Showing papers on "Plant breeding published in 2006"

Common bean breeding for resistance against biotic and abiotic stresses: From classical to MAS breeding

Abstract: Breeding for resistance to biotic and abiotic stresses of global importance in common bean is reviewed with emphasis on development and application of marker-assisted selection (MAS). The implementation and adoption of MAS in breeding for disease resistance is advanced compared to the implementation of MAS for insect and abiotic stress resistance. Highlighted examples of breeding in common bean using molecular markers reveal the role and success of MAS in gene pyramiding, rapidly deploying resistance genes via marker-assisted backcrossing, enabling simpler detection and selection of resistance genes in absence of the pathogen, and contributing to simplified breeding of complex traits by detection and indirect selection of quantitative trait loci (QTL) with major effects. The current status of MAS in breeding for resistance to angular leaf spot, anthracnose, Bean common mosaic and Bean common mosaic necrosis viruses, Beet curly top virus, Bean golden yellow mosaic virus, common bacterial blight, halo bacterial blight, rust, root rots, and white mold is reviewed in detail. Cumulative mapping of disease resistance traits has revealed new resistance gene clusters while adding to others, and reinforces the co-location of QTL conditioning resistance with specific resistance genes and defense-related genes. Breeding for resistance to insect pests is updated for bean pod weevil (Apion), bruchid seed weevils, leafhopper, thrips, bean fly, and whitefly, including the use of arcelin proteins as selectable markers for resistance to bruchid seed weevils. Breeding for resistance to abiotic stresses concentrates on drought, low soil phosphorus, and improved symbiotic nitrogen fixation. The combination of root growth and morphology traits, phosphorus uptake mechanisms, root acid exudation, and other traits in alleviating phosphorus deficiency, and identification of numerous QTL of relatively minor effect associated with each trait, reveals the complexity to be addressed in breeding for abiotic stress resistance in common bean.

Increasing salt tolerance in the tomato

Abstract: In this paper, a number of strategies to overcome the deleterious effects of salinity on plants will be reviewed; these strategies include using molecular markers and genetic transformation as tools to develop salinity-tolerant genotypes, and some cultural techniques. For more than 12 years, QTL analysis has been attempted in order to understand the genetics of salt tolerance and to deal with component traits in breeding programmes. Despite innovations like better marker systems and improved genetic mapping strategies, the success of marker-assisted selection has been very limited because, in part, of inadequate experimental design. Since salinity is variable in time and space, experimental design must allow the study of genotype x environment interaction. Genetic transformation could become a powerful tool in plant breeding, but the growing knowledge from plant physiology must be integrated with molecular breeding techniques. It has been shown that the expression of several transgenes promotes a higher level of salt tolerance in some species. Despite this promising result, the development of a salt-tolerant cultivar by way of transgenesis has still not been achieved. Future directions in order to overcome the present limitations are proposed. Three cultural techniques have proved useful in tomato to overcome, in part, the effects of salinity: treatment of seedlings with drought or NaCl ameliorates the adaptation of adult plants to salinity; mist applied to tomato plants grown in Mediterranean conditions improves vegetative growth and yield in saline conditions; and grafting tomato cultivars onto appropriate rootstocks could reduce the effects of salinity.

Statistical and Biometrical Techniques in Plant Breeding

Abstract: Statistical and biometrical techniques in plant breeding , Statistical and biometrical techniques in plant breeding , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Bringing wild relatives back into the family: recovering genetic diversity in CIMMYT improved wheat germplasm

