Large Starch Grains Research Articles

Kinetin and spermine mediated induction of salt tolerance in wheat plants: Leaf area, photosynthesis and chloroplast ultrastructure of flag leaf at ear emergence

The antagonistic effects of kinetin and spermine on stress imposed by seawater on leaf area, pigment, Hill reaction, 14CO2 fixation and chloroplast ultrastructure of wheat flag leaf were investigated. Irrigation of wheat plants by seawater at 25% caused marked decrease in leaf area, pigment content, Hill activity and photosynthetic efficiency of wheat flag leaf at ear emergence. Grain priming with kinetin, spermine or their interaction alleviated the adverse effect of seawater stress by stimulating leaf area expansion, pigment production as well as photosynthetic activity. From transmission electron microscopy micrographs, a continuous “end-to-end” distribution of regular (oval or elliptical) chloroplasts around the cell's periphery was observed in flag leaf mesophyll cells of control wheat plants. Conversely for seawater-stressed plants, the irregular spherical chloroplasts appeared “bulbous” and discrete, the cells also displayed extensive but thin peripheral cytoplasmic regions devoid of chloroplasts. Grain presoaking in 0.1 mM kinetin caused the chloroplast of stressed wheat plants to be more regular, with organized membrane system, large starch grains and projections in the form of tails. Furthermore, ultrastructure analysis cleared that grain priming with spermine, either alone or in combination with kinetin, caused the chloroplast in flag leaf mesophyll cells of stressed wheat plants to be more regular in shape with more starch grains. The changes in pigment content and photosynthetic activity of flag leaf appeared to depend mainly on chloroplast ultrastructure and its numbers, showing a positive correlation between chloroplasts number and pigment content.

Morphology, histochemistry, and ultrastructure of foliar mucilage-producing trichomes of Harpagophytum procumbens (Pedaliaceae)

The morphology, histochemistry, and ultrastructure of foliar mucilage-producing trichomes of Harpagophytum procumbens are investigated using a combination of light and electron microscopy. The leaves of H. procumbens bear short and long glandular trichomes comprising 1 or 2 basal epidermal cells, a stalk of 1-3 cells, a short neck cell, and a head of 2-5 cells. These trichomes are distributed on both leaf sides with a greater abundance on the abaxial side. Both types of trichomes secrete copious amounts of secretion as droplets onto the leaf surface, and the release occurs through micropores in the head cuticles. The secreted material is mainly constituted of mucilaginous polysaccharides, in addition to phenolic compounds and total lipids. The stalk surfaces of long trichomes are densely covered by numerous micropapillae helping the mucilage droplets to slide onto the leaf surface. The short and long trichomes have a similar ultrastructure: the secretory head cells are cytoplasmically dense due to the abundance of mitochondria, ribosomes, small vacuoles, plastids, Golgi bodies, and elements of endoplasmic reticulum. Golgi-derived vesicles are developed in the head cells, and each plastid contains large starch grains.

Structural Analysis of Reproductive Development in Pistillate Flowers of <i>Laurus nobilis</i> L.

In Laurus nobilis L. (Lauraceae) the development of female flowers (pistillate), between floral meristem differentiation and fruit formation was inspected through histological sections and SEM techniques. The reproductive development of the female flower starts when the apical meristem converts into a floral meristem. Four tepals, four stamens and a carpel are developed from the floral meristem in turn. Filaments emerge however, anther development is arrested, and stamens become nonfunctional staminodes. The stigma is of the dry type. The solid style being short and thick consists of an epidermis, a cortex, a vascular bundle and a core of transmitting tissue composed of elongated cells. In the style a funnel-shaped zone extending from within the stigma to the stylar base is visible. The presence of high amounts of sugars and lipid substances within and around the vascular bundles are identified by histochemical techniques. The ovary contains an anatropous, bitegmic and crassinucellate ovule. Starch grains are present throughout the development of nucellar tissue. The chalazal region of nuclear endosperm forms a short haustorium. Endosperm does not exist in mature seed; the cotyledons are piled with considerably large starch grains. Idioblasts are observed in all stages of development.

