scholarly journals Infection of Winter Wheat by a β-Glucuronidase-Transformed Isolate of Cephalosporium gramineum

2001 ◽  
Vol 91 (3) ◽  
pp. 232-239 ◽  
Author(s):  
G. W. Douhan ◽  
T. D. Murray
Keyword(s):  
Winter Wheat ◽  
Vascular System ◽  
Root Tips ◽  
Cortical Cells ◽  
Freezing Soil ◽  
Root Epidermis ◽  
Soil Temperatures ◽  
Cephalosporium Gramineum ◽  
Gain Access ◽  
Secondary Roots

Field-grown winter wheat was inoculated with a β-glucuronidase-transformed isolate of Cephalosporium gramineum in two field seasons to elucidate the mode of infection in resistant and susceptible cultivars. Colonization of viable root epidermis and cortical cells occurred as soon as 15 days postinoculation and the pathogen was found in the vascular tissues by 20 days postinoculation, well before freezing soil temperatures occurred. Penetration occurred directly through the root epidermis and through wounds adjacent to emerging secondary roots. The pathogen also penetrated through root cap cells and colonized meristematic tissues near root tips to gain access to the vascular system. Lower stem base colonization was observed where the pathogen penetrated directly through the epidermis, wounds, or senescent tissues. Appressorium-like structures, which appeared to aid penetration of cell walls, were often found within cells of both roots and stems after initial colonization. The mechanisms of resistance were not apparent, but less colonization occurred in resistant than in susceptible cultivars.

scholarly journals Virulence of Rhizoctonia oryzae on Wheat and Barley Cultivars from the Pacific Northwest

Plant Disease ◽  
2003 ◽  
Vol 87 (1) ◽  
pp. 51-55 ◽  
Author(s):  
T. C. Paulitz ◽  
J. D. Smith ◽  
K. K. Kidwell
Keyword(s):  
Winter Wheat ◽  
Pacific Northwest ◽  
Spring Wheat ◽  
Spring Barley ◽  
Root Diameter ◽  
Natural Soil ◽  
Root Tips ◽  
Barley Cultivars ◽  
Rhizoctonia Oryzae ◽  
Waitea Circinata

Rhizoctonia oryzae (teleomorph = Waitea circinata) causes sheath spot of rice and root rot of wheat and barley. R. oryzae commonly is isolated from barley, wheat, and pea plants in eastern Washington and Idaho. Eight representative isolates were tested for virulence on spring barley (Hordeum vulgare cv. Baronesse), soft white winter wheat (Triticum aestivum cv. Madsen), and hard red spring wheat (cv. Scarlet) planted in natural soil in the greenhouse and maintained at 16°C. All isolates caused significant reduction of emergence in barley, but only seven of the eight isolates and one of the eight isolates reduced emergence of winter wheat and spring wheat, respectively. All isolates caused significant stunting and reduction in the number of seminal roots, root length, and number of root tips on wheat and barley. Some isolates also reduced the frequency of fine secondary roots, resulting in a reduction of the average root diameter. Spring barley was more susceptible to R. oryzae than winter or spring wheat. The main effects of both cultivar and isolate were significant, and there was a significant isolate-cultivar interaction. R. oryzae isolate 80042 was the most virulent on barley, whereas R. oryzae isolate 801387 was the most virulent on wheat. The two isolates from pea were intermediate in virulence on wheat and barley. When screening germ plasm for potential resistance, isolates exhibiting the maximum virulence for each host should be used.

scholarly journals Effect of Postsowing Compaction on Cold and Frost Tolerance of North China Plain Winter Wheat

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Caiyun Lu ◽  
Chunjiang Zhao ◽  
Xiu Wang ◽  
Zhijun Meng ◽  
Jian Song ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Soil Temperature ◽  
North China Plain ◽  
North China ◽  
Growth Parameters ◽  
Soil Layer ◽  
Frost Tolerance ◽  
Cold Weather ◽  
Shoot Number ◽  
Soil Temperatures

