The development of precise genetic stocks in two wheat cultivars and their use in genetic analysis

Summary The results of genetic studies of common wheat that have been conducted in Novosibirsk, Russia, over the past 20 years by a research team are summarized. The research strategy was to develop a collection of aneuploids and substitution lines to be further used for chromosomal localization of genes and in the study of the genetic variability of wheat. On the basis of two cultivars, namely Saratovskaya 29 and Diamant, we have developed 6 sets of aneuploids with a complete set of monosomic lines for each, plus sets of lines ditelosomic and monotelosomic for standard arms. Exploiting the monotelosomics, 108 single chromosome intervarietal substitutions, 13 lines with alien substitutions (mono- and disomics) and 11 addition lines have been developed. A collection of lines isogenic for dominant marker genes of morphological characters has also been developed. The genetic collection was used in chromosomal localization of 15 genes, for many of which chromosome arms have been determined. Positively or negatively, the question of allelism within some loci has been answered.     

Physiological complexity and plant genetic manipulation

Summary One of the limiting factors in the development of new cultivars in a reasonable time using recombinant DNA techniques, is an inability to predict the interaction between the introgressed gene(s) and the host genome and metabolism.This review presents a survey of the literature on the constraints determining the coherence between alien sequences and their products, and the organization of the receiving genome and its physiological equilibrium. An hypothesis supported by preliminary experimental data is put forward that such constraints derive from coadaptation during the evolution of gene complexes driven by external selection pressure, and by changes in genes coding for key factors of plant metabolism. Conclusions are finally drawn on a series of possible methods to be used in genetic engineering, in relation to breeding practice, compatible with the rules governing the organization of physiological networks.     

A preliminary genetic analysis of fibre traits and the use of new genomic SSRs for genetic diversity in jute

Jute is one of the most important fibre crops, which is second only to cotton in providing environment-friendly (biodegradable and renewable) ligno-cellulose fibre. In order to improve this largely neglected crop, we conducted a preliminary study involving the following: (i) analysis of nature and extent of the genetic variability for fibre yield and four other related traits in a set of 81 genotypes belonging to two commercially cultivated Corchorus species (45 genotypes of C. olitorius + 36 genotypes of C. capsularis), (ii) development and analysis of a set of simple sequence repeat (SSR) markers from C. olitorius, and (iii) use of a sub-set of SSRs for assessment of genetic diversity in the above set of 81 genotypes. The results suggested quantitative nature of fibre yield and other related traits, with a preponderance of dominance component in genetic variance. A sub-set of 45 SSRs derived from C. olitorius, when used for a study of DNA polymorphism and genetic diversity, showed high transferability of these C. olitorius SSRs to C. capsularis. The average number of alleles for individual SSRs was surprisingly low (3.04 for both species, 2.02 for C. capsularis and 2.51 for C. olitorius), and so was the average polymorphic information content (PIC; 0.23 and 0.24 in two species). In the dendrogram obtained using a similarity matrix, the 81 genotypes were grouped into three clusters, which largely corresponded to the two species, Cluster I belonging mainly to C. capsularis and the other two closely related clusters (clusters II and III) belonging to C. olitorius. It was also shown that a minimum of 15 SSRs could give the same information as 41 SSRs, thus making many SSRs redundant. The SSR markers developed during the present study and to be developed in future will prove useful not only for evaluation of genetic diversity, but also for molecular mapping/QTL analysis, and for comparative genome analysis of the two Corchorus species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Heritability and genetic correlation in daylily selection

Daylily (Hemerocallis × hybrida Hort.) is a popular ornamental plant and hybrid cultivars are frequently selected for medium size, large number of flowers per stem, and flower color diversity. However, daylily selection is limited due to the lack of information on genetic parameters and their correlation to phenotypic characteristics. This study aimed at estimating genetic parameters and genetic correlations among full sib families of 13 daylily cultivars using REML/BLUP (restricted maximum likelihood/best linear unbiased prediction) and to select families with high genotypic values for plant height and number of floral buds per stem. Crosses were performed among those cultivars and 24 families were obtained. In the third year, plant height, leaf length and width, stem number, number of floral buds per stem, and number of floral buds per plant were evaluated. The estimates of average heritability of families were superior to the estimates of restrict individual heritability for all characters evaluated. High heritability estimates were obtained for plant height, leaf length, leaf width, stem number, and number of floral buds per plant. Selected families showed genetic gain of 19.80% for plant height, 32.48% for stem number, and 38.64% for number of floral buds per plant.     

Molecular genetic mapping of peach

Summary A project to develop a linkage map of the peach (Prunus persica) genome is underway using an F2 population segregating for several morphological characters and pest resistance e.g., nectarine (g), weeping shape (pl) and aphid resistance (Rml). The RAPID technique was used to analyse 270 plants. Linkage analysis of the F2 population was performed using the MAPMAKER software. Eight linkage groups were established and RAPID markers flanking thepl gene were found.     

