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Showing papers on "Plant breeding published in 1986"


Journal ArticleDOI
13 Jun 1986-Science
TL;DR: Brassicas are a highly diverse group of crop plants that have great economic value as vegetables and as sources of condiment mustard, edible and industrial oil, animal fodder, and green manure.
Abstract: Rapid-cycling populations of six economically important species in the genus Brassica have unusual potential for resolving many problems in plant biology and for use in education. Rapid-cycling brassicas can produce up to ten generations of seed per year and serve as models for research in genetics, host-parasite relations, molecular biology, cell biology, plant biochemistry, population biology, and plant breeding. Brassicas are a highly diverse group of crop plants that have great economic value as vegetables and as sources of condiment mustard, edible and industrial oil, animal fodder, and green manure. These plants can also be used in the classroom as convenient, rapidly responding, living plant materials for "hands on" learning at all levels of our educational system.

298 citations


Book ChapterDOI
J.M. Dunwell1
01 Jan 1986

85 citations


Journal ArticleDOI
TL;DR: There was a tendency for larger yields to be achieved from cultivar x season combinations where the optimum population was larger, which suggested that commercial seed rates should be re-examined when changes to plant types or yield levels are made.
Abstract: Eight spring bread wheat cultivars (Triticum aestivum L.), differing widely in their nominal yield component characteristics, were tested under rain-fed conditions for three years at sowing densities ranging from 50 to 800 seeds m-2. The objectives of the experiments were to estimate the relationship between grain yield and particular yield components, the expression of plant type (yield components) in relation to plant density, and the plant population x cultivar interaction for grain yield over a range of seasons in a given environment. The 'optimum' plant population (at maximum grain yield) varied over 30-220 plants m-2, depending on season and cultivar. In general, variation in the 'optimum' population was greater between seasons for a given cultivar than between cultivars within seasons. The relationship between grain yield and yield components was examined at the 'optimum' population rather than at an arbitrary population at which grain yield may have been suboptimal for some cultivars or seasons. Grain yields at the optimum populations for the various cultivar x season combinations were positively related to culms m-2, spikes m-2 and seeds m-2. They were not clearly related to culm mortality (%). When averaged across seasons, cultivar grain yields were positively related to harvest index, but the general relationship was not so clear when seasons and cultivars were examined individually. Spike size (seeds spike-I or spike weight) and seed size were also not clearly related to grain yield at the 'optimum' population, and it was thus postulated that the production and survival of large numbers of culms, which in turn led to large numbers of seeds per unit area, were the source of large grain yields. Some interactions were found between yield components and plant population for some cultivars that could have implications for plant breeders selecting at low plant densities. The implications for crop ideotypes of the individual plant characters at the 'optimum' population are also discussed. Interactions between cultivars and plant populations implied that some cultivars required different populations to achieve maximum yields in some seasons. There was a tendency for larger yields to be achieved from cultivar x season combinations where the optimum population was larger, which suggested that commercial seed rates should be re-examined when changes to plant types or yield levels are made.

