scholarly journals Older leaf tissues in younger plants are more susceptible to soybean rust

2017 ◽  
Vol 39 (1) ◽  
pp. 17 ◽  
Author(s):  
Sheila Ariana Xavier ◽  
Daiane Cristina Martins ◽  
Lucas Henrique Fantin ◽  
Marcelo Giovanetti Canteri
Keyword(s):  
Experimental Design ◽  
Disease Severity ◽  
Leaf Age ◽  
Reproductive Stage ◽  
Soybean Rust ◽  
Soybean Plant ◽  
Phenological Stage ◽  
Susceptibility To Infection ◽  
Leaf Tissues ◽  
Soybean Leaf

The aim of this study was to clarify the relationship between soybean leaf/plant age and the susceptibility to infection by Phakopsora pachyrhizi. Two studies were conducted in the greenhouse during the 2009/2010 season using the BRS 232 cultivar. The experimental design for Study 1 was fully randomized in a 2 x 3 factorial arrangement (phenological stage x age of the 4th, 5th and 6th trifoliate at the time of inoculation), and in Study 2, the experimental design was fully randomized with five treatments (T) and four replicates. The variables assessed were disease severity, number of lesions, uredinia per lesion, and viable spores. In Study 1, it was observed that disease severity was lower when the plant was in the growth stage V6 (11.4%), compared to the reproductive stage R4 (16.9%). The regression for disease severity and leaf age at the time of inoculation showed that older trifoliates on the plants in the reproductive stage exhibited higher severity. However, in Study 2, for trifoliates of the same age on plants of different ages, the trifoliates of younger plants were more susceptible to the disease. It was concluded that soybean plant susceptibility to soybean rust was directly proportional to the age of the trifoliate on a given plant and the phenological stage of the plant at the time of inoculation. 

scholarly journals Performance and profitability of rain-based thresholds for timing fungicide applications in soybean rust control

2020 ◽  
Author(s):  
Gustavo C. Beruski ◽  
Emerson Medeiros Del Ponte ◽  
André B. Pereira ◽  
Mark L. Gleason ◽  
Gil M. S. Câmara ◽  
...  
Keyword(s):  
Disease Severity ◽  
Disease Risk ◽  
Climatic Conditions ◽  
Soybean Rust ◽  
Yield Data ◽  
Growing Seasons ◽  
Action Threshold ◽  
Temperature Thresholds ◽  
Fungicide Mixtures ◽  
Control Disease

AbstractSoybean rust (SBR), caused by the fungus Phakopsora pachyrhizi, is the most damaging disease of soybean in Brazil. Effective management is achieved by means of calendar-timed sprays of fungicide mixtures, which do not explicitly consider weather-associated disease risk. Two rainfall-based action thresholds of Disease Severity Values (DSV50 and DSV80) were proposed and compared with two leaf wetness duration-temperature thresholds of Daily Values of Infection Probability (DVIP6 and DVIP9) and with a calendar (CAL) program, with regards to performance and profitability. An unsprayed check treatment plot was included for calculating relative control. Disease severity and yield data were obtained from 29 experiments conducted at six sites across four states in Brazil during 2012-13, 2014-15 and 2015-16 growing seasons, which represented different growing regions and climatic conditions. The less conservative rainfall action threshold (DSV80) resulted in fewer fungicide sprays compared with the other treatments and the more conservative one (DSV50) resulted in fewer sprays than the DVIP thresholds. Yield was generally higher with the increase of spray number, but the economic analysis showed no significant differences on the risk of not offsetting the costs of fungicide sprays regardless of the system. Therefore, based on the simplicity and the profitability of the rain-based model, the system is a good candidate for incorporating into management of SBR in soybean production fields in Brazil.

Comparative studies of the exotoxins of Pseudomonas glycinea and Pseudomonas phaseolicola

1978 ◽  
Vol 56 (3) ◽  
pp. 282-287 ◽  
Author(s):  
Randall S. Murch ◽  
Suresh S. Patil
Keyword(s):  
High Voltage ◽  
Membrane Filter ◽  
Thin Layers ◽  
Gel Chromatography ◽  
Ornithine Carbamoyltransferase ◽  
Aspartate Carbamoyltransferase ◽  
Leaf Tissues ◽  
Soybean Leaf ◽  
Soybean Leaves ◽  
High Voltage Electrophoresis

A sensitive and quantitative bioassay, based on the ability of the exotoxin of Pseudomonas glycinea to inhibit ornithine carbamoyltransferase of bean, was employed in a comparative study of the P. glycinea and P. phaseolicola toxins using high-voltage electrophoresis, thin-layer chromatography, ultrafiltration, and Sephadex-gel chromatography. The P. glycinea toxin (glytoxin) has an elution volume/void volume (Ve/V0) ratio different from that of phaseotoxin when chromatographed on Sephadex G-25. Glytoxin passes through a membrane filter with an exclusion limit of 500 daltons whereas phaseotoxin does not. High voltage electrophoresis in buffers of different pH values showed that glytoxin, like phaseotoxin, migrates as an anion but shows greater mobility than phaseotoxin. Both toxins degrade on thin layers of silica gel. Glytoxin induces chlorosis in bean and soybean leaf tissues, and like phaseotoxin, is an inhibitor of ornithine carbamoyltransferase but not of aspartate carbamoyltransferase. Glytoxin is presumably responsible for the accumulation of ornithine which was observed in soybean leaves infected with P. glycinea. Our studies show that glytoxin and phaseotoxin are similar but not identical.

scholarly journals Evaluation of Foliar Diseases for Soybean Entries in the Pan-African Trials in Malawi and Zambia

Plant Disease ◽  
2020 ◽  
Vol 104 (8) ◽  
pp. 2068-2073
Author(s):  
Christabell Nachilima ◽  
Godfree Chigeza ◽  
Mwila Chibanda ◽  
Hapson Mushoriwa ◽  
Brian D. Diers ◽  
...  
Keyword(s):  
Disease Severity ◽  
The United States ◽  
Sub Saharan Africa ◽  
Brown Spot ◽  
Soybean Rust ◽  
Growth Stages ◽  
Foliar Diseases ◽  
Pan African ◽  
Private And Public ◽  
Sub Saharan

Soybean production has expanded worldwide including countries in sub-Saharan Africa. Several national and international agencies and research groups have partnered to improve overall performance of soybean breeding stocks and have introduced new germplasm from Brazil and the United States with the goal of developing new high-yielding cultivars. Part of this effort has been to test improved soybean lines/cultivars accumulated from private and public sources in multilocational trials in sub-Saharan Africa. These trials are known as the Pan-African Soybean Variety Trials, and the entries come from both private and public breeding programs. The objective of this research was to evaluate entries in the trials that include commercial cultivars or advanced experimental lines for the incidence and severity of foliar diseases. All trials were planted in December 2018 with six located in Zambia and one in Malawi. Plants were evaluated during the reproductive growth stages using a visual pretransformed severity rating scale. Foliar disease ratings were recorded for three bacterial diseases, six fungal diseases, one oomycete, and viruses. The overall occurrence of most of the diseases was high except for soybean rust and target spot, which were only found at two and one location, respectively. However, disease severity was generally low, although there were differences in disease severity ratings among the entries at some of the locations for brown spot, downy mildew, frogeye leaf spot, red leaf blotch, and soybean rust.

Inorganic pyrophosphatases in leaves during plant development and senescence

1971 ◽  
Vol 49 (2) ◽  
pp. 311-316 ◽  
Author(s):  
W. E. Rauser
Keyword(s):  
Leaf Age ◽  
Maximum Level ◽  
Inorganic Pyrophosphatase ◽  
Leucine Incorporation ◽  
Biosynthetic Activity ◽  
Delayed Senescence ◽  
Plant Parts ◽  
Leaf Tissues ◽  
Pyrophosphatase Activity ◽  
Alkaline Activity

The activities of inorganic pyrophosphatases were determined in developing and senescing leaf tissues as indicators of biosynthetic activity. The level of alkaline inorganic pyrophosphatase varied with leaf age and leaf position on the plant. In younger plants alkaline inorganic pyrophosphatase increased up the plant to a maximum and then decreased with leaf proximity to the apex. In older plants the enzymatic activity decreased in the lower leaves and the maximum level occurred in leaves closer to the apex. Retardation of leaf senescence with benzyladenine maintained the high levels of enzyme activity. In cucumber plants removal of the shoot at any time before cotyledon death rejuvenated the cotyledons leading to excessive growth, regreening, and dramatic increases in alkaline inorganic pyrophosphatase. Alkaline inorganic pyrophosphatase activity correlated highly with 14C-leucine incorporation into protein of bean leaf discs, supporting the view that this enzyme is involved in making biosynthetic pathways irreversibly anabolic. Acid inorganic pyrophosphatase activity was not proportional to the alkaline activity, suggesting that two separate enzymatic proteins are being assayed. It is concluded that the level of alkaline inorganic pyrophosphatase can be used to indicate which plant parts have high biosynthetic capacity. Also, delayed senescence of leaves or cotyledons, with benzyladenine or apex excision, is associated with maintained biosynthesis.