Abstract: The dangers of a narrow genetic base of the world's major domesticated food crops have become a great global concern in recent decades. The efforts of the International Maize and Wheat Improvement Center (CIMMYT) to breed common wheat cultivars for resource poor farmers in the developing world (known as the Green Revolution wheats) has met with notable success in terms of improved yield, yield stability, increased disease resistance and utilization efficiency of agricultural inputs. However, much of the success was bought at the cost of an overall reduction in genetic diversity in the species; average Modified Roger's distances (MRD) within groups of germplasm fell from 0.64 in the landraces to a low of 0.58 in the improved lines in the 1980s. Recent efforts by CIMMYT breeders to expand the genetic base of common wheat has included the use of landraces, materials from other breeding programs, and synthetic wheats derived from wild species in the pedigrees of new advanced materials. The result, measured using SSR molecular markers, is a highly significant increase in the latent genetic diversity of recently developed CIMMYT breeding lines and cultivars compared to the original Green Revolution wheats (average MRD of the latest materials (0.63) is not significantly different from that of the landraces, as tested using confidence intervals). At the same time, yield and resistance to biotic and abiotic stresses, and end-use quality continue to increase, indicating that the Green Revolution continues to this day.

Plant Breeding: Principles and Methods

Abstract: Plant breeding: principles and methoels , Plant breeding: principles and methoels , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Modern Biotechnology as an Integral Supplement to Conventional Plant Breeding: The Prospects and Challenges

Abstract: The art of plant breeding was developed long before the laws of genetics became known. The advent of the principles of genetics at the turn of the last century catalyzed the growth of breeding, making it a science-based technology that has been instrumental in substantial improvements in crop plants. Largely through exploitation of hybrid vigor, grain yields of several cereal crops were substantially increased. Intervarietal and interspecific hybridizations, coupled with appropriate cytogenetic manipulations, proved useful in moving genes for resistance to diseases and insect pests from suitable alien donors into crop cultivars. Plant improvement has been further accelerated by biotechnological tools of gene transfer, to engineer new traits into plants that are very difficult to introduce by traditional breeding. The successful deployment of transgenic approaches to combat insect pests and diseases of important crops like rice (Oryza sativa L.), wheat (Triticum aestivum L.), maize (Zea mays L.), barley (Hordeum vulgare L.), and cotton (Gossypium hirsutum L.) is a remarkable accomplishment. Biofortification of crops constitutes another exciting development in tackling global hunger and malnutrition. Golden Rice, genetically enriched with vitamin A and iron, has, for example,the real potential of saving millions of lives. Yet another exciting application of transgenic technology is in the production of edible vaccines against deadly diseases. How these novel approaches to gene transfer can effectively supplement the conventional breeding programs is described. The current resistance to acceptance of this novel technology should be assessed and overcome so that its full potential in crop improvement can be realized. A PARAMOUNT FACTOR in the evolution of human civilizations was a steady supply of food. Food production is therefore the oldest profession of humanity. The processes of crop cultivation and selection were an integral part of human activity. Although early “plant breeding” was developed essentially as an art, its scientific basis became well established with the rediscovery of laws of genetics at the turn of the last century. And with the application of the principles of genetics to crop improvement, the period from 1930 to 1970 witnessed a phenomenal increase in crop yields, particularly of cereal grains (Khush, 1999). Largely through exploitation of hybrid vigor, maize, pearl millet [Pennisetum glaucum (L.) R. Br.], and sorghum [Sorghum bicolor (L.) Moench]registeredaconsiderableincreaseingrainyields

Breeding Effects on Nitrogen Use Efficiency of Spring Cereals under Northern Conditions

Abstract: Spring cultivars of barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) are the most important crops in Finnish agricultural systems. The increasing need to reduce pollution from N fertilizer is concomitantly strengthening the importance of improving the understanding of nitrogen use efficiency (NUE) of these crops. The aim of this work was to study the differences in NUE, defined as the crop's ability to produce yield with one available N unit, among spring cereal cultivars, and to determine the achievements of plant breeding in NUE under northern European growing conditions. Field experiments were conducted in Finland during 2003 and 2004. Samples from matured plants of 17 to 18 cultivars of each of the three cereal species released between 1909 and 2002 were studied. There were no clear differences in NUE among modern spring cultivars. However, there were cultivar differences within species and significant NUE improvements on wheat and particularly for oat across time. There was no clear trend of NUE and year of release of cultivars in two-row spring barley, probably because breeding for malting barley involves consistent selection for low-protein cultivars. The study revealed that most breeding effects on NUE were associated with changes in nitrogen uptake efficiency (UPE).