Seed coat ultrastructure of hard-seeded and soft-seeded varieties of Vicia sativa

The mature seed coat structure in hard-seeded and soft-seeded varieties of Vicia sativa L. was examined by scanning and transmission electron microscopy to investigate differentiation in cytological and morphological features between these varieties. The outer layer of the seed coats was composed of macrosclereid (Malpighian) cells in the hard-seeded and soft-seeded varieties of Vicia sativa. The walls of the macrosclereid cells were thickened, and the cell vacuoles were filled with tannin. The cytoplasm of the macrosclereids contained small- and large-sized vacuoles and ribosomes, mitochondria, and endoplasmic reticulum. Under this layer there was a hypodermal layer composed of osteosclereids separated by large intercellular spaces. The bottom layer consisted of parenchyma cells. Thin-walled parenchyma cells were filled with amyloplasts that contained large starch grains, protein bodies, and a few organelles. Seed size and colour are important characteristics for distinguishing between hard-seeded and soft-seeded varieties. The hard seeds of Vicia sativa are smaller than the soft seeds.

Structure and immunocytochemical localization of photosynthetic enzymes in the lamina joint and sheath pulvinus of the C4 grass Arundinella hirta

The C(4) grass Arundinella hirta exhibits a unique C(4) anatomy, with isolated Kranz cells (distinctive cells) and C(4)-type expression of photosynthetic enzymes in the leaf sheath and stem as well as in the leaf blade. The border zones between these organs are pale green. Those between the leaf blade and sheath and between the sheath and stem are called the lamina joint and sheath pulvinus, respectively, and are involved in gravity sensing. We investigated the structure and localization of C(3) and C(4) photosynthetic enzymes in these tissues. In both zones the epidermis lacked stomata. The inner tissue was composed of parenchyma cells and vascular bundles. The parenchyma cells were densely packed with small intercellular spaces and contained granal chloroplasts with large starch grains. No C(4)-type cellular differentiation was recognized. Western blot analysis showed that the lamina joint and pulvinus accumulated substantial amounts of phosphoenolpyruvate carboxylase (PEPC), pyruvate,Pi dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco). Immunogold electron microscopy revealed PEPC in the cytosol and both PPDK and rubisco in the chloroplasts of parenchyma cells, suggesting the occurrence of C(3) and C(4) enzymes within a single type of chlorenchyma cell. These data indicate that the lamina joint and pulvinus have unique expression patterns of C(3) and C(4) enzymes, unlike those in C(4)-type anatomy.

Genotype-dependent efficiency of endosperm development in culture of selected cereals: histological and ultrastructural studies

The paper reports studies, including histological and ultrastructural analyses, of in vitro cell proliferation and development of immature endosperm tissue isolated from caryopses of Triticum aestivum, Triticum durum, and Triticosecale plants. Endosperm isolated at 7-10 days post-anthesis developed well on MS medium supplemented with auxins and/or cytokinins. The efficiency of endosperm response was highly genotype-dependent and best in two winter cultivars of hexaploid species. The pathways of development and proliferation were very similar among the selected species and cultivars. Histological and scanning electron microscope (SEM) analysis revealed that only the part of the endosperm not touching the medium surface continued growth and development, resulting in swelling. The central part of swollen regions was composed mainly of cells containing many large starch grains. The peripheric parts of developed endosperm consisted of highly vacuolated cells and small cells with dense cytoplasm. SEM showed that cells from the swollen region were covered partially with a membraneous structure. Transmission electron microscope studies of cells from the outer part of the developing region showed features typical for cell activity connected with lipid metabolism.

