Growth Chamber Conditions Research Articles

First Report of Root Rot of Watermelon Caused by Ceratobasidium sp. in Sonora, Mexico.

Watermelon is one of the major crops grown in Mexico and represents 4% of the total cultivated area with fruits in this country. In 2013, Sonora State was ranked second in the production of watermelon at a national level. Fungal and oomycete diseases are among the main biotic factors affecting watermelon production, particularly those caused by species of the genera Fusarium, Phytophthora, Pythium, and Rhizoctonia. During the spring of 2013, wilting or death symptoms were confirmed in approximately 50% of ungrafted watermelon plants grown in four sampled fields along the coast of Hermosillo and Guaymas Valley in Sonora, Mexico. On both roots and stems of infected plants, localized lesions were found that were 0.2 to 2.0 cm long, reddish brown, and slightly sunken on the stem base. In some cases, the discolorations encompassed nearly 90% of the root system. One-centimeter pieces from the edge of lesions on stems and roots were superficially disinfected with 1% sodium hypochlorite, then rinsed with sterile distilled water, placed onto petri dishes containing potato dextrose agar (PDA), and incubated at 25°C for 3 days. Fungal colonies were white initially, then turned brown, and septate hyphae were 3.7 to 4.3 μm in diameter and branched at right angles with a constriction at the origin of the branch point. These characteristics are typical of the genus Rhizoctonia. Binucleate cells from five isolates were observed using a lactophenol aniline blue solution stain, according to Ceratobasidium morphological descriptions. Mycelia from five isolates grown on PDA was used for DNA extraction. The rDNA-ITS region was amplified using PCR with the universal fungal primers ITS1 and ITS4 (3). The purified products were separately sequenced in both directions using the same primer pair. The sequences obtained were 99% similar to those of Ceratobasidium sp. AG-F and AG-Fa isolates (accessions KC193238.1 on Tagetes erecta, HQ168370.1 on Musa spp., and JX913821.1 on soy-rice-weeds, respectively) from GenBank (2,4). The pathogenicity of the fungus was tested under growth chamber conditions. Sets of seven healthy watermelon seedlings of the Sugar red variety were inoculated with five isolates of Ceratobasidium. Three disks (8 mm in diameter) of mycelia grown on PDA were placed around the roots of each plantlet. The pots were maintained at 27 ± 0.1°C for 14 days with a photoperiod of 12 h. Seven uninoculated seedlings were used as a control. Initial symptoms showing water-soaked lesions developed on all inoculated seedlings within 6 to 7 days, while typical disease symptoms appeared after 10 to 14 days after inoculation. Seedlings without inoculum were free from infection. The fungus was re-isolated from the inoculated seedlings on PDA, and identified as Ceratobasidium sp., confirmed using morphological characteristics. A similar disease has been reported recently in Italy and Arizona (1); however, this report is the first description of a Ceratobasidium sp. causing root rot of watermelon in Sonora, Mexico. Agricultural areas where the study was carried represent 90% of the total area cultivated with watermelon in this state, so it is necessary to evaluate the impact of this pathogen in the crop.

Componentes de resistencia a Xanthomonas vesicatoria raza T2 en genotipos de tomate en condiciones de invernadero y cámara de crecimiento

La mancha bacteriana es una de las principales enfermedades que afectan al cultivo de tomate. Los agentes causales son cuatro especies del género Xanthomonas. En Uruguay, la especie predominante es Xanthomonas vesicatoria raza T2.Debido a la baja efectividad de las herramientas de control, la resistencia genética adquiere gran interés para mejorar el manejo de la enfermedad. El objetivo de este trabajo fue identificar fuentes de resistencia a mancha bacteriana raza T2 entomate en invernadero y cámara de crecimiento a través de la determinación de los componentes de resistencia. Los componentes evaluados fueron el período de latencia, número de manchas en el folíolo terminal y la población bacteriana en el tejido. También se determinó la severidad en hoja mediante una escala diagramática. Los cultivares Hawaii 7981 y Loica, así como las líneas LB 76 y LB 97 presentaron la menor severidad en el follaje, el menor número de manchas y las poblaciones bacterianas más bajas, resultando los genotipos con mayores niveles de resistencia. Tanto el número de manchas como el monitoreo de la población bacteriana permitieron diferenciar los genotipos por su resistencia a mancha bacteriana en condiciones controladas. Sin embargo, el período de latencia no difirió significativamente entre los genotipos. Las variedades Loica y Hawaii 7981 se identificaron como nuevas fuentes de resistencia parcial a la raza T2.

