Estimation of Genetic Divergence and Character Association Studies in Local and Exotic Diversity Panels of Soybean (<i>Glycine max</i> L.) Genotypes

The availability of favorable genetic diversity is a thriving vitality for the success of a breeding program. It provides a firm basis of selecting superior breeding lines for the development of high yielding crop genotypes. In this context, present investigation aimed to generate information on genetic divergence and character association in a diversity panel of 123 local and exotic soybean genotypes. Analysis of variance revealed significant response of the evaluated genotypes based on studied attributes. It depicted the probability of selecting desirable soybean genotypes by focusing on character association studies and genetic diversity analysis. Correlation analysis revealed that seed yield per plant showed high positive correlation with 100-seed weight followed by pods per plant and plant height. Furthermore, path coefficient analysis exposed that pods per plant had maximum direct contribution in seed yield per plant followed by 100-seed weight, days to flowering and SPAD measurement. Genotype named “G-10” showed maximum yield per plant followed by 24607, G-52, 24593, Arisoy, 24566, 17426, A-3127, 24570 and 24567. Genetic diversity analysis grouped the evaluated germplasm into 17 clusters. All clusters showed zero intra-cluster variability; while inter-cluster divergence ranged from 9.00 to 91.11. Cluster V showed maximum inter-cluster distance with cluster XII followed by that of between V and VIII. Moreover, cluster IV with superior genotypes (G-10, 24607, 24593 and 24566), VI (17426 and 24567), XIII (24570) and X (Arisoy and G-52) showed above mean values for most of the studied characters. Overall, the results of hybridization between the superior genotypes of these cluster pairs might be useful for soybean breeding with improving agronomic traits and adaptability.     

The role and basics of computer simulation in support of critical decisions in plant breeding

A number of crucial decisions face the plant breeder before any field activities directed to crop genetic improvement are actually initiated, primarily related to choice of parents and breeding strategy options. Because of the impact, the complexity of these decisions, and the cost of implementing multiple options, computer simulation can be an important resource for the modern breeder. To maximize utility, the simulation tool must be based on effective models of the genome, the breeding process, and other ‘processes’ involved in genetic recombination, identification, and production of new cultivars. Additionally, the statistical methodology employed has ramifications for predicting performance and breeding outcome. The objective of this work is to highlight the role of computer simulation in the planning phases of crop genetic improvement, the basics of model building, statistical considerations, and key issues to be addressed. Examples of publicly available simulation software for plant breeding scenarios are described (features, functionalities, and assumptions) and new directions for improved/expanded approaches and tools are discussed.     

Genomic selection in soybean: accuracy and time gain in relation to phenotypic selection

Genomic selection (GS) can potentially accelerate genetic improvement of soybean [Glycine max L. (Merrill)] by reducing the time to complete breeding cycles. The objectives of this study were to (1) explore the accuracy of GS in soybean, (2) evaluate the contribution of intrapopulational structure to the accuracy of GS, and (3) compare the efficiencies of phenotypic selection and GS in soybean. For this, phenotypic and genotypic data were collected from 324 soybean genotypes (243 recombinant inbred lines and 81 cultivars) and GS was performed for five yield related traits. BayesB methodology with a 10-fold cross-validation was used to compute accuracies. The GS accuracies were evaluated for grain yield, plant height, insertion of first pod, days to maturity, and 1000-grain weight at eight locations. We found that GS can reduce the time required to complete a selection cycle in soybean, which can lead to increased production of this commercially important crop. Furthermore, genotypic accuracy was similar regardless of population structure correction.     

Identification of quantitative trait loci controlling gene expression during the innate immunity response of soybean

Microbe-associated molecular pattern-triggered immunity (MTI) is an important component of the plant innate immunity response to invading pathogens. However, most of our knowledge of MTI comes from studies of model systems with relatively little work done with crop plants. In this work, we report on variation in both the microbe-associated molecular pattern-triggered oxidative burst and gene expression across four soybean (Glycine max) genotypes. Variation in MTI correlated with the level of pathogen resistance for each genotype. A quantitative trait locus analysis on these traits identified four loci that appeared to regulate gene expression during MTI in soybean. Likewise, we observed that both MTI variation and pathogen resistance were quantitatively inherited. The approach utilized in this study may have utility for identifying key resistance loci useful for developing improved soybean cultivars.     