33 citations


Journal ArticleDOI
TL;DR: Because of restrictions imposed by crossing barriers, crested wheatgrass breeders have usually limited themselves to selection and hybridization within ploidy levels i.e., diploid, tetraploids, or hexaploid populations, but interploidy breeding appears to be a feasible approach in the crested Wheatgrass complex.
Abstract: Because of restrictions imposed by crossing barriers, crested wheatgrass breeders have usually limited themselves to selection and hybridization within ploidy levels i.e., diploid (2n=14), tetraploid (2n=28), or hexaploid (2n=42) populations. Several procedures have now been devised and evaluated to transfer genetic traits among ploidy levels, and interploidy breeding appears to be a feasible approach in the crested wheatgrass complex. Plant scientists with the USDA-ARS at Utah State University have developed a superior breeding population by hybridizing induced tetraploid Agropyron cristatum (L.) Gaertn. with natural tetraploidA. desertorum (Fisch. ex Link) Schult. The cultivar 'Hycrest' was released from this germplasm base in 1984. Chromosome number of the Hycrest breeding population ranged from 2n=28 to 32 and averaged 30. Chromosome pairing relationships were similar to those observed in natural tetraploids and the cultivar was as fertile as the parental species. Hycrest produced significantly more seeds per spike than 'Nordan,' and ample genetic variability for seed set existed in the population to make additional improvement through selection. Hycrest produced significantly (P<0.05) more forage than Nordan and Fairway in 9 of 12 comparisons at 5 semiarid range sites. The superiority of the cultivar was most noteworthy during and immediately after stand establishment on harsh sites. The need to expand the genetic base of the present population with selected parental materials is recognized. Since its successful introduction from Eurasia in 1906 (Dillman 1946), crested wheatgrass has had more impact on revegetation of western rangelands than any other grass. This widely adapted cool-season perennial grass is actually a complex of diploid (2n=2x=14), tetraploid (2n=4x=28), and hexaploid (2n=6x=42) taxa. The diploid form is represented in North America by fairway [Agropyron cristatum (L.) Gaertn.]. The most common tetraploids are standard [A. desertorum (Fisch. ex Link) Schult.] and siberian [A. fragile (Roth) Candargy]. The tetraploids are most prevalent on rangelands in the U.S. and the diploids are the most important form in Canada (Asay and Knowles 1985). New sources of diploid germplasm have recently been reported (Dewey and Asay 1982, Dewey and Hsiao 1984) and may be instrumental in future breeding efforts. Although hexaploid ecotypes have been introduced in North America and eventually may be a factor in rangeland improvement, observations to date indicate that they have limited merit in a plant breeding program. Based on chromosome pairing relationships in interploidy hybrids, Dewey (1974) concluded that the same basic genome, modified by structural rearrangements, occurred at the three ploidy levels. He advised crested wheatgrass breeders to treat the species in the complex as a single gene pool. Although interploidy crosses are often difficult to make and sterility problems are encountered in hybrid progenies, all possible crosses have been made among the diploid (2x), tetraploid (4x), and hexaploid (6x) levels and several schemes have been devised and tested to effect interploidy genetic transfer (Asay and Dewey 1983). The most progress from interploidy breeding to date has been achieved at the 4x level. Hybridization schemes involving 6x-2x, 6x-4x, 4x-2x, and hybrids between colchicine-induced tetraploids (C4x) and natural tetraploids (N4x) have shown potential for Authors are research geneticists, range scientist retired, support scientist, and graduate assistant, USDA-ARS, Crops Research Laboratory, Utah State University, UMC-63, Logan, Utah 84322. Manuscript accepted 8 August 1985. expanding the genetic resources of 4x breeding populations (Asay and Dewey 1979; Dewey 1969, 1971, 1974; Dewey and Pendse 1968; Knowles 1955). Plant materials from C4x-N4x crosses have been particularly promising. Tai and Dewey (1966) found that C4x tetraploids were relatively fertile and crossed readily with natural tetraploids. Although the fertility of the F1 hybrid was variable, average seed set compared favorably with that of the parental lines. Dewey and Pendse's (1968) data also indicated that selection for improved fertility would be effective. Many of the hybrid clones were substantially more vigorous than the parental species. In 1974, progenies from 295 F3 clones of the C4x-N4x hybrid were entered in the USDA-ARS grass breeding at Logan, Utah. On the basis of evaluation in an 8,000-plant source nursery and subsequent progeny tests, 18 clonal lines were selected and isolated in a crossing block to form the parentage of a synthetic strain. Selection criteria included vigor of seedlings and mature plants, yield of forage and seed, leafiness, resistance to plant pests, and response to environmental stress. The experimental strain, subsequently released as the cultivar 'Hycrest' (Asay et al. 1985), is the first interspecific hybrid of crested wheatgrass to be released. The objectives of these studies were to determine the range in chromosome number, meiotic regularity, and fertility of the C4xN4x hybrid and to compare the agronomic merit of the hybrid with commercially available cultivars of crested wheatgrass. The data will provide a basis to evaluate the potential of combining the genetic resources of diploid and tetraploid crested wheatgrass through interploidy hybridization. Materials and Methods Plant materials consisted of the F5 generation of the C4x-N4x crested wheatgrass hybrid represented by the Syn-l generation of the cultivar Hycrest. The research was conducted in 2 phases: (1) cytological studies of meiotic regularity and fertility of the hybrid, and (2) evaluation of the hybrid's seedling vigor, forage yield, and seed yield on semiarid range sites. The commercially available cultivars 'Nordan' and 'Fairway' were included in the second phase for comparative purposes. One-hundred clones, randomly selected from a breeding nursery consisting of 3,000 Syn-l (F5) plants, were included in the studies of meiotic regularity and fertility. Spikes for cytological analyses were collected from 20 clones, fixed in Carnoy's (6:3:1) solution, and stored under refrigeration in 70% ethanol. Squash preparations of pollen mother cells were made with acetocarmine as the strain. Chromosome pairing relationships, number of lagging chromosomes, and frequency of micronuclei were determined at metaphase-1, anaphase-1, and the quartet stages of meiosis, respectively. Pollen viability was estimated by staining pollen grains with aqueous 12-KI solution. At seed maturity, 10 open pollinated (OP) spikes were collected from each of the 100 plants for determination of seed set (seeds/ spike). Stand establishment data and forage yield were obtained at 5 locations (A E) in Utah, Idaho, and Montana (Table 1). Studies were arranged as randomized complete blocks at all locations with 4 replicates at locations A and B and 2 replicates at C, D, and E. Plot size was 1.5 by 40 m at Location A, 3 by 15 m at B, 3 by 30 m at C and E, and 1.5 by 30 m at D. Drilled rows within plots were spaced 0.3 m apart at all locations. Forage yields were determined from 1-iM2 samples randomly chosen in each plot. Two to 3 samples were taken per plot at locations with 2 replicates. Forage samples JOURNAL OF RANGE MANAGEMENT 39(3), May 1986 261 This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 05:28:55 UTC All use subject to http://about.jstor.org/terms Table 1. Descripton of study sites from which stand establishment and forage yield were determined. Avg. Annual Site Location Precip. (cm) Soil Series Planting Date Harvest Dates A Decker Montana 31.8 + 10 Oct. 83 2 Aug. 84 Coal Surface Mine B Utah State Univ. 36.6 Kearns 24 April 84 9 July 84 Blue Creek Exp. (silt loam)

28 citations


Book ChapterDOI
01 Jan 1986

23 citations


Book ChapterDOI
TL;DR: Gametophytic selection as a method of plant breeding has been proposed only recently, therefore its role in the evolution of crop plants should be considered as natural selection acting in combination with sporophytic natural and artificial selection.
Abstract: Gametophytic selection (GS) as a method of plant breeding has been proposed only recently, therefore its role in the evolution of crop plants should be considered as natural selection acting in combination with sporophytic natural and artificial selection. The genetical basis of GS is revealed by the large extent of post-meiotic gene expression and of gametophytic-sporophytic genetic overlap (haplo-diploid gene expression). The high efficiency of GS for those traits expressed during the gametophytic phase is the result of the large number of pollen grains produced by each plant and the haploid state of the gametophytic generation. Moreover for several crop plants it is to be expected that special environmental factors in cultivated fields will produce higher intensity of GS. Male gametophytic fitness varies in both natural populations and in crop varieties. This variability can be due to pollen viability, pollen competition within the anther and post-pollination competition. Several experimental results indicate that at least a significant portion of this variability is due to post-meiotic gene expression. A number of studies have been carried out to prove that GS can modify sporophytic traits. These effects have been found for plant and kernel development, plant fertility, environmental stress and desease resistances and for characters which regulate the breeding system. This large body of data indicates the importance of GS in the evolution of crop species. However present knowledge is still too fragmentary to assess the contribution of GS in comparison with natural and artificial selection.

