Shikimate leaf disc assay for early detection of glyphosate resistance in Conyza canadensis and relative transcript levels of EPSPS and ABC transporter genes

Lolium spp. are troublesome weeds mainly found in winter cereal crops worldwide, including Europe. In recent years resistant mechanisms have been evolved to several important herbicides. In this study we investigated the mechanisms responsible for conferring glyphosate resistance in some Lolium spp. populations. A holistic approach was used, based on dose-response experiments, determination of shikimic acid concentration in plant leaf tissue, as well as molecular analyses. More specifically, in three Lolium spp. populations the existence of a mutation in the Pro-106 codon of the 5-enolpyruvylshikimate-3 phosphate synthase (EPSPS) gene was investigated as well as the relative transcript levels of four ABC-transporter genes were monitored at three time points after glyphosate application. The results demonstrated that glyphosate resistance is a multifactor phenomenon. Relative transcript levels of the ABC-transporter genes were abundant at very early time points after glyphosate treatments. Dose-response experiments and shikimate analyses were in accordance with the findings of the quantitative PCR (qPCR) analyses. We suggest that relative expression ratio of ABC-transporter genes can be a useful tool to rapidly identify Lolium spp. populations resistant to glyphosate.

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Evaluation of powdery mildew resistance in various melon (Cucumis melo L.) genotypes

Agricultural Science and Technology ◽

10.15547/10.15547/ast.2018.04.053 ◽

2018 ◽

Vol 10 (4) ◽

pp. 279-284

Author(s):

Zh. Ivanova ◽

K. Vasileva ◽

N. Velkov ◽

S. Grozeva

Keyword(s):

Powdery Mildew ◽

Genetic Resistance ◽

Leaf Disc ◽

Breeding Program ◽

Vegetable Crops ◽

Plant Materials ◽

South Central ◽

Leaf Disc Assay ◽

Disc Assay

Abstract. Powdery mildew, caused by Podosphaera xanthii and Golovinomyces cichoracearum, is an economically important disease in melon worldwide. Genetic resistance is one of the most suitable strategies to control powdery mildew. During the last few years several races of the pathogens have been reported. The need to develop resistant varieties is a challenge for each breeding program. Leaf disc assay was used in phytopathology and breeding programs as a rapid and reliable method for evaluation of disease resistance in a large number of plant materials. The purpose of this study was to establish species and races of powdery mildew in Plovdiv region, South Central Bulgaria; to develop a suitable system of pathogen isolation and cultivation; to determine the resistance levels in different melon genotypes available in Maritsa Vegetable Crops Research Institute (MVCRI) - Plovdiv collection by the leaf disc assay. Fifty-three melon genotypes, including lines, varieties, hybrids and ten differential lines were tested. The data showed that causal agent of powdery mildew was race 1 of P. xanthii in Plovdiv region. Our experimental results indicated that for the long-term storage of powdery mildew it is preferable to keep a whole plant under in vitro conditions. This allows the preservation of powdery mildew for two months before transferring on a new tissue. Thirty-four of the tested melon genotypes reacted as immune or resistant and nineteen as susceptible. Resistant melon genotypes are a suitable source in initiating a new breeding program aimed to increase resistance to powdery mildew.

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Shikimate Accumulation in Sunflower, Wheat, and Proso Millet after Glyphosate Application

Weed Science ◽

10.1614/ws-06-065.1 ◽

2007 ◽

Vol 55 (1) ◽

pp. 1-5 ◽

Cited By ~ 30

Author(s):

W. Brien Henry ◽

Dale L. Shaner ◽

Mark S. West

Keyword(s):

Leaf Disc ◽

Spectrophotometric Assay ◽

The Other ◽

Proso Millet ◽

Glyphosate Drift ◽

Leaf Disc Assay ◽

Disc Assay

Experiments were conducted to examine the utility of a spectrophometric leaf disc assay for detecting shikimate accumulation after glyphosate application in sunflower, proso millet, and wheat. The assay was conducted on both greenhouse- and field-grown plants. Glyphosate was applied at five rates ranging from 840 to 53 g ae ha−1. Shikimate accumulation data were generated at 1, 4, 7, and 14 d after application (DAA). Sunflower accumulated shikimate more rapidly and at lower glyphosate rates than the other two species. At 14 DAA, glyphosate at the two highest rates remained detectable in all three species. Plants receiving lower glyphosate doses (210, 105, and 53 g ae ha−1) had begun to grow out of the injury, or at least the shikimate levels in the plants were no longer significantly different than that present in the untreated controls. This spectrophotometric assay is both rapid and simple, with respect to other means of detecting shikimate, and it can be used to detect glyphosate drift. For it to be used by crop managers, samples from potentially drift-affected crops should be taken as soon as possible after the suspected drift event or immediately after the appearance of glyphosate injury.

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Assessment of two nondestructive assays for detecting glyphosate resistance in horseweed (Conyza canadensis)

Weed Science ◽

10.1614/ws-05-010r ◽

2005 ◽

Vol 53 (4) ◽

pp. 438-445 ◽

Cited By ~ 23

Author(s):

Clifford H. Koger ◽

Dale L. Shaner ◽

W. Brien Henry ◽

Talia Nadler-Hassar ◽

Walter E. Thomas ◽

...

Keyword(s):

Leaf Disc ◽

Glyphosate Resistance ◽

Conyza Canadensis ◽

Dependent Manner ◽

Leaf Discs ◽

Plant Sensitivity ◽

Soybean Plants ◽

Nondestructive Assays ◽

Dose Dependent

Two rapid, nondestructive assays were developed and tested for their potential in differentiating glyphosate-resistant from glyphosate-susceptible biotypes of horseweed. In one assay, leaves of glyphosate-resistant and -susceptible corn, cotton, and soybean plants, as well as glyphosate-resistant and -susceptible horseweed plants, were dipped in solutions of 0, 300, 600, and 1,200 mg ae L−1glyphosate for 3 d, and subsequent injury was evaluated. In the second assay, plant sensitivity to glyphosate was evaluated in vivo by incubating excised leaf disc tissue from the same plants used in the first assay in 0.7, 1.3, 2.6, 5.3, 10.6, 21.1, 42.3, and 84.5 mg ae L−1glyphosate solutions for 16 h and measuring shikimate levels with a spectrophotometer. The leaf dip assay differentiated between glyphosate-resistant and -susceptible crops and horseweed biotypes. The 600 mg L−1rate of glyphosate was more consistent in differentiating resistant and susceptible plants compared with the 300 and 1,200 mg L−1rates. The in vivo assay detected significant differences between susceptible and glyphosate-resistant plants of all species. Shikimate accumulated in a glyphosate dose–dependent manner in leaf discs from susceptible crops, but shikimate did not accumulate in leaf discs from resistant crops, and levels were similar to nontreated leaf discs. Shikimate accumulated at high (≥ 21.1 mg ae L−1) concentrations of glyphosate in leaf discs from all horseweed biotypes. Shikimate accumulated at low glyphosate concentrations (≤ 10.6 mg L−1) in leaf discs from susceptible horseweed biotypes but not in resistant biotypes. Both assays were able to differentiate resistant from susceptible biotypes of horseweed and could have utility for screening other weed populations for resistance to glyphosate.

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A Non-destructive Leaf Disc Assay for Rapid Diagnosis of Weed Resistance to Multiple Herbicides

Weed Science ◽

10.1017/wsc.2021.15 ◽

2021 ◽

pp. 1-32

Author(s):

Chenxi Wu ◽

Vijaya Varanasi ◽

Alejandro Perez-Jones

Keyword(s):

False Negative ◽

Leaf Disc ◽

Population Level ◽

Lower Sensitivity ◽

Individual Plant ◽

Weed Species ◽

Non Destructive ◽

Weed Resistance ◽

Leaf Disc Assay ◽

Disc Assay

Abstract Weed resistance survey that monitors the spread of resistant weeds has been mainly conducted through time-consuming, labor-intensive and destructive greenhouse herbicide screens. As an alternative, we here introduce a non-destructive leaf disc assay based on chlorophyll fluorescence (Fv/Fm values which measure photosynthesis efficiency) allowing the detection of resistance to both systemic and contact herbicides within ˜48h. Current study validated the assay on detecting resistance to fomesafen, glyphosate, and dicamba in Palmer amaranth (Amaranthus palmeri S. Watson), waterhemp [Amaranthus tuberculatus (Moq.) Sauer], kochia [Bassia scoparia (L.) A.J. Scott] and goosegrass [Eleusine indica (L.) Gaertn.]. Negative correlation between the Fv/Fm values and the spray injury levels was observed in all herbicide-weed combinations at the discriminating doses, except for glyphosate in Amaranthus. The correlation coefficients were -0.41 for fomesafen (10µM, p<0.0001) in Amaranthus, -0.92 for glyphosate in E. indica (250µM, p<0.0001), and -0.44 for dicamba in B. scoparia (800 µM, p=0.0023), respