Authors:R. Liu, Q.N. Zhang, J. Lu, C.H. Zhang, L. Zhang and Y. Wu
Salt stress is one of the major abiotic stress which severely limits plant growth and reduces crop productivity across the world. In the present study, the effects of exogenous pyridoxal-5-phosphate (vitamin B6, VB6) on seedling growth and development of wheat under salt stress were investigated. The results showed that exogenous application of pyridoxal-5-phosphate (VB6) significantly increased the RWC, biomass, the concentration of photosynthetic pigments, proline, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), together with decreasing the content of Malondiadehyde (MDA) and hydrogen peroxide (H2O2) in wheat leaves under salt stress. Meanwhile, the transcript level of P5CR, P5CS, SOD, TaSOS1 and TaSOS4 were also up-regulated after treatment with pyridoxal-5-phosphate. VB6 acts as a signal in regulating the activities of plant antioxidant enzymes and SOS pathway to improve resistance to salt stress. The current study results may give an insight into the regulatory roles of VB6 in improving salt stress and VB6 could be an easily and effective method to improve salt-stress tolerance to wheat in the field condition. It is urgency to understand the molecular mechanism of VB6 to enhance the salt tolerance of wheat in the next work.
Authors:C. Maucieri, C. Caruso, S. Bona, M. Borin, A. C. Barbera and V. Cavallaro
In many world regions, osmotic and salt stresses are becoming the primary environmental conditions limiting successful establishment of crops. The old durum wheat landraces may provide a source of genes useful to enhance crop resilience to the abiotic stresses of dryland areas or foreseen as a result of climate change. With this in mind, in order to determine the effects of salt and osmotic stresses on durum wheat germination, an old Sicilian durum wheat landrace “Timilia” and a relatively recent cultivar “Mongibello” were investigated at various iso-osmotic solutions of NaCl and mannitol at osmotic potentials of: 0 – control, –0.125, –0.250, –0.500 and –0.750 MPa.
Under stress conditions, different germination and early growth behavior was observed in the two durum wheat genotypes. Timilia presented almost stable germination even at the highest osmotic stresses (96.7% and 88.3% seed germination at 0 and –0.750 MPa, respectively) showing a higher capacity of seed imbibition than Mongibello. The latter thus showed a higher sensitivity than the old landrace to the studied stresses. The variability ascertained in the response to salinity stress indicate that Timilia could be a source of interesting genes for breeding programs.
Authors:J.Q. Xu, L. Wang, B.L. Liu, T.F. Xia, D.C. Liu, X. Chang, T.W. Zhang, H.G. Zhang and Y.H. Shen
As one of the world’s earliest domesticated crops, barley is a model species for the study of evolution and domestication. Domestication is an evolutionary process whereby a population adapts, through selection; to new environments created by human cultivation. We describe the genome-scanning of molecular diversity to assess the evolution of barley in the Tibetan Plateau. We used 667 Diversity Arrays Technology (DArT) markers to genotype 185 barley landraces and wild barley accessions from the Tibetan Plateau. Genetic diversity in wild barley was greater than in landraces at both genome and chromosome levels, except for chromosome 3H. Landraces and wild barley accessions were clearly differentiated genetically, but a limited degree of introgression was still evident. Significant differences in diversity between barley subspecies at the chromosome level were observed for genes known to be related to physiological and phenotypical traits, disease resistance, abiotic stress tolerance, malting quality and agronomic traits. Selection on the genome of six-rowed naked barley has shown clear multiple targets related to both its specific end-use and the extreme environment in Tibet. Our data provide a platform to identify the genes and genetic mechanisms that underlie phenotypic changes, and provide lists of candidate domestication genes for modified breeding strategies.
Authors:J. Chen, G. Hu, J. Zhang, C. Chu and Y. Wu
Drought is a severe abiotic stress that affects wheat production worldwide. In order to identify candidate genes for tolerance to water stress in wheat, sequences of 11 genes that have function of drought tolerance in other plant species were used to identify the wheat ortholog genes via homology searching in the wheat EST database. Atotal of 11 primer pairs were identified and amplified PCR products in wheat. Of them, 10 STS markers were mapped on 11 chromosomes in a set of nulli-tetrasomic lines of ‘Chinese Spring’ wheat; six were mapped on chromosomes 1A, 1B, 4B, 7A, 2B and 5D, respectively, in a spring wheat mapping population (POP1). The marker XTaABH1 mapped on 7A in POP1 was the only one mapped but characterized in a winter wheat mapping population (POP2) for grain yield, kernel weight and diameter, and height in four-field trials applied different water stress or irrigation. The marker XTaABH1 was significantly associated with grain yield under rainfed condition, with kernel weight under terminal stress and non-irrigation conditions, with kernel diameter and height under non-irrigated condition. The STS primers, map information and marker-trait association produced in the currently study would be of interest to researchers working on drought tolerance.
Salinity stress is one of the important abiotic stresses affecting rice germination and reduces establishment of seedlings in the field. Six varieties of rice were included in a full diallel mating design and together with their progenies were evaluated for salinity tolerance. General combining ability (GCA) effect was significant for germination percentage reduction (GP) and radicle length reduction (RL); whereas specific combining ability (SCA) were significant for all of traits contain GP, RL, germination rate reduction (GR) and coleoptile length reduction (CL). The negative value of heterosis, due to inverse relation of reduction of traits and salinity tolerance, indicated ideal heterosis. The highest value of negative heterosis for GP, GR, RL and CL were displayed in Shahpasand × Sepidrod, Hassani × Sepidrod, Shahpasand × IRFAON-215 and Sepidrod × IRFAON-215, respectively. The parents with negative GCA are superior for salinity tolerance traits. The Genotype, Genotype-by-Environment (GGE) biplot analysis showed that Sepidrod contributed resistance to GP, GR and IRFAON-215 was the best parent for RL and CL. Respondent this view, Sepidrod and IRFAON-215 can be used either as best parents for selection programs due to their GCA effects, or as a superior parent hybrid programs on their SCA effects.