Improper postsowing compaction negatively affects soil temperature and thereby cold and frost tolerance, particularly in extreme cold weather. In North China Plain, the temperature falls to 5 degrees below zero, even lower in winter, which is period for winter wheat growing. Thus improving temperature to promote wheat growth is important in this area. A field experiment from 2013 to 2016 was conducted to evaluate effects of postsowing compaction on soil temperature and plant population of wheat at different stages during wintering period. The effect of three postsowing compaction methods—(1) compacting wheel (CW), (2) crosskill roller (CR), and (3) V-shaped compacting roller after crosskill roller (VCRCR)—on winter soil temperatures and relation to wheat shoot growth parameters were measured. Results showed that the highest soil midwinter temperature was in the CW treatment. In the 20 cm and 40 cm soil layer, soil temperatures were ranked in the following order of CW > VCRCR > CR. Shoot numbers under CW, CR, and VCRCR treatments were statistically 12.40% and 8.18% higher under CW treatment compared to CR or VCRCR treatments at the end of wintering period. The higher soil temperature under CW treatment resulted in higher shoot number at the end of wintering period, apparently due to reduced shoot death by cold and frost damage.

The influence of rotation, tillage and row spacing on near-surface soil temperature for winter wheat in southern Alberta

2003 ◽  
Vol 83 (1) ◽  
pp. 89-98 ◽  
Author(s):  
F. J. Larney ◽  
T. Ren ◽  
S. M. McGinn ◽  
C. W. Lindwall ◽  
R. C. Izaurralde
Keyword(s):  
Winter Wheat ◽  
Soil Temperature ◽  
Management Practices ◽  
Spacing Effect ◽  
Triticum Aestivum L ◽  
Conventional Tillage ◽  
Row Spacing ◽  
Near Surface ◽  
Soil Temperatures ◽  
Surface Soil Temperature

Soil and crop management practices and their effects on surface residue levels can modify soil temperature. Our study investigated the effect of rotation, tillage and row spacing on near-surface (0.025 m) soil temperature under winter wheat (Triticum aestivum L.) in 1993-1994 and 1994-1995. The main treatment was winter wheat rotation: continuous winter wheat (WW); winter wheat-canola (Brassica campestris L.) (WC) or winter wheat-fallow (WF)] with tillage sub-treatments of conventional tillage (CT) vs. zero tillage (ZT) and row spacing treatments of uniform row (UR) vs. paired row (PR) spacing. From fall 1993 to spring 1994, ZT was cooler than CT by 1.2°C on the WC rotation, 1.1°C on WW and 0.4°C on the WF rotation. From fall 1994 to spring 1995, the magnitude of tillage differences was lower on all three rotations with ZT being cooler than CT by 0.1–0.9°C. The magnitude of the row spacing effect on soil temperature was less than that of the tillage effect. Extreme differences in soil temperature due to tillage were generally higher (1.0–4.9°C) on the WW and WC than the WF rotation (0.6–2.5°C) due to the presence of more crop residue. Results demonstrate that while ZT promotes overall cooler soils under winter wheat from fall to late spring, especially on continuously cropped (WW, WC) rotations, it also allows moderation of soil temperatures during extremely cold periods. Key words: Soil temperature, winter wheat, rotation, tillage, row spacing

Regeneration of whole plants from cultured root tips of Limnophila indica

1981 ◽  
Vol 59 (6) ◽  
pp. 969-973 ◽  
Author(s):  
Sunanda Rao ◽  
H. Y. Mohan Ram
Keyword(s):  
Liquid Medium ◽  
Root Tip ◽  
Root Tips ◽  
Cortical Cells ◽  
Starch Grains ◽  
Histological Studies ◽  
Shoot Buds ◽  
Whole Plants

Root tips (1 cm long) were excised from in vitro grown plants of Limnophila indica (L.) Druce and cultured in liquid medium with 2% sucrose. The explants floated horizontally on the surface of the medium; they became green, and their tips started to grow geotropically into the medium. Four to six shoot buds each were differentiated in 84.5% of the cultures in 4 weeks. Subsequently, shoot buds covered the surface of the bent part of the root and portions above and below it. No buds were formed at the cut end or near the growing root tip. Buds failed to differentiate in roots in which the apex was not growing. Histological studies of the roots showed that the buds originated from proliferating cortical cells, which had prominent chloroplasts and starch grains. The shoot buds grew into entire plants which flowered eventually.

scholarly journals Seed-transmitted beneficial endophytic Stagonospora sp. can penetrate the walls of the root epidermis, but does not proliferate in the cortex, of Phragmites australis

