Field-grown Wheat Plants Research Articles

Fusarium pseudograminearum biomass and toxin accumulation in wheat tissues with and without Fusarium crown rot symptoms.

Fusarium crown rot (FCR) is an important and devastating disease of wheat (Triticum aestivum) caused by the fungus Fusarium pseudograminearum and related pathogens. Using two distinct susceptible cultivars, we investigated the isolation frequencies of F. pseudograminearum and quantified its biomass accumulation and the levels of the associated toxins deoxynivalenol (DON) and DON-3-glucoside (D3G) in inoculated field-grown wheat plants. We detected F. pseudograminearum in stem, peduncle, rachis, and husk tissues, but not in grains, whereas DON and D3G accumulated in stem, rachis, husk, and grain tissues. Disease severity was positively correlated with the frequency of pathogen isolation, F. pseudograminearum biomass, and mycotoxin levels. The amount of F. pseudograminearum biomass and mycotoxin contents in asymptomatic tissue of diseased plants were associated with the distance of the tissue from the diseased internode and the disease severity of the plant. Thus, apparently healthy tissue may harbor F. pseudograminearum and contain associated mycotoxins. This research helps clarify the relationship between F. pseudograminearum occurrence, F. pseudograminearum biomass, and mycotoxin accumulation in tissues of susceptible wheat cultivars with or without disease symptoms, providing information that can lead to more effective control measures.

Seed Transmission of Wheat Streak Mosaic Virus and Triticum Mosaic Virus in Differentially Resistant Wheat Cultivars.

Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are important viral pathogens of wheat in the Great Plains. These viruses individually or in mixed infections with High Plains wheat mosaic virus cause a devastating wheat streak mosaic (WSM) disease. Although seed transmission of WSMV has been studied, no information is currently available on that of TriMV. Furthermore, no study has explored the implications of mixed infections of WSMV and TriMV on seed transmission of one or both viruses. To study both aspects, seeds from differentially resistant field-grown wheat plants (cv. TAM 304 (susceptible), Joe (WSMV resistant, Wsm2 gene), and Breakthrough (BT) (WSMV and TriMV resistant, Wsm1 gene)) showing characteristic WSM symptoms were collected and analyzed to quantify both viruses using qRT-PCR. The percentage of seeds tested positive for WSMV or TriMV individually and in mixed infection varied with cultivar and virus combinations; 13% of TAM 304 seeds tested positive for WSMV, followed by 8% of BT and 4% of Joe seeds. Similarly, TriMV was detected in 12% of BT seeds, followed by 11% of TAM 304 and 8% of Joe seeds. Lastly, mixed infection was detected in 7% of TAM 304 seeds, followed by 4% in BT, and 2% in Joe. Dissection of field-collected seeds into three parts, embryo, endosperm, and seed coat, revealed both WSMV and TriMV accumulated only in the seed coat. Consistent with seeds, percent infection of WSMV or TriMV in the plants that emerged from infected seeds in each treatment varied with cultivar and virus combinations (WSMV: BT 3%; Joe 2%; TAM 304 9%; TriMV: BT 7%; Joe 8%; and TAM 304 10%). Plants infected with mixed viruses showed more pronounced WSM symptoms compared to individual infections. However, both viruses were present only in a few plants (BT: 2%, Joe: 1%, and TAM 304: 4%). Taken together, this study showed that TriMV was transmitted vertically at a higher frequency than WSMV in resistant cultivars, and the seed transmission of TriMV with WSMV increased the virulence of both pathogens (measured via WSM symptom severity) in the emerged plants. Furthermore, Wsm1 and Wsm2 genes considerably reduced WSMV transmission via infected seeds. However, no such effects were observed on TriMV, especially in progeny plants. These results reiterated the importance of planting clean seeds and highlighted the immediate need to identify/develop new sources of TriMV resistance to effectively manage the recurring WSM epidemic.

In situ measurements of winter wheat diurnal changes in photosynthesis and environmental factors reveal new insight into photosynthesis improvement by super-high-yield cultivation

In past 30 years, the wheat yield per unit area of China has increased by 79%. The super-high-yield (SH) cultivation played an important role in improving the wheat photosynthesis and yield. In order to find the ecophysiological mechanism underneath the high photosynthesis of SH cultivation, in situ diurnal changes in the photosynthetic gas exchange and chlorophyll (Chl) a fluorescence of field-grown wheat plants during the grain-filling stage and environmental factors were investigated. During the late grain-filling stage at 24 days after anthesis (DAA), the diurnal changes in net CO2 assimilation rate were higher under SH treatment than under high-yield (H) treatment. From 8 to 24 DAA, the actual quantum yield of photosystem II (PSII) electron transport in the light-adapted state (ΦPSII) in the flag leaves at noon under SH treatment were significantly higher than those under H treatment. The leaf temperature, soil temperature and soil moisture were better suited for higher rates of leaf photosynthesis under SH treatment than those under H treatment at noon. Such diurnal changes in environmental factors in wheat fields could be one of the mechanisms for the higher biomass and yield under SH cultivation than those under H cultivation. ΦPSII and CO2 exchange rate in wheat flag leaves under SH and H treatments had a linear correlation which could provide new insight to evaluate the wheat photosynthesis performance under different conditions.

