Papers by Konstantina Kocheva
Journal of Plant Nutrition, 2021
Abstract Among other crop plants legumes are of great significance for agricultural practice sinc... more Abstract Among other crop plants legumes are of great significance for agricultural practice since they represent a major source of proteins for human and animal consumption. Through their participation in symbiotic nitrogen fixation in a tight relationship with soil bacteria, atmospheric nitrogen is reduced to ammonium which is a more suitable form of N for utilization of nearly all plant species. Symbiotic nitrogen fixation is a natural means for improving soil fertility advantageous over chemical fertilizing which has lower efficiency and greater economic and ecological costs. High soil salinity seriously decreases crop yield and productivity. In this review, we examine the current knowledge and understanding of the effect of salinity stress on legumes and symbiotic nitrogen fixation and discuss mechanisms and management strategies for improving crop performance. The potential of using legumes as green manure in order to ameliorate plant productivity in saline environments is discussed. Promising technologies for increasing crops nutrient content like the utilization of plant growth-promoting bacteria and the newest research efforts involved in transferring nitrogen-fixing capacity to non-legumes and economically important plant species are outlined.
ABSTRASCT The effect of PEG-induced osmotic stress on relative water content and electrolyte leak... more ABSTRASCT The effect of PEG-induced osmotic stress on relative water content and electrolyte leakage from the leaves of two contrasting wheat (Triticum aestivum, L) cultivars was compared in the study. Drought tolerant cv. Katya retained higher water content in the leaves after imposition of osmotic stress in comparison with cv. Prelom. Higher amount of potassium ions tended to leak from the leaves of stressed cv. Prelom plants and the overall electrolyte leakage from the leaves of this cultivar was also greater in comparison with cv. Katya. It was concluded that capacity for better water retention in the tolerant cv. Katya could be connected with the retention of potassium ions which participate in many cellular processes and represent the major osmotic solute in plant cells. Lower electrolyte leakage from stressed Katya leaves in comparison to Prelom was indicative of less damaged cellular membrane permeability which could be connected with superior protective mechanisms. Wheat is...
Botanica, 2021
Revealing stress tolerance mechanisms in plants would contribute to the selection of crop varieti... more Revealing stress tolerance mechanisms in plants would contribute to the selection of crop varieties with a higher capacity for surviving in unfavourable environments. In this regard, it is essential to identify possible physiological features that might be beneficial for increasing plant resistance to stress. Two contrasting common wheat (Triticum aestivum L.) cultivars with different drought tolerance were subjected to 48 h treatment with 20% polyethylene glycol 8000, which provoked an extra degree of osmotic and oxidative stress as well as distinct physiological responses. Better water retention capacity in leaves and lesser extent of membrane injury found in cultivar ‘Guinness’ compared to cultivar ‘Niki’ correlated with increased osmotic adjustment by accumulating higher amounts of proline and higher antioxidant scavenging capacity in the former. Compared to soluble sugars and total free amino acids, proline contributed to a greater extent to preserving leaf water. It was specul...
Botanica, 2021
Cytokinins are known to enhance stress tolerance in plants. The present study aimed to assess the... more Cytokinins are known to enhance stress tolerance in plants. The present study aimed to assess the possible protective effect of exogenous phenylurea-type cytokinin (4PU-30) on alleviating salt (NaCl) stress. Young pea (Pisum sativum L.) plants were sprayed with cytokinin 4PU-30 and were subsequently subjected to NaCl treatment. The effect of 4PU-30 on cell membrane stability was assessed based on electrolyte leakage from leaves of control and NaCl stressed plants. A previously established model system employing the kinetics of ion leakage served to evaluate the effect of the 4PU-30 application on plants response to salinity. Salt treatment caused a moderate decrease in leaf water content. Accumulation of proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) in the leaves of NaCl treated plants indicated the development of oxidative stress, which was significantly alleviated by pretreatment with phenylurea-type cytokinin 4PU-30. Foliar application of 4PU-30 reduced the damagin...
ABSTRASCT Osmotic stress induced by incubation of young wheat (Triticum aestivum, L) plants roots... more ABSTRASCT Osmotic stress induced by incubation of young wheat (Triticum aestivum, L) plants roots in PEG 8000 solution led to reduction in leaf relative water content and caused increased ion leakage from the leaves. Higher amounts of metal caions tended to leak from the leaves of stressed compared to untreated plants and the overall electrolyte leakage from PEG-treated samples was also greater. It was concluded that the capacity for better water retention could be connected with the retention of potassium ions, which participate in many cellular processes and represent the major osmotic solute in plant cells. Enhanced electrolyte leakage from stressed leaves could be indicative of altered membrane permeability or could be connected with specific protective mechanisms involved in the process of osmotic adjustment at the cellular level.
Растежната активност на петдневни прорастъци от обикновена зимна пшеница в условия на осмотичен с... more Растежната активност на петдневни прорастъци от обикновена зимна пшеница в условия на осмотичен стрес, е оценявана по натрупана биомаса, депресия на растежа, индекс на увреждане и оводненост. Използвани са семена от българските сортове Катя, Гинес, Гея-1 и Ники от три вегетационни години 2012-2014 г. Кълновете са подлагани на осмотичен стрес за 48 часа в термостат с разтвори на захароза с воден потенциал от-0.55 и-1.33 МРа. Беше установено, че след стреса при сортовете Гинес и Гея-1 свежата и сухата маса на колеоптила е по-голяма и се повлиява по-слабо негативно в сравнение със свежата и сухата маса при сорт Ники, като при Гинес и Гея-1 дължината на колеоптила е по-голяма от тази при Ники. Катя и Гинес показват по-висока оводненост на колеоптила при умерен стрес от-0.55 МРа, което корелира с депресията на растежа на органа. Силният воден стрес от-1.33 МРа предизвиква еднаква депресия на растежа на органите без разлика между сортовете. Най-чувствителен към умерен и силен воден стрес по тези показатели е сорт Ники. Кривите на регресионните зависимости между сухата маса и оводнеността на колеоптила и сухата маса и коефициента на депресия при умерен стрес доказват, че сортовете Катя, Гинес и Гея-1 притежават адаптивни механизми към стреса, за разлика от сорт Ники.
Summary. Wheat (Triticum aestivum L.) seedlings of cv. Chinese Spring (CS) and hybrid Line 73 (br... more Summary. Wheat (Triticum aestivum L.) seedlings of cv. Chinese Spring (CS) and hybrid Line 73 (breeding material based on a wide cross CS x Aegilops geniculata Roth) were grown for 7 days on a half strength Hoagland nutrient solution and afterwards transferred to 15 % PEG 6000. Changes in the parameters of cell membrane stability (electrolyte leakage kinetics), level of oxidative stress (MDA and hydrogen peroxide content) and leaf water status assessed by RWC during 5-days (mild) and 8-days (strong) water stress were investigated. The longer stress duration caused stronger dehydration. RWC of the leaves was strongly reduced in both genotypes. The level of water stress in the parental genotype correlated with greater lipid peroxidation (assessed as higher content of MDA) and reduced membrane stability (higher electrolyte leakage from damaged tissues) in leaves. These disturbances in the parental genotype corresponded to higher concentration of hydrogen peroxide of which Line 73 showe...
Nutrient stress may modify plant reaction to herbicide treatment. On the other hand, herbicides m... more Nutrient stress may modify plant reaction to herbicide treatment. On the other hand, herbicides might induce or aggravate nutrient disorders. The separate and combined effects of chlorsulfuron (ClS) and iron supply on growth, photosynthetic pigment content and functional state of the photosynthetic apparatus, assessed by chlorophyll fluorescence measurements, were compared. Young pea plants were grown hydroponically in a growth chamber, supplied with iron, ranging from complete deficiency to excess (0, 2optimum concentration, 10 or 50 mg.l-1 Fe) and sprayed with ClS (0. 10-6 or 10-5M). Both Fe deficiency and strong Fe excess reinforced the inhibitory effect of ClS on shoot and root biomass, while low Fe excess (10 mg.l-1 Fe) slightly mitigated the herbicide effect on growth, but affected negatively PSII activity. Separately, Fe deficiency and ClS decreased the chlorophyll and carotenoids content. Due to a concentration effect, when both factors were in combination the chlorosis of F...
Plant, Soil and Environment, 2021
Field experiments were conducted with two winter wheat cultivars that were primed with 6-benzylam... more Field experiments were conducted with two winter wheat cultivars that were primed with 6-benzylaminopurine (6-BA) or kinetin at the concentration 10 mg/L twice during the grain filling stage. After priming, wheat physiological parameters were measured in the field, and the analysis of yield was performed after harvest. Harvested seeds were subjected to low temperature storage for 12 months at –18 °С simulating conservation conditions in genebanks. In field experiments, treated plants exhibited up to 14% higher productivity, higher fresh and dry weight, and chlorophyll content index of flag leaves. Priming significantly improved germination, seedling vigour and growth parameters. In 5-days-old seedlings developed from low temperature stored seeds of field primed plants, the average accumulation of malondialdehyde and H2O2 was estimated 25% lower, which contributed to higher cell membrane stability. These results correlated positively with growth characteristics of 15-days-old seedlin...
Cereal Research Communications, 2021
Plants, 2021
Genetic diversity and population structure are key resources for breeding purposes and genetic st... more Genetic diversity and population structure are key resources for breeding purposes and genetic studies of important agronomic traits in crops. In this study, we described SNP-based genetic diversity, linkage disequilibrium and population structure in a panel of 179 bread wheat advanced cultivars and old accessions from Bulgaria, using an optimized wheat 25K Infinium iSelect array. Out of 19,019 polymorphic SNPs, 17,968 had a known chromosome position on the A (41%), B (42%) and D (11%) genome, and 6% were not assigned to any chromosome. Homoeologous group 4, in particular chromosome 4D, was the least polymorphic. In the total population, the Nei’s gene diversity was within the range 0.1–0.5, and the polymorphism information content ranged from 0.1 to 0.4. Significant differences between the old and modern collections were revealed with respect to the linkage disequilibrium (LD): the average values for LD (r2), the percentage of the locus pairs in LD and the LD decay were 0.64, 16% a...
Plants, 2021
Strategies and coping mechanisms for stress tolerance under sub-optimal nutrition conditions coul... more Strategies and coping mechanisms for stress tolerance under sub-optimal nutrition conditions could provide important guidelines for developing selection criteria in sustainable agriculture. Nitrogen (N) is one of the major nutrients limiting the growth and yield of crop plants, among which wheat is probably the most substantial to human diet worldwide. Physiological status and photosynthetic capacity of two contrasting wheat genotypes (old Slomer and modern semi-dwarf Enola) were evaluated at the seedling stage to assess how N supply affected osmotic stress tolerance and capacity of plants to survive drought periods. It was evident that higher N input in both varieties contributed to better performance under dehydration. The combination of lower N supply and water deprivation (osmotic stress induced by polyethylene glycol treatment) led to greater damage of the photosynthetic efficiency and a higher degree of oxidative stress than the individually applied stresses. The old wheat var...
Physiology and Molecular Biology of Plants, 2020
The performance of two contrasting Bulgarian wheat varieties (Slomer, an old tall cultivar, and E... more The performance of two contrasting Bulgarian wheat varieties (Slomer, an old tall cultivar, and Enola, a modern semi-dwarf one) to nitrogen deficiency was compared by measuring biochemical parameters characterizing N uptake and assimilation as well as growth and photosynthetic activity of young seedlings. The old genotype displayed better photosynthetic capacity, higher N assimilation expressed by elevated amino acid synthesis and better overall performance under N limitation. This could be explained by the fact that selection of old varieties was performed mostly in environments with low nutrient availability and consequently these genotypes proved to be more suitable for growing on low-input conditions. Upon limiting N supply modern variety preferentially accumulated sugars while the old one retained higher amino acids levels. It was demonstrated that processes involved in N metabolism were tightly interrelated with photochemical reactions and carbon assimilation even at early developmental stage.
