Open-pollinated Populations Research Articles

Breeding of improved open-pollinated populations of spring-sown onions

SummaryVarious population improvement methods were applied to the spring-sown bulb onion crop. Synthetic populations were developed by recurrent selection, basing this selection on the performance of inbred lines per se for improved yield, bulb quality and storage performance. From the synthetic populations, partially inbred populations were also developed by half-sib selection methods. Results showed that gains, primarily in storage performance and marketable yield, were obtained in many of the synthetics. The mean gain in yield per cycle was of a similar magnitude to gains reported for maize using similar selection procedures although individual onion synthetic populations varied considerably in their achieved gains. Further gains in quality and storage performance, with no reduction in yield, were obtained by the development of partially inbred populations from the synthetics. These results are discussed in relation to the breeding of improved onion cultivars in the U.K.

RELATIONSHIP OF MORPHOLOGICAL PLANT CHARACTERISTICS OF SUNFLOWER TO BIRD FEEDING

Bird damage to sunflower (Helianthus annuus L.) is a serious problem in many areas where the crop is grown commercially. This study identifies morphological characters of sunflower that could be used in breeding programs to develop genotypes with improved resistance to bird feeding. An open-pollinated population of sunflower genotypes was tested in four environments for the effects of head shape, bract length, achene size, achene color, plant height, head diameter, distance between head and stem, and head angle. Feeding damage from blackbirds (Agelaius phoeniceus L.) and house sparrows (Passer domesticus L.) was visually estimated. Concave heads, medium distances between the heads and stems, and white achenes discouraged blackbird feeding. Concave heads and downturned heads were aversive to sparrows.Key words: Sunflower, plant characteristics, bird feeding, Helianthus annus L.

The relative performance of inbreds and open-pollinated populations of spring-sown onions

SUMMARYFirst (I1), second (I2) and third-generation (I3) inbreds were compared with openpollinated spring-sown onion populations in field trials at five sites over 2 years. The open-pollinated populations were earlier maturing and gave higher yields and a lower proportion of bullnecked plants than the inbreds but the latter had a lower proportion of unmarketable double bulbs. The mean level of expression of each character differed considerably between individual trials. The effect on sprouting within each year resulted from factors operating prior to storage; bulbs from all sites were stored at Wellesbourne in a common environment yet large differences in the proportion of sprouted bulbs from different sites occurred by the following spring.Interactions were found between the type of population (inbred and open-pollinated) and the macro-environment. Inbred populations showed a greater linear response to environment for yield, skin colour and proportion of bullnecked plants, but were less responsive for percentage of double bulbs.The results are discussed in relation to the evaluation procedures for inbreds.

Contrasting Success of Natural Hybridization in Two Eucalyptus Species Pairs

A morphological study with univariate and principal component analyses of mature tree and open-pollinated seedling populations shows that natural hybridization is occurring between Eucalyptus melanophloia and E. crebra, and E. populnea and E. crebra (subgenus Symphyomyrtus, section Adnataria). The level of successful hybridization in these two systems, where fundamental genetic (reproductive) and ecological (habitat and spatial) barriers are absent, is examined. Within the ecotone, hybrids between E. melanophloia and E. crebra are about one-fifth as frequent as those between E. populnea and E. crebra. Analyses of the phenotype/genotype compositions of the hybrid populations, the patterns of segregation, and outcrossing frequencies between the species pairs indicate the level of development of the hybrid populations. All E. melanophloia × E. crebra hybrids appear to be F1 hybrids. In contrast, the E.populnea x E. crebra hybrid population attains a much higher level of development in terms of both hybrid number and genotypic complexity. Flowering phenology is a major barrier to E. melanophloia × E. crebra hybrid formation compared with the other hybrids, although it is considered an incomplete barrier and alone may not explain the diversity of hybrid success which occurs.A theory of plant hybridization which incorporates the concept of hybridization success is presented and discussed in relation to the two hybridizing systems, as a basis for further investigating the mechanisms involved.

Studies on Breeding Sweet Potato Varieyies Adapted to True Se ed Planting. : I.Flowering Habit, Seed-Seting and Adaptability of Natural Flowering Population to True Seed Planting

To eliminate the usual plant bed costs and to mechanize planting, sweet potato varie-ties adapted to true seed planting (direct sowing of true seeds) is expected to produce. Thus the recurrent selection procedure was applied using natural flowering population, and. the appropriate breeding procedure for developing synthetic varieties was discussed in this paper. In experiment I, flowering habits of natural flowering population were observed under stick-training culture in which two vines per plant were trained along the supporting sticks picking the leaf axils, and also yielding treLits such as number of roots, root weight, root size and dry matter percentage were recorded under the ordinary trans planting culture. In experiment II, yielding traits of the strains selected for number of seeds in the open-pollination of experiment I were evaluated under the true seed planting culture and the strains with high root weight and high dry matter percentage were selected to make a first cycle synthetic variety. Moreover the individuals were selected from the polycross progeny of the selected strains to make the second cycle open-pollinated population.