The structure of elaiophores in Oncidium cheirophorum Rchb.f. and Ornithocephalus kruegeri Rchb.f. (Orchidaceae)

The shining appearance of the flowers of <i>Oncidium cheirophorum</i> and <i>Ornithocephalus kruegeri</i> results from the presence of lipids on the flower surface. The lipids are produced by elaiophores - secretory structures situated symmetrically at the base of the labellum or upon the callus. In <i>O. cheirophorum</i>, the elaiophores are epithelial type. They consist of one layer of cuboidal secretory cells and subsecretory parenchyma. The thick cuticle covering the outer, tangential wall of epithelial cells becomes distended and wrinkled as secreted oil accumulates beneath its surface. Oil secretion begins at the bud stage and lasts till the end of anthesis, that is 22 days, on average. Pollination does not influence oil production. In <i>O. kruegeri</i>, trichomatous elaiophores are situated on the central part of the callus. Unicellular trichomes project from the epidermis cells. Their outer walls are covered by a thin cuticle. In the dense cytoplasm of the trichomes, small plastids with few starch grains occur, whereas subsecretory parenchyma cells contain amyloplasts with large starch grains and raphides. The oil is already produced at the bud stage, about one week before flower opening, and lasts till the end of anthesis.

Chilling-induced ultrastructural changes to mesophyll cells of Arabidopsis grown under short days are almost completely reversible by plant re-warming

Exposure of plants to chilling (low temperatures above freezing) limits growth and development in all environments outside the lowest latitudes. Cell ultrastructure and morphometric studies may allow associations to be made between chilling-induced changes at the ultrastructural level, molecular events and their physiological consequences. We examined changes in the shape, size and membrane organization of the organelles of mesophyll cells in Arabidopsis thaliana (Col 0), a cold-resistant species, after subjecting 6-week-old plants grown at normal growth temperatures to chilling (2.5-4°C; 14-h dark/10-h light cycle) for 6, 24 and 72 h and after a re-warming period of 50 h. No ultrastructural differences were seen in the first 6 h of chilling but after 24 h we observed swollen and rounded chloroplasts with larger starch grains and dilated thylakoids compared to control plants. By 72 h, chilling had resulted in a large accumulation of starch in chloroplasts, an apparent crowding of the cytosol and a lower abundance of peripheral reticulum than in the controls. The average area per chloroplast in cell sections increased after 72-h chilling while the number of chloroplasts remained the same. Ring-shaped and other morphologically aberrant mitochondria were present in significantly higher abundance in plants given 72 h chilling than in the controls. Plant re-warming for 50 h reduced chloroplast size to those of the controls and returned mitochondria to standard morphology, but peripheral reticulum remained less abundant than in plants never given a cold treatment. The near full return to normal ultrastructure upon plant re-warming indicates that the morphological changes may be part of acclimation to cold.

Morphology, developmental ultrastructure and ultracytochemistry of staminal hairs in Bulbine inflata (Asphodelaceae) in relation to function

Results of light and electron microscopy and preliminary ultracytochemical studies of the staminal hairs of Bulbine inflata at different stages of development are reported here. The staminal filaments are covered with yellow, unicellular, linear, erecto-patent hairs. These staminal hairs arise directly as single cell outgrowths from epidermal cells of the filament. The surface of each hair is patterned with helical wall thickenings in an anticlockwise direction. This wall is covered by a thick folded cuticle, and formed of a loosely fibrillar cellulose layer. The hair cell possesses a cytoplasm rich in organelles. Especially ribosomes are abundant. Plastids contain large starch grains and peripheral lipid droplets. The smooth endoplasmic reticulum cisternae (SER) encircle the plastids and mitochondria; it is extended in the cytoplasm along the hair length. These hairs have functions in flower pollination attracting pollinators visually, secreting specific substances, providing increased surface area, protecting the filaments and being involved in their movement and vibration.