Plant physiology and biochemistry : PPB, 2018
Haberlea rhodopensis is a chlorophyll-retaining resurrection plant, which can survive desiccation... more Haberlea rhodopensis is a chlorophyll-retaining resurrection plant, which can survive desiccation to air dry state under both low light and sunny environments. Maintaining the integrity of the membrane during dehydration of resurrection plants is extremely important. In the present study, the diffusion model was improved and used for a first time to evaluate the changes in ion leakage through different cellular compartments upon desiccation of H. rhodopensis and to clarify the reasons for significant increase of electrolyte leakage from dry leaves. The applied diffusion approach allowed us to distinguish the performance of plants subjected to dehydration and subsequent rehydration under different light intensities. Well-hydrated (control) shade plants had lower and slower electrolyte leakage compared to control sun plants as revealed by lower values of phase amplitudes, lower rate constants and ion concentration. In well-hydrated and moderately dehydrated plants (50% relative water ...
Photosynthesis research, 2018
Assessment of photosynthetic traits and temperature tolerance was performed on field-grown modern... more Assessment of photosynthetic traits and temperature tolerance was performed on field-grown modern genotype (MG), and the local landrace (LR) of wheat (Triticum aestivum L.) as well as the wild relative species (Aegilops cylindrica Host.). The comparison was based on measurements of the gas exchange (A/c, light and temperature response curves), slow and fast chlorophyll fluorescence kinetics, and some growth and leaf parameters. In MG, we observed the highest CO assimilation rate [Formula: see text] electron transport rate (J) and maximum carboxylation rate [Formula: see text]. The Aegilops leaves had substantially lower values of all photosynthetic parameters; this fact correlated with its lower biomass production. The mesophyll conductance was almost the same in Aegilops and MG, despite the significant differences in leaf phenotype. In contrary, in LR with a higher dry mass per leaf area, the half mesophyll conductance (g) values indicated more limited CO diffusion. In Aegilops, we...
Journal of Plant Nutrition, 2017
ABSTRACT Growth and physiological parameters of intercropped subterranean clover (Trifolium subte... more ABSTRACT Growth and physiological parameters of intercropped subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) were investigated under controlled and field conditions. Nitrogen nutrition was accomplished in symbiotic and heterotrophic forms in both the species studied under controlled concentration of mineral elements in the media and by in oculation with appropriate rhizobial strain. Intercropped variants were also grown in sand culture as follows: subterranean clover – 100%, cocksfoot – 100%, subterranean clover:cocksfoot– 75:25(%), subterranean clover: cocksfoot– 50:50(%), and subterranean clover:cocksfoot– 25:75(%). In hydroponic cultures, subterranean clover to cocksfoot proportion was always 50:50(%). Subterranean clover reacted positively with growth up to 1.25 mM nitrate concentration in the medium with stimulation of number of nodules formed and their nitrogenase activity. When separately grown, both subclover and cocksfoot reacted with higher plant biomass formation under higher nitrate nutrition. When intercropped, the process of growth stimulation in subclover was more prominent than in cocksfoot.
Ratarstvo i povrtarstvo, 2015
Nitrogen content in plant biomass yield of subterranean clover (Trifolium subterraneum L.) and co... more Nitrogen content in plant biomass yield of subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) was determined as related to the different concentrations of nitrogen supply. Plants were grown sole and in mixture as symbiotrophic or heterotrophic cultures under controlled mineral elements concentration in the media and inoculation with rhyzobial strain. Two concentrations of inorganic nitrogen were tested: 0.125 mM (N1) and 1.25 mM (N2). Experimental variants: subterranean clover (100%) + N1; subterranean clover (100%) + N2; cocksfoot (100%) + N1; cocksfoot (100%) + N2; subterranean clover + cocksfoot (50:50%) + N1; subterranean clover + cocksfoot (50:50%) + N2. Inorganic nitrogen concentration had greater effect on shoot yield nitrogen content than on root yield nitrogen content for both crops. Nitrogen content in whole plant biomass yield of subterranean clover grown either sole or in mixture with cocksfoot was almost three times greater under high nitrogen concentration. Nitrogen use efficiency was highest in the mixture.