2006 ◽  
Vol 84 (6) ◽  
pp. 981-988 ◽  
Author(s):  
Kexiang Gao ◽  
Kurt Mendgen
Keyword(s):  
Phragmites Australis ◽  
Endophytic Fungus ◽  
Hyphal Growth ◽  
Root Surface ◽  
Cortical Layer ◽  
Epidermal Cells ◽  
Cortical Cells ◽  
Root Epidermis ◽  
Wall Appositions

Stagonospora sp. (4/99-1) is a beneficial endophytic fungus frequently transmitted by seeds of Phragmites australis [Cav.] Trin. ex Steudel. Here we show that this fungus also penetrates the root epidermis. At first, hyphae were attracted by the root and proliferated on the root surface, preferably over the anticlinal walls. Penetration occurred directly by undifferentiated hyphae or was facilitated by hyphopodia. Hyphal growth within the root was restricted to the walls of epidermal cells and the walls of the cells of the outermost cortical layer. Deeper growth by the fungus elicited wall appositions and ingress into the cytoplasm of cortical cells was blocked by papillae. In the rare cases, the fungus managed to penetrate into cortical cells, these reacted with necrosis. Immunological studies suggested that fungal material reached the host plasmalemma and may have been taken up by endocytotic events. Our observations explain the endophytic lifestyle of hyphae close to the epidermis and the restricted development within the cortex.

Oral bacteria: masters of disguise and distant site invaders

2012 ◽  
Vol 3 (4) ◽  
pp. 192-197
Author(s):  
Helen Petersen
Keyword(s):  
Infective Endocarditis ◽  
Heart Valves ◽  
Vascular System ◽  
Clinical Excellence ◽  
Oral Bacteria ◽  
Commensal Bacteria ◽  
Low Grade ◽  
Distant Site ◽  
Everyday Activities ◽  
Gain Access

Oral bacteria have long been recognised as pathogens in distant site infections, most notably infective endocarditis (IE). Current changes in guidelines from the National Institute for Health and Clinical Excellence have highlighted the fact that these bacteria do not rely on a single surgical event to gain access to the vasculature and travel to the heart valves. Low grade, repetitive transient bacteraemia caused by everyday activities such as tooth brushing are thought to be more important in initiating IE. This article tells the story of the mechanisms by which oral commensal bacteria gain access to the vascular system to invade distant sites, including the heart valves.

Diagnostic Guide: Wheat Soil-Borne Mosaic

2018 ◽  
Vol 19 (2) ◽  
pp. 163-167 ◽  
Author(s):  
Duncan R. Kroese ◽  
Sudeep Bag ◽  
Ken E. Frost ◽  
Tim D. Murray ◽  
Christina H. Hagerty
Keyword(s):  
Winter Wheat ◽  
Mosaic Virus ◽  
Virus Replication ◽  
Spring Wheat ◽  
Yield Loss ◽  
Geographic Location ◽  
Polymyxa Graminis ◽  
Soil Temperatures ◽  
Important Host

Wheat soil-borne mosaic is caused by the rod-shaped Soil-borne wheat mosaic virus (SBWMV), which is in the genus Furovirus. SBWMV is vectored by Polymyxa graminis. Economic hosts of SBWMV include wheat, barley, and rye. Winter wheat is the most economically important host; spring wheat infections are possible but rare owing to unfavorable soil temperatures slowing virus replication. Yield loss owing to SBWMV infection is variable among season and geographic location.

Histopathology of Pythium infected strawberry roots

1972 ◽  
Vol 50 (5) ◽  
pp. 1091-1096 ◽  
Author(s):  
S. Nemec
Keyword(s):  
Root Hairs ◽  
Petri Dish ◽  
Root Tip ◽  
Test Results ◽  
Root Tips ◽  
Cortical Cells ◽  
Pythium Irregulare ◽  
Infected Root ◽  
Cortical Infection ◽  
Host Parasite