Evaluation of genotypic variation in heat tolerance of tall fescue by functional traits

Tall fescue is an important cool season turfgrass. Summer high temperature negatively affects the performance of tall fescue in transitional and warm climate zones. To identify heat tolerant material, 120 tall fescue accessions from different regions of the world were collected and subjected to high temperature under the greenhouse and the growth chamber conditions. Average temperature was 43 °C in the greenhouse trial. Meanwhile, in the growth chamber trial there were 38/30 °C (day/night) and 25/16 °C for heat stress and control, respectively. Leaf water content, leaf dry weight, leaf fresh weight, growth rate (GR), turf quality (TQ), survival rate (SR), chlorophyll content (Chl), evapotranspiration rate (ET) and electrolyte leakage were determined. Significant effects of accessions, duration time and heat treatment on most characteristics were observed. Wild accessions exhibited higher variations in most of the studied traits than commercial cultivars. There were differences in GR and ET with greater variation coefficients than other traits between accessions, suggesting GR and ET could be effective indices for evaluating heat tolerance of tall fescue accessions. Three principal components in growth chamber trial and two principal components in greenhouse trial were extracted. Principal component analysis indicated that common PC1, correlated with TQ, SR and Chl, was named as “turf performance component”, which explained 43.17 % and 39.24 % of genetic variations in the greenhouse trial and the growth chamber trial, respectively. PC2 that defined as “growth potential component” could explain 23.26 % of total variability in the greenhouse trial and 20.36 % in the growth chamber trial. PC3 was named as “leaf water potential component”. Two regression models (F = 0.65 × F1 + 0.35 × F2) and (F = 0.54 × F1 + 0.28 × F2 + 0.18 × F3) were formulated by factor analysis to evaluate heat tolerance of tall fescue accessions in greenhouse and growth chamber trials, respectively. Accessions from subtropical monsoon climate zone generally exhibited better heat tolerance. In contrast, accessions from East Asia showed more heat sensitive. Finally, five accessions including PI 598574, PI 608787, PI 559374, Pure Gold and PI 527504 were selected as heat tolerant accessions for future tall fescue breeding.

Concomitant CAM and C3 Photosynthetic Pathways in Dendrobium officinale Plants

Dendrobium officinale, endemic to China, is a rare and endangered medicinal herb. As a result of its high economic value, slow growth, and diminishing wild population, protected cultivation is preferred. However, little information is available on its growing environment and photosynthetic characteristics. In this study, the photosynthetic patterns of D. officinale were investigated under various environmental conditions by measuring the net CO2 exchange rates continuously for several days or weeks. Under non-stressed growth chamber conditions with 12-hour light and 12-hour dark periods, D. officinale had concomitance of C3 and crassulacean acid metabolism (CAM) photosynthesis patterns. Different degrees of CAM in D. officinale, expressed as the percentage of CO2 exchanges in the dark period to the daily amount of CO2 exchanges, were observed depending on environmental conditions. With decreasing substrate water content, a typical CAM pattern was found, and concomitance of C3 and CAM patterns was found again when plants were rewatered. The accumulation of leaf titratable acidity during a dark period increased as substrate dried out but decreased again as plants were rewatered. A shorter light–dark cycle (4-hour light and 4-hour dark periods) led to a C3 pattern alone. The substrate moisture and light–dark cycle were inducible factors for switching between C3 and CAM patterns in D. officinale. These results indicate that D. officinale is a facultative CAM plant and the C3 pathway can be induced by controlling the growing environment. Further studies are needed to identify the optimal environmental conditions to enhance the growth of D. officinale.

Growth and physiological responses of creeping bentgrass (Agrostis stolonifera) to elevated carbon dioxide concentrations.

The atmospheric carbon dioxide level has increased and is predicted to continue increasing, which may affect various aspects of plant growth. The objective of this study was to investigate the effects of doubling the carbon dioxide level on the growth and physiological activities of a widely utilized cool-season turfgrass species, creeping bentgrass (Agrostis stolonifera L. ‘Penncross’). ‘Penncross’ plants were established in fritted clay medium and maintained under well-irrigated and well-fertilized conditions in growth chambers. The plants were exposed to either ambient carbon dioxide concentrations (400±10 µmol L−1) or elevated carbon dioxide concentrations (800±10 µmol L−1) for 12 weeks. Plants grown under elevated carbon dioxide displayed a significantly faster growth rate of their lateral stems (stolons) and increased shoot and root dry weight but a reduced specific leaf area compared to those plants at ambient carbon dioxide levels. Fast stolon growth is a highly desirable trait for turfgrass establishment and recovery from physical damage. The root length and surface area were also increased due to the elevated CO2, which may facilitate water uptake and serve critical drought-avoidance roles when irrigation water is limited. Elevated carbon dioxide caused an increase in the leaf net photosynthetic rate but a reduction in the stomatal conductance and transpiration rate, contributing to improved water use efficiency in creeping bentgrass. Efficient water use is especially important for turfgrass plant survival when irrigation water is limited. Our results suggested that cool-season turfgrass species may greatly benefit from increasingly elevated carbon dioxide concentrations via growth promotion and increasing water use efficiency.

Translational research: from pot to plot

Plant molecular biology has been the key driver to elucidate molecular pathways underlying plant growth, development and stress responses during the past decades. Although this has led to a plethora of available data, the translation to crop improvement is lagging behind. Here, we argue that plant scientists should become more involved in converting basic knowledge into applications in crops to sustainably support food security and agriculture. As the translatability from model species to crops is rather poor, this kind of translational research requires diligence and a thorough knowledge of the investigated trait in the crop. In addition, the robustness of a trait depends on the genotype and environmental conditions, demanding a holistic approach, which cannot always be evaluated under growth chamber and greenhouse conditions. To date, the improved resolution of many genome-wide technologies and the emerging expertise in canopy imaging, plant phenotyping and field monitoring make it very timely to move from the pathway specifics to important agronomical realizations, thus from pot to plot. Despite the availability of scientific know-how and expertise, the translation of new traits to applications using a transgene approach is in some regions of the world, such as Europe, seriously hampered by heavy and nontranslucent legislation for biotech crops. Nevertheless, progress in crop improvement will remain highly dependent on our ability to evaluate improved varieties in field conditions. Here, we plead for a network of protected sites for field trials across the different European climates to test improved biotech traits directly in crops.

Improved in vitro regeneration and propagation of Tunceli garlic (Allium tuncelianum L.)

SummaryOver-exploitation of endemic and threatened Tunceli garlic [Allium tuncelianum (Kollman) N. Ozhatay, B. Mathew & Siraneci] for household purposes has threatened the species and requires that a reliable, improved tissue culture protocol be developed for its conservation. Leaf tips, the middle portions of leaves, leaf bases, vertically-sectioned halved or quartered bulbs, horizontally-sectioned upper and lower bulb halves, and root tip explants were cultured on 1.0× Murashige and Skoog (MS) medium containing 1.0, 2.0, 3.0, 4.0, or 5.0 mg l–1 2,4-dichlorophenoxyacetic acid (2,4-D) or 1.0, 2.0, 3.0, 4.0, or 5.0 mg l–1 6-benzylaminopurine (BAP) plus 0.5 mg l–1 α-naphthaleneacetic acid (NAA). The results indicated that root tip explants were most suitable for bulblet regeneration on 1.0× MS medium containing 5.0 mg l–1 BAP plus 0.5 mg l–1 NAA. All other explants failed to regenerate on different concentrations of BAP plus NAA, or on 2,4-D. The regenerated bulblets were acclimatised at 24º ± 1ºC and 80.0% relative humidity under growth chamber conditions, then transferred to pots containing peat-moss in a greenhouse. The results will be important for garlic breeders and researchers.

The occurrence of Fusarium spp. on oat (Avena sativa L.) and susceptibility of seedlings of selected genotypes to infection with Fusarium graminearum Schwabe