Culture-based Methods for Studying the Bacterial Root Microbiome of Wheat.

Beneficial plant-microbe interactions are important and desirable for sustainable intensification of agriculture. Here, we describe methods to isolate microbes from the roots of field-grown wheat plants. This includes the rhizosphere and rhizoplane soil, as well as the root endosphere. We also describe a method to test for endosphere competence of putative endophytes.

Recovering Wind-Induced Plant Motion in Dense Field Environments via Deep Learning and Multiple Object Tracking.

Understanding the relationships between local environmental conditions and plant structure and function is critical for both fundamental science and for improving the performance of crops in field settings. Wind-induced plant motion is important in most agricultural systems, yet the complexity of the field environment means that it remained understudied. Despite the ready availability of image sequences showing plant motion, the cultivation of crop plants in dense field stands makes it difficult to detect features and characterize their general movement traits. Here, we present a robust method for characterizing motion in field-grown wheat plants (Triticum aestivum) from time-ordered sequences of red, green, and blue images. A series of crops and augmentations was applied to a dataset of 290 collected and annotated images of ear tips to increase variation and resolution when training a convolutional neural network. This approach enables wheat ears to be detected in the field without the need for camera calibration or a fixed imaging position. Videos of wheat plants moving in the wind were also collected and split into their component frames. Ear tips were detected using the trained network, then tracked between frames using a probabilistic tracking algorithm to approximate movement. These data can be used to characterize key movement traits, such as periodicity, and obtain more detailed static plant properties to assess plant structure and function in the field. Automated data extraction may be possible for informing lodging models, breeding programs, and linking movement properties to canopy light distributions and dynamic light fluctuation.

Development of PSP1, a Biostimulant Based on the Elicitor AsES for Disease Management in Monocot and Dicot Crops.

In this work, we present a novel biostimulant for sustainable crop disease management, PSP1, based on the plant defense-elicitor AsES, an extracellular protease produced by the strawberry fungal pathogen Acremonium strictum. Fungal fermentation conditions and downstream processing were determined to maximize extracellular protein production, product stability and a high plant defense-eliciting activity, as monitored by anthracnose resistance in supernatant-treated strawberry plants subsequently infected with a virulent strain of Colletotrichum acutatum. Fermentation batches were shown to reduce anthracnose development by 30–60% as compared to infected non-treated plants. Product formulation was shown to be stable for 6 months when stored at temperatures up to 45°C and toxicological tests showed that PSP1 was harmless to beneficial organisms and non-toxic to mammalian species at concentrations 50 times higher than those used in plant experiments. Furthermore, disease protection studies using dilutions of PSP1 indicated that there is a minimum threshold protease activity needed to induce pathogen defense in strawberry and that this induction effect is dose-independent. A significant characteristic of PSP1 is its broad-range protection against different diseases in various crop species. In soybean, PSP1 reduced the symptomatology by 70% of Corynespora cassiicola, etiological agent of the target spot. This protection effect was similar to the commercial inducer BION 500 WG based on BTH, and both products were shown to induce an oxidative burst and up-regulated PR1-gene expression in soybean. Furthermore, a double PSP1-treatment on greenhouse-grown sugarcane plants provided protection against bacterial red stripe disease caused by Acidovorax avenae and a double foliar application of PSP1 on field-grown wheat plants significantly increased resistance against Fusarium graminearum, causal agent of head blight disease, manifested mainly in an increased seed germination rate. In summary, these disease protection studies demonstrated an effective control against both bacterial and fungal pathogens in both monocot and dicot crop species, which together with its low production cost, effectiveness at low concentrations, long shelf-life, tolerance to high temperatures, harmlessness to non-target organisms and simple handling and application, make PSP1 a very promising candidate for effective and sustainable disease management in many crop species.

