Stem infection of tobacco plants with three strains of Peronospora tabacina Adam

1966 ◽  
Vol 17 (1) ◽  
pp. 39 ◽  
Author(s):  
M Mandry
Keyword(s):  
Plant Growth ◽  
Vascular System ◽  
Original Strain ◽  
Resistant Line ◽  
Peronospora Tabacina ◽  
Highly Pathogenic ◽  
Tobacco Plants ◽  
Stem Infection ◽  
Probable Occurrence ◽  
Cool Conditions

The pathogenicity of three strains of Peronospora tabacina Adam., APT1, APT2, and APT3, in stems of tobacco plants and their effect on the development and survival of plants were determined. (1) APT1, APT2, and APT3 are highly pathogenic in stems of cv. Virginia Gold and in two varieties of Oriental tobacco. Stems of cv. SO1 plants (resistant line) are unaffected by the original strain APTl but are severely infected by the two new strains APT2 and APT3. (2) Severe stem infection developed in injected plants at a temperature of 15–25°C and R.H. higher than 80°. Mycelium of the pathogen rapidly invaded all stem tissues. Of affected plants, 40–75% were killed and the survivors remained dwarfed with small and severely wilted leaves. Under humid and cool conditions APTl and APT3 were more destructive than APT2. (3) Mild stem infection developed at a temperature of 20–30°C and R.H. not higher than 70%. Under these conditions APT2 was more pathogenic than APTl or APT3. The mycelium of the fungus was associated mainly with the vascular system. General plant growth and leaf areas were only slightly reduced. (4) It is concluded that present methods of controlling blue mould in tobacco plants need extension. Consideration should be given to breeding for resistance to stem infection with due regard to the two new strains of P. tabacina described in this paper and the probable occurrence of further physiologic strains of this pathogen in the future.

Host-pathogen relationship in tobacco plants with stems infected by Peronospora tabacina Adam

1960 ◽  
Vol 11 (1) ◽  
pp. 16 ◽  
Author(s):  
M Mandryk
Keyword(s):  
Secondary Xylem ◽  
Vascular System ◽  
Early Stage ◽  
Infected Leaf ◽  
Flowering Stage ◽  
Peronospora Tabacina ◽  
Axillary Shoots ◽  
Daily Temperature Range ◽  
Stem Infection ◽  
Nicotiana Tabacum L

Stem infection of tobacco (Nicotiana tabacum L. cv. Virginia Gold) with Peronospora tabacina Adam was established and its development studied. Mycelium of the pathogen spread from parenchyma tissue of the infected leaf blade into the vascular system of midrib and petiole and thence into the stem. In small seedlings mycelium was usually associated with all tissues and often killed the plant. In plants at the flowering stage necrosis was chiefly confined to the periphery of secondary xylem, the cambium, and the inner part of the external phloem region. As xylem aged it acted as a barrier to the spread of mycelium from external to internal phloem and to the pith. Cortex was not penetrated readily by the pathogen. When the pathogen became established in the cambium region of the stem at an early stage of plant growth, development of xylem was often inhibited. Such plants, when full grown, were brittle at the base and snapped off readily. Development of the pathogen in the stem was favoured by high humidity but was arrested by exposing the plants to benzol vapour, or to a daily temperature range of 75-105°F when humidity was not higher than 70 per cent. High temperature during the day followed by low temperature at night did not prevent spread of the pathogen from the leaves into the stem. Mycelium sometimes spread from infected stems into new axillary shoots with subsequent sporulation on leaves.

The role of temperature in the development of blue mould (Peronospora tabacina Adam.) disease in tobacco seedlings. II. Effect on plant growth

1965 ◽  
Vol 16 (4) ◽  
pp. 609 ◽  
Author(s):  
AV Hill
Keyword(s):  
Plant Growth ◽  
Leaf Size ◽  
Stem Length ◽  
Peronospora Tabacina ◽  
Tobacco Plants ◽  
Temperature Regimes ◽  
Affected Plant ◽  
Wide Range ◽  
Tobacco Seedlings ◽  
Stem Necrosis

Healthy tobacco plants and tobacco plants inoculated with conidia of Peronospora tabacina were subjected to a wide range of temperature conditions. Two strains of the pathogen were used. Both affected plant growth, the greatest and most obvious effects being at night temperatures of 16–24°C. Growth, as measured by stem length, leaf number, and leaf size in plants inoculated with strain APT2, was limited by stem necrosis rather than by leaf necrosis. There was less stem necrosis at the higher day temperatures and fewer dead leaves at all temperature regimes, with strain APT2 than with APT1. At high day temperatures, stem necrosis tended to be restricted to the region of the external phloem, with consequently less severe effects on growth.

scholarly journals MgONPs Can Boost Plant Growth: Evidence from Increased Seedling Growth, Morpho-Physiological Activities, and Mg Uptake in Tobacco (Nicotiana tabacum L.)