SOYBEAN LEAF DISEASES DETECTION AND CLASSIFICATION USING RECENT IMAGE PROCESSING TECHNIQUES

2020 ◽  
Vol 8 (3) ◽  
pp. 01-08
Author(s):  
Arpan Singh Rajput ◽  
Shailja Shukla ◽  
S. S. Thakur
Keyword(s):  
Image Processing ◽  
Early Stage ◽  
Weather Condition ◽  
Plant Diseases ◽  
Soybean Plant ◽  
Plant Leaf ◽  
Image Processing Techniques ◽  
Soybean Leaf ◽  
Processing Techniques ◽  
Soybean Diseases

Purpose: India is an agricultural country and soybean production is one of the major sources of earning. Due to the major factors like diseases, pest attacks, and sudden changes in the weather condition, the productivity of the soybean crop decreases. Automatic detection of soybean plant diseases is essential to detect the symptoms of soybean diseases as early as they appear on the growing stage. This paper proposed a methodology for the analysis and detection of soybean plant leaf diseases using recent digital image processing techniques. In this paper, experimental results demonstrate that the proposed method can successfully detect and classify the major soybean diseases. Methodology: MatLab 18a is used for the simulation for the result and machine learning-based recent image processing techniques for the detection of the soybean leaf disease. Main Findings: The main finding of this work is to create the soybean leaf database which includes healthy and unhealthy leaves and achieved 96 percent accuracy in this work using the proposed methodology. Applications of this study: To detect soybean plant leaf diseases in the early stage in Agricultural. The novelty of this study: Self-prepared database of healthy and unhealthy images of soybean leaf with the proposed algorithm.

Effects of Soybean Leaf and Plant Age on Susceptibility to Initiation of Infection by Phakopsora pachyrhizi

2012 ◽  
Vol 13 (1) ◽  
pp. 25 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner
Keyword(s):  
Leaf Area ◽  
Plant Age ◽  
Phakopsora Pachyrhizi ◽  
Susceptibility To Infection ◽  
Soybean Leaf ◽  
Growth Chambers ◽  
Relationship Of ◽  
Inoculum Pressure ◽  
Rule Out ◽  
Plant Basis

To help resolve the question of relationship of soybean leaf and plant age to susceptibility to infection by Phakopsora pachyrhizi, we inoculated 50-day-old plants of cv. Williams 82 with a suspension at 3 × 103 urediniospores/ml, placed in growth chambers under a range of temperature conditions, and later examined for number of lesions. In addition, plants ranging in age from 20 days to 79 days were inoculated, placed in a greenhouse, and examined by leaf for number of lesions. Results showed that Williams 82 did not vary in susceptibility among leaves at different positions regardless of temperature, or among leaves at different positions (up to 11 trifoliolates) on individual plants ranging in age from 20 to 79 days at inoculation. However, on a per-plant basis, there was a gradual decrease in numbers of lesions as plants increased in age at inoculation. For example, whereas 37 lesions/cm2 leaf area were produced on 20-day-old plants, only 10 were produced on 79-day-old plants. Although the study does not rule out the possibility that there might be cultivar dependent differences in age response, it does strengthen the possibility that older plants are less susceptible, and that the increase in disease observed in the field during fall months may be due to an increase in favorability of the environment for disease or increase in inoculum pressure. Accepted for publication 23 November 2011. Published 27 February 2012.

scholarly journals Evaluation of Simplified Leaf Inoculation Procedures for Identification of Quantitative Resistance to Sclerotinia trifoliorum in Alfalfa Seedlings

Plant Disease ◽  
1998 ◽  
Vol 82 (10) ◽  
pp. 1161-1164 ◽  
Author(s):  
R. G. Pratt ◽  
D. E. Rowe
Keyword(s):  
Disease Severity ◽  
Large Scale ◽  
Germ Plasm ◽  
Quantitative Resistance ◽  
Rapid Screening ◽  
Sclerotinia Trifoliorum ◽  
Screening Programs ◽  
Screening For Resistance ◽  
Leaf Tissues ◽  
Agar Media