Heterosis and Combining Ability Estimates in Isoflavone Content Using Different Parental Soybean Accessions: Wild Soybean,a Valuable Germplasm for Soybean Breeding

Isoflavone, a group of secondary metabolites in soybean, is beneficial to human health. Improving isoflavone content in soybean seeds has become one of the most important breeding objectives. However, the narrow genetic base of soybean cultivars hampered crop improvement. Wild soybean is an extraordinarily important gene pool for soybean breeding. In order to select an optimal germplasm for breeding programs to increase isoflavone concentration, 36 F1 soybean progenies from different parental accessions (cultivars, wild, Semi-wild and Interspecific) with various total isoflavone (TIF) concentration (High, Middle, Low) were analyzed for their isoflavone content. Results showed that male parents, except for Cultivars, showed positive GCA effects. In particular, wild soybean had higher positive GCA effects for TIF concentration. Both MP and BP heterosis value declined in the hybrid in which male parents were wild soybean, semi-wild soybean, interspecific offspring and cultivar in turn. In general, combining ability and heterosis in hybrids which had relative higher TIF concentration level parents showed better performance than those which had lower TIF concentration level parents. These results indicated characteristics of isoflavone content were mainly governed by additive type of gene action, and wild relatives could be utilized for breeding of soybean cultivars with this trait. A promising combination was found as the best potential hybrid for isoflavone content improvement.     

Breeding Plants for Resistance to Nematodes

Plant breeders and nematologists have developed improved cultivars of important crop species with resistance to plant-parasitic nematodes. The effectiveness of these breeding efforts has depended on the availability of efficient screening procedures, identification of adequate sources of durable resistance, nature of the nematode feeding habit, and knowledge of the inheritance of resistance. These factors determine to a large degree the breeding method and potential success of the research. Systematic searches for nematode resistance have identified resistant germplasm lines within crop species or from related species. When the resistance gene(s) is from related species, incongruity barriers or sterility of the resulting hybrids often must be overcome. In these situations, backcrossing is usually necessary to incorporate the resistance gene(s) and recover the desirable commercial traits of the crop species. If the resistance gene(s) is present within the crop species, the choice of breeding method depends on the inheritance of the resistance, type of screening procedure, and other important breeding objectives for the species. In the future, plant molecular biologists and geneticists will make available novel sources of nematode resistance through incorporation of transgenes from other genera. These efforts will likely require conventional breeding strategies before commercial utilization of an improved resistant cultivar.     

Photosynthesis of soybean cultivars released in different decades after grafting onto record-yield cultivars as rootstocks

While photosynthesis of soybean has been enhanced by breeding, it remains to be clarified whether the improvement of root function could bring a further increase of photosynthetic capacity for the development of soybean cultivars. The objective of this grafting experiment was to determine the influence of record-yield soybean cultivars, Liaodou14 (L14) and Zhonghuang35 (Z35), as rootstocks on photosynthetic traits of cultivars released in different decades. Grafting of various soybean cultivars onto L14 or Z35 rootstocks showed a higher root physiological activity, which resulted in significant increases in some photosynthetic traits at the late grain-filling stage compared with the non-grafted and self-grafted plants. The genetic gain for some photosynthetic traits of cultivars released from 1966 to 2006 increased by using L14 and Z35 as rootstocks. It suggested that the photosynthetic traits of the recently released cultivars could increase more if their root functions are improved.     

1H NMR-based metabolite profiling as a potential selection tool for breeding passive resistance against Fusarium head blight (FHB) in wheat

¹H NMR measurements on protein-free extracts from wheat leaf and stem tissue were used to investigate the biochemical correlates of partial resistance to fungal species implicated in the Fusarium head blight (FHB) disease complex. The wheat genotypes included five commercial wheat cultivars and 116 wheat genotypes, from the CIMMYT international FHB breeding programme in Mexico, that had been bred for FHB disease resistance, utilizing exotic, typically Chinese, resistance sources. Principal component analysis of the nuclear magentic resonance (NMR)-derived metabolite profiles revealed distinct separation of the commercial wheat cultivars from the majority of the CIMMYT wheat genotypes with the commercial cultivars exhibiting markedly higher carbohydrate concentrations. A cross-validated partial least squares (PLS) regression model of the metabolite profile against the partial disease resistance component latent period (delay in sporulation of the fungus on the plant tissue) predicted latent periods that were significantly correlated with the experimentally determined values ( R ² = 0.34, P  < 0.001). Identified metabolites that were found in plants with shorter latent periods (higher disease susceptibility) included choline, the single most influential metabolite in the PLS model, betaine, the amino acids glutamine, glutamate and alanine, trans -aconitate and sucrose. Metabolites related to increased disease resistance included glucose and unassigned resonances in the carbohydrate and aromatic regions of the NMR spectra. The current study has demonstrated the potential of metabolite profiling as a tool for marker-assisted selection in commercial breeding for resistance to FHB in wheat.     