<p>The present study was carried out in the years 2010–2012 in the fields of the Strzelce Plant Breeding Company Ltd., belonging to the Plant Breeding and Acclimatization Institute in Radzików, and it included 39 oat genotypes. At the six-week seedling stage, the percentage of plants with root and leaf sheath necrosis symptoms was evaluated. In 2010 the percentage of seedlings with disease symptoms ranged from 6.5% to 25%, in 2011 it ranged from 17% to 34.5%, whereas in 2012 from 10% to 25%. In 2010 the disease index ranged from 1.4 to 5.7, in 2011 from 4.5 to 8.8, while in 2012 it was between 2.0 and 5.4.</p><p>Mycological analysis showed that large numbers of <em>Fusarium </em>spp. colonies were obtained both from the roots and leaf sheaths. Isolates of these fungi accounted for 63.48% of the total fungi isolated from seedlings. Seedlings grown under the conditions of central Poland were damaged by the species <em>F. culmorum</em>, <em>F. avenaceum, </em>and <em>F. solani</em>. The investigation of the susceptibility of 15 oat genotypes to infection with two <em>Fusarium graminearum </em>strains – Tz 56 and Tk 235 – was carried out under growth chamber conditions at a temperature of 22–23°C and relative air humidity of 85%. The <em>F. graminearum </em>strain Tz 56 proved to be the most pathogenic to seedlings of the breeding lines STH 0.9403 and POB 1316/08, for which the disease index was 80.5 and 75.5, respectively. The lowest pathogenicity of the a.m. strain was recorded in the case of the genotype DC 1832/05, for which the disease index was 26.5. The <em>F. graminearum </em>strain Tk 235 proved to be the most pathogenic to the genotypes STH 0.9403 and STH 0.9423, for which the disease index was 70.5 and 70.0, respectively, whereas this strain was least pathogenic to the breeding line DC 2112/05, in the case of which the disease index was 25.5.</p>

Evaluation of Indigenous Fungal Pathogens from Horse Purslane (Trianthema portulacastrum) for Their Relative Virulence and Host Range Assessments to Select a Potential Mycoherbicidal Agent

Periodic surveys were conducted to seek potential indigenous fungal agents for development as mycoherbicides against horse purslane, a major weed of agricultural fields in India. Pathogenic fungal species were isolated and identified from naturally infected horse purslane. The biocontrol potential of these pathogens for horse purslane was evaluated by studying their host range and virulence under growth chamber and greenhouse conditions. Three candidates,Alternaria alternata, Fusarium oxysporum, andPhoma herbarum, were identified as potential candidates for biological control of horse purslane. Preliminary host-range tests and pathogenicity studies, conducted using 45 crop and weed plants belonging to 18 families, demonstrated thatP. herbarumprovided effective weed control and was safe to most of the plant species tested. Further mycoherbicidal application ofP. herbarumas plant spray under field condition caused mortality of horse purslane 60 d after application of the inoculums.Phoma herbarumis a good mycoherbicide candidate against horse purslane.

Isolation and characterization of rhizosphere bacteria for the biocontrol of the damping-off disease of tomatoes in Tunisia

Fluorescent Pseudomonas spp., isolated from tomato and pepper plants rhizosphere soil, was evaluated in vitro as a potential antagonist of fungal pathogens. Pseudomonas strains were tested against the causal agents of tomatoes damping-off (Sclerotinia sclerotiorum), root rot (Fusarium solani), and causal agents of stem canker and leaf blight (Alternaria alternata). For this purpose, dual culture antagonism assays were carried out on 25% tryptic soy agar, King B medium and potato dextrose agar to determine the effect of the strains on mycelial growth of the pathogens. In addition, strains were screened for their ability to produce exoenzymes and siderophores. All the strains significantly inhibited Alternaria alternata, particularly in 25% TSA medium. Antagonistic effect on Sclerotinia sclerotiorum and Fusarium solani was greater on King B medium. Protease was produced by 30% of the strains, but no strain produced cellulase or chitinase. Finally, the selected Pseudomonas strain, Psf5, was evaluated on tomato seedling development and as a potential candidate for controlling tomato damping-off caused by Sclerotinia sclerotiorum, under growth chamber conditions. In vivo studies resulted in significant increases in plant stand as well as in root dry weight. Psf5 was able to establish and survive in tomato plants rhizosphere after 40days following the planting of bacterized seeds.