Previous studies established that excised leaf tissues of alfalfa can be inoculated with Sclerotinia trifoliorum to select for heritable resistance, but the original procedures were not practical for use in large-scale screening programs. In this study, simplified leaf inoculation procedures for more rapid screening for resistance, based on direct application of leaf tissues to colonies of the pathogen on agar media, were evaluated. Cotyledons, unifoliate leaves, and leaflets of trifoliolate leaves of plants 7 to 21 days old from three relatively susceptible cultivars and one resistant germ plasm were applied, with and without wounding, directly to colony margins of S. trifoliorum on cornmeal agar, V8 juice agar, and water agar. Leaves were scored according to the rate and extent of development of necrosis. Significant differences between alfalfa populations were expressed in unifoliate leaves and trifoliolate leaflets but not in cotyledons. Disease severity in the resistant germ plasm (Mississippi Sclerotinia-Resistant [MSR]) was less than in the three cultivars on all agar media. Wounding of leaf tissues increased disease severity and greatly reduced the incidence of symptomless leaves, which are indicated to be escapes, but wounding generally did not prevent expression of resistance in MSR. Results indicate that initial screening for resistance to S. trifoliorum in alfalfa seedlings may be accomplished by applying wounded unifoliate leaves and leaflets of trifoliolate leaves directly to colonies on cornmeal or V8 juice agars.

scholarly journals Reaction of Selected Soybean Genotypes to Isolates of Fusarium solani f. sp. glycines and Their Culture Filtrates

Plant Disease ◽  
1998 ◽  
Vol 82 (9) ◽  
pp. 999-1002 ◽  
Author(s):  
Y. H. Huang ◽  
G. L. Hartman
Keyword(s):  
Great Lakes ◽  
Disease Severity ◽  
Culture Filtrate ◽  
Fusarium Solani ◽  
Stem Length ◽  
Soybean Plant ◽  
Foliar Disease ◽  
Plant Introductions ◽  
Disease Progress ◽  
Progress Curve

Four soybean plant introductions, PI 520.733, PI 567.374, PI 567.650B, and PI 567.659, and one soybean cultivar, Great Lakes 3202, were inoculated under greenhouse conditions with four isolates of Fusarium solani f. sp. glycines. Foliar disease severity rating was greatest on PI 567.659, followed by Great Lakes 3202, PI 520.733, PI 567.650B, and PI 567.374. There was no significant interaction between isolates and soybean entries for foliar disease severity ratings. Experiments also were conducted to determine if disease development and root colonization differed among entries. Root infection of the five entries did not differ (P = 0.05). Foliar disease progress curves increased faster for PI 567.659 and Great Lakes 3202 than for PI 567.374. The area under the disease progress curve (AUDPC) value for PI 567.374 was the lowest and differed (P = 0.01) from AUDPC values for Great Lakes 3202 and PI 567.659. There were no differences (P = 0.01) in length of taproot lesions, losses in root dry weight, and vascular stem length discoloration among the entries, and there was no correlation (P = 0.05) between these measurements and foliar AUDPC values. Cut seedling stems immersed in culture filtrate developed interveinal chlorosis on leaves of each entry within 2 days. Disease severity on cut seedlings of PI 567.374 was lower (P = 0.01) than on the other entries. There was a positive correlation (r = 0.94, P = 0.05) between AUDPC values of the five entries inoculated with the fungus and the cut seedling test using culture filtrate.

Dynamics of gastropod infection by first-stage larvae of protostrongylid nematodes — a model

Parasitology ◽  
1993 ◽  
Vol 107 (5) ◽  
pp. 537-544 ◽  
Author(s):  
P. Řezáč ◽  
P. Kindlmann ◽  
I. Dostálková ◽  
E. Holasová
Keyword(s):  
Experimental Design ◽  
Infective Larva ◽  
Snail Infection ◽  
Instantaneous Rate ◽  
Rate Of Penetration ◽  
Susceptibility To Infection ◽  
Species Specific ◽  
Design Factors ◽  
Best Fit ◽  
Penetration Probability

SUMMARYFor the description of the dynamics of snail infection by the 1st-stage larvae of protostrongylid nematodes, Skorping (1988) used the miracidia-snail model (Anderson, 1978). Here it is shown that, in contrast to miracidia, in protostrongylids the instantaneous rate of infection, α, is strongly dependent on the experimental design (factors like host size and size of the experimental arena). With respect to this, Anderson's model is modified by incorporation of the experimental design. The parameter α in its new sense as the rate of penetration (probability that the infective larva will penetrate into the host during a time unit) is shown to remain dependent, although much less so, on the experimental design. Only the inclusion of the assumed effect of mucus, which decreases the rate of penetration, yields a parameter α0 (the initial rate of penetration), which is completely independent of the design of the experiment, is species-specific, and also gives the best fit to the empirical data. As the above-mentioned factors can strongly influence the value of the instantaneous rate of infection in the laboratory experiments, α0 is more suitable as a measure of either the larval infectivity for the snail or snail susceptibility to infection by the protostrongylid larvae.

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