Stable transformation and tissue culture response in current European winter wheats (Triticum aestivum L.)

In order to efficiently complement traditional wheat breeding with genetic transformation technology it will be desirable to introduce transgenes into the ideal genetic background. Poor tissue culture performance is limiting the number of wheat genotypes that can be stably transformed. We statistically analysed the tissue culture response of 38 current European winter wheats and discuss genetic factors influencing this trait. Although regenerable callus cultures could be initiated from immature embryos of all 38 winter wheats analysed, the number of regenerated plants per cultured explant differed highly significantly (p<0.01) among genotypes. Ten cultivars with excellent ranking in this parameter were selected for transformation experiments. Independent transgenic plants were recovered from nine winter wheat genotypes with a frequency ranging between 0.2% and 2.0% of the cultured immature embryos after biolistic transfer of the bar gene and bialaphos selection. The nine transformable winter wheat genotypes included a recently released high-yielding, disease-resistant cultivar (cv. Certo), well established cultivars with elite bread-making quality (cv. Tarso, Alidos) and current breeding lines differing in yield, disease resistance and grain quality. Transgene integration and expression were confirmed by Southern blot analysis, polymerase chain reaction, phosphinothricin acetyltransferase activity assay and herbicide application. Transgene expression was stably transmitted to the sexual progeny of all transgenic lines analysed and segregated in a Mendelian fashion in the majority of lines. The introduction of transgenes into the ideal genetic background will allow a thorough evaluation of their crop improvement potential.     

Production of nutritionally desirable fatty acids in seed oil of Indian mustard (Brassica juncea L.) by metabolic engineering

Development of a designer oilseed crop with improved yield attributes and enhanced nutritional quality for the benefits of mankind and animal husbandry is now achievable with the combination of genetic engineering and plant breeding. In spite of their immense importance, the fatty acid profiles of most oilseed crops are imbalanced that necessitate the use of metabolic engineering strategies to overcome the various shortfalls in order to improve the nutritional quality of these edible oils. Indian mustard (Brassica juncea L.), being one of the important oilseed crops in Indian subcontinent naturally contains ~50 % nutritionally undesirable very long chain unsaturated fatty acids (VLCUFAs), e.g. erucic acid (C_22:1). For the purpose of nutritional improvement of B. juncea seed oil, several metabolic engineering strategies have been employed to divert the carbon flux from the production of VLCUFAs to other important fatty acids. Stearic acid, being a saturated but nutritionally neutral fatty acid, is naturally inadequate in most of the conventional oil seeds. Due to its neutral effect on consumer’s health and as an important industrial ingredient, increased in planta production of stearic acid in the seed oil not only helps in reduction of production cost but also lessens the trans fatty acid production during commercial hydrogenation process. In this review metabolic engineering strategies to minimize the VLCUFAs along with increased production of stearic acid in the seed oil of B. juncea are discussed, so that further breeding attempts can be made to improve the nutritionally desirable fatty acid profile in the suitable cultivars of this important oilseed crop.     

Searching for the optimum multivariate profile of an ash gourd [<Emphasis Type="Italic">Benincasa hispida</Emphasis> (Thunb.) Cogn.] genotype

Ash gourd is an important vegetable especially in the Indo-China region, but also in America and Africa. It is a monotypic genus, and its genetic pool is considered little diverse, which makes breeding of good ash gourd cultivars difficult. A pool of 56 genotypes, of which 10 are released cultivars and 46 indigenous lines collected from different parts of India, was studied in a two-year experiment. Various traits are important when breeding new cultivars, so an optimum multivariate performance is studied in this germplasm, with a special focus on traits of the greatest importance, namely fruit yield per plant, flesh thickness, vine length, and number of days to female and male flowering. Such performance is studied for the best-yielding genotypes, and promising genotypes in terms of multivariate performance are selected.     

Agro-Morphological Characterization and Genetic Dissection of Linseed (<i>Linum usitatissimum</i> L.) Genotypes

Linseed is a multipurpose crop and the crop needs further improvement to increase production and yield due to its high value and demand. This study aimed to assess the extent and pattern of genetic variability of forty linseed genotypes based on diverse agro–morphological and yield attributes. The field experiment was conducted following a Randomized Complete Block Design with three replications. Linseed germplasm showed a wide range of phenotypic expression, genetic variability and heritability for 30 studied traits. A low to high phenotypic coeffi- cient of variation (PCV) and genotypic coefficient of variation (GCV) were observed. The lowest genotypic (σ² g) and phenotypic variances (σ² p) were found in capsule diameter (CD), length of calyx (LC), capsule length (CL), seed length (SL), and seed breadth (SB). High broad-sense heritability (h²_b) with high genetic advance as a percentage of mean (GAM) were observed in days to germination started (DGS), days to 80% emergence (DE), plant height at 28 and 40 DAS, number of flowers (NFPP), filled capsules (NFCPP) and yield per plant (YPP) indicating additive gene action exists for these characters. Hierarchical cluster analysis separated 40 genotypes into five clusters, where Clusters I to V assembled with 13, 4, 4, 5 and 14 genotypes, respectively. Considering yield and yield attributes, Cluster-IV (G3, G4, G6, G10 and G31) genotypes showed promising while, Cluster-II (G2, G16, G35, G36) and Cluster-III (G1, G33, G39 and G40) genotypes were dominant on plant morphological traits. Based on principal component analysis (PCA), few characters such as YPP, NFPP, NFCPP, days to first flowering and capsule formation, early emergence, days to branch initiation and plant heights at different growth stages revealed important and effective traits for consideration in the selection of linseed breeding programs.     

Functional Role of miRNAs: Key Players in Soybean Improvement

Soybean (Glycine max (L.) Merr) is an agro-economic crop growing across the world to cater nutrition for both human and animal feed due to the high oil and protein content in its edible seeds. The genes and QTLs associated with important agronomic traits in this crop have already been identified and validated for soybean cyst nematode (SCN), Phytophthora root and stem rot, Pythium root rot and aphid resistance, seed quality, nutrient values, and also employed for genetic improvement in soybean. In the last decade, micro RNAs (miRNAs) have been considered the effector molecules, so the detection and characterization of novel miRNAs in soybean have been taken up by several workers. The advancement in the strategy of sequencing and tools of bioinformatics during last decade has contributed to the discovery of many soybean miRNAs, thus miRNA can be used as a tool in molecular breeding studies, and this has opened new vistas for miRNA mediated genetic improvement of soybean to augment crop productivity as well as nutritional quality. This review addresses the current state of understanding of miRNAmediated stress responses, nutrient acquisition, plant development and crop production processes in soybean.     

不同大豆基因型对农杆菌敏感性研究及优异种质筛选

大豆遗传转化一直是植物基因工程领域的难点之一,受体品种对农杆菌的敏感程度以及不同农杆菌菌株对靶组织的侵染能力是影响转化效率的主要因素。本研究利用GUS组织瞬时表达技术,比较了4个农杆菌菌株对靶组织子叶节的侵染能力差异,同时利用筛选到的侵染能力最强的菌株评估了33个不同受体基因型对农杆菌的敏感性。结果表明,超毒农杆菌菌株Ag10对靶组织的侵染能力最强,优于其他3个菌株;地方与野生大豆种质在农杆菌侵染后GUS的平均瞬时表达效率显著高于选育品种。此外,通过鉴定筛选出6个对农杆菌敏感性较高的受体材料,其对农杆菌的敏感性优于前人报道的敏感材料Peking,为大豆高效遗传转化体系的建立和新型转化受体的开发提供了参考。     

大豆炸荚发生规律及分子遗传基础

炸荚是野生大豆繁衍后代的一种原始自然属性,同时也是栽培大豆减产的主要原因之一,因此对其发生规律和分子遗传基础的研究具有重要的理论意义和潜在的育种应用价值。文章在剖析抗炸荚大豆荚部细胞学微观组织结构特征的基础上,总结了大豆炸荚的发生规律和大豆炸荚表型性状的鉴定指标与方法,介绍了抗炸荚种质鉴定与抗炸荚品种选育概况,同时详细阐述了大豆抗炸荚性状的分子遗传基础研究进展,最后对大豆抗炸荚性的研究与应用进行了展望。     

Characterization of bright tobaccos by multivariate analysis of C CPMAS NMR spectra

Univariate and multivariate statistics were applied to characterize cured bright tobacco samples on the basis of their ¹³C CPMAS NMR spectra and leaf constituent analysis. NMR spectra were obtained for 55 samples selected from a set of 134 samples of graded bright tobacco leaves from crop year 1999. Historical leaf constituent analyses were available for total alkaloids, reducing sugars, total nitrogen, and insoluble ash. In addition, we applied HPLC to quantify the two abundant plant polyphenols, chlorogenic acid, and rutin. Principal component analysis (PCA) and partial least squares (PLS) of the NMR spectra revealed systematic relationships between groups of samples related to these substances and afforded predictive quantitative models for the analyzed constituents. Analysis of the PLS significant variables showed that leaf polysaccharides, alkaloids, and minerals are major determinants influencing the grading of cured bright tobacco leaves.     

Crop improvement through tissue culture

Plant tissue culture comprises a set of in vitro techniques, methods and strategies that are part of the group of technologies called plant biotechnology. Tissue culture has been exploited to create genetic variability from which crop plants can be improved, to improve the state of health of the planted material and to increase the number of desirable germplasms available to the plant breeder. Tissue-culture protocols are available for most crop species, although continued optimization is still required for many crops, especially cereals and woody plants. Tissueculture techniques, in combination with molecular techniques, have been successfully used to incorporate specific traits through gene transfer. In vitro techniques for the culture of protoplasts, anthers, microspores, ovules and embryos have been used to create new genetic variation in the breeding lines, often via haploid production. Cell culture has also produced somaclonal and gametoclonal variants with crop-improvement potential. The culture of single cells and meristems can be effectively used to eradicate pathogens from planting material and thereby dramatically improve the yield of established cultivars. Large-scale micropropagation laboratories are providing millions of plants for the commercial ornamental market and the agricultural, clonally-propagated crop market. With selected laboratory material typically taking one or two decades to reach the commercial market through plant breeding, this technology can be expected to have an ever increasing impact on crop improvement as we approach the new millenium.D.C.W. Brown is with Agriculture and Agri-Food Canada, Central Experimental Farm, Plant Research Centre, Ottawa, Ontario, K1A 0C6, Canada. T.A. Thorpe is with the Plant Physiology Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada     

Epistatic association mapping in homozygous crop cultivars

The genetic dissection of complex traits plays a crucial role in crop breeding. However, genetic analysis and crop breeding have heretofore been performed separately. In this study, we designed a new approach that integrates epistatic association analysis in crop cultivars with breeding by design. First, we proposed an epistatic association mapping (EAM) approach in homozygous crop cultivars. The phenotypic values of complex traits, along with molecular marker information, were used to perform EAM. In our EAM, all the main-effect quantitative trait loci (QTLs), environmental effects, QTL-by-environment interactions and QTL-by-QTL interactions were included in a full model and estimated by empirical Bayes approach. A series of Monte Carlo simulations was performed to confirm the reliability of the new method. Next, the information from all detected QTLs was used to mine novel alleles for each locus and to design elite cross combination. Finally, the new approach was adopted to dissect the genetic basis of seed length in 215 soybean cultivars obtained, by stratified random sampling, from 6 geographic ecotypes in China. As a result, 19 main-effect QTLs and 3 epistatic QTLs were identified, more than 10 novel alleles were mined and 3 elite parental combinations, such as Daqingdou and Zhengzhou790034, were predicted.     

In vitro mutagenesis of Chrysanthemum morifolium cultivars using ethylmethanesulphonate (EMS) and mutation assessment by ISSR and IRAP markers

Plant Cell, Tissue and Organ Culture (PCTOC) - Mutation induction is a feasible and established breeding method for crop improvement and genetic diversity creation to introduce new plant cultivars....