Origins of unintentional incorporation of gallium in InAlN layers during epitaxial growth, part II: Effects of underlying layers and growth chamber conditions

We systematically study the origins and mechanisms for unintentional incorporation of gallium (Ga) during epitaxial growth of ternary InAlN thin-film layers. The origins of auto-incorporation of Ga have been investigated by using different underlying layers, regrown layers, and growth chamber conditions. It is shown that Ga-containing deposition on a wafer susceptor/carrier and on surrounding surfaces of uncooled parts in a growth chamber can be responsible for Ga in the InAl(Ga)N layers, while a GaN underlying layer below an InAl(Ga)N layer does not contribute to the auto-incorporation of Ga in the InAl(Ga)N layers. Especially, the Ga-containing deposition on the surfaces inside the chamber is believed to be the dominant source of auto-incorporated Ga, possibly due to the high vapor pressure of a liquid phase as a result of eutectic system formation between indium (In) and Ga. The pressure of liquid-phase Ga, pGa=~3.67×10−4Torr, can be significant as compared to precursor partial pressures with pTMAl=3.7×10−4Torr and pTMIn=2.4×10−5Torr. In addition, magnesium (Mg) or magnesium precursor (Cp2Mg) in the growth chamber is shown to promote the auto-incorporation of Ga in the InAl(Ga)N layers.

Use of an Insecticide in Field-Scale Plant—Herbivore Studies: No Side Effects of Synthetic Pyrethrin onBetula pendulaGrowth or Chemistry

Birches are ecologically and economically important trees in forest ecosystems and commonly used in studies of plant—herbivore interactions. Such studies often require manipulation of natural levels of herbivory. In field conditions, this can be executed using insecticides, but such experiments have to assume that the insecticide has no side effects on the study plant. Here we (1) provide results of a test of the effects of synthetic Pyrethrin, deltamethrin, on growth, leaf and litter chemistry and litter decomposition rate of Betula pendula seedlings in controlled growth chamber conditions, and (2) illustrate effectiveness of the insecticide in a field study of the effects of insect herbivory on B. pendula. The field effects, a significant reduction in leaf damage and a corresponding increase in growth, show that we used an effective dose of deltamethrin, while the results of the growth chamber experiment show that the dose did not cause any side effects on B. pendula seedling growth or chemistry. We conclude that Pyrethrin compounds can be safely used for reducing insect-herbivore load on B. pendula in field-scale studies of tree—herbivore interactions.

Identification of pre‐ and posthaustorial resistance to rust (Uromyces viciae‐fabae) in lentil (Lens culinaris) germplasm

AbstractLentil (Lens culinaris Medik.) is an important cool‐season legume that can be severely damaged by rust (Uromyces viciae‐fabae (Pers.) Schröt.) in many parts of the world. In this work, a collection of L. culinaris germplasm accessions was screened under growth chamber conditions for response to U. viciae‐fabae. Several sources of incomplete resistance have been identified, both of hypersensitive and of non‐hypersensitive nature. Incomplete hypersensitive resistance was due to a late‐acting host cell necrosis that resulted in an intermediate infection type (IT). Incomplete non‐hypersensitive resistance was due to a hampered cell penetration not associated with host cell necrosis, reducing the number of haustoria per colony and therefore hindering the growth of the colony and reducing and retarding disease development in spite of a high IT.

Mitigation of Drought Stress Damage by Exogenous Application of a Non-Protein Amino Acid γ– Aminobutyric Acid on Perennial Ryegrass

Perennial ryegrass (Lolium perenne) is an important forage and turfgrass species that is sensitive to drought stress. The objective of this study was to investigate whether gamma aminobutyric acid (GABA) may play a role in promoting drought tolerance in grass species. GABA was exogenously applied as a foliar spray at the rate of 50 or 70 mm to perennial ryegrass ‘CSI’ under well-watered or drought-stressed conditions in a controlled-environment growth chamber. The effect of GABA on the growth physiology, drought stress response, antioxidant activity, and lipid peroxidation of perennial ryegrass exposed to drought stress was measured. GABA-treated perennial ryegrass exposed to drought stress had higher relative water content (RWC), turf quality, and peroxidase activity and lower wilt rating, canopy temperature depression, electrolyte leakage, and lipid peroxidation compared with untreated plants. GABA application had no significant effect on the activity of superoxide dismutase and catalase under well-watered and drought conditions. GABA application at 50 mm was found to be more effective in alleviating drought stress damage in perennial ryegrass. The results from this study suggest that GABA mitigated drought stress damage in perennial ryegrass by maintaining higher RWC and membrane stability.