Diversity of potato genetic resources

A considerable number of highly diverse species exist in genus Solanum. Because they can adapt to a broad range of habitats, potato wild relatives are promising sources of desirable agricultural traits. Potato taxonomy is quite complex because of introgression, interspecific hybridization, auto- and allopolyploidy, sexual compatibility among many species, a mixture of sexual and asexual reproduction, possible recent species divergence, phenotypic plasticity, and the consequent high morphological similarity among species. Recent researchers using molecular tools have contributed to the identification of genes controlling several types of resistance as well as to the revision of taxonomical relationships among potato species. Historically, primitive forms of cultivated potato and its wild relatives have been used in breeding programs and there is still an enormous and unimaginable potential for discovering desirable characteristics, particularly in wild species Different methods have been developed to incorporate useful alleles from these wild species into the improved cultivars. Potato germplasm comprising of useful alleles for different breeding objectives is preserved in various gene banks worldwide. These materials, with their invaluable information, are accessible for research and breeding purposes. Precise identification of species base on the new taxonomy is essential for effective use of the germplasm collection.     

Cytoplasmic genetic diversity in bananas and plantains

Summary Concerns over yield declines in bananas and plantains due to the spread of Black Sigatoka disease in Musa have drawn attention to the collection of Musa germplasm and its use in conventional and biotechnological improvement programs. This report demonstrates the use of chloroplast DNA (cpDNA) restriction fragment length polymorphisms (RFLPs) for differentiating cytoplasms of various Musa clones. DNA was extracted from lyophilized leaf blade tissue and digested with either Eco R1, Hind III, Bam H1 or Pst I. Southern blots onto nylon membranes were probed with radioactively labeled heterologous orchid and lettuce cpDNA fragments. Among the 14 Musa clones examined, a single balbisiana and four acuminata-type cytoplasms were differentiated. The ability to distinguish between cytoplasms and to place plants within a cytoplasmic grouping demonstrates the usefulness of RFLP technology in evaluating diversity and determining the ancestry of Musa clones.     

Environmental risks of genetic engineering

Summary Before release into commerce, genetically engineered organisms are first assessed for possible risks, including risks to the environment. The present paper first identifies the environmental risks recognized by regulators, and reviews the parameters considered predictive of risk. Recent field-scale studies suggest opportunities for improvement of the environmental risk assessment process. Risks unique to genetically engineered crops – if any – could pertain to the specific traits chosen for commercialization and to unintended trait expression caused by the process of transgene insertion itself. Both the standard against which to compare genetically engineered traits and the scale of exposure need to be considered when assessing environmental impact. Evidence of environmental risk in the recognized areas of weediness on agricultural land, invasiveness of unmanaged systems, and non-target impacts from Bacillus thuringiensis (Bt) maize is presented. Targeted, statistically sound, rigorously conducted, multi-trophic studies analogous to the Field Scale Evaluation trials recently completed in the UK are needed to clarify the many questions which remain unanswered.     

保护作物种质资源推进改良创新利用--今后贵州作物品种资源研究工作的思考

种质资源是作物优良基因的载体，切实保护现有保存种质资源的遗传多样性，努力推进改良创新利用是当前乃至长远种质资源研究工作的主要内容，也是实施农业可持续发展战略的重要举措。概述了贵州稻种资源研究的主要进展、存在问题，并围绕其保护与利用的主题提出今后的主要任务与建议。     

Challenges and opportunities for conservation of forest genetic resources

Increased use of forest resources and a shrinking forestland base threaten the sustainability of forest genetic resources and highlight the importance of conservation and sustainable management of these resources. As forest trees are normally the keystone species of forest ecosystems, their continued existence is essential for many floral and faunal associations of these ecosystems. Major concepts, challenges and opportunities for conservation of forest genetic resources are briefly discussed in this paper. The major challenges include population decline and population structure changes due to forest removal and conversion of forest land to other uses,forest fragmentation, forestry practices, climate change, disease conditions,introduced pests, atmospheric pollution, and introgressive hybridization. Developing scientifically sound conservation strategies, maintaining minimum viable population sizes, and deployment of genetically engineered organisms represent other important challenges in conservation. The usefulness of various biochemical and molecular genetic markers, adaptive traits, and genetic diversity measures for developing conservation strategies for in situ and ex situ genetic resource conservation are also discussed. Major opportunities for conservation of forest genetic resources include: use of molecular genetic markers and adaptive traits for developing conservation strategies; in situ conservation through natural reserves,protected areas, and sustainable forest management practices; ex situ conservation through germplasm banks, common garden archives, seed banks, DNA banks, and tissue culture and cryopreservation; incorporation of disease, pest, and stress tolerance traits through genetic transformation;plantation forestry; and ecological restoration of rare or declining tree species and populations. Forest genetic resource conservation and resource use should be considered complementary rather than contradictory to each other. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stability and genetic improvement of maize yield in Argentina