Photoinhibition and photoprotection in senescent leaves of field-grown wheat plants

Photosynthesis, photosystem II (PSII) photochemistry, photoinhibition and the xanthophyll cycle in the senescent flag leaves of wheat ( Triticum aestivum L.) plants grown in the field were investigated. Compared to the non-senescent leaves, photosynthetic capacity was significantly reduced in senescent flag leaves. The light intensity at which photosynthesis was saturated also declined significantly. The light response curves of PSII photochemistry indicate that a down-regulation of PSII photochemistry occurred in senescent leaves in particular at high light. The maximal efficiency of PSII photochemistry in senescent flag leaves decreased slightly when measured at predawn but substantially at midday, suggesting that PSII function was largely maintained and photoinhibition occurred in senescent leaves when exposed to high light. At midday, PSII efficiency, photochemical quenching and the efficiency of excitation capture by open PSII centers decreased considerably, while non-photochemical quenching increased significantly. Moreover, compared with the values at early morning, a greater decrease in CO 2 assimilation rate was observed at midday in senescent leaves than in control leaves. The levels of antheraxanthin and zeaxanthin via the de-epoxidation of violaxanthin increased in senescent flag leaves from predawn to midday. An increase in the xanthophyll cycle pigments relative to chlorophyll was observed in senescent flag leaves. The results suggest that the xanthophyll cycle was activated in senescent leaves due to the decrease in CO 2 assimilation capacity and the light intensity for saturation of photosynthesis and that the enhanced formation of antheraxanthin and zeaxanthin at high light may play an important role in the dissipation of excess light energy and help to protect photosynthetic apparatus from photodamage. Our results suggest that the well-known function of the xanthophyll cycle to safely dissipate excess excitation energy is also important for maintaining photosynthetic function during leaf senescence.

The enclosed and exposed part of the peduncle of wheat (Triticum aestivum) – spatial separation of fructan storage

• Although fructan accumulation is reported in photosynthetically active organs, the long-term storage of fructan mainly occurs in more heterotrophic tissues. Significant amounts of fructan are stored in the internodes during grain filling of wheat (Triticum aestivum). The uppermost internode (peduncle) of wheat consists of a lower unexposed (i.e. enclosed by the flag leaf sheath and thus heterotrophic part, Pl ) and an upper exposed autotrophic part (Pu ). • Diurnal and long-term changes of fructan and sucrose (the precursor of fructan synthesis) contents were studied in Pl and Pu of potted wheat plants. • At mid grain-filling the sucrose concentration in Pu increased almost threefold during the light period and decreased in the following night. Diurnal changes in sucrose concentration were much less expressed in Pl . Fructan concentration was significantly higher in Pl than in Pu and did not change during the light period. • In another experiment, field grown wheat plants were sampled at regular intervals between 5d before anthesis and grain maturity. At the time of maximum fructan content, 88% of the fructans in the total peduncle were stored in the heterotrophic Pl . Within Pl , fructan accumulation started in the older segments. The reason for the sharp separation of fructan storage between Pl and Pu remains unclear.

Photosynthesis and chlorophyll afluorescence during flag leaf senescence of field-grown wheat plants

The characteristics of photosynthetic gas exchange, chlorophyll a fluorescence, and xanthophyll cycle pigments during flag leaf senescence of field-grown wheat plants were investigated. With senescence progressing, the light-saturated net CO 2 assimilation rate expressed either on a basis of leaf area or chlorophyll decreased significantly. The apparent quantum yield of net photosynthesis decreased when expressed on a leaf area basis but increased when expressed on a chlorophyll basis. The maximal efficiency of PSII photochemistry decreased very little while actual PSII efficiency, photochemical quenching, and the efficiency of excitation capture by open PSII centers decreased considerably. At the same time, non-photochemical quenching increased significantly. A substantial decrease in the contents of violaxanthin and zeaxanthin, but a slight decrease in the content of antheraxanthin were observed. However, the de-epoxidation status of the xanthophyll cycle was positively correlated with progressive senescence. This increase was due mainly to a smaller decrease in zeaxanthin than in violaxanthin. Our results suggest that PSII apparatus remained functional, but a down-regulation of PSII occurred under the steady state of photosynthesis in senescent flag leaves. Such a down-regulation was associated with the closure of PSII centers and an enhanced xanthophyll cycle-related thermal dissipation in the PSII antennae.

Senescence and protein degradation in leaf segments of young winter wheat: influence of leaf age

Leaf senescence in intact wheat plants can be strongly influenced by altered source/sink relations. Interactions with other plant parts are no longer possible in detached leaves and therefore differences in their senescence behaviour reflect the physiological status of the leaf before cutting. The net degradation of chlorophylls and of selected enzyme proteins (detected by SDS-PAGE and immunoblotting) was delayed in detached young leaves as compared to senescing or mature leaves excised from the same field-grown wheat plants. The physiological leaf age was therefore decisive for the velocity of artificial senescence. Net degradation rates of the enzymes investigated varied in detached leaves. The protein quantities of plastidial glutamine synthetase, phosphoribulokinase and phosphoglycolate phosphatase decreased more rapidly than those of ferredoxin-dependent glutamate synthase and nitrite reductase. Differences were also detected between two enzymes involved in the same metabolic pathway (photorespiratory carbon cycle) but located in different subcellular compartments: the plastidial enzyme phosphoglycolate phosphatase was lost more rapidly than glycolate oxidase (peroxisomal enzyme).