English

  This study was performed to investigate the effects of water and light intensity on the growth and anatomical aspects (that is, stomatal density and chloroplasts ultrastructure) of cork oak (Quercus suber L.) seedlings from acorns collected from Tabarka (Northern Tunisia). Seedlings, four-month after germination, were planted at 3 L pots with artificial soil and were cultivated for 5 months at the greenhouse. The experiments were divided into two treatments: Water stress (well-watered: 25 to 35% of water contents, moderate drought stress: 15 to 20%, and severe drought stress: 7 to 10%) and light intensity stress (full sunlight: 100% of full sunlight, 1,200μmol m-2 s-1; moderate sunlight: 65 to 70% of full sunlight, 800 μmol m-2 s-1; low sunlight: 20 to 25% of full sunlight, 300 μmol m-2 s-1; and extremely low sunlight: 3 to 4% of full sunlight, 40 μmol m-2 s-1). Growth varied among water stress, but this variation was typically smaller than light intensity. Seedlings grown under well-watered treatment showed the increased above ground growth as compared with deep root growth of severe drought stress. In contrast, seedlings grown under severe drought stress increased in root growth than in the above ground part. Q. suber seedlings grown under the shade-exposed low light intensity indicated adaptation such as the increased leaf area and increased specific leaf area than the leaves grown in full sunlight. In different light intensity treatments, the highest specific leaf area indicated at the extremely low light. Seedlings grown under severe drought stress increased in root growth. The palisade parenchyma chloroplasts of well-watered treatment were well developed: their shape was regular, chloroplast envelope membranes and grana were distinct, and an abundance of starch grains and a scarce of plastoglobuli was also visible inside in the chloroplasts. In severe drought stress, the ultrastructural features of the abaxial leaf surface were folded and shrunken, and was observed in a higher stomatal frequency, the thicker palisade and spongy parenchyma (containing three layers of palisade parenchyma). The severe drought stress indicated a swelling and disruption of the thylakoid, large starch grains, increased plastoglobuli, and accumulation of the reactive oxygen species (ROS), hydrogen peroxide (H2O2). The main features in the chloroplasts ultrastructure caused by the extremely low sunlight revealed not only the higher grana stacks and the broader grana, but also the higher stacking degree of thylakoids. Furthermore, seedlings grown under the extremely low sunlight showed no starch or exhibited only little starch in the chloroplasts, occupied the intracellular space in all organelles, and presented numerous small vacuoles and lipid droplets in the cytoplasm of these cells as compared with the well-watered and the severe drought stress. These results suggested that Q. suber has a well-developed mechanism to drought compared with shade stress by structural adaptations such as a deeper root system, a smaller reduction in stomatal density, and a smaller leaf area.   Key words: Water stress, light intensity stress, growth, stomatal density, palisade parenchyma, starch grains, plastoglobuli, Quercus suber L.

Morphological and proteomic analyses of sugar beet cultures and identifying putative markers for cell differentiation

Normal (N), habituated nonorganogenic (HNO), and tumour (T) sugar beet cell lines were analysed in order to establish specific patterns of extracellular proteins and identify protein markers that might explain the distinct phenotypical characteristics. Electron microscopy showed that the ultrastructure of N cells corresponds to that of parenchyma cells, and that these cells contain plastids with large starch grains. HNO and T cells had enlarged, lobed nuclei with an increased number of nucleoli; the number of nuclei in HNO cells was greater than in T cells. The T plastids were elongated, with reduced thylakoids and abundant phytoferritin deposits, while HNO plastids were small and vacuolated, with an irregular, underdeveloped thylakoid system. The extracellular proteome of the cells was separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Greater differences in protein expression were observed between the HNO and N lines than between the T and N lines. Sixteen of the most prominent bands differentially expressed among the cell lines were cut out from the gel and analyzed by mass spectrometry. Cell wall-modifying enzymes were identified, including a peroxidase whose expression was twofold higher in N and T tissue than in HNO tissue; pectinesterase, which was expressed at a level threefold lower in the T line than in the other cell lines; and xyloglucan endotransglucosylase, which was expressed at a level sixfold higher in HNO and T tissue. Three proteins belonged to the chitinase gene family and their expression was higher in HNO and T tissue than in N tissue. The differential expression of these proteins suggests that these play a role in cell line-specific cell wall composition and cell-to-cell adhesion.

Involvement of Deg5 protease in wounding-related disposal of PsbF apoprotein

Deg5 is a serine-type protease peripherally attached to luminal side of thylakoid membrane. Given the lack of knowledge concerning its function homozygous T-DNA insertion line depleted in Deg5 was prepared to study the functional importance of this protease in Arabidopsis thaliana. deg5 mutants displayed a pleiotropic phenotype with regard to fourth whorl leaves of four-weeks old plants. The alterations involved an increased leaf area, reduced leaf thickness, reduced cross-sectional area of palisade mesophyll cells as well as changed chloroplast ultrastructure including lack of signs of entering the senescence phase (e.g. presence of much smaller plastoglobules) and the accumulation of large starch grains at the end of the dark period. It was shown that whereas PsbA, C and F apoproteins of photosystem II reaction center undergo an extensive disappearance in response to a set of brief stresses deg5 mutant was fully resistant to the disappearance of PsbF apoprotein which follows an exposition of leaves to wounding. Our results demonstrate that Deg5 is of seminal importance for normal plant development and degradation of PsbF which occurs following brief wounding.

米粉パン中における米粉割合の推定方法の検討

In this study, a method of estimating the rice flour content of rice bread was discussed to ensure the food labeling information of products.1) The absorption spectrum of iodine-starch of rice (Koshihikari) flour was different from that of the strong-type wheat grain. Under a microscope, only the smaller 5μm starch grains were detected in the Koshihikari rice. On the other hand, 15-40μm starch grains were observed in the strong-type wheat grain.2) The maximum absorption wavelength in the spectra of the iodine-starch complexes (λmax) was specifically different among every rice cultivar, although the λmax among the various products from wheat were similar. In products made from rice, the λmax values were not affected by the size of the starch grains in the rice flour and the contents of the other materials except for the rice.3) Based on the increase in the rice flour content, the λmax of breads made from flour mixed with rice and wheat decreased. Many large starch grains considered to come from the wheat were examined from the 100% whole wheat bread. On the other hand, the large starch grains decreased as the rice flour content increased and no large starch grains were detected in the 100% whole rice bread.4) For the marketed products, the λmax of the 100%whole rice bread was lower than that of the 100% whole wheat bread. Only small starch grains considered to be rice starch were observed in the 100% whole rice bread. However, large starch grains regarded to come from the wheat were found in bread containing wheat flour. The results of this study indicated that the method to examine the λmax of rice bread and to observe the size and form of starches from rice and wheat under a microscope was useful to estimate the rice flour rough content of rice bread.

Efekty zróżnicowanego nawożenia mineralnego aplikowanego doglebowo i dolistnie w uprawie ziemniaka skrobiowego

The objective of this study was to determine the effect of varied (280 and 420 kg NPK ha –1 ) soil and foliar application of mineral fertilizers (Basfoliar 12-4-6, ADOB Mn, Solubor DF) on the yield and qualitative traits of late-maturing potato variety Jasia. An exact, two-factorial field experiment was conducted by the randomized split-plot method, in four replications, in the years 2004–2006 in the Masurian Lakeland. The total yield of potato tubers, the content and yield of starch, and the grain size fractions of starch were determined in the study. The applied fertilizers, regardless of their rates, had no significant effect on the total yield of potato tubers and starch yield. The starch content of potatoes was affected by soil fertilization. An increase in the rate of mineral fertilizers from 280 to 420 kg NPK ha –1 caused a decrease in starch content. Large starch grains (> 40 μm in diameter), which enable to reduce the overall loss during the removal of starch from the potato pulp, dominated in the experimental material.

The progamic phase of an early-divergent angiosperm, Annona cherimola (Annonaceae).

Background and AimsRecent studies of reproductive biology in ancient angiosperm lineages are beginning to shed light on the early evolution of flowering plants, but comparative studies are restricted by fragmented and meagre species representation in these angiosperm clades. In the present study, the progamic phase, from pollination to fertilization, is characterized in Annona cherimola, which is a member of the Annonaceae, the largest extant family among early-divergent angiosperms. Beside interest due to its phylogenetic position, this species is also an ancient crop with a clear niche for expansion in subtropical climates.MethodsThe kinetics of the reproductive process was established following controlled pollinations and sequential fixation. Gynoecium anatomy, pollen tube pathway, embryo sac and early post-fertilization events were characterized histochemically.Key ResultsA plesiomorphic gynoecium with a semi-open carpel shows a continuous secretory papillar surface along the carpel margins, which run from the stigma down to the obturator in the ovary. The pollen grains germinate in the stigma and compete in the stigma-style interface to reach the narrow secretory area that lines the margins of the semi-open stylar canal and is able to host just one to three pollen tubes. The embryo sac has eight nuclei and is well provisioned with large starch grains that are used during early cellular endosperm development.ConclusionsA plesiomorphic simple gynoecium hosts a simple pollen–pistil interaction, based on a support–control system of pollen tube growth. Support is provided through basipetal secretory activity in the cells that line the pollen tube pathway. Spatial constraints, favouring pollen tube competition, are mediated by a dramatic reduction in the secretory surface available for pollen tube growth at the stigma–style interface. This extramural pollen tube competition contrasts with the intrastylar competition predominant in more recently derived lineages of angiosperms.

Effects of aluminum on growth and structure of red pepper (Capsicum annuum L.) leaves

Four-day-old seedlings of red pepper (Capsicum annuum L.) cv. “Trapez” were grown in nutrient solution containing 0, 10, 20 and 40 mg dm−3 of AlCl3·6H2O for 14 days. Observations of leaves were carried out by light microscopy, as well as transmission and scanning electron microscopies. Exposure to aluminum resulted in reduction in the size and thickness of the leaf blades related to a decrease in the size of cells composing the leaves, as well as an increase in the number of stomata in the abaxial epidermis, with a simultaneous reduction of their size. The outer cell wall of the epidermis of the leaves was marked by a significant thickening in the presence of aluminum. The mesophyll cells contained enlarged chloroplasts having a disturbed structure of the lamellar system, filled with large starch grains. Rounded mitochondria were characterised by the electron lighter matrix and the destruction of the mitochondrial cristae. In the vacuoles of the parenchyma cells, as well as in the epidermis of the leaves, dark electron-dense bodies, presumably aluminum deposits, were observed.

Impact of elevated CO 2 concentration on ultrastructure of pericarp and composition of grain in three Triticum species of different ploidy levels

Triticum species of three ploidies were grown under ambient (375 μl/l) or elevated (FACE, 550 μl/l) CO 2 concentration [CO 2] to evaluate their response to CO 2 enrichment. The consistent effect of elevated CO 2 was an increase in concentration of starch and decrease in concentration of protein in the grain. Transmission electron micrographs revealed an increase in width and area of chloroplasts, and change in shape from elliptical in ambient to round in elevated [CO 2]. There was a corresponding increase in starch grain size and number in chloroplasts. The large starch grains distributed among thylakoids resulted in separation and distortion of internal membrane system in chloroplasts. The level of response was different in species of different ploidy levels. Maximum increase in starch concentration, and least decrease in protein concentration, was observed in Triticum dicoccoides, which also proved the most suitable species in terms of C:N ratio.

Role of Crop Load in Chloroplast Ultra-structure and Zonal Chlorosis, a Physiological Disorder in ‘Honeycrisp’ Apple Trees

‘Honeycrisp’ is a relatively new apple cultivar (Malus ×domestica Borkh.) with a unique crisp fruit texture that makes it highly desirable. However, the leaves often develop a zonal chlorosis that resembles potato leafhopper damage. Other researchers have determined that the symptoms correlate with decreasing crop load rather than leafhopper damage. This study investigates the possibility that the zonal chlorosis is related to the buildup of starch grains causing rupture of chloroplasts. Transmission electron microscopy was used to document ultrastructural changes in chloroplasts in trees with three different crop loads from the beginning of the season to the end of the season. In trees with extremely low crop loads, we observed abnormalities of chloroplast membrane structure and accumulation of larger and more numerous starch grains. These appear before the appearance of chlorotic symptoms. By early August, the chloroplasts from chlorotic regions of leaves on trees with light crop loads are completely disrupted and abnormally large starch grains are found in place of chloroplasts. As the season progresses, trees with moderate and heavy crop loads showed less severe chloroplast disruption and smaller starch grain accumulation than trees with light crop load.

Removal of high‐abundance proteins for nuclear subproteome studies in rice (Oryza sativa) endosperm

Endosperm is a highly specialized storage organ with three sets of genomes. It is one of the most economically important organs in plants. Endosperm development involves parental imprinting and endoreduplication. A thorough study of the endosperm proteome, particularly the nuclear proteome, may provide critical insight into the regulation of seed development. Unfortunately, endosperm is extremely rich in starch grains and protein bodies of different sizes, making proteome studies on nonstorage proteins, particularly the low-abundance proteins, very challenging. Here we have developed a chromatographic method to remove large starch grains and an electrophoresis method to recover low-abundance proteins, respectively. Using these methods, we have identified 468 proteins from the nuclear enriched fraction of rice endosperm, including transcription factors, histone modification proteins, kinetochore proteins, centromere/microtubule binding proteins, and transposon proteins. Among the 468 proteins, 208 (44%) are hypothetical proteins, indicating that the endosperm proteome is poorly explored. In addition, analyses of the MS/MS data using BioWorks 3.1 have identified 59 putative acetylated proteins and 40 putative methylated proteins. Our studies have developed a method to remove starch grains and recover low-abundance proteins, respectively. The methods should be applicable to other organisms.

Ultrastructural and Immunocytochemical Studies on Effects of Barley Yellow Dwarf Virus – Infection on Fusarium Head Blight, Caused by Fusarium graminearum, in Wheat Plants

AbstractThe interactions between barley yellow dwarf virus (BYDV) and Fusarium head blight (FHB), caused by Fusarium graminearum, were studied in the two winter wheat cultivars (cvs.), Agent (susceptible to FHB) and Petrus (moderately resistant to FHB), using ultrastructural and immunocytochemical methods. Infections of wheat plants of both cvs. by BYDV increased susceptibility to FHB. BYDV infection caused numerous cytological changes in lemma tissue of both cvs. such as formation of vesicles in the cytoplasm, degradation of fine structures of chloroplasts of both cvs. and accumulation of large starch grains in the chloroplasts. Electron microscopical studies showed that the development of F. graminearum on spike surfaces was not affected in BYDV‐infected plants. After penetration and intercellular growth in lemma tissue, defence responses to Fusarium infections were markedly reduced in BYDV‐diseased plants compared to the tissue of virus‐free plants. At sites of contact of fungal cells with host tissue, depositions of cell wall material were distinctly less pronounced than in tissues of virus‐free plants of cv. Petrus. Detection of β‐1,3‐glucanases and chitinases in lemma tissue of cv. Agent revealed no appreciably increased accumulation of both defence enzymes in F. graminearum‐infected virus‐free and BYDV‐infected tissues compared to the non‐infected control tissue. On the other hand, in cv. Petrus, infection with F. graminearum induced a markedly enhanced activity of both enzymes 3 days after inoculation. The increase of both enzyme activities was less pronounced in BYDV‐infected plants than in tissue exclusively infected with F. graminearum. Cytological studies suggest that in contrast to the susceptible cv. Agent postinfectional defence responses may play still an important role in the resistance of the moderately resistant cv. Petrus to FHB.