurated vs. indurated glumes; (iv) inclination of the kernels toward the rachis, and (v) distichous vs. polystichous central staminate spike. All traits showed a simple mode of inheritance except for paired female spikes, which appeared to be controlled by two genes. The loci controlling these major changes were mapped with RFLP markers to four chromosomal regions. These results support the suggestion that maize became differentiated from teosinte with as few as five major gene changes.

Callus induction and plantlet formation through culture of isolated microspores of eggplant (Solanum melongena L.)

Morphogenic calli were obtained efficiently from ab initio cultures of isolated microspores in eggplant. Initial culture of freshly isolated microspores in sucrose-free medium at high temperature (35°C) for 3 d was a prerequisite for callus induction. The microspores were re-cultured in modified NLN medium containing 2% sucrose and phytohormones (NAA 0.5 mg l(-1), BA 0.5 mg l(-1)) in the dark. After 4 weeks of re-culture, small calli derived from microspores were transferred to MS medium containing 4 mg l(-1) zeatin and 0.2 mg l(-1) IAA for shoot regeneration. The ploidy of 12 randomly selected regenerants was assessed by chromosome counts in root tips. Only one of the regenerants was haploid, 7 were diploid, 3 were triploid and one was tetraploid. The diploids set seeds after self-pollination and showed no segregation for morphological traits in the progeny, suggesting that they were spontaneously doubled haploids.

RFLP tagging of a salt tolerance gene in rice

A salt tolerant rice mutant (M-20) was obtained through selection in vitro. Its tolerance was stably inherited over eight generations and most traints between M-20 and its sensitive original 77–170 ( Oryza sativa) were very similar. By deriving an F 2 population of M-20 × 77–170 and splitting every F 2 individual into two parts, with one part planted in normal conditions and another part in saline conditions, the inheritance of salt tolerance in rice was studied. Under normal conditions, there was no apparent segregation among F 2 individuals. Under saline conditions, however, the segregation of traits was obvious. According to our standards, the ratio of salt sensitive:moderately-tolerant:tolerant plants was 25:42:18, in accordance with a 1:2:1 ratio. It suggested that the improvement of salt tolerance in our materials was induced by the mutation of a major tolerant gene which showed incomplete dominance. By use of 130 RFLP probes distributed throughout the rice genome, the gene was tagged by a single copy DNA probe, RG4, which was located on chromosome 7. The genetic distance between the salt tolerant gene and RG4 was 7.0 ± 2.9 cM. Based on the split method, a method which could be currently used to evaluate the damage of salt stress in rice was proposed.

Homozygous Variation in Rice Somaclones: Nonrandom Variation Instead of Mitotic Recombination

Mitotic recombination has been postulated by some researchers as a mechanism to explain the lack of segregation for certain traits in plants derived from tissue culture. Three genetic marker lines were used to examine whether mitotic recombination could be detected from plants regenerated from rice (Oryza sativa L.) tissue culture. One line, CI 11014, had two dominant genes An (awned) and Gl (pubescence) in linkage group 12. The other two, CI 11020 and CI 245714, had two corresponding recessive genes an (awnless) and gl (glabrous). A total of 1788 R1 plants regenerated from immature panicles of F1 plants from the crosses CI 11020 × CI 11014 and CI 245714 × CI 11014, and from the parental lines, were evaluated from 1988 to 1990 in the greenhouse, and 360 R2 lines derived from these F1 plants and parental lines were evaluated in the field. No mitotic recombination occurred for the genes investigated in this experiment. A high somaclonal variation frequency (47.5%) for the awnless characteristic was observed. The variation was not due to mutation of the dominant gene An, but was apparently caused by mutation of an inhibitor gene. Results from these experiments suggested that somaclonal variation was not always random and that specific loci had higher mutation rates during the somaculture procedure. Previous suggestions that changes in DNA methylation pattern caused by the tissue culture process were not random were consistent with the data from our studies.