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3375 ◽  
Author(s):  
Lin Cai ◽  
Minghong Liu ◽  
Zhongwei Liu ◽  
Huikuan Yang ◽  
Xianchao Sun ◽  
...  
Keyword(s):  
Plant Growth ◽  
Chlorophyll Content ◽  
Germination Rate ◽  
Paraffin Section ◽  
Growth Stimulation ◽  
Physiological Changes ◽  
Tobacco Plants ◽  
Tobacco Roots ◽  
The Impact ◽  
Mg Content

In this study, we documented the impact of magnesium oxide nanoparticles (MgONPs) on the various morpho-physiological changes by root irrigation in tobacco plants in the matrix media, as well as the uptake and accumulation of the NPs over a range of concentrations (50–250 μg/mL). Our results showed that the seed germination rate was not affected following exposure to MgONPs for 5 days. Enhanced plant growth together with increased peroxidase activity (39.63 U mg−1 protein in the 250 μg/mL MgONPs treatment, 36.63 U mg−1 protein in the control), superoxide dismutase activity (30.15 U mg−1 protein compared to 26.95 U mg−1 protein in the control), and chlorophyll content (the chlorophyll a and b contents in 0 and 250 μg/mL of MgONPs were 0.21, 0.12 μg/g to 1.21, 0.67 μg/g, respectively) were observed after 30 days of MgONP treatment. However, the malondialdehyde, protein, and relative water contents did not differ significantly, indicating that the NPs in the test concentrations had no phytotoxicity and even promoted plant growth. Scanning electron microscopy and paraffin section observations indicated that the MgONPs did not affect the plant tissue structures and cells. In addition, an elevated Mg content was detected in the plant tissues exposed to MgONPs, suggesting that the Mg was taken up by the tobacco roots and translocated to the shoots and leaves, which were probably the most important tools to cause an increase in the chlorophyll content and stimulate growth. In particular, compared with the controls, a substantially higher Mg content was observed in the leaves (12.93 mg/g in the MgONPs treatment, 9.30 mg/g in the control) exposed to 250 μg/mL MgONPs, especially in the lower and middle leaves. This result confirmed that the contents of plant Mg-element in the old leaves were increased by MgONPs. In summary, this study investigated increased Mg uptake and growth stimulation, as well as the induction of various positive morpho-physiological changes to tobacco plants when exposed to MgONPs. Results elucidate the promotional impact of the NPs on plant health and their implications for agricultural safety and security.

scholarly journals The Internal Glycine-Rich Motif and Cysteine Suppress Several Effects of the HpaGXooc Protein in Plants

2006 ◽  
Vol 96 (10) ◽  
pp. 1052-1059 ◽  
Author(s):  
Fengquan Liu ◽  
Hongxia Liu ◽  
Qin Jia ◽  
Xiaojing Wu ◽  
Xiaojing Guo ◽  
...  
Keyword(s):  
Plant Growth ◽  
Pseudomonas Syringae ◽  
Growth Promotion ◽  
Marker Genes ◽  
Pathogen Defense ◽  
Hypersensitive Cell Death ◽  
Tobacco Plants ◽  
Tomato Plants ◽  
Aerial Parts ◽  
Stimulate Plant Growth

