Showing papers on "Plant breeding published in 2004"

Global impact of mutation-derived varieties

Abstract: During the past seventy years, worldwide more than 2250 varieties have been released that have been derived either as direct mutants or from their progenies Induction of mutations with radiation has been the most frequently used method for directly developed mutant varieties The prime strategy in mutation-based breeding has been to upgrade the well-adapted plant varieties by altering one or two major traits, which limit their productivity or enhance their quality value In this paper, the global impact of mutation-derived varieties on food production and quality enhancement is presented In addition, the economic contribution of the selected mutant varieties of rice, barley, cotton, groundnut, pulses, sunflower, rapeseed and Japanese pear is discussed In several mutation-derived varieties, the changed traits have resulted in synergistic effect on increasing the yield and quality of the crop, improving agronomic inputs, crop rotation, and consumer acceptance In contrast to the currently protected plant varieties or germplasm and increasing restrictions on their use, the induced mutants have been freely available for plant breeding Many mutants have made transnational impact on increasing yield and quality of several seed-propagated crops Induced mutations will continue to have an increasing role in creating crop varieties with traits such as modified oil, protein and starch quality, enhanced uptake of specific metals, deeper rooting system, and resistance to drought, diseases and salinity as a major component of the environmentally sustainable agriculture Future research on induced mutations would also be important in the functional genomics of many food crops

Unused natural variation can lift yield barriers in plant breeding.

Abstract: Natural biodiversity is an underexploited sustainable resource that can enrich the genetic basis of cultivated plants with novel alleles that improve productivity and adaptation. We evaluated the progress in breeding for increased tomato (Solanum lycopersicum) yield using genotypes carrying a pyramid of three independent yield-promoting genomic regions introduced from the drought-tolerant green-fruited wild species Solanum pennellii. Yield of hybrids parented by the pyramided genotypes was more than 50% higher than that of a control market leader variety under both wet and dry field conditions that received 10% of the irrigation water. This demonstration of the breaking of agricultural yield barriers provides the rationale for implementing similar strategies for other agricultural organisms that are important for global food security.

Molecular diversity in French bread wheat accessions related to temporal trends and breeding programmes.

Abstract: A set of 41 wheat microsatellite markers (WMS), giving 42 polymorphic loci (two loci on each chromosome), was used to describe genetic diversity in a sample of 559 French bread wheat accessions (landraces and registered varieties) cultivated between 1800 and 2000. A total of 609 alleles were detected. Allele number per locus ranged from 3 to 28, with a mean allele number of 14.5. On the average, about 72% of the total number of alleles were observed with a frequency of less than 5% and were considered to be rare alleles. WMS markers used showed different levels of gene diversity: the highest PIC value occurred in the B genome (0.686) compared to 0.641 and 0.659 for the A and D genomes, respectively. When comparing landraces with registered varieties gathered in seven temporal groups, a cluster analysis based on an F st matrix provided a clear separation of landraces from the seven variety groups, while a shift was observed between varieties registered before and after 1970. There was a decrease of about 25% in allelic richness between landraces and varieties. In contrast, when considering only registered varieties, changes in diversity related to temporal trends appeared more qualitative than quantitative, except at the end of the 1960s, when a bottleneck might have occurred. New varieties appear to be increasingly similar to each other in relation to allelic composition, while differences between landraces are more and more pronounced over time. Finally, considering a sub-sample of 193 varieties representative of breeding material selected during the twentieth century by the six most important plant breeding companies, few differences in diversity were observed between the different breeding programmes. The observed structure of diversity in French bread wheat collections is discussed in terms of consequences, both for plant breeders and for managers of crop genetic resources.

Puroindoline genes and their effects on grain quality traits in southern Australian wheat cultivars

Abstract: Grain hardness is a major determinant of the classification and end-use of wheat. Two genes, Pina-D1 and Pinb-D1, have a major effect on this trait, so for wheat breeding programs it is important to identify the alleles of these genes present in elite germplasm. This study was conducted to identify the alleles present in southern Australian germplasm, and to determine if they affected quality characteristics other than grain hardness. Only 3 genotypes were identified. These were Pina-D1a/Pinb-D1a producing soft grain, Pina-D1a/Pinb-D1b producing moderately hard grain, and Pina-D1b/Pinb-D1a producing very hard grain. WW15 was the probable source of Pina-D1a/Pinb-D1b in most cultivars; however, Halberd represented another source. An important source of Pina-D1b/Pinb-D1a was the CIMMYT line Pavon, with sources from the old Australian cultivars Gabo and Falcon probably still present in modern germplasm. In an analysis of grain quality data from the Victorian Institute for Dryland Agriculture breeding program, the Pina-D1b/Pinb-D1a genotype had a significantly higher water absorption and significantly lower milling yield than the Pina-D1a/Pinb-D1b genotype, which indicates that these genes will impede the development of hard-grained cultivars that combine high water absorption and high milling yield.

