Akaline, saline and mixed saline-alkaline stresses induce physiological and morpho-anatomical changes in Lotus tenuis shoots

Saline, alkaline and mixed saline–alkaline conditions frequently co-occur in soil. In this work, we compared these plant stress sources on the legume Lotus tenuis, regarding their effects on shoot growth and leaf and stem anatomy. In addition, we aimed to gain insight on the plant physiological status of stressed plants. We performed pot experiments with four treatments: control without salt (pH = 5.8; EC = 1.2 dS·m−1) and three stress conditions, saline (100 mm NaCl, pH = 5.8; EC = 11.0 dS·m−1), alkaline (10 mm NaHCO3, pH = 8.0, EC = 1.9 dS·m−1) and mixed salt–alkaline (10 mm NaHCO3 + 100 mm NaCl, pH = 8.0, EC = 11.0 dS·m−1). Neutral and alkaline salts produced a similar level of growth inhibition on L. tenuis shoots, whereas their mixture exacerbated their detrimental effects. Our results showed that none of the analysed morpho-anatomical parameters categorically differentiated one stress from the other. However, NaCl- and NaHCO3-derived stress could be discriminated to different extents and/or directions of changes in some of the anatomical traits. For example, alkalinity led to increased stomatal opening, unlike NaCl-treated plants, where a reduction in stomatal aperture was observed. Similarly, plants from the mixed saline–alkaline treatment characteristically lacked palisade mesophyll in their leaves. The stem cross-section and vessel areas, as well as the number of vascular bundles in the sectioned stem were reduced in all treatments. A rise in the number of vessel elements in the xylem was recorded in NaCl-treated plants, but not in those treated exclusively with NaHCO3.Fil: Paz, Rosalia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto de Biología Agrícola de Mendoza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico Chascomús. Instituto de Investigaciones Biotecnológicas (sede Chascomús); ArgentinaFil: Reinoso, Herminda Elmira. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Biología Agrícola. Cátedra de Morfología Vegetal; ArgentinaFil: Espasandin, Fabiana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); ArgentinaFil: Gonzalez Antivilo, Francisco Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Sansberro, Pedro Alfonso. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); ArgentinaFil: Rocco, Ruben Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico Chascomús. Instituto de Investigaciones Biotecnológicas (sede Chascomús); ArgentinaFil: Ruiz, Oscar Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico Chascomús. Instituto de Investigaciones Biotecnológicas (sede Chascomús); ArgentinaFil: Menendez, Ana Bernardina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico Chascomús. Instituto de Investigaciones Biotecnológicas (sede Chascomús); Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentin

Finding invisible quantitative trait loci with missing data

Summary Evolutionary processes during plant polyploidization and speciation have led to extensive presence-absence variation (PAV) in crop genomes, and there is increasing evidence that PAV associates with important traits. Today, high-resolution genetic analysis in major crops frequently implements simple, cost-effective, high-throughput genotyping from single nucleotide polymorphism (SNP) hybridization arrays; however, these are normally not designed to distinguish PAV from failed SNP calls caused by hybridization artefacts. Here, we describe a strategy to recover valuable information from single nucleotide absence polymorphisms (SNaPs) by population-based quality filtering of SNP hybridization data to distinguish patterns associated with genuine deletions from those caused by technical failures. We reveal that including SNaPs in genetic analyses elucidate segregation of small to large-scale structural variants in nested association mapping populations of oilseed rape (Brassica napus), a recent polyploid crop with widespread structural variation. Including SNaP markers in genomewide association studies identified numerous quantitative trait loci, invisible using SNP markers alone, for resistance to two major fungal diseases of oilseed rape, Sclerotinia stem rot and blackleg disease. Our results indicate that PAV has a strong influence on quantitative disease resistance in B. napus and that SNaP analysis using cost-effective SNP array data can provide extensive added value from missing data. This strategy might also be applicable for improving the precision of genetic mapping in many important crop species

Effects of salinity and ascorbic acid on growth, water status and antioxidant system in a perennial halophyte