Improving Lives: 50 Years of Crop Breeding, Genetics, and Cytology (C‐1)

Abstract: During the past 50 yr, we have witnessed a revolution in the science of plant breeding, genetics, and cytology, and its impact on human lives (e.g., the Green Revolution). Because of increased productivity, breeding objectives evolved from predominantly improving yield to include greater quality and value-added traits. The discovery of the chemical nature of deoxyribonucleic acid (DNA), coupled with Mendelian genetics led to the refinement of quantitative genetics, the robust use of molecular markers, and transgenic crop plants. Cytogenetics elucidated the physical structure of chromosomes, aided trait and molecular mapping, and greatly enhanced the exploitation of genetic variation from wild relatives, as have transgenes and mutations. The fundamental process of selection has been improved by a better understanding of gene action, when to select, and better methods to select plants and analyze their relationship to the environments in which they grow. Single-seed descent plant breeding methods were popularized and evolved to doubled haploid breeding. Plant breeding, genetics, and cytology remain impact sciences that will continue to improve lives as part of the Evergreen Revolution.

Impact of plant breeding on genetic diversity of the Canadian hard red spring wheat germplasm as revealed by EST-derived SSR markers

Abstract: Genetic diversity changes in wheat germplasm have been studied using different molecular markers, but little is known about the impact of plant breeding on the transcribed segments of the wheat genome. The objective of this study was to assess diversity changes in 75 Canadian hard red wheat cultivars released from 1845 to 2004 using 37 EST-derived microsatellite (eSSR) markers. These markers were derived from at least 19 transcribed sequences with putative functions assigned and sampled 17 wheat chromosomes. A total of 138 eSSR alleles was detected, and their allelic frequencies ranged from 0.01 to 0.99 with an average of 0.41. Allelic counts were significantly reduced at three loci for cultivars released after 1990. Sixteen alleles at 14 loci in pre-1910 cultivars were lost in cultivars released after 1990. The lost alleles had frequencies ranging from 0.03 to 0.17 and averaging 0.07. Partitioning the eSSR variation showed the four ancestral families accounted for 14.7% of the variation, followed by the six breeding periods with 12.8% and the eight breeding programs with 5.8%. A genetic shift was observed in the cultivars released over the six breeding periods, reflecting the various breeding efforts. These results illustrate the impact of the Canadian wheat breeding on the transcriptional segments of the wheat genome. These findings, along with those from genomic SSR markers, suggest the Canadian wheat breeding programs have reduced genetic diversity in the hard red spring wheat.

Source-sink effects on grain weight of bread wheat, durum wheat, and triticale at different locations.

Abstract: Source limitation during grain filling is important for both management and breeding strategies of grain crops. There is little information on the sensitivity of grain weight of temperate cereals to variations in source–sink ratios, and no studies are available on the comparative behaviour of temperate cereals growing together in the same experiment. The objective of the current study was to evaluate, under field conditions, the response of grain weight to different source–sink ratios during grain filling in high-yielding cultivars of bread wheat, durum wheat, and triticale at 2 contrasting locations. Two experiments were carried out at C. Obregon and El Batan in Mexico. In each location, 6 genotypes (2 bread wheat, 2 durum wheat, 2 triticale) were evaluated. A week after anthesis, 2 source–sink (control and halved spikes) treatments were imposed. Location and genotype significantly (P < 0.01) affected grain yield and components. Significant grain weight increases (P < 0.05) were found only in 2 cases in El Batan. The highest response of 17% was found in triticale, with less than 10% in most of the other genotypes. The effect of genotype and location is discussed.

Development of a composite collection for mining germplasm possessing allelic variation for beneficial traits in chickpea

Abstract: Chickpea is one of the most important grain legume crops in the world. Large collections of genetic resources are maintained in the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and International Center for Agricultural Research in the Dry Areas (ICARDA) genebanks. Association mapping using neutral markers has been suggested as a means to identify useful alleles in the vast reservoirs of genetic diversity existing in the germplasm collections that could be associated with the phenotypes among the population individuals. ICRISAT in collaboration with ICARDA developed a global composite collection of 3000 accessions that will be profiled using 50 polymorphic simple sequence repeat (SSR) markers. The data generated through this collaborative effort will be used to define the genetic structure of the global composite collection and to select a reference sample of 300 accessions representing the maximum diversity for the isolation of allelic variants of candidate gene associated with beneficial traits. It is then expected that molecular biologists and plant breeders will have opportunities to use diverse lines in functional and comparative genomics, in mapping and cloning gene(s), and in applied plant breeding to diversify the genetic base of the breeding populations which should lead to the development of broad-based elite breeding lines/cultivars with superior yield and enhanced adaptation to diverse environments.

Molecular genetic resources for development of 1% linolenic acid soybeans

Abstract: Advanced plant breeding will incorporate the most efficient methods available to introgress new traits and develop improved crops. Molecular markers that are specifically targeted to desirable alleles are important molecular genetic resources for selection of traits. Reducing the amount of linolenic acid in soybeans [Glycine max (L.) Merr.] is a desired breeding objective so that oxidatively stable soybean oil can be produced without the production of trans fatty acids. The objective of this work was to determine the molecular genetic basis for soybeans containing 1% (10 g kg 21 ) linolenic acid in the seed oil fraction and to develop molecular markers specific for identified alleles. Utilizing the soybean homologs of Arabidopsis FAD3 as candidate genes, mutations were discovered in all three GmFAD3 genes in the soybean line A29. The mutations were associated with the linolenic acid phenotype in segregating populations. Molecular markers specific for the mutant alleles enabled capture of the phenotype. Novel combinations of mutant alleles at the three GmFAD3 loci allowed the development of new germplasm containing 1% linolenic acid in the seed oil along with SNP-based molecular markers that can be used in a backcross breeding strategy. T

Genetic analysis of resistance to yellow rust in hexaploid wheat using a mixture model for multiple crosses

Abstract: DNA-based molecular markers have been used in numerous studies for tagging specific genes in wheat for subsequent use in marker-assisted selection. Usually in plant breeding, procedures for mapping genes are based on analysis of a single segregating population. However, breeding programmes routinely evaluate large numbers of progeny derived from multiple-related crosses with some parental lines shared. In most such related crosses, the number of progeny is quite small. Thus, statistical techniques for detecting quantitative trait loci (QTLs) using data from conventional multi-cross breeding programmes are interesting. The objective of this study is to present a mixture model for QTL mapping in crosses of multiple inbred varieties with non-normal phenotype distributions and to use this model to map QTLs for yellow rust resistance in elite wheat breeding material. Three doubled haploid populations consisting of 41, 42 and 55 lines, respectively, originating from four parental varieties were studied. Multi-cross QTL analysis with three specific pathogen isolates of Puccinia striiformis f. sp. tritici and a mixture of the isolates revealed QTLs for resistance at four different genomic locations. These QTLs were found on chromosome 2AL, 2AS, 2BL and 6BL and explained between 21 and 41% of the phenotypic variation. Two of these QTLs, one on the long arm of chromosome 2A and one on the short arm of chromosome 2A were identical to the known yellow rust resistance genes Yr32 and Yr17, respectively, whereas the QTLs located on the long arms of chromosomes 2B and 6B may reflect types of resistance to yellow rust, which have not previously been mapped.

Impact of plant breeding on genetic diversity of agricultural crops: searching for molecular evidence

Abstract: There is a long-standing concern that modern plant breeding reduces crop genetic diversity, which may have consequences for the vulnerability of crops to changes in pests, diseases, climate and agricultural practices. Recent molecular assessments of genetic diversity changes in existing genepools of major agricultural crops may shed some light on the impact of plant breeding on crop genetic diversity. Reviewing published assessments revealed different impacts of plant breeding on improved genepools, not only narrowing or widening their genetic base, but also shifting their genetic background. In general, the genome-wide reduction of crop genetic diversity accompanying genetic improvement over time is minor, but allelic reduction at individual chromosomal segments is substantial. More efforts are needed to assess what proportion of lost alleles is associated with undesirable traits.

