Lower Leaf Sheath Research Articles

Tonoplast-Localized OsMOT1;2 Participates in Interorgan Molybdate Distribution in Rice

Molybdenum (Mo) is an essential element for plant growth and is utilized by several key enzymes in biological redox processes. Rice assimilates molybdate ions via OsMOT1;1, a transporter with a high affinity for molybdate. However, other systems involved in the molecular transport of molybdate in rice remain unclear. Here, we characterized OsMOT1;2, which shares amino acid sequence similarity with AtMOT1;2 and functions in vacuolar molybdate export. We isolated a rice mutant harboring a complete deletion of OsMOT1;2. This mutant exhibited a significantly lower grain Mo concentration than the wild type (WT), but its growth was not inhibited. The Mo concentration in grains was restored by the introduction of WT OsMOT1;2. The OsMOT1;2-GFP protein was localized to the vacuolar membrane when transiently expressed in rice protoplasts. At the reproductive growth stage of the WT plant, OsMOT1;2 was highly expressed in the 2nd and lower leaf blades and nodes. The deletion of OsMOT1;2 impaired interorgan Mo allocation in aerial parts: relative to the WT, the mutant exhibited decreased Mo levels in the 1st and 2nd leaf blades and grains but increased Mo levels in the 2nd and lower leaf sheaths, nodes and internodes. When the seedlings were exposed to a solution with a high KNO3 concentration in the absence of Mo, the mutant exhibited significantly lower nitrate reductase activity in the shoots than the WT. Our results suggest that OsMOT1;2 plays an essential role in interorgan Mo distribution and molybdoenzyme activity in rice.

Fusarium crown rot caused by Fusarium pseudograminearum in cereal crops: recent progress and future prospects.

Diseases caused by Fusarium pathogens inflict major yield and quality losses on many economically important plant species worldwide, including cereals. Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, is a cereal disease that occurs in many arid and semi-arid cropping regions of the world. In recent years, this disease has become more prevalent, in part as a result of the adoption of moisture-preserving cultural practices, such as minimum tillage and stubble retention. In this pathogen profile, we present a brief overview of recent research efforts that have not only advanced our understanding of the interactions between F.pseudograminearum and cereal hosts, but have also provided new disease management options. For instance, significant progress has been made in the genetic characterization of pathogen populations, the development of new tools for disease prediction, and the identification and pyramiding of loci that confer quantitative resistance to FCR in wheat and barley. In addition, transcriptome analyses have revealed new insights into the processes involved in host defence. Significant progress has also been made in understanding the mechanistic details of the F.pseudograminearum infection process. The sequencing and comparative analyses of the F.pseudograminearum genome have revealed novel virulence factors, possibly acquired through horizontal gene transfer. In addition, a conserved pathogen gene cluster involved in the degradation of wheat defence compounds has been identified, and a role for the trichothecene toxin deoxynivalenol (DON) in pathogen virulence has been reported. Overall, a better understanding of cereal host-F.pseudograminearum interactions will lead to the development of new control options for this increasingly important disease problem. Taxonomy: Fusarium pseudograminearum O'Donnell & Aoki; Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes; Subclass Hypocreomycetidae; Order Hypocreales; Family Nectriaceae; Genus Fusarium. Disease symptoms: Fusarium crown rot caused by F.pseudograminearum is also known as crown rot, foot rot and root rot. Infected seedlings can die before or after emergence. If infected seedlings survive, typical disease symptoms are browning of the coleoptile, subcrown internode, lower leaf sheaths and adjacent stems and nodal tissues; this browning can become evident within a few weeks after planting or throughout plant development. Infected plants may develop white heads with no or shrivelled grains. Disease symptoms are exacerbated under water limitation. Identification and detection: Fusarium pseudograminearum macroconidia usually contain three to five septa (22-60.5× 2.5-5.5μm). On potato dextrose agar (PDA), aerial mycelia appear floccose and reddish white, with red or reddish-brown reverse pigmentation. Diagnostic polymerase chain reaction (PCR) tests based on the amplification of the gene encoding translation elongation factor-1a (TEF-1a) have been developed for molecular identification. Host range: All major winter cereals can be colonized by F.pseudograminearum. However, the main impact of this pathogen is on bread (Triticum aestivum L.) and durum (Triticum turgidum L. spp. durum (Dest.)) wheat and barley (Hordeum vulgare L.). Oats (Avena sativa L.) can be infected, but show little or no disease symptoms. In addition, the pathogen has been isolated from various other grass genera, such as Phalaris, Agropyron and Bromus, which may occur as common weeds. Useful websites: https://nt.ars-grin.gov/fungaldatabases/; http://plantpath.psu.edu/facilities/fusarium-research-center; https://nt.ars-grin.gov/fungaldatabases/; http://www.speciesfungorum.org/Names/Names.asp.