Influence of climatic and nutritional factors on yeast population dynamics in the phyllosphere of wheat

The role of saprophytic phyllosphere yeasts in removing aphid honeydew and other nutrients from wheat leaves was evaluated in growth cabinet experiments at different temperatures and relative humidities. Population densities of both pink and white yeasts (Sporobolomyces roseus and Cryptococcus laurentii, respectively) increased between 12 and 24°C, if nutrients were supplied. White yeast numbers increased rapidly at a constant vapor pressure deficit (VPD) of 0.10 kPa and alternating VPDs of 0.10 and 0.61 kPa (each 12 hours per day) but decreased at a constant VPD of 0.61 kPa. In growth cabinet experiments with aphids on wheat plants, the amount of aphid honeydew on the leaves was lower when yeast population densities were high. Addition of amino acids to leaves with honeydew had no effect on yeast population density or the rate of honeydew consumption. This indicated that low concentrations of amino acids in aphid honeydew are not a limiting factor for honeydew consumption by the yeasts. The naturally occurring saprophytes efficiently removed fructose, sucrose, and melezitose from the phyllosphere of field-grown wheat plants.

Nucleoside/nucleotide pools in wheat leaves naturally infected with powdery mildew. II. Effects of leaf age and intensity of infection

The effects of Erysiphe graminis infection on nucleoside/nucleotide pools in the different leaves of field grown wheat plants were determined. Plants protected by fungicides were used as controls. In non-protected plants infection intensity markedly increased with leaf age; some of the nucleotide pools were unaffected by any level of infection while others varied according to the degree of infection. Thus pools of total adenine nucleotides (as well as energy charge), adenosine and UDP-glucose were very similar in both infected and control plants only declining with leaf senescence. In contrast levels of UDP-N-acetylglucosamine, the precursor for fungal chitin synthesis, and uridine content, both low in uninfected control plants, increased as the level of infection increased. This latter result suggests that the fungus exploits host carbohydrate metabolism for precursor for hyphal wall synthesis. The observation of high uridine pools correlating with the degree of infection is indicative of recycling of the UDP moiety of UDP-N-acetylglucosamine during chitin synthesis.

Effect of Spraying Crude Aqueous Extract of the Fruits of Lantana camara L on wheat plants

Crude aqueous extract of the fruits of Lantana camara was sprayed on the field grown wheat plants at different concentrations, viz., 25%, 50%, 100%. Data were collected on the morphological changes of the plants together with grain yield. It was evident that due to spray, more or less all characters of the treated plants showed better result over untreated control. The ear emergence was about 10-15 days earlier in the treated plants. The total yield was enhanced by about 19% over control due to the spraying of 100% extract. Besides different nutritional components present in the spraying material i. e.. in the crude extract of the fruits of Lantana camara, gibberellin As-like substance was also detected from this sample.

Ameliorating effect of urea spray on wheat Triticum aestivum plants exposed to sulphur dioxide

Field-grown wheat plants were exposed to 1 ppm SO 2 for 2h daily for 80 days between the ages of 20 and 100 days of their life cycle and, at the ages of 41, 71 and 101 days, a 3% aqueous solution of urea was intermittently sprayed on the plant foliage. Plant samples were collected periodically and their morphological characteristics, biomass and productivity, chlorophyll content, nitrogen and sulphur content and grain characteristics were determined. It has been observed that urea spray has an ameliorating effect on various changes caused by the pollutant. This suggests that the vegetation damage and crop-yield reduction by SO 2 can be modified or reduced to a certain extent by increasing resistance in plants through nitrogen supply.

Total hemicelluloses from wheat at different stages of growth

The changes in total hemicellulose composition of leaf and stem tissues of field-grown wheat plants have been examined. In each plant tissue the percentage of xylose in the total hemicellulose increases with increasing plant maturity, that of galactose varies little and those of L-arabinose, D-glucose, and uronic acid decrease. There is a markedly higher proportion of D-glucopyranuronosyl than of 4- O-methyl- D-glucopyranuronosyl residues in leaf and stem tissues at all stages of maturity. The ratio of β(1 → 3) to β(1 → 4) linkages in the β-glucans, and the DP of these β-glucans decrease concommitantly with tissue maturity.