Evaluation of the effectiveness of biocontrol bacteria against avocado white root rot occurring under commercial greenhouse plant production conditions

Avocado white root rot (WRR) is a disease of significant importance in the Mediterranean area and is caused by the emerging pathogen Rosellinia necatrix. Five Pseudomonas spp. and three Bacillus subtilis strains were selected for this study based on their rhizospheric soil survival, antagonistic and biocontrol activities under experimental conditions. After a single inoculation, Pseudomonas spp. showed higher persistence in rhizospheric soil, and B. subtilis strains were not detected for longer than ten days. In biocontrol assays, B. subtilis CB115 protected the plants against WRR under experimental growth chamber conditions at a similar level to the biocontrol reference strain Pseudomonas chlororaphis PCL1606. The strains B. subtilis CB115, P. chlororaphis CB254 and PCL1606 and Pseudomonas fluorescens CB306 were further selected to explore their biocontrol abilities under commercial greenhouse conditions. B. subtilis CB115 showed consistent biocontrol with protection levels similar to the biocontrol strain P. chlororaphis PCL1606. Although B. subtilis CB115 did not show persistence features, repeated applications by direct soil drenching led to the detection of a stable population that was mainly composed of spores in the avocado rhizospheric soil after 74days. Our results indicate that both P. chlororaphis PCL1606 and B. subtilis CB115 can help control R. necatrix under commercial greenhouse conditions. This is the first study investigating the performance of biocontrol bacteria against avocado WRR under commercial greenhouse settings.

A stable‐isotope methodology for measurement of soil‐applied zinc‐fertilizer recovery in durum wheat (Triticum durum)

AbstractA growth‐chamber study was used to develop a zinc stable‐isotope (67Zn) tracing technique to directly measure the amount of soil‐applied zinc (Zn) granular fertilizer taken up by durum wheat (Triticum durum L.) in four different soil types. The 67Zn‐tracer technique was then applied under field conditions at one site to test the ability of the method to measure the crop recovery of soil‐applied Zn granular fertilizer (67Zn). The technique was developed by comparing plants treated with nil Zn fertilizer to natural‐abundance‐Zn‐coated fertilizer and 67Zn‐coated fertilizer with plant parts analyzed for Zn isotopic composition using inductively coupled plasma–mass spectrometry. Zinc‐fertilizer recovery under growth‐chamber conditions was inversely related to the concentration of labile Zn in soils, with the plants on the most Zn‐deficient soils having the greatest amount of Zn derived from the added fertilizer. Zinc derived from fertilizer ranged from 0.3% (Luvisol) to 0.6% (Solonetz) to 13% (Calcisol) and 18% (Lixisol) for soils with DTPA‐extractable Zn of 3.5–0.21 mg kg–1. Across the experiments, fertilizer recovery was measurable but very low (< 1% of added fertilizer being recovered by durum wheat). The recovery of Zn added to the Luvisol was slightly higher in the field than in the glasshouse (but all < 0.1%). Using this stable‐isotope technique, it was possible to directly assess the supply of soil‐applied Zn fertilizers to crop plants.

Growth Performance and Species Interaction of Festuca rupicola Heuff. and Dianthus carthusianorum L. Subjected to Temperature Increase and Nitrogen Addition

Global processes, such as warming and eutrophication, affect plant-plant interactions. The positive (facilitation) and negative (competition) interactions depend on environmental conditions and species’ characteristics and play a key role in regulating the composition, productivity, structure and dynamics of communities and ecosystems. Recently, biodiversity in former species-rich, semi-dry grasslands has decreased due to the abandonment of traditional land use, under which grass species expanded and dicots declined. The hypothesis that this phenomenon will intensify with warming and eutrophication is tested on the expanding grass Festuca rupicola (F) and the dicot Dianthus carthusianorum (D). A competition experiment were conducted with conditions simulating current average summer temperatures (20 oC during day/10 oC during night) and predicted warmer conditions (22/15 oC) in growth-chambers, both under nutrient-poor (simulated natural habitat conditions) and nutrient-rich conditions (simulated annual N deposition). The plants were placed in pots with constant densities (five individuals per pot) but under varying mixture ratio (F5, D5, D4/F1, D3/F2, D2/F3, D1/F4). The measured plant parameters (biomass, leaf number and leaf length) and the interactions varied species-dependent: under nutrient poor conditions the performance of both species was low and the interactions were weak. After nutrient addition, growth parameters of both species developed between twofold and tenfold better and the species interacted more markedly. Under both nutrient levels, D. carthusianorum was significantly promoted by warming. But, warmed conditions did not affect the biomass and leaf length of F. rupicola, whereas leaf number significantly decreased under both nutrient levels. As such, the dicot became competed against and the grass facilitated under current conditions, while under warmed conditions the competitive ability of the grass declined and that of the dicot increased, indicating that interactions between both species reverses with warming climate. This suggests, that under predicted climate conditions, the expanding grass will decline, while the dicot will be promoted, which can have positive effects on biodiversity of semi-dry grasslands.