Photosynthetic Characteristics of Segregates from Hybrids between Flaveria brownii (C4 Like) and Flaveria linearis (C3-C4).

Characteristics related to C4 photosynthesis were studied in reciprocal F1 hybrids and F2 plants from Flaveria brownii (C4 like) and Flaveria linearis (C3-C4). The reciprocal F1 plants differed in 13C/12C ratios of leaves and the percentage of 14C initially incorporated into C4 acids, being more like the pollen parents in these traits. They did not differ in apparent photosynthesis or in O2 inhibition of apparent photosynthesis and differed only slightly in CO2 compensation concentration at 175 [mu]mol quanta m-2 s-1 and 400 mL L-1 O2. The 13C/12C ratios of 78 F2 progeny from the two F1 plants exhibited a normal distribution centered between those of the parents, with a few values slightly higher and lower than the parents. Apparent photosynthesis at 130 [mu]L L-1 CO2 and inhibition of photosynthesis by O2 was nearly normally distributed in the F2 population, but no values for F2 plants approached those for F. brownii (15.4 [mu]mol m-2 s-1 and 7.8%, respectively). Distribution of the CO2 compensation concentration measured at 1000 [mu]mol quanta m-2 s-1 and 400 mL L-1 of O2 in the F2 population was skewed toward F. brownii with 72% of the progeny having values <9 [mu]L of CO2 L-1 compared to 1.5 and 27.2 [mu]L L-1 for F. brownii and F. linearis, respectively. Correlations among traits of F2 plants were low (coefficients of 0.30 to -0.49), indicating that the C4- related traits are not closely linked in segregating populations. Plants in the F2 population selected for high or low apparent photosynthesis at 130 [mu]L of CO2 L-1 (six each) did not rank consistently high or low for 13C/12C ratios, O2 inhibition of apparent photosynthesis, CO2 compensation concentration, or activities of phosphoenolpyruvate carboxylase or NADP-malic enzyme. This study confirms results of earlier work that indicates independent segregation of C4 traits and also shows that the C4-like parental type can be recovered, at least for some characteristics (13C/12C ratio), in segregating populations. Recovery of fully functional C4 plants awaits further experimentation with C4 x C3 or C4 x C3-C4 hybrid plants that produce fertile progeny.

Transfer of a dominant gene for powdery mildew resistance and DNA from Hordeum bulbosum into cultivated barley (H. vulgare)

In an attempt to transfer traits of agronomic importance from H. bulbosum into H. vulgare we carried out crosses between four diploid barley cultivars and a tetraploid H. bulbosum. Eleven viable triploid F1 plants were produced by means of embryo rescue techniques. Meiotic pairing between H. vulgare and H. bulbosum chromosomes was evidenced by the formation of trivalents at a mean frequency of 1.3 with a maximum of five per cell. The resulting triploid hybrids were backcrossed to diploid barley, and nine DC1 plants were obtained. Three of the BC1 plants exhibited H. bulbosum DNA or disease resistance. A species specific 611-bp DNA probe, pSc119.2, located in telomeres of the H. bulbosum genome, clearly detected five H. bulbosum DNA fragments of about 2.1, 2.4, 3.4, 4.0 and 4.8 kb in size present in one of the BC1 plants (BC1-5) in BamHI-digésted genomic Southern blots. Plant BC1-5 also contained a heterozygous chromosomal interchange involving chromosomes 3 and 4 as identified by N-banding. One of the two translocated chromosomes had the H. bulbosum sequence in the telomeric region as detected using in situ hybridization with pSc119.2. Two other BC1 plants (BC1-1 and BC1-2) were resistant to the powdery mildew isolates to which the barley cultivars were susceptible. Seventy-nine BC2 plants from plant BC1-2 segregated 32 mildew resistant to 47 susceptible, which fits a ratio of 1∶1, indicating that the transferred resistance was conditioned by a single dominant gene. Reciprocal crosses showed a tendency towards gametoselection that was relative to the resistance. Mildew resistant plant BC1-2 also had a 1-kb H. bulbosum DNA fragment identified with a ten-base random primer using polymerase chain reaction (PCR). Forty-three BC1 plants, randomly sampled from the 79 BC1 plants, also segregated 23∶20 for the presence versus absence of this 1-kb H. bulbosum DNA fragment, thereby fitting a 1∶1 ratio and indicating that the PCR product originated from a single locus. The 1-kb DNA fragment and disease resistance were independently inherited as detected by PCR analysis of bulked DNA from 17 resistant and 17 susceptible plants as well as by trait segregation in the 43 individual plants. The progenies produced could serve as an important resistant source in plant breeding. This is the first conclusive report of the stable transfer of disease resistance and DNA from H. bulbosum to H. vulgare.