Salinity causes oxidative stress in plants by enhancing production of reactive oxygen species, so that an efficient antioxidant system, of which ascorbic acid (AsA) is a key component, is an essential requirement of tolerance. However, antioxidant responses of plants to salinity vary considerably among species. Limonium stocksii is a sub-tropical halophyte found in the coastal marshes from Gujarat (India) to Karachi (Pakistan) but little information exists on its salt resistance. In order to investigate the role of AsA in tolerance, 2-month-old plants were treated with 0 (control), 300 (moderate) and 600 (high) mM NaCl for 30 days with or without exogenous application of AsA (20 mM) or distilled water. Shoot growth of unsprayed plants at moderate salinity was similar to that of controls while at high salinity growth was inhibited substantially. Sap osmolality, AsA concentrations and activities of AsA-dependant antioxidant enzymes increased with increasing salinity. Water spray resulted in some improvement in growth, indicating that the growth promotion by exogenous treatments could partly be attributed to water. However, exogenous application of AsA on plants grown under saline conditions improved growth and AsA dependent antioxidant enzymes more than the water control treatment. Our data show that AsA-dependent antioxidant enzymes play an important role in salinity tolerance of L. stocksii.Higher Education Commission of Pakistan for provision of funds under a research grant entitled ‘Salt-induced Oxidative Stress: Consequences and Possible Management’

Biotechnological Perspective of Reactive Oxygen Species (ROS)-Mediated Stress Tolerance in Plants

All environmental cues lead to develop secondary stress conditions like osmotic and oxidative stress conditions that reduces average crop yields by more than 50% every year. The univalent reduction of molecular oxygen (O2) in metabolic reactions consequently produces superoxide anions (O2•−) and other reactive oxygen species (ROS) ubiquitously in all compartments of the cell that disturbs redox potential and causes threat to cellular organelles. The production of ROS further increases under stress conditions and especially in combination with high light intensity. Plants have evolved different strategies to minimize the accumulation of excess ROS like avoidance mechanisms such as physiological adaptation, efficient photosystems such as C4 or CAM metabolism and scavenging mechanisms through production of antioxidants and antioxidative enzymes. Ascorbate-glutathione pathway plays an important role in detoxifying excess ROS in plant cells, which includes superoxide dismutase (SOD) and ascorbate peroxidase (APX) in detoxifying O2•−radical and hydrogen peroxide (H2O2) respectively, monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in recycling of reduced substrates such as ascorbate and glutathione. Efficient ROS management is one of the strategies used by tolerant plants to survive and perform cellular activities under stress conditions. The present chapter describes different sites of ROS generation and and their consequences under abiotic stress conditions and also described the approaches to overcome oxidative stress through genomics and genetic engineering

Plant–Microbe Interaction

Plant–microbe interaction is a complex, dynamic and continuous process that is as old as plant colonization on Earth [...

Genomic Variations and Mutational Events Associated with Plant–Pathogen Interactions

Phytopathologists are actively researching the molecular basis of plant–pathogen interactions. The mechanisms of responses to pathogens have been studied extensively in model crop plant species and natural populations. Today, with the rapid expansion of genomic technologies such as DNA sequencing, transcriptomics, proteomics, and metabolomics, as well as the development of new methods and protocols, data analysis, and bioinformatics, it is now possible to assess the role of genetic variation in plant–microbe interactions and to understand the underlying molecular mechanisms of plant defense and microbe pathogenicity with ever-greater resolution and accuracy. Genetic variation is an important force in evolution that enables organisms to survive in stressful environments. Moreover, understanding the role of genetic variation and mutational events is essential for crop breeders to produce improved cultivars. This review focuses on genetic variations and mutational events associated with plant–pathogen interactions and discusses how these genome compartments enhance plants’ and pathogens’ evolutionary processes

Impact of Exogenous Ascorbic Acid on Antioxidant Activity and Some Physiological Traits of Common Bean Subjected to Salinity Stress

The role of ascorbic acid as a key molecule antioxidant involves in biotic and abiotic stress has already been well described. Recent study indicates that it also participates in the detoxification of generated reactive oxygen species due to abiotic stresses. Thus, In order to study effects of salt stress and ascorbic acid on antioxidant enzyme activity, chlorophyll content, lipid peroxidation and abscisic acid accumulation of bean an experiment was conducted. The exogenous application of ascorbic acid in nutrition solution of bean plants indicated that later is involve in reduction of antioxidant enzyme activity and increase of resistance to salt stress. We observed that antioxidant enzyme activity increased due to salt stress and ascorbic acid via eliminating of reactive oxygen species decreased activities. Moreover, abscisic acid and lipid peroxidation were affected of salt stress. Increase of ascorbic acid concentration at 100 mM NaCl treatment prevented of lipid peroxidation and decreased generation of malondialdehyde as final product of peroxidation of membrane lipids. However, at high level of salinity, ascorbic acid did not significant effect on reduction of lipid peroxidation. Whereas, chlorophyll content decreased by reactive oxygen species. Ascorbic acid increased chlorophyll content at all of stressed and non-stressed treatments. Abscisic acid assay showed that, accumulation of this hormone increased under salt stress treatments and raise of ascorbic acid concentration in nutrition solution of stressed plants prevented of abscisic acid accumulation. Our data provide strong support to the hypothesis that exogenous of ascorbic acid reduces the harmful effects of salinity and increases resistance to salinity in bean plant

Effect of Salinity on Growth, Xylem Structure and Anatomical Characteristics of Soybean

This research was conducted in order to evaluation the salinity stress effect on growth parameters and stem anatomical changes of soybean grown under controlled conditions. Soybean seeds were surface sterilized and then sown into plastic pots filled up with perlite and vermiculite. Seeds were irrigated with Broughton and Dilworth solution daily. At full folded cotyledons stage (5 day after sowing), salinity stress was induced by adding NaCl into nutrition solution with final concentration of 0, 25, 50 and 100 mM. Thirty days after sowing plants were harvested and growth parameters and anatomical changes were evaluated. The results showed that, salinity stress was significantly decreased shoot and root weight either fresh weight or dry weight, in addition, total plant weight, plant height and leaf number were decreased due to salinity stress. Interestingly, leaf area was not affected by salinity stress. Stem microscopic study demonstrated that, salinity stress significantly increased cutin mass and trichome density on epidermal cells. On the other hand, cortex thickness was decreased because of salinity stress while xylem thickness had upward increase when soybean plants were grown under salinity stress especially high level of salinity. Additionally, there were changed in xylem formation and arrangement in stressed plants

Impact of Inter-Row Spacing on Yield and Yield Components of several Annual Medics Species

A field study was conducted in Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran to evaluate the effects of three within-row spacing treatments (20, 30 and 40 cm) on forage and seed production of five species of annual medics (Medicago scutellata cv. �Sava�; M. littoralis cv. �Herald�; M. polymorpha cv. �Santiago�; M. minima cv. �Orion� and M. truncatula cv. �Mogul�). The experiment was carried out in Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. The results of the experiment indicated that M. polymorpha had the highest forage yield out of the highest plant population. Latter with average 443.09 Kg ha-1 and M. scutellata with average 409.99 Kg ha-1 produced the highest seed yield. Also, the last species with 1306.78 Kg ha-1 had the highest pod yields. The highest seed yield and pod yield were produced at 20 cm within-row spacing because there were not adequate plants for maximum seed and pod yields in 30 and 40 cm within-row spacing. The tested plant densities did not affect on seeds number per pod, 1000 seeds weight and seeds to burr pod weight ratio. The M. truncatula and M. minima have the highest seeds number per pod. In addition, M. scutellata had the highest 1000 seeds weight with an average of 12.57 g. The highest seeds to burr pod ratio was observed in M. polymorpha. The most pod numbers were obtained in 20 and 30 cm within-row spacing and M. polymorpha while, the least pod numbers was observed in M. scutellata. Plant densities did not affect on pod numbers of the mentioned species. The highest dry forage yield was produced in 20 cm within-row spacing. Among the tested tested species, M. truncatula had the highest forage yield with average 870.07 Kg ha-1. This experiment indicated that there is possibility for seed and forage production of tested annual medics in the mentioned zone with the considering suitable plant densities