Summary Yield stability and the genetic improvement of maize (Zea mays L.) grain yield in the humid pampas of Argentina were evaluated.Stability parameters were computed for 15 varieties grown in 35 environments. To analyze genetic improvement of grain yield, data were obtained from trials grown in four locations and twelve years. Two locations represented the typical maize area, while the remaining two were considered marginal. Simple correlation and linear regression coefficients were computed to study the relationships between yield, stability parameters, number of days to 50% tassel emergence, and year of release. Genetic improvement of grain yield was analyzed from linear regression of the average yield of the three highest-yielding varieties (as percentage of the average yield of five common checks) on year of trial.Yield differed significantly among varieties. Significant variety x environment (linear) interaction was also detected. Significant linear relationships were found between regression coefficient for yield (stability parameter 1) and days to tassel emergence, stability parameter 1 and yield, year of release and days to tassel emergence, and year of release and stability parameter 1. Thus, newer maize varieties tended to flower later and had greater responsiveness to favorable environments than did older varieties. Yields have increased for both the typical and marginal areas, with average yearly increases of 114 and 182 kg/ha, respectively.Breeding programs with nurseries located in the typical maize area have raised yield potential in both areas studied. However, if present trends continue, future releases could prove inadequate in low-yielding or short season environments.     

In situ and on-farm management of plant genetic resources

For establishing an effective maintaining programme for plant genetic resources (PGR), an integrated system is necessary considering the three principal ways of germplasm management—ex situ, in situ and on-farm. The scientific concept for on-farm conservation is relatively new and desires a special discussion. Differences in conservation and management strategies are defined here with respect to three countries. Germany is used as an example for an industrialized country, relatively poor in landraces. Italy may suit as example for an industrialized country with high diversity in agricultural products and production techniques, and Cuba is an example for a tropical country, scarcely industrialized and extremely rich in PGR. The following categories of countries are defined here: (a) Category 1: country e.g. Cuba; (b) Category 2: country e.g. Italy; (c) Category 3: country e.g. Germany. The definition of specific categories with respect to the different situations of these countries is extremely helpful in valuation of ex situ, in situ and on-farm measures regarding their effectiveness and necessary finances in the context of realization of the requests of the Convention on Biological Diversity to protect the diversity in countries and regions. First of all, management of germplasm including breeding and selection in the hands of the farmers has to be secured. On-farm management is a dynamic approach and the present expectations to this are high and tend to overload this concept. More realistic is an integrated approach considering the respective country and local conditions including farmers’ preferences and application of all conservation systems.     

RFLP variation and genetic relationships in cultivated cucumber

Summary Two sets of cucumber (Cucumis sativus L.) germplasm were used to determine the potential use of restriction fragment length polymorphisms (RFLPs) for estimating genetic relationships. Sixteen accessions [15 domesticated variety sativus and one feral variety hardwickii (PI 183967)] of diverse origin were used to assess RFLP variation in cucumber, and to determine if genetic relationships based on RFLPs were similar to those obtained by isozyme analysis. Additionally, 35 commercial lines or cultivars were surveyed to determine genetic relationships among and within common cucumber types (narrow genetic base). The 16 accessions were surveyed with 440 low copy clones from two libraries (Pst I partial genomic and cDNA) using two restriction enzymes. Data from a subset of 104 random (mapped and unmapped) and a set of 30 mapped RFLPs were used to estimate genetic relationships among the 16 cultigens. Variability was low among RFLPs (33% of all probes) and putative alleles ( 2.2 polymorphic fragments/probe). RFLP variation between sativus lines and hardwickii (21±4%) was greater than among sativus lines (12±2%). RFLPs among the 16 accessions revealed genetic relationships which agree with those obtained using isozymes. Genetic relationships estimated using mapped and unmapped RFLPs were similar. The 35 elite lines were surveyed using a set of 40 RFLPs from 3 libraries (Pst I and EcoR I partial genomic and cDNA) to evaluate the discriminatory value of RFLPs among and between commercial cucumber types. The RFLP-derived genetic relationships among this germplasm were in agreement with predictions based on fruit type and pedigree information. Thus, RFLPs are a useful addition to the morphological characters and isozyme loci currently used for taxonomic classification and plant variety protection of cucumber.     

Marker-assisted increase of genetic diversity in a double-low seed quality winter oilseed rape genetic background

Generation of novel genetic diversity for maximization of heterosis in hybrid production is a significant goal in winter oilseed rape breeding. Here, we demonstrate that doubled haploid (DH) production using microspore cultivation can simultaneously introgress favourable alleles for double‐low seed quality (low erucic acid and low‐glucosinolate content) into a genetically diverse Brassica napus genetic background. The DH lines were derived from a cross between a double‐low quality winter rapeseed variety and a genetically diverse semisynthetic B. napus line with high erucic acid and high glucosinolates (++ quality). Twenty‐three low‐glucosinolate lines were identified with a genome component of 50–67% derived from the ++ parent. Four of these lines, with a genome component of 50–55% derived from the ++ parent, also contained low erucic acid. Heterosis for seed yield was confirmed in test‐crosses using these genetically diverse lines as pollinator. The results demonstrate the potential of marker‐assisted identification of novel genetic pools for breeding of double‐low quality winter oilseed rape hybrids.     

Isozymes as genetic markers in bananas and plantains

Summary Twenty-four clones of banana and plantain representing various levels of ploidy and diploid M. balbisiana, were analysed for enzyme variants of malate dehydrogenase, phosphoglucomutase, glutamate oxaloacetate transaminase, shikimate dehydrogenase and peroxidase. Polymorphism was detected in all 5 enzyme systems. In addition, the four principal Cavendish clones, Robusta, Giant Cavendish, Dwarf Cavendish and Pisang masak hijau were found to be monomorphic for isozymes of 10 additional enzymes. Isozymes of glutamate oxaloacetate transminase were the most useful for discriminating among clones of a particular genomic group.Florida Agricultural Experiment Stations Journal Series No. 6858.     

Plant genetic adaptedness to climatic and edaphic environment

Summary Genetic adaptation implies the shaping of population and species gene pools in response to environmental challenges. The two components of the abiotic land environment are climate and soil, both of which determine much of the evolutionary adaptedness of plants as, besides representing a set of surrounding physical, chemical and sometimes limiting traits, they determine the availability of nutrients and energy, of which they are the immediate source. Ecogeographical distribution of species and ecotypes and different physiological mechanisms and developmental patterns are good evidence of plant adaptedness to soil and climate. However, it is not always easy to determine the underlying genetics of adaptive processes, because 1) environmental factors to which the plants are responding are not always evident and are sometimes too complex, 2) several genes may be involved in the response to a given environmental factor, and 3) the same gene/s may be involved in different adaptive responses. In particular, data on Avena species and temperature as a key environmental factor will be used to illustrate some examples of climatic and edaphic adaptedness. Temperature affects the genetic evolution and geographical distribution of all organisms, and a great deal of evidence indicates that species and populations are genetically adapted to different temperature regimes. Isozymes and other molecular markers have helped in the understanding of the genetic basis of adaptedness. There are many examples of correlation between isozyme and DNA-marker variation and environmental differences. For many population geneticists, isozyme markers are just genetic markers with little or no direct involvement in adaptation. However, metabolic processes are controlled by enzymes, influenced by the environment and used to react in response to it. Evidence that isozymes, and perhaps other molecular polymorphisms, are directly involved in adaptedness will be also presented. Molecular genetic analyses at gene and population levels are opening the ways to a better understanding of plant genetic adaptation.     

DNA-RAPDs detect genetic variation and paternity in Malus

Summary DNA amplification fingerprinting using arbitrary primer(s) was applied to the identification of Malus species. Highly variable DNA fragment patterns were clearly detected by polyacrylamide gel electrophoresis of the amplified extension products, although three sports of Delicious exhibited the same fingerprint as the original cultivar. The fingerprinting of two triploid apple cultivars suggested that the parent contributing the 2n gamete was the female. We applied this fingerprinting to paternity analysis of an apple cultivar of which the pollen parent was unknown. By using 5 arbitrary primers and RFLP analysis of the amplified products, one cultivar was singled out for paternity among six putative candidates.     

Population genetic simulation and data analysis with Plabsoft

Computer simulations are a useful tool to solve problems in population genetics for which no analytical solutions are available. We developed Plabsoft, a powerful and flexible software for population genetic simulation and data analysis. Various mating systems can be simulated, comprising planned crosses, random mating, partial selfing, selfing, single-seed descent, double haploids, topcrosses, and factorials. Selection can be simulated according to selection indices based on phenotypic values and/or molecular marker scores. Data analysis routines are provided to analyze simulated and experimental datasets for allele and genotype frequencies, genotypic and phenotypic values and variances, molecular genetic diversity, linkage disequilibrium, and parameters to optimize marker-assisted backcrossing programs. Plabsoft has already been employed in numerous studies, we chose some of them to illustrate the functionality of the software.