20 citations



Book ChapterDOI
01 Jan 1986
TL;DR: Phenotypic variation was observed in plants regenerated from cultured immature embryos and inflorescences of hexaploid wheat, and experiments were carried out to examine the nature, frequency and stability of this variation.
Abstract: Phenotypic variation was observed in plants regenerated from cultured immature embryos and inflorescences of hexaploid wheat (Triticum aestivum; 2n=6x=42), and experiments were carried out to examine the nature, frequency and stability of this variation. In a cytological study of regenerated plants, 30% were found to be aneuploid and structural changes of the chromosomes were also seen. The selfed progeny of more than 800 regenerated plants were assessed in field trials comparable to those employed in conventional plant breeding programmes. The majority of lines (~95%) were healthy, uniform and similar to seed-derived control material; but in some cases clear differences in height and morphology were evident, and most of these changes were transmitted to plants of the next generation. None of the variation observed appeared to be different to that which can be obtained by conventional means, and most of the variant lines would have been discarded in standard breeding trials. Analysis was also made of the gliadin storage proteins of seeds of 590 regenerated plants, and again the frequency of variation was very low (~1%). Many of the different phenotypically variant plants were euploid, but in some examples variation was associated with aneuploidy.

14 citations




Patent
14 Feb 1986
TL;DR: In this paper, a method for forming diploid tomato plants is described, which is useful in plant breeding programs to produce new assortments of genes in true-breeding lines without the several backcrossing steps otherwise required.
Abstract: A method is disclosed for forming haploid tomato plants. Plants so formed are normal, flowering plants but are sterile. Methods are taught of doubling the chromosome number of the haploid plants to form fetile, true breeding diploid tomato plants. Such methods are useful in plant breeding programs to produce new assortments of genes in true-breeding lines without the several backcrossing steps otherwise required.

Journal Article
TL;DR: Tissue culture-induced variability in regenerated plant appears to be an effective way of obtaining undirected genetic change that can enhance disease resistance and yield and alter the growth habit of crops that are normally propagated vegetatively or by seed.
Abstract: In vitro procedures are playing a major role in plant breeding. Embryo rescue, either through the culture of excised embryos derived from incompatible crosses or by means of ovule culture, has been a standard procedure for the introgression of genes conferring disease resistance into economically important plants. Somatic hybridization (i.e., protoplast fusion) has also been demonstrated to have some potential in obtaining hybrids that result from very wide interspecific and intergeneric crosses. Wide crosses have also been achieved by means of in vitro pollination of excised ovaries or ovules. Tissue culture-induced variability in regenerated plant (i.e., somaclonal variation) appears to be an effective way of obtaining undirected genetic change that can enhance disease resistance and yield and alter the growth habit of crops that are normally propagated vegetatively (e.g., potato) or by seed (e.g., tomato). In the near future, the isolation and sequencing of genes that confer resistance to specific plant pathogens will be possible, and transfer of this information between species will become a reality.




Journal ArticleDOI
TL;DR: ‘Gwylan’ is a commercial feed barley cultivar, produced by the doubled haploid technique at the Welsh Plant Breeding Station and selected for its agronomic merit at the Crop Research Division, DSIR, Lincoln.
Abstract: ‘Gwylan’ is a commercial feed barley (Hordeum vulgare L.) cultivar, produced by the doubled haploid technique at the Welsh Plant Breeding Station and selected for its agronomic merit at the Crop Research Division, DSIR, Lincoln. It is recommended for well-drained, heavy soils, and for medium soils under irrigation. Its breeding, description, and performance are presented.