Cereal Research Communications, 2015
The potentials of an electrochemical and a physical technique for detection of physiological diff... more The potentials of an electrochemical and a physical technique for detection of physiological differences in three wheat cultivars under optimal growth conditions were outlined in the study. Electrolyte leakage kinetics was established by continuous measurements of conductivity of solutions in which leaf pieces were incubated for 24 hours. Impedance spectra were obtained from intact leaves at frequency range from 7 to 2010 Hz and 250 mV measuring voltage applied between two gold plated silicon substrates serving as electrodes. The obtained spectra were approximated by a model employing two ARC elements connected in series. Parameters of the previously described diffusion model based on time course conductivity measurements were inversely correlated with electrical impedance spectroscopy data, thus the genotype with highest ion leakage (cultivar Prelom) exhibited lowest impedance magnitude. It was concluded that the two methods were able not merely to distinguish the three studied cultivars but also to rank them in the same order based on their electrical properties.
Journal of Agronomy and Crop Science, 2014
Wheat reduced height (Rht) genes encode modified DELLA proteins, which are gibberellin insensitiv... more Wheat reduced height (Rht) genes encode modified DELLA proteins, which are gibberellin insensitive, accumulate under stress, restrain growth and affect plant stress response. The seedling reaction to soil water deficit regarding leaf gas exchange and chlorophyll fluorescence was compared in near-isogenic lines carrying the alleles Rht-B1a (tall), Rht-B1b (semi-dwarfing) and Rht-B1c (dwarfing) and was related to leaf water content and anatomy. Under drought, Rht-B1c line was characterized by less decreased CO 2 assimilation, delayed non-stomatal limitation of photosynthesis and higher instantaneous water use efficiency. The functional state of its photosynthetic apparatus was better preserved as evidenced by the less decreased actual quantum yield (Φ PSII) and potential maximum quantum yield (F v /F m) of PSII, and the less increased quantum yield of non-regulated energy dissipation (Φ NO). Rht-B1b line also tended to perform better than Rht-B1a, but differences were less pronounced. Although the leaves of both dwarf lines were smaller, thicker and more pubescent, their water content was not higher in comparison with the tall line. Nevertheless, in Rht-B1c, leaf thickness was less decreased and mesophyll cells were less shrunk under drought. The more effective performance of the photosynthetic machinery of dwarf lines under water deficit could be explained by a combination of morpho-anatomical and metabolic characteristics.
Journal of Biosciences, 2014
The reaction to soil drying was evaluated in two Triticum aestivum near-isogenic lines carrying d... more The reaction to soil drying was evaluated in two Triticum aestivum near-isogenic lines carrying different alleles of the height-reducing gene Rht-B1 based on an improved method for assessment of electrolyte leakage. The two lines were previously shown to differ in their physiological responses to induced water deficit stress. Drought was imposed for 6 days on 10-day-old seedlings. Ion efflux from leaves was measured conductometrically in multiple time points during the 24 h incubation period, and the obtained biphasic kinetics was interpreted according to a previously developed theoretical model proposing different leakage rates through the apoplast and the symplast. Most of the model parameters were able to properly differentiate the two closely related genotypes. The mutant Rht-B1c displayed lower and slower electrolyte leakage in comparison with the wild-type Rht-B1a. It was speculated that the Rht genes expressing defective DELLA proteins might be involved in water stress response through modulation of cell wall stiffness, which influences its capacity for ions retention, and also by their contribution to ROS detoxification, thus indirectly stabilizing cellular membranes. The presented analytical approach relating processes of ion and water flow in and out of the cell could be used for characterization of membrane and cell wall properties of different genotypes under normal and stress conditions.
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Papers by Konstantina Kocheva