Host–parasite interactions between eight Pythium species, previously isolated from necrotic strawberry root tissue, and Fragaria × ananassa Duch. runner plant main roots were studied. When excised roots were placed in water on petri dish cultures, P. rostratum and P. hypogenum infection was limited to the root tip epidermis. Pythium irregulare, P. perniciosum, P. dissotocum, P. sylvaticum, P. ultimum, and unidentified isolate 1E penetrated the epidermis several centimeters along the zone of maturation. Penetration occurred most frequently through root hairs by hyphae; resulting infections usually stopped in the epidermis or adjacent cortex, and here hyphae formed sporangium-like structures, oogonia, and oospores. Extensive cortical infection by hyphae was primarily limited to the zone of elongation. Extent of epidermal and cortical infection in roots grown in soil with P. irregulare, P. dissotocum, and P. sylvaticum was similar to petri dish test results. Stelar infection by P. sylvaticum and P. dissotocum occurred mainly in phloem cells, but did not advance far into the region of maturation. Numerous oogonia formed in infected steles and usually in adjacent cortical cells. Infected roots ranged from a white to grey, water-soaked color. Extensively infected root tips typically were unhealthy, succulent, and thin.

scholarly journals Relationship between Incidence of Cephalosporium Stripe and Yield Loss in Winter Wheat

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
M. C. Quincke ◽  
C. J. Peterson ◽  
C. C. Mundt
Keyword(s):  
Winter Wheat ◽  
Pacific Northwest ◽  
Kernel Weight ◽  
Test Weight ◽  
Wheat Varieties ◽  
The Pacific ◽  
Yield Test ◽  
The Usa ◽  
Serious Disease ◽  
Cephalosporium Gramineum

Cephalosporium stripe (caused byCephalosporium gramineum) can be a serious disease of winter wheat (Triticum aestivumL.) in the Pacific Northwest of the USA. Effects of Cephalosporium stripe on yield, test weight, protein, and kernel characteristics were examined using 12 winter wheat varieties in field plots inoculated and not inoculated with the pathogen. Averaged over varieties, inoculation decreased yield, test weight, kernel weight, and kernel diameter; grain protein and the standard deviations of kernel weight and kernel diameter were increased by inoculation. Grain yield of the susceptible check was reduced by as much as 41% with addition of inoculum. The most resistant and the most susceptible varieties performed similarly for yield in the two environments, while varieties with intermediate levels of resistance were sometimes inconsistent. There was a linear relationship between yield and % whiteheads (sterile heads caused by disease) in one environment and a curvilinear relation in the other.

scholarly journals Specifics of soil temperature under winter wheat canopy

2013 ◽  
Vol 43 (3) ◽  
pp. 209-223 ◽  
Author(s):  
Jana Krčmáŕová ◽  
Hana Stredová ◽  
Radovan Pokorný ◽  
Tomáš Stdŕeda
Keyword(s):  
Soil Moisture ◽  
Winter Wheat ◽  
Soil Temperature ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Soil Surface ◽  
Regression Equations ◽  
Experimental Plot ◽  
Near Surface ◽  
Soil Temperatures

Abstract The aim of this study was to evaluate the course of soil temperature under the winter wheat canopy and to determine relationships between soil temperature, air temperature and partly soil moisture. In addition, the aim was to describe the dependence by means of regression equations usable for phytopathological prediction models, crop development, and yield models. The measurement of soil temperatures was performed at the experimental field station ˇZabˇcice (Europe, the Czech Republic, South Moravia). The soil in the first experimental plot is Gleyic Fluvisol with 49-58% of the content particles measuring < 0.01 mm, in the second experimental plot, the soil is Haplic Chernozem with 31-32% of the content particles measuring < 0.01 mm. The course of soil temperature and its specifics were determined under winter wheat canopy during the main growth season in the course of three years. Automatic soil temperature sensors were positioned at three depths (0.05, 0.10 and 0.20 m under soil surface), air temperature sensor in 0.05 m above soil surface. Results of the correlation analysis showed that the best interrelationships between these two variables were achieved after a 3-hour delay for the soil temperature at 0.05 m, 5-hour delay for 0.10 m, and 8-hour delay for 0.20 m. After the time correction, the determination coefficient reached values from 0.75 to 0.89 for the depth of 0.05 m, 0.61 to 0.82 for the depth of 0.10 m, and 0.33 to 0.70 for the depth of 0.20 m. When using multiple regression with quadratic spacing (modeling hourly soil temperature based on the hourly near surface air temperature and hourly soil moisture in the 0.10-0.40 m profile), the difference between the measured and the model soil temperatures at 0.05 m was −2.16 to 2.37 ◦ C. The regression equation paired with alternative agrometeorological instruments enables relatively accurate modeling of soil temperatures (R2 = 0.93).

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