Authors:V. Mladenov, B. Banjac, A. Krishna and M. Milošević
Quality of wheat grain is a complex trait that depends mostly on the quantity and quality of protein and unified interactions between high molecular glutenin, gliadin, low molecular glutenins and abiotic stresses. The objective of this study was to evaluate the effects of genotype, environment and genotype × environment interaction on quality and some agronomic traits in wheat. Twenty divergent genotypes of winter wheat, per five from Serbia, Russia, France and Hungary were analysed in this paper. Variability was observed for quality (grain protein content and sedimentation) and agronomic traits (thousand-grain weight and test weight) in three growing seasons (2007/08, 2008/09 and 2009/10). Genotypes were statistically analysed [basic statistical parameters, AMMI biplot for the content of protein, correlation and Principal Component Analysis (PCA)] in order to assess the impact of different growing seasons on selected cultivars. AMMI analysis determined that 2008/09 was very significant for most of the genotypes. The Hungarian cultivar GK-Zugoly had the highest grain protein content (14.4%). Correlation analysis showed different relationships between the traits. PCA indicated that the total variation reflected the first two components represented with 80%, but the first principal component was more important. Results of this paper indicate that the varieties MV-Csardas and Pamyati Kalinenko can be used as a good source of genetic material for future breeding program for agro-ecological conditions of Vojvodina.
Triticum dicoccoides, wild emmer wheat, is the direct progenitor of cultivated wheats, has the same genome formula as durum wheat, and has contributed two genomes to bread wheat. It harbors many useful genes, more than can be used for wheat improvement. These genes are associated with many agronomic traits, abiotic stress tolerances, biotic stress resistances, grain protein content and micronutrient mineral concentrations. In this review, we summarized the achievements regarding gene discovery, i.e. gene identification, mapping and cloning in wild emmer wheat. These genes, controlling important agronomic traits, disease resistance, drought tolerance, high protein content and micronutrient mineral content, should be very useful for improvement of wheat production and food nutrition. However, the majority of genetic resources in wild emmer remain untapped, demonstrating the need for further exploration and utilization for wheat breeding programs. The large number of molecular markers, genomics tools and efficient cloning techniques available for wheat will greatly accelerate the application of wild emmer germplasm to wheat improvement and ensure sustainability of global wheat production.
Authors:A. Mujeeb-Kazi, G. Fuentes-Davilla, Alvina Gul and Javed Mirza
Bridge crosses utilizing the D genome synthetic hexaploids (SH),
Triticum turgidum / Aegilops tauschii
(2n = 6x = 42, AABBDD), are a potent means of improving bread wheat (
) for biotic and abiotic stresses. The synthetic germplasm enables incorporation of the genetic diversity of
cultivars together with the attributes of the
accessions. In this research, SH wheats were screened for karnal bunt in Obregon, Mexico over six crop cycles and several SHs were earlier identified with an immune response. These SHs have unique
accessions as parents. Phenologically descriptors and additional trait evaluations led us to develop a sub-set of the most desirable combinations for wheat breeding. The SH wheats are generally tall, late to mature, have good agronomic type, and are non-free threshing with a high 1000 kernel weight. All have a spring growth habit with several possessing multiple stress resistances. The resistance exhibited by SH wheats has been transferred into elite but KB susceptible bread wheat cultivars thus generating a new and unique genetic resource that can be readily exploited by conventional breeding programs.
Authors:C. M. Mutshinda, Z. V. Finkel, C. E. Widdicombe and A. J. Irwin
Ecological communities are shaped by a complex interplay between abiotic forcing, biotic regulation and demographic stochasticity. However, community dynamics modelers tend to focus on abiotic forcing overlooking biotic interactions, due to notorious challenges involved in modeling and quantifying inter-specific interactions, particularly for species-rich systems such as planktonic assemblages. Nevertheless, inclusive models with regard to the full range of plausible drivers are essential to characterizing and predicting community response to environmental changes. Here we develop a Bayesian model for identifying, from in-situ time series, the biotic, abiotic and stochastic factors underlying the dynamics of species-rich communities, focusing on the joint biomass dynamics of biologically meaningful groups. We parameterize a multivariate model of population co-variation with an explicit account for demographic stochasticity, density-dependent feedbacks, pairwise interactions, and abiotic stress mediated by changing environmental conditions and resource availability, and work out explicit formulae for partitioning the temporal variance of each group in its biotic, abiotic and stochastic components. We illustrate the methodology by analyzing the joint biomass dynamics of four major phytoplankton functional types namely, diatoms, dinoflagellates, coccolithophores and phytoflagellates at Station L4 in the Western English Channel using weekly biomass records and coincident measurements of environmental covariates describing water conditions and potentially limiting resources. Abiotic and biotic factors explain comparable amounts of temporal variance in log-biomass growth across functional types. Our results demonstrate that effective modelling of resource limitation and inter-specific interactions is critical for quantifying the relative importance of abiotic and biotic factors.