HpaGXooc, produced by Xanthomonas oryzae pv. oryzicola, is a member of harpin group of proteins that stimulate plant growth, hypersensitive cell death (HCD), and pathogen defense. The protein contains two copies of the glycine-rich motif (GRM), a characteristic of harpins, and a cysteine, which is absent in other harpins. Genetic modification generated the pro-tein mutants HpaGXoocMG (MG) by deleting GRMs and HpaGXoocC47T (C47T) by replacing cysteine with threonine. When applied to tobacco plants, C47T and MG were 1.2- and 1.7-fold stronger, respectively, than HpaGXooc in inducing HCD, which occurred consistently with expression of the marker genes hin1 and hsr203. The proteins markedly alleviated infection of tobacco by Tobacco mosaic virus and Arabidopsis and tomato by Pseudomonas syringae. Treating tobacco plants with HpaGXooc, C47T, and MG decreased the viral infection by 58, 81, and 92%, respectively. In Arabidopsis and tomato plants treated with HpaGXooc, C47T, or MG, P. syringae multiplication was inhibited; bacterial population multiplied in 5 days in these plants were ca. 160-, 1,260-, or 15,860-fold smaller than that in control plants. So pathogen defense was induced in both plants. Defense-related genes Chia5, NPR1, and PR-1a were expressed consistently with resistance. In response to HpaGXooc, C47T, and MG, aerial parts and roots of tomato plants increased growth by 15 and 53%, 25 and 77%, and 46 and 106%, relative to controls. The expansin gene, EXP2, involved in the cell expansion and plant growth was expressed coordinately with plant growth promotion. These results suggest that the presence of GRM and cysteine in HpaGXooc represses the effects of the protein in plants.

Colonization and persistence of a plant growth-promoting bacterium Pseudomonas fluorescens strain CS85, on roots of cotton seedlings

2004 ◽  
Vol 50 (7) ◽  
pp. 475-481 ◽  
Author(s):  
Chunxia Wang ◽  
Daoben Wang ◽  
Qi Zhou
Keyword(s):  
Plant Growth ◽  
Pseudomonas Fluorescens ◽  
Growth Promotion ◽  
Lateral Roots ◽  
Marker Genes ◽  
Original Strain ◽  
Plant Growth Promoting Bacteria ◽  
Plant Growth Promoting ◽  
Growth Promoting ◽  
Root Surfaces

Pseudomonas fluorescens CS85, which was previously isolated from the rhizosphere of cotton seedlings, acts as both a plant growth-promoting bacterium and a biocontrol agent against cotton pathogens, including Rhizoctonia solani, Colletotrichum gossypii, Fusarium oxysporum f sp. vasinfectum, and Verticillium dahliae. Strain CS85 was labeled separately with luxAB and gusA. The labeled strains were stably maintained and had high levels of expression of the marker genes, luxAB and gusA, after successive transfers on nonselective medium, long-term preservation, and after recovery from soil. The labeled strains displayed similar biocontrol characteristics (e.g., antibiosis, effects of growth -promotion and disease -control) to the original strain. The labeled strains colonized all surfaces of the young plant root zones, such as roots hairs and lateral roots, although the distribution of the labeled strains on the root surfaces was not uniform. Moreover, the population densities of the labeled strains on the root surface were stably maintained at high levels during the first 2 weeks of plant growth in the native soil, so that about 107–108 CFU/g root were detected, then decreased gradually. Nevertheless, approximately 106 CFU/g root of the labeled strains were observed on the root surfaces 35 d after planting.Key words: plant growth-promoting bacteria, luxAB, gusA, root colonization.

Soil as a factor in the incidence of Peronospora tabacina Adam on tobacco

1962 ◽  
Vol 13 (4) ◽  
pp. 650 ◽  
Author(s):  
AV Hill
Keyword(s):  
Organic Matter ◽  
Field Conditions ◽  
Wide Area ◽  
Peronospora Tabacina ◽  
Tobacco Plants ◽  
Juvenile Phase ◽  
Pasture Land ◽  
Leaf Maturity ◽  
Severity Of Disease ◽  
Source Of Infection

(1) Plants of a flue-cured variety of tobacco (cv. Virginia Gold) were grown on several soils and subjected to attack by P. tabacina. (2) Leaves of plants grown in soils high in organic matter were large, soft, and succulent and retained the juvenile phase of susceptibility to attack by P. tabacina. Leaves with similar characteristics were not produced following addition of nitrogen to soils low in organic matter. (3) Severity of disease increased during the period of delayed leaf maturity caused by addition to the soil of nitrogen in excess of that required by flue-cured tobacco plants. (4) Soils high in organic matter or in added nitrogen are unsuitable for the growth of flue-cured tobacco, and plants grown in the former are more susceptible to P. tabacina than those grown on the latter. Under field conditions tobacco plants grown on pasture land or on other soils that arc also high in organic matter arc very susceptible to P. tabacina and can be the source of infection for crops grown in a wide area.

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