Individual and multi-environment combined analyses identify QTLs for morphogenetic and reproductive development traits in white clover (Trifolium repens L.)

Abstract: White clover (Trifolium repens L.) is a key component legume of temperate pasture agriculture and an important target for molecular marker-assisted plant breeding. A genetic map of white clover has been used to assess genetic control of agronomically important traits that vary in the F2(I.4R×I.5J) mapping family. Phenotypic analysis was performed for a range of vegetative morphogenesis traits (such as leaf area, internode length, plant height and plant spread) and reproductive morphogenesis and development traits (such as flowering date, floral intensity and seed yield), with both spatial and temporal replication. A multi-environment combined analysis (combined analysis) has been performed for traits assessed across multiple experimental datasets in order to identify consistent genetic effects. Quantitative trait locus (QTLs) were detected for the majority of traits, and the locations and magnitudes of QTL effects were compared between individual and combined analyses. This molecular genetic dissection of agronomic traits in white clover provides the basis for equivalent studies in more complex populations, design of marker-assisted selection strategies and comparative genetics with model legume species. Selection for QTLs derived from the combined analysis will permit robust improvement of phenotypic traits over different environments.

TraitMill: a functional genomics platform for the phenotypic analysis of cereals

Abstract: The improvement of quality and quantitative traits in industrial crops is among the most important goals in plant breeding. Many traits of interest are controlled by multiple genes and improvements have so far only been obtained through conventional breeding. The use of biotechnological tools to modify quantitative traits is highly challenging. CropDesign has developed TraitMill™, an automated plant evaluation platform allowing high-throughput testing of the effect of plant-based transgenes on agronomically valuable traits in crop plants. The focus of the platform is currently on rice, a good model for other important cereals such as maize and wheat. TraitMill™ offers a high-throughput prediction of gene function. Genes of validated function that confer trait improvement can then be transferred to other cereal crop species such as maize, but also to dicots, trees and ornamentals. TraitMill™ involves the following key components: (i) selection of candidate trait improvement genes among genes involved in signal transduction, cell cycle control, transcription, nutrient metabolism, etc.; (ii) a suite of validated constitutive or tissue-specific promoters from rice allowing for the selection of the most appropriate promoter–gene combination in view of the desired trait improvement; (iii) an industrialized plant transformation system generating tens of thousands of transgenic plants annually; and (iv) a robotized trait evaluation set-up for plant evaluation, proprietary image analysis software for measuring plant performance parameters and statistical analysis of results.

Molecular plant breeding: achievements in green biotechnology and future perspectives

Abstract: Since one decade ago, transgenic crop plants are globally grown; in 2004, it was estimated to cover a total of 81 Mio ha in 17 countries. At present, four plant species (soybean, maize, cotton and rapeseed) dominate with two traits (herbicide tolerance and insect resistance). The traits on which research concentrates and the constructs which might come next onto the market are outlined. The procedure on how to clone such genes of interest, e.g. via map-based cloning, and some other helpful approaches of green biotechnology, like high throughput techniques and functional markers, are summarised, and a rough calculation about the market value of transgenic crops in US dollars is quoted.

Application of Molecular Markers in Breeding for Nitrogen Use Efficiency

Abstract: Summary Nitrogen use efficiency (NUE) is defined as dry matter yield produced per unit of N supplied and available in the soil NUE is approximately 33% for cereal production worldwide Increased cereal NUE must accompany increased yield needed to feed the growing world population Consequently, continued efforts are needed to include plant selection under low N input which is not often considered a priority by plant breeders Molecular markers have accelerated plant breeding in a number of areas including biotic (disease and insect) resistance and abiotic (drought, low nitrogen fertilization and frost) tolerance Marker-based technology has already provided scientists with a powerful approach for identifying and mapping quantitative trait loci (QTL) and would lead to the development of a better understanding of genetic phenomena Two main NUE studies have been discussed The first study identified QTL for NUE in maize involved the grain yield and secondary morphological traits of interest, such as plant