Genetic structures in finite, open-pollinated plant populations: a model and its application to seed orchards

A model has been constructed to investigate the consequences of the rate of self-fertilization, pollen-dispersal, population-size, and number of clones on the genetic structure of finite seed plant populations. Derivations have been performed for two different cases: A) Parental genetic structure explicitly given: inferences for the expected genetic structure of the resulting seed population; B) Extension of case A) to several non-overlapping generations. If random cross-fertilization is assumed for case A) the genetic composition does not change and the genetic distance between the corresponding Hardy-Weinberg-structure and the expected offspring-structure is 0 if the rate of self-fertilization is equal to 1/N (N = population-size); any deviation from 1/N causes an increase in genetic distance.in case B) the expected genetic structures have been derived for all generations and it was possible to establish a comparatively simple dependence on the coefficient of inbreeding. In addition the variance of the allele-frequency has been presented. All the above influential components can be summarized by a single quantity, called M. After proving that 1/M can be conceived as the effective population-size, all the results obtained could be presented depending on this effective size and the average rate of self-fertilization only.Applying the findings of the model to the situation realized approximately in a seed-orchard, the following statements can be made:Case A) Again assuming random cross-fertilization, a deviation of the parental population from the corresponding Hardy-Weinberg-proportions can, with increasing rate of self-fertilization, be exceeded by the respective deviation of the seed population. Case B) The influence of pollen dispersal on the effective population size has been investigated, assuming no variation of the individual rates of self-fertilization, pollen and seed production within the population. Only extremely small differences between effective and actual population size were obtained, which indicates that the influence of pollen dispersal is of minor importance in this case. For different rates of self-fertilization, significant differences in the increments per generation for the coefficients of inbreeding, as well as the frequency of homozygotes, were obtained for the first generation only. Decreasing number of clones influences the rate of self-fertilization and the effective population size simultaneously by increasing the first and decreasing the latter. This is transferred to the coefficient of inbreeding, frequency of the homozygotes and the variance of the allele frequency by an increase of increments for all generations.

Angewandt-genetische Studien zur cytoplasmatischen Pollensterilität bei Winterroggen

Restorer test crosses of ten open-pollinated populations to CMS-line L1-P (P = 'Pampa' cytoplasm) in 1973 yielded 28 % male-fertile (mf), 27% partially male-sterile (pms), and 45 % male-sterile (ms) plants. In 1974, with CMS-tester-linie L3-P, the respective values were 7, 56 and 37 %. Significant differences between populations were found for the ms-proportions only. Averaged over the two tests they ranged from 16 to 57%.Tested to L1-P in 1971, 3 homozygous inbred lines were found to be restorers, 38 partial restorers, and 46 nonrestorers. Tested to L3-P in 1974, the respective numbers were 1,155 and 41 lines. 18 (out of 87) lines were classified in both tests as nonrestorers, but none as a restorer.Continued search for CMS sources was successful in 15 cases up to 1974. Four forms trace back to the Argentinian cultivar 'Pampa', ten to samples of Persian primitive rye and one to European adapted material.By means of diallel crosses, six genotypes (single crosses) were combined with three cytoplasms (Pampa-2 and two Persian sources). Three of the genotypes reacted equally with each of the cytoplasms: one as a restorer, one as a partial restorer, and one as a nonrestorer. The remaining combinations displayed pronounced plasmotype/ genotype interactions.Since 1971 an experiment has been in progress; to test the CMS mechanics for large scale hybrid seed production. Throughout, seed setting on the ms mother plants was similar to that on the pollinator plants. Fields were about 3 ha, and seed and pollinator parents were grown in strips 7, 50 m and 2, 50 m broad, respectively.

A model for genetic relationship among offspring from open-pollinated plant populations

Based on monoecious, diploid plant species, a model is constructed to determine genetic relationship within the seed production of an open-pollinated population, characterized by its rates of self-fertilization, population density and mode of pollen dispersal. Genetic relationship is measured by the coefficient of inbreeding of a seed produced by a mother plant located at a specified place, or by the coefficient of kinship between two seeds, produced from the same mother plant or produced from two different mother plants separated by a certain distance. The influence of the single parameters on these coefficients is demonstrated by some typical examples, which show that dimensionality of the habitat (one- or two-dimensional), as well as, range and type of pollen dispersal, has little influence on the relationship between seed produced from the same mother plant and, on the other hand, emphasize the important role of the rate of self-fertilization and population density. Some remarks on how to apply Wright's concept of neighbourhood to continuous plant populations close this paper.

Biosystematics of the genus Populus. III. Naturally occurring Manitoba hybrids of introduced P. × petrowskyana with native P. deltoides var. occidentalis and P. balsamifera

Collections of hybrid poplars made in the Roseisle area of Manitoba appear to have resulted from hybridization of introduced P. × petrowskyana Schneid. with native P. deltoides Marsh. var. occidentalis Rydb. and P. balsamifera L. This interpretation was supported by morphology of an open-pollinated seedling population of P. × petrowskyana and by chromatographic analyses. Gas chromatographic results were effective in distinguishing the three parent species; however, the hybrid nature of P. × petrowskyana made chromatographic documentation of hybridization very difficult. High fertility, indicated by abundant production of sound seed, was noted for several mature P. × petrowskyana × P. deltoides var. occidentalis female trees. No barriers were found that would prevent a three species complex of all three hybridizing species.

ESTIMATION OF THE MATING SYSTEM IN OPEN-POLLINATED MAIZE POPULATIONS USING ISOZYME POLYMORPHISMS

mating system by which a given population reproduces plays an imT g t a n t role in determining its genetic structure. In maize, random mating has usually been assumed. However, GUTTIEREZ and SPRAGUE (1959), in a shtdy of polycross plantings of ten stocks which were homozygous for recessive markers, found marked differences in the effectiveness of the stocks as male and female parents. They showed that these differences related to attributes of the mating system such as time of silking and time of pollen shedding. The investigation reported here was undertaken to determine whether such marked deviations from random mating occur in advanced generation open-pollinated populations of maize. Isozyme variants were adopted as markers in this investigation because of their many advantages in studying such populational processes as the mating system. However, isozymes are frequently expressed only at some specific stage in the life cycle and then only in materials grown under carefully controlled conditions. Further, sampling an individual for enzymatic assay may cause damage that upsets the growth pattern and ultimately affects mating behavior; this applies particularly when isozymes are expressed only in seedlings, as is often the case. These difficulties can be circumvented by collecting seeds from mature plants in the field, and inferring the genotype of the maternal parent from progeny tests of seedlings grown under controlled conditions. In this situation an appropriate statistical method for estimating the relevant mating system parameters is required. Such an estimation procedure is described and discussed in the first part of this paper. Following this the results obtained when the method was applied to isozyme data from two open-pollinated populations of maize are presented.

An improved method for the evaluation and selection of sugar beets (Beta vulgaris L.) 1. The selection of individual plants

Materials and Methods Three heterozygous , open-pollinated populations and one f, hybrid were used in this investigation. The three populations 'were: (a) CS7, an open-pollinated , high-yielding population selected tor .,\lberta conditions; (b) A90-54, an open-pollinated, high-sucrose-content population Udycz A, originally obtained hom Poland; (c) 5957, an open-pollinated increase of plants selected from Udycz A for decument tops. The f, hybrid, A213, was obta ined from Dr. .J. S. McFarlane of the USDA as NBI X NB4. The experiments d escribed below were conducted at the R esearch Farm , Canadian Sugar Factories, T aber , Alberta.

Variations in Chromosomal Association and Behavior During Meiosis Among Plants from Open-Pollinated Populations of Dactylis glomerata

1. Chromosomal association and behavior during meiosis was determined from duplicate collections of twelve plants and single collections of eight plants from open-pollinated populations of Dactylis glomerata. 2. The average number of quadrivalents per sporocyte ranged from 2.42 to 4.39 for the twenty plants. The differences among plants and between dates of collection were statistically significant. 3. The percentage of metaphase I sporocytes with univalents varied from 0 to 16.8. P was less than 0.05 and 0.01, respectively, for comparisons of differences among plants and between dates of collection. 4. From 1.7 to 34.0 per cent of the anaphase I sporocytes of the different plants had lagging chromosomes which were dividing equationally. The difference between dates of collection was significant. For comparison of variance due to plants with the interaction plants x days, F was slightly less than F for P of 0.05. From 0.5 to 13.8 per cent of the anaphase I sporocytes had dicentric chromatid bridges accomp...