The impact of plant breeding on the grain yield and competitive ability of wheat in Australia

Abstract: Fourteen wheat (Triticum aestivum L) cultivars released to Australian growers over the last century were examined to determine the impact of crop breeding on competitive ability with weeds In 1999 and 2000 the weed used in the field study was annual ryegrass (Lolium rigidum Gaud) and in 2001 oats (Avena sativa cv Marloo) was the weedy competitor In 2 out of 3 years (1999 and 2001), when Puccinia recondita (leaf rust) infection was not a problem, there were consistent trends for improvement in yielding ability through breeding effort over time In these 2 seasons the yielding ability of wheat increased by around 15 kg/hayear as compared with a yield increase of only 47 kg/hayear in 2000 due to a heavy P recondita infection In 1999 and 2000, when annual ryegrass was used as the weedy competitor, there was no systematic trend for changes in crop yield loss with time (r = 047 in 1999; r = 008 in 2000, P > 005) However, in 2001, when oat was used as the weed, there was a significant positive linear relationship (r = 081, P < 001) between the year of cultivar release and crop yield loss, indicating inferior competitive ability of the modern cultivars Old cultivars such as Nabawa not only provided superior weed suppression, they were also more tolerant of weeds as indicated by the smaller yield loss Plant height appeared to be an important contributor to the superior competitiveness of the standard height, older cultivars Other morphological traits contributing to superior competitive ability included greater leaf length and width, light interception, and flag leaf length To improve the competitive ability of modern wheats without compromising their yielding ability, morphological traits that enhance early crop vigour (size of leaf 1 and 2) and light interception without affecting harvest index may need to be incorporated from carefully selected germplasm

Advances in pasture plant breeding for animal productivity and health

Abstract: Plant breeding has had a substantial effect on the productivity and health of ruminant animals in New Zealand by improving the quantity, quality and reliability of grazed temperate pastures. Genetic changes have affected annual pasture productivity, seasonal growth, digestibility, protein/energy balance, level of rumen undegradable protein, leaf properties affecting intake, resistance to foliar diseases, and reductions in compounds that have an adverse impact on the health, welfare and reproductive fertility of ruminant animals. Most plant improvement programmes have achieved genetic gains in excess of 1% per year for a variety of target traits, and these gains are likely to continue given the high genetic variation available within forage plants. Significant heritable variation exists to improve forage quality, particularly for soluble carbohydrate and fibre fractions in grasses, and in the rate at which these change during the season. Deleterious animal health and welfare effects can be alleviated through the use of non-toxic endophytes in grasses, that do not produce lolitrem B and ergovaline. Use of improved cultivars, with the appropriate management, can add value to animal products.

Short Communication Comparison of genetic diversity of flax (Linum usitatissimum L.) between Canadian cultivars and a world collection

Abstract: This study reports results of phenotypic measurements of genetic diversity in the world collection of flax maintained by Plant Gene Resources of Canada (PGRC) and compares the range of diversity in the world collection with the diversity observed in 19 Canadian registered flax cultivars. Morphological and seed-oil characters were used to describe the phenotypic diversity in 2331 flax accessions. The plants were grown by PGRC at Saskatoon, Saskatchewan, Canada, in 1998 and 1999. The comparison between the Canadian cultivars and the world collection was based on single characters, as well as on character complexes by application of an existing intraspecific classification for the species. Considering single quantitative or qualitative character expressions, the Canadian cultivars represented a wide range in diversity for the species. The variation of characters Canadian plant breeders have selected for (e.g. plant height, seed weight, seed colour, petal colour, oil content) was reduced further than those characters not focused on by plant breeders (e.g. dotting of the sepals, style colour, ciliation of capsule septa, oil quality characters). A comparison of diversity based on the intraspecific classification proposed for flax by Kulpa and Danert, who described 28 botanical varieties, showed that all Canadian cultivars belong to two botanical varieties. This study demonstrates the usefulness of agrobotanical characterization of genebank collections for plant breeding and illustrates the application of the traditional method of intraspecific classification for comparison of gene pools.

Resistance of maize to the corn leaf aphid: a review.

Abstract: The corn leaf aphid [Rhopalosiphum maidis (Fitch)] is a worldwide pest of maize (Zea mays L.), sorghum [Sorghum bicolor(L.) Moench], barley (Hordeum vulgare L.), and wheat (Triticum aestivum L. em. Thell.). Breeding efforts toward resistance to the corn leaf aphid, however, have been limited. The aphid is present every year in the U.S. and significant insect populations are associated with grain yield loss and virus transmission. All parts of the maize plant are subject to injury, although aphid infestation produces the greatest damage in the tassel, causing varying degrees of barrenness. Phenotypic and genotypic responses of land races, pure-lines, and hybrids of maize indicate that resistance to the corn leaf aphid is inherited. Inheritance of resistance, however, has been reported to be simple as well as complex across different genetic backgrounds. Additive gene effects have been found to be the predominant type of gene action. Therefore, multiple genes with large environmental influence might be involved in resistance. Climatic conditions play an important role in determining the rate of colony development and grain yield reduction. Biochemical and physical barriers to the corn leaf aphid have been successful in some cases as well as biological control through numerous aphid predators. Cultural and chemical mechanisms of control are the most common method of limiting corn leaf aphid populations. Breeding for aphid resistance in maize continues to be a challenge due to the difficulty in obtaining reliable natural infestations and the presence of genotype by environment interactions.

Molecular Markers for Genetics and Breeding: Development and Use in Pepper (Capsicum spp.)

Abstract: The genus Capsicum is a member of the Solanaceae family that includes tomato, potato, eggplant, tobacco, petunia and others. Pepper is grown worldwide. It is the world’s second most important Solanaceae vegetable after tomato. Because of its very large variability and its great geographical distribution, pepper has multiple uses. It can be consumed fresh, cooked or dried. It is also used as an alimentary colorant or by the chemical industries for the composition of drugs. Finally, it is being used more and more as an ornamental plant (Palloix et al. 2003). In 2002, world production was more than 22million tons (FAO 2002; http://www.fao.org/) on about 1.6million ha, with China, Mexico, and Turkey as the main growers. Spain, Italy and now the Netherlands are the main growers in Europe. The seed industries are very active in Europe and particularly in France, with an increasing number of inscriptions of F1 hybrids. The breeding objectives are essentially yield improvement, environment adaptation, fruit traits, and disease resistance. Because of its widespread geographical distribution all over the world from the intertropical belt to northern Europe latitudes, pepper is vulnerable to a great number of pathogens. Complexes of viruses transmitted by aphids and the Oomycete Phytophthora capsici cause major damage all over the world (Yoon et al. 1991). The great intraand interspecific variability is of great help for breeding programs. In Europe, the germplasm numbers about 12,000 accessions, located mainly in seven European research centres (Daunay et al. 2001). In addition, numerous tools of cellular biology are available, such as the immature embryo rescue, in order to assist interspecific crosses, and the production of doubled haploid lines, to accelerate the fixation of improved material. The stable transformation to produce transgenic plants is really difficult in pepper. Some research groups published positive results (Lim et al. 1999; Shin et al. 2002; Li et al. 2003). Finally, the advent of DNA-based genetic markers offers useful tools for genome-wide studies and for assisting selection. This chapter gives an overview of the development and use of molecular markers in plant breeding and crop improvement related to pepper. It is sub-

Genetic diversity of maize inbred lines in relation to downy mildew

Abstract: A major emphasis in maize breeding in Asian countries has been the improvement for resistance to downy mildew, a serious disease that causes significant yield losses. A total of 102 inbred lines, including lines from Asian breeding programs, Mexico, USA and Germany, were analyzed with 76 SSR markers to measure diversity and investigate the effect of selection for downy mildew resistance. A mean polymorphism information content of 0.59, with a range of 0.14 to 0.83, was observed. Diversity at the gene level showed an average of 5.4 alleles per locus and a range of two to 16 alleles per locus, with a total of 409 alleles. About half of the alleles in the Asian lines had frequencies of 0.10 or less, and only 2% had frequencies > 0.80, indicating the presence of many alleles, and thus a high level of diversity. Some of the high-frequency alleles were in chromosomal regions associated with disease resistance. However, the frequencies of alleles in three SSR loci that are linked to a QTL for resistance to downy mildews in Asia were not significantly different in the subtropical/tropical Asian lines as compared to all the lines in the study. Lines from the US, Germany, and China, comprised three clusters of temperate maize(GS = 0.31), while those from India, Indonesia, Philippines, Thailand, Vietnam and CIMMYT comprised seven indistinct clusters of subtropical and subtropical maize (GS = 0.29). We conclude that maize breeding activity in Asia has not caused a decline in the overall amount of diversity in the region.

Genetic analysis of quantitative traits in rice (Oryza sativa L.) exposed to salinity

Abstract: The release of rice cultivars with improved performance in saline environments is reliant on an understanding of the genetic control of plant and panicle characters in plants exposed to salinity. The regulation of agro-physiological characters of rice plants grown in a saline environment was thus investigated. A complete diallel cross was prepared from 8 parental rice accessions with a range of tolerances to salinity. F1 hybrids and parents were grown in saline-sodic soil in artificially constructed salinity blocks. At maturity, the plant height, productive tiller number per plant, panicle length, primary branch number per panicle, panicle fertility, time to maturity, shoot dry weight, shoot Na, Ca, and K concentrations, and paddy yield were recorded. Additive and dominant genetic effects contributed significantly to the total heritable variation observed for plant height, panicle length, and sodium and potassium shoot concentrations. Additive genetic effects were important for the expression of variation of productive tiller number per plant and the number of primary branches per panicle, while dominant genetic effects were important for the expression of variation of the number of days to maturity. Plant height and primary branch number per panicle are traits that may be readily improved by selection in saline environments.

Pollination and breeding of eggplants

Abstract: The purpose of this review article is to provide clear and brief information on pollination and breeding of eggplant to increase yield and improve fruit quality. Considerable progress in artificial pollination and plant breeding techniques have played a very important role in increasing plant, including eggplant, yield and improving fruit quality. With classical methods, homozygous diploid lines can be obtained in 5-8 years depending on the species. In-vitro techniques such as anther and pollen culture have been very successful in shortening the required time for this process. Artificial pollination and proper breeding techniques substantially increase eggplant yield and improve its fruit quality.

Assessment of gene flow using tetraploid genotypes of perennial ryegrass (Lolium perenne L.)

Abstract: Ryegrass species are among the most important species in sown pastures, turf settings, and weed populations worldwide. Perennial ryegrass (Lolium perenne L.) is an outcrossing, wind-pollinated grass. Recent research has demonstrated the feasibility of developing transgenic perennial ryegrass varieties. In order to model the consequences of gene flow from transgenic grass genotypes in a field situation, the model non-transgenic trait of fertility among autotetraploid genotypes was chosen. Gene flow over distance and direction from a donor plot to surrounding sexually compatible recipient plants was studied. Reproductive isolation was achieved through the fertility barrier that arises between tetraploid and diploid ryegrass genotypes, despite the presence of diploid plants in a meadow situation. Fertility was used as an indication of effective gene flow over distance and direction. Measures of the fertility of recipient plants included total seed production (TSP), floret site utilisation (FSU), and relative fertility of recipient plants as a percentage of those within the donor plot (RF%). A leptokurtic distribution for gene flow was identified, with differences in the rate of decline over distance depending on direction. Simple sequence repeat (SSR) polymorphism was used to identify the paternity of progeny plants. The proportional representation of parents among the progeny was not significantly different from that expected due to the numerical representation of the different donor parent genotypes. The results of this research will have important implications for risk analysis prior to the field release of transgenic ryegrasses, fescues, and other pasture grass species, and for seed production in terms of cultivar purity and optimum isolation distance.

Embryogenesis, callogenesis and plant regeneration from anther cultures of spring rape (Brassica napus L.)

Abstract: Anther culture is a very important and useful tool in plant breeding for haploid production. The investigation was carried out with three spring rape cultivars, 'Trend', 'Landmark' and 'Auksiai'. Rape anthers were cultivated in modifi ed Nitch and Nitch induction medium supplemented with 13 % sucrose and 0.4 % agarose. Embryo regeneration took place in a modifi ed B 5 Gamborg nutrient medium supplemented with 0.1 mg l -1 GA 3 and 0.8 % agar. Temperature pretreatment of fl ower buds was at 35 °C for 72 h. After 72 h thermal shock pretreatment, the callus formation frequency differed for the tested genotypes. Thermal shock pretreatment on the callogenesis process appeared to be genotype dependent, since this treatment failed to signifi cantly increase for 'Auksiai' and signifi cantly decrease callus formation for the 'Landmark' and 'Trend' cultivars. Further embryo development was noted only in genotype 'Trend'. The frequency of embryo formation from anthers treated with high temperature was higher than the control. It was observed that in haploids the stomata length was reduced by 1.4 and their number in the vision fi eld increased by approximately 1.1 in comparison with the diploid parent plants. The height of the haploid plants was 1.4 times less than parent plants. Plant regenerants were 100 % haploids.

A Century of Advances in Plant Breeding Methodologies

Abstract: Plant breeding in the first half of the twentieth century which started with the rediscovery of Mendel’s work, mainly involved development of pure-line(s), clones, hybrids, synthetics and composites with higher yield, stability, better quality and resistance to biotic and abiotic stresses. Following the early success, significant contributions were made in the development of semi-dwarf high yielding varieties of wheat by Borlaug and his colleagues at CIMMYT, Mexico, and of rice by Beachell and his colleagues at IRRI, Philippines. Also, high yielding hybrids were developed in maize, sorghum, pearl millet, sunflower, cotton, rice, pigeonpea and in other crops. Efforts are currently also underway to develop hybrids based on genetically engineered male-sterility systems and apomixis. The twentieth century also saw significant developments in mutation breeding, quantitative genetics and other areas relevant to plant breeding, which helped in a better understanding of the genetic architecture of a trait for formulating suitable breeding strategies. Advances in molecular genetics in the last twenty years have opened up altogether new possibilities in analyzing genetic diversity, fingerprinting genotypes, and using molecular marker assisted selection. The last decade of the twentieth century also saw the development of transgenics, the genetically engineered varieties in a number of crop plants for commercial cultivation. This paper takes a journey in the world of plant breeding through the 20th century.

Molecular Mapping and Marker‐Assisted Selection of Quantitative Trait Loci in Plants

Abstract: Since the dawn of agriculture, mankind has tried to mould crop plants into more useful types. Over the years, experience and intuition led to the development of sophisticated and successful artificial selection (breeding) of many types of plants for human food, fibre, shelter, profit and pleasure. Just compare the cultivated tomato with some of its small- and green-fruited relatives, or cultivated maize to teosinte. Most of this ‘improvement’ was probably through simple field selection and propagation of desirable genotypes. Scientifically based plant breeding, not appearing until the 20th century, has also had great successes in plant improvement, particularly in disease resistance and yield. Breeders have achieved good results for both single-gene traits and polygenic traits, but the polygenic traits, encoded by multiple genes often referred to as quantitative trait loci (QTL), are much more difficult to work with. Advances in molecular genetics in the last 20 years have enabled the placement of molecular markers on to maps of the chromosomes of most major crop plants and the subsequent tagging of genes of interest by their placement near these markers. A major goal of these efforts is marker-assisted selection (MAS), the use of molecular markers to track traits in breeding programmes. In this chapter, we will discuss the basics of molecular mapping in crop plants, the identification of the location of QTL and MAS. While not intended as an exhaustive review of the techniques nor of successes in this field, this chapter will provide lists of crops with linkage maps and QTLs identified to serve as entry points into the literature for investigators interested in pursuing this technology in a particular crop. Keywords: molecular linkage maps; quantitative trait loci (QTL); marker assisted selection (MAS)

Molecular Markers in Improvement of Wheat and Brassica

Abstract: Recent developments in DNA-based marker technology have opened up newer avenues for the studies on plant molecular genetics. The new marker systems have enabled researchers to construct genetic maps and to examine directly the genotypes of plant species rather than phenotypes. These markers have also provided means to address problems related to genome structure and evolution, understand the genetic basis of morphological variation, and study the genomic distribution of genes and the pattern of inter- generic/inter-specific gene flow. Genetic maps based on molecular markers have been constructed for a number of plant species such as Arabidopsis thaliana, Brassica species, Oryza sativa, Triticum aestivum, Zea mays, Hordeum vulgare, Pisum sativum, to name a few. The most important and practical application of these maps has been in generating markers linked to both qualitative and quantitative traits of agronomic importance and employing them in marker assisted breeding. The focus of this review is to summarise recent developments in the area of DNA marker technology with special reference to wheat (Triticum aestivum) and Brassica coenospecies and highlight its applications in specific areas of plant breeding.