A genetic bridge to utilize Tripsacum germpiasm in maize improvement

Abstract: Eastern gamagrass (Tripsacum dactyloides L.) is known to possess genes conferring tolerance to corn rootworm (Diabrotica sp.), drought, and adaptation to acidic soils without incurring damage from aluminum toxicity. Plant breeders, however, have generally been unable to utilize these and other valuable gamagrass traits for effective maize improvement because of sterility in maize-gamagrass hybrids. By crossing Eastern gamagrass with diploid perennial teosinte (Zea dipioperennis Iltis, Doebley and Guzman), a closer wild relative that is cross-fertile with maize, Eubanks obtained fully fertile recombinants that are cross-fertile with maize. The gamagrassteosinte recombinants provide a new means for moving valuable genes from gamagrass into maize with conventional plant breeding methods. Progress developing gamagrass-introgressed, elite breeding lines with rootworm, drought, and acid-soil tolerance is described.

Heterosis and Combining Ability Effects for Callus Growth of Wheat (Triticum durum, Desf.) In Vitro

Abstract: This investigation studied the ability of tissue culture technique as early testing for heterosis and combining ability in durum wheat. Genetic determination of callus growth in vitro of four genotypes of wheat in a diallel cross. Combining ability analysis showed that m ean square due to general (G CA) a nd specific (SCA) combining ability were highly significant for callus growth and also for grain yield. Data also revealed that additive genetic effects were dominant and pl ayed t he major role in t he inheritance of callus growth. Correlation analys between callus growth in vitro and grain yield of plants in vivo showed a strong relationship. It could be concluded that tissue culture technique is a useful tool for early screening for combining ability analysis and for the choice of the best parent and also hybrid in the plant breeding programs.

Problems and Prospects of Banana Breeding in India

Abstract: Banana breeding programme in India involves maintenance of various genetic resources of banana, of which triploids constitute the maximum share over diploids or tetraploids. RAPD studies conducted in these clones exhibit many distinct genotypes. During a hybridization programme, although many crosses were made, seed set and seed germination were relatively poor in many crosses. Male fertility in banana hybrids could be assessed by pollen output per anther; pollen viability and pollen size, which vary from cross to cross, and also from ploidy to ploidy. Ploidy levels in hybrids are estimated by phenotypic appearance (scoring technique) and confirmed either by stomatal density, size and number of chloroplast per guard cell pair or root tip mitosis. However, flow cytometry appears to be the most reliable method in many disputed cases. Generation of parthenocarpic hybrids depends largely upon selection and utilization of parents with parthenocarpic pedigree in a breeding programme. Evaluation of hybrids and parents indicated the nature of inheritance with respect to plant height and suckering habit but no definite trend could be ascribed to the traits of bunch orientation. Diploid x Diploid breeding approach has led to identification of a superior triploid hybrid, NPH 02-01, while Triploid (with AB)xDiploid approach has led to the development of a promising diploid hybrid H.212 and a triploid hybrid H.96/7 (ABB). Similarly, the Triploid x Diploid breeding programme resulted in development of many potential tetraploids that need further improvement. Innovative breeding approaches through in vitro mutation breeding and in vitro polyploidazation resulted in the development of many potentially useful variants. Breeding for resistance against biotic stresses such as Fusarium wilt and nematodes holds promise in banana, and, biochemical mechanisms for resistance in resistant genotypes/hybrids have been elucidated.

Integration of commercial plant breeding and genomic technologies

Abstract: The invention relates to a method for integration of commercial breeding of plants and genomic methodology comprising the steps of: a) plant population development by crossing a Parent 1 and a Parent 2 to generate a Population I; b) crossing Parent 1 with individuals from Population I to generated a Population II; c) crossing Parent 1 with individuals from population II to generate a Population III; d) randomly selecting at least one plant per each line in Population III and collecting genetic material from the random plant; e) self pollinating selected plants from population III to generate a Population IV; f) evaluating and selecting plants of Population IV; and g) using selecting progeny plants of Population IV in test crosses for evaluating the potential to develop new commercial cultivars; where the genetic material in step d) is used to develop marker profiles of each plant to map QTL and major gene loci as part of the evaluation of plants in step f).