Bovine Genome Study and Its Goals

The consensus conclusion of several recent major international livestock genetics conferences is that genomic localization of economic trait loci and subsequent marker-assisted selection for these traits will rapidly facilitate genetic improvement of livestock. Genetic improvement of cattle, specifically for efficiency of food utilization, reproductive performance, resistance to disease, and higher quality of beef and dairy products ranks high among the world's agricultural research needs. The necessary tool for large scale improvement of such a diverse array of phenotypes by marker-assisted selection is a 20 centiMorgan map of the bovine genome, consisting of highly polymorphic loci that can be easily scored by teams of investigators studying the segregation of desirable traits. This same map can subsequently be developed to a high level of resolution in regions around genes of particular interest and used to isolate and clone genes involved in the expression of economically important traits.&#x0D; Experiments in our laboratory (1, 2, 3) and others (4, 5) demonstrate that the methods that have revolutionized human genetics in the last decade can do the same for cattle genetics. Bovine cells readily hybridize with mouse L cells or hamster E36 cells and segregate cattle chromosomes (1). Genetic analysis of these segregating hybrid cells has produced the current syntenic map of the cow which consists of more than 270 genes including markers of every bovine chromosome. Fifteen of the autosomal syntenic groups have been assigned to chromosomes. Our laboratory has participated in these assignments (6, 7). We have selected genes for physical mapping based on their potential role in key physiological processes and their value in defining the limits of chromosomal conservation with the human and mouse maps. We have used Southern blotting of more than 200 bovine and heterologous probes and more recently, the polymerase chain reaction (PCR) with published primer sequences to generate these maps.

The real objective of Mendel's paper: A response to Monaghan and Corcos

Mendel's work in hybridization is ipso facto a study in inheritance. He is explicit in his interest to formulate universal generalizations, and at least in the case of the independent segregation of traits, he formulated his conclusions in the form of a law. Mendel did not discern, however, the inheritance of traits from that of the potential for traits. Choosing to study discrete non-overlapping traits, this did not hamper his efforts.

A Method for Genetic Analysis ofGlomerella graminicola(Colletotrichum graminicola) from Maize

Strains derived from nine different isolates of Colletotrichum graminicola from maize participated in the production of perithecia when incubated on pieces of autoclaved corn leaves in a humidity chamber. Matings occurred between self-fertile and self-sterile strains, and also between certain self-sterile strains. As many as 200 ascospore progeny were recovered easily from individual perithecia. Characterization of progeny showed that sexual recombination and Mendelian segregation of distinct traits could be detected. Segregation of markers for chlorate resistance (Chl R ), benomyl resistance (Bml R ), and melanin deficiency (Mel − ) approximated a 1:1 ratio and defined three separate linkage groups (...)