First Report of Marasmiellus mesosporus Causing Marasmiellus Blight on Seashore Paspalum.

Seashore paspalum (Paspalum vaginatum Sw.) is a newly cultivated C4 turfgrass that has exceptional salinity tolerance and is highly suited for use on golf courses in coastal areas. In October 2008 and June 2009, circular patches of blighted seashore paspalum ranging from 30 cm to >3 m in diameter were observed in fairways, tees, and roughs established with 'Supreme' seashore paspalum at Roco Ki Golf Club in Macao, Dominican Republic. Affected patches were initially chlorotic followed by reddish brown necrosis of leaves and leaf sheaths. Reddish brown-to-gray lesions were also observed on leaf sheaths during the early stages of necrosis. During periods of wet or humid weather from June through October, basidiocarps were produced on necrotic plant tissue and identified as Marasmiellus mesosporus Singer (2). Three isolates were obtained by plating symptomatic leaf sheaths that were surface sterilized with a 0.5% NaOCl solution on potato dextrose agar amended with 50 ppm each of streptomycin, chloramphenicol, and tetracycline (PDA+++). Sequences of the internal transcribed spacer (ITS) region of rDNA, obtained from these three isolates and three stipes of basidiocarps, were identical to each other and 99% similar to a M. mesosporus sequence deposited in the NCBI database (Accession No. AB517375). To confirm pathogenicity, a M. mesosporus isolate obtained from symptomatic plant tissue was inoculated onto 6-week-old P. vaginatum ('Seaspray') planted (0.5 mg seed/cm2) in 10-cm-diameter pots containing a mixture of 80% sand and 20% reed sedge peat. Two weeks prior to inoculation, the isolate was grown on a sterilized mixture of 100 cm3 of rye grain, 4.9 ml of CaCO3, and 100 ml of water. Infested grains were placed 0.5 cm below the soil surface for inoculation. Pots were inoculated with five infested grains or five sterilized, uninfested grains with three replications of each treatment. After inoculation, pots were placed in a growth chamber with a 12-h photoperiod set to 30°C during the day and 26°C at night. Approximately 20% of plants in inoculated pots were necrotic 7 days postinoculation and this increased to 75% by 21 days postinoculation. Diseased plants in inoculated pots exhibited symptoms similar to those observed in the field. Leaves were initially chlorotic with brown lesions on lower leaf sheaths and eventually turned necrotic, reddish brown, and collapsed. Pots receiving uninfested grains were healthy and showed no symptoms on all rating dates. At 21 days postinoculation, basidiocarps were observed emerging from three colonized plants at the base of the oldest leaf sheath near the crown. Three reisolations were made on PDA+++ from stem lesions surface sterilized with a 0.5% NaOCl solution. All reisolations were confirmed as M. mesosporus by culture morphology and ITS sequence data. M. mesosporus was previously reported causing disease on American beachgrass (Ammophila breviligulata Fernald) in North Carolina (1) and recently in Japan (3). The pathogen was initially placed in the genus Marasmius and reported as the cause of the disease Marasmius blight (1). Subsequent morphological observation found that the pathogen belonged in the genus Marasmiellus (2). To our knowledge, this is the first report of M. mesosporus causing Marasmiellus blight on seashore paspalum, a high-amenity turfgrass.

Behavior of Erwinia ananas transformed with bioluminescence genes on rice plants

Erwinia ananas, the causal agent of bacterial palea browning of rice, was transformed with bioluminescence genes to clarify their behavior on rice plants. Transformant CTB009T2 was used to inoculate rice plants, and the subsequent bioluminescence of CTB009T2 was observed using a two-dimensional luminometer. Luminous spots frequently appeared on anthers after flowering and on dead tissues such as leaf tips, lower leaf sheaths, and leaf blades. In spikelets that developed the disease symptom on the palea, luminous spots appeared 48 h after flowering on stigmas, basal parts of ovaries, and lodicules. These results indicate that postflowering anthers and dead tissues on rice plants are important sites for a rapid increase in the pathogen population, and that the multiplication of the pathogen on internal tissues of spikelets after flowering is associated with the appearance of browning.

Identity and Pathogenicity of Fungi Associated with Root and Crown Rot of Soft Red Winter Wheat Grown on the Upper Coastal Plain Land Resource Area of Mississippi

Seedling stand, disease severity and fungal incidence were determined from untreated ‘Wakefield’ soft red winter wheat planted on a Leeper silty clay loam in field tests conducted at the Mississippi Agricultural and Forestry Experiment Station, Plant Science Research Center, Mississippi State University, Starkville, Mississippi during the 1996–97 and 1997–98 growing seasons. Seedling stand was reduced by 40% each year in plots established with untreated seed. Cochliobolus sativus was the most frequently isolated fungus. Fusarium acuminatum, Fusarium equiseti and Fusarium solani were the most prevalent Fusarium spp. Seven other Fusarium spp. and 23 species of other fungal genera were isolated. Pathogenicity tests with three isolates each of C. sativus, Cochliobolus spicifer, F. acuminatum, F. solani, F. equiseti, Fusarium compactum, Embellisia chlamydospora and Microdochium bolleyi were performed in test tube culture and two isolates each of C. sativus, C. spicifer, F. acuminatum, E. chlamydospora and M. bolleyi under greenhouse conditions. In test tubes and in the greenhouse, seedlings infected with isolates of C. sativus developed seedling blight, discoloration and necrosis, primarily in seminal roots and crowns. In the greenhouse, C. sativus induced lesions on the lower leaf sheath and reduced seedling height, seedling emergence, dry and fresh weight of roots and shoots. Isolates of F. acuminatum, F. solani, F. equiseti, F. compactum, E. chlamydospora and M. bolleyi induced slight to moderate orange to light‐brown discoloration of crown and seminal roots in test tubes. Cochliobolus spicifer isolates had the most pre‐emergence activity, inducing black root discoloration and root pruning of wheat seedlings and reducing seedling emergence, root fresh weight and shoot dry weight. In the greenhouse, F. acuminatum reduced seedling height, seedling emergence and root and shoot dry weights. Microdochium bolleyi and E. chlamydospora reduced fresh and dry weight of roots, plant emergence and shoot dry weight. Fusarium acuminatum and C. spicifer reduced the growth rate of wheat seedlings. All fungi evaluated showed increased disease severity compared to the untreated control. The high frequency of isolation of C. sativus from crown and root tissues can be partially explained by the dry, warm conditions during the early stages of wheat seedling development in the Upper Coastal Plain Land Resource Area of Mississippi.

Responses of Susceptible and Resistant Wheat Associated with Hessian Fly (Diptera: Cecidomyiidae) Infestation

Cytological analysis of wheat infested by the Hessian fly, Mayetiola destructor (Say), indicated that on susceptible plants, virulent larvae (biotype L, virulent to resistance genes H3,5,6,7/8) caused a generalized increase in cuticular-membrane permeability of cells in the lower leaf sheath. On resistant plants, feeding by avirulent larvae (biotype GP, no genes for virulence) resulted in localized responses. This suggests that plant responses limited the ability of avirulent larvae to elicit generalized changes in cell permeability. Analyses of plant protein patterns by polyacrylamide gel electrophoresis and immunoblots indicated that separate changes in protein metabolism occurred in susceptible versus resistant wheat in association with Hessian fly infestation. In susceptible wheat, ribulose-l,5-bisphosphate carboxylase (Rubisco) increased in the lower leaf sheath in association with infestation. In resistant wheat (cv. Caldwell, H6 gene for resistance), proteins of low molecular weight appeared in the lower leaf sheath in association with infestation by avirulent larvae. Protein changes associated with infestation were not elicited by physical wounding of plants. Protein changes detected in resistant wheat infested by avirulent larvae (biotype GP) did not appear when the plants were infested with virulent larvae (biotype L). Results support the hypothesis that hypersensitivity is the phenotypic basis of resistance in the Hessian fly-wheat interaction and involves “recognition” of an avirulence gene product or process.