Trehalose Accumulation in Wheat Plant Promotes Sucrose and Starch Biosynthesis

Seeds of Triticum aestivum L. (cv. Sakha 93) were sown in pots and grown under controlled conditions in growth chamber. The plants were irrigated with half strength of Hoaglad solution without or with 10 or 30 µM validamycin A, a potent inhibitor of trehalase. Plants were collected at three different stages of growth (17, 24 and 31 DAP). Validamycin A decreased the activity of trehalase which leads to the accumulation of trehalose in shoot and root of wheat plants. Raising trehalose level in the plant tissues was accompanied by increase in the sucrose content and starch content of the shoot. The increased contents in sucrose and starch were mainly attributed to the increased levels of trehalose. The effect of trehalose on the sucrose degrading enzymes (alkaline and acid invertases and sucrose synthase) showed stimulation of alkaline invertase activity and inhibition of acid invertase and sucrose synthase. The opposite behavior of sucrose degrading enzymes suggests a regulation mechanism controlling the sucrose pool.

Bazı pamuk çeşitlerinin Verticillum dahliae Kleb’in iki farklı patotipine karşı duyarlılıklarının belirlenmesi

Cotton is one of the most important agricultural crops providing raw material for many industrial sectors of our country. Also, Verticillium wilt (Verticillium dahliae Kleb.) is one of the important factors limiting production in cotton growing areas. There is no effective control method for Verticillium wilt disease, but the most effective control method against the disease is to use resistant cultivars. The experiment was conducted to determine susceptible of some cotton genotypes growing prevalent in Turkey against defoliating (T1) and nondefoliating (SS4) pathotypes of V. dahliae in the growth chamber conditions. Randomized plot design with 5 replications was set up in the experiment. Total 21 genotypes including two control cultivars (Giza 45,a resistant genotype and Albani 61-72, a susceptible genotype) were inoculated with conidial suspension method into crown. According to variance analysis (ANOVA) exhibited significant differences (P<0.05) among genotypes in terms of susceptibility against verticillium wilt. From the data, PYDV6 isolate (defoliating pathotype-T1) had higher disease incidence than Vd11 isolate (nondefoliating pathotype-SS4). Using PYDV6 and Vd11 isolates of V. dahliae, resistant control Giza 45 (0.39-0.69) had the lowest disease incidence, and followed by Julia (0.62), St-373 (0.63), Fibermax 819 (0.64) and Gloria (0.66) genotypes. On the other hand, susceptible control Albania 61-72 showed the highest disease incidence (2.00-3.02).

Water-Deficit Inducible Expression of a Cytokinin Biosynthetic Gene IPT Improves Drought Tolerance in Cotton

Water-deficit stress is a major environmental factor that limits agricultural productivity worldwide. Recent episodes of extreme drought have severely affected cotton production in the Southwestern USA. There is a pressing need to develop cotton varieties with improved tolerance to water-deficit stress for sustainable production in water-limited regions. One approach to engineer drought tolerance is by delaying drought-induced senescence via up-regulation of cytokinin biosynthesis. The isopentenyltransferase gene (IPT) that encodes a rate limiting enzyme in cytokinin biosynthesis, under the control of a water-deficit responsive and maturation specific promoter PSARK was introduced into cotton and the performance of the PSARK::IPT transgenic cotton plants was analyzed in the greenhouse and growth chamber conditions. The data indicate that PSARK::IPT-transgenic cotton plants displayed delayed senescence under water deficit conditions in the greenhouse. These plants produced more root and shoot biomass, dropped fewer flowers, maintained higher chlorophyll content, and higher photosynthetic rates under reduced irrigation conditions in comparison to wild-type and segregated non-transgenic lines. Furthermore, PSARK::IPT-transgenic cotton plants grown in growth chamber condition also displayed greater drought tolerance. These results indicate that water-deficit induced expression of an isopentenyltransferase gene in cotton could significantly improve drought tolerance.