INTERSPECIFIC HYBRIDIZATION OF ORNITHOGALUM

Three species of Ornithogalum are extensively grown. They are O. umbellatum, arabicum and thyrsoides. All three have white flowers. Another species, O. dubium, has deep orange flowers, but produces a weak inflorescence. Hybrids have been produced within a species but no wide crosses have been reported. Embryo rescue was successfully applied to develop new hybrids between O. dubium with strong color and O. thyrsoides with a strong inflorescence. The F1 hybrids produced buff-colored flowers on strong inflorescences with short internodes and long strong pedicels. The meiosis of these hybrids was not normal with univalent, laggards and bridges present. The F1 hybrids were slightly fertile and F2 and backcross progeny were produced. The progeny showed considerable segregation for both flower color and inflorescence traits. Clones were obtained which combined the orange flower colors of dubium with the strong inflorescence of thyrsoides.

Intrageneric asymmetric hybrids between Nicotiana plumbaginifolia and Nicotiana sylvestris obtained by ‘gamma-fusion’

Asymmetric nuclear hybrids have been obtained by fusion between protoplasts from nitrate reductase deficient mutants of Nicotiana plumbaginifolia and gamma-irradiated protoplasts of Nicotiana sylvestris (dose 500 and 1000 Gy). Fusion products were recovered at a frequency of 0.13%–0.29% following selection for genetic complementation of nitrate reductase function. The somatic segregation of genetic traits as a consequence of radiation damage and in vitro passage has been demonstrated by studying the expression and transfer of biochemical traits from the donor, e.g. expression of the enzyme lysopine dehydrogenase and several isozymes; transfer of ribosomal 25S DNA. A dose effect relation could also be observed by correlating the regeneration efficiency and the relative expression of these markers with the retention of donor chromosomes and fragements in regenerated plants. The asymmetric hybrids were only partially self-fertile and progeny has usually been obtained by back-cross. This particular somatic fusion combination between compatible species allowed us to isolate large numbers of asymmetric hybrids and to study the elimination of donor genetic material as a function of radiation effects and in vitro passage.

Segregation of Organelle Traits Following Protoplast Fusion in Nicotiana

Protoplasts from plants with different organelle-types were fused in order to monitor the fate of mixed cytoplasms in plants regenerated from fused protoplasts. Protoplasts of Nicotiana tabacum (tobacco) were fused with two experimental lines containing N. tabacum nucleus but containing the cytoplasm (chloroplasts and mitochondria) of either N. repanda or N. suaveolens. Fused cells were microisolated so that the plants regenerated could be traced to a single fusion product with mixed cytoplasms. In these fusion products the chloroplasts appeared to segregate randomly while mitochondria segregated toward male sterile-type. While most regenerated plants segregated by maturity some clones segregated for chloroplast type in the R1 generation implying the presence of two chloroplast types in individual cells of the parental clone. Data from these fusions gives us a better understanding of how organelles behave following protoplast fusion.

Somatic hybridization in Nicotiana: Segregation of organellar traits among hybrid and cybrid plants

Protoplasts from a nitrate reductase-deficient mutant of Nicotiana tabacum L. were fused with protoplasts from a stamen-less, cytoplasmically malesterile cultivar of tobacco containing the cytoplasm from N. suaveolens Lehm. Plants were regenerated from the fused protoplasts and characterized with respect to stamen development, chromosome number, and chloroplast composition. Of 29 regenerated plants, stamen production was restored in 26 plants and pollen production in 22. One plant was male sterile and two plants have never flowered. Analysis of the electrophoretic mobility of ribulose-1,5-bisphosphate carboxylase (RuBPcase) showed that 19 of the plants contained RuBPcase of the N. suaveolens type, six plants contained enzyme of the N. tabacum type, and four plants contained both types. Analysis of resistance to tentoxin in seedlings from 20 of the plants demonstrated that 14 had N. suaveolens-type chloroplasts, three had N. tabacum type, and three contained both types. Many of the plants which produced stamens and pollen still contained chloroplasts of the N. suaveolens type. Thus, the trait of cytoplasmic male sterility in tobacco is not an expression of the type of chloroplast genetic material.