Staggers induced by consumption of perennial ryegrass in cattle and sheep from northern California

Summary Staggers was diagnosed in sheep and cattle from the northern California coast. The diagnosis was made on the basis of history of ingestion of perennial ryegrass (Lolium perenne) stubble, clinical signs of transient ataxia, which was aggravated by stimulation, and nearly complete recovery after removal of ryegrass as the primary forage. Morbidity was high, but death did not occur in any affected animals. The toxic endophyte, Acremonium lolii, was in most lower leaf sheaths from the ryegrass. Injection of extracts of the ryegrass from affected farms into mice induced signs of toxicosis. Additionally, ryegrass from all 3 farms contained the tremorgenic mycotoxin, lolitrem-B.

Transmission of Atkinsonella hypoxylon (Clavicipitaceae) by cleistogamous seed of Danthonia spicata (Gramineae)

Atkinsonella hypoxylon is a systemic parasite of the grasses Danthonia spicata, D. compressa, and Stipa leucotricha. The means by which this fungus and other Balansiae (Balansia, Balansiopsis, Epichloë, and Myriogenospora) are transmitted from one plant to another is poorly understood. Host grasses of A. hypoxylon normally produce spikelets of open, wind-pollinated chasmogamous flowers at the apex of the flowering culm and spikelets of self-pollinated cleistogamous flowers in the lower leaf sheaths of the same culm. Plants of D. spicata infected by A. hypoxylon regularly produce cleistogamous spikelets in the lowermost leaf sheaths, although chasmogamous spikelets are aborted by hypothallus development. Embryos of the seeds resulting from these flowers were surrounded by hyphae. The seeds were germinated and when the plants flowered, they produced deformed flowering culms and hypothalli, indicating that A. hypoxylon is transmitted from parent to offspring through cleistogamous seed.

Wojnowicia hirta . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Wojnowicia hirta . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Cereals and grasses ( Agropyron, Avena, Bromus, Calamagrostis, Calamovilfa, Dacrylis, Distichlis, Elymus, Festuca, Hordeum, Koeleria, Phleum, Poa, Secale, Sorghastrum, Sorghum, Spartina, Stipa, Triticum ). DISEASE: Secondary foot rot or root rot of cereals and grasses. Also referred to as rot of mature straw. Rot of cereals and grasses is very common (5, 223; 6, 272; 7, 370; 11, 503; 12, 685; 16, 242; 48, 120; 1602) and considered to be of definite economic importance (Sprague, 1950). In France infected wheat plants have been reported to become etiolated and progressively shrivelled without producing lesions (4, 662). As the disease progresses, cells at the base of the culms were claimed to collapse resulting in the breaking of the stems and general lodging of plants in infected areas (5, 223; 12, 685). Subsequently pycnidia were reported appearing on lower leaf-sheaths above and below the soil line (1, 288). Sometimes affected wheat plants have been found to show discolouration of culm bases and roots (5, 223), or dark brown to black spots and streaks on the stem which are partly superficial (7, 370, Sprague, 1935). GEOGRAPHICAL DISTRIBUTION: Africa (Morocco, South Africa, Tunisia); Asia (Turkey); Australasia and Oceania (Australia, New South Wales, South Australia, Victoria, Western Australia); Europe (Belgium, Bulgaria, Czechoslovakia, Finland, France, Germany, Irish Republic, Italy, Netherlands, Poland, Rumania, Spain, Switzerland, UK, USSR); North America (Canada, Alberta, Saskatchewan; USA, Arkansas, California, Colorado, Dakota, Idaho, Kansas, Montana, Oregon, Washington, Wyoming). TRANSMISSION: Infected soil has been found to be the chief mode of transmission where stubble has been ploughed under (3, 191). It has also been reported that W. hirta occurs on culms overwintered in the field usually at the 2nd node (9, 639-641).

Cultivar Differences among Calcium‐deficient Kentucky Bluegrass Seedlings1

AbstractSince many improved Kentucky bluegrass (Poa pratensis L.) cultivars are available for turf purposes, it is important to develop methods of distinguishing among cultivars to insure correctness of labeling of seed in this respect. To detect differences in the seedling stage plants were grown in sand and were supplied either with a complete nutrient solution or with solutions lacking various essential elements. Cultivars differed greatly when plants were grown without calcium. Of 23 cultivars tested, most seedlings of five cultivars were green and healthy after 4 weeks without Ca. Most plants of nine cultivars were very chlorotic, and plants of the other nine were intermediate or were mixtures of healthy and chlorotic plants. Leaf blade tips of many Ca‐deficient plants became red, and cultivars differed in percentage of plants showing this characteristic.Previous research has shown cultivars to differ in development of anthocyanin in lower leaf sheaths. This pigment was increased by moderate Ca deficiency. Our results indicate that growing seedlings without Ca is a useful technique in cultivar identification.

Varietal Differences among Phosphor‐Deficient Oat Seedlings1

Seedlings of ‘Russell’ oats watered with a nutrient solution lacking phosphorus developed red anthocyanin pigment in coleoptiles and lower leaf sheaths. ‘Garry,’ ‘Niagara,’ ‘Orbit,’ and ‘Tioga’ seedlings were entirely green. Two‐thirds of the ‘Rodney’ seedlings were classed as having slight red color. ‘Clintland’ seedlings had a moderate amount of red color, but had much less than Russel.

Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice : LXVI. Studies on the method for controlling the length of a given leaf-blade, sheath and inter-node in rice plants.

Subjecting the rice plants to nitrogen-depletion treatments, nitrogen top-dressing treatments and root-pruning treatments at different growth stages, the authors examined the effects of the treatments on the lengths of leaf-blade, sheath and inter-node born on each node by comparing the lengths with those of non-treatments, succeeded in establishing a method for controlling their lengths. 1. Increasing the supply of nitrogen is quite effective for lengthening each leaf-blade, sheath and inter-node, while decreasing the supply is most important for shortening them. 2. There is found a definite e synchronous growth among leaf-blades, sheaths and inter-nodes, i. e., taking B1, B2, B3, B4………as the 1st (upper-most), 2nd 3rd and 4th leaf-blade from above and taking S1, S2, S3, S4………as 1st (upper-most), 2nd, 3rd and 4th sheath from above and taking No, N1, N2, N3………as the upper-most (between the neck-node of a ear and the node of an upper-most leaf), 2nd, 3rd, 4th inter-node from above, B1 grows simultaneously with S2 and N3, and B2 grows simultaneously with S3 and N4, and B3 with S4 and N5, and so forth. Therefore, if B1 is lengthened, or shortened, S2 and N3 are also lengthened or shortened synchronously, and if B2 is lengthened or shortened, S3 and N4 are also lengthened or shortened synchronously. Thus, there are synchronously growing leaf-blades, sheaths and inter-nodes in the growth of rice plants, and so each leaf-blade grows synchronously with its own corresponding sheath and inter-node. 3. When one wants to shorten a given leaf-blade (for instance B3), one has to restrict the nitrogen supply (by cutting roots or other methods) at or just before the time when the top of that leaf-blade (B3) begins to appear from the immediate lower sheath (S4), and when one wants to lengthen a given leaf-blade (B3), one ought to top-dress nitrogen at the time when the top of the previous leaf-blade (B4) begins to appear from the immediate lower leaf-sheath (S5). When one wants to shorten a given sheath (for instance S4), one has to reduce thc nitrogen supply at or just before the time when the top of B3 start to appear from the immediate lower sheath (S4). 4. By microscopic and anatomical observations the most susceptible developmental stage of a leaf-blade has been found to be the stage II in fig. 3. The stage II is just after the time at which the sheath of a leaf has been differentiated and the sheath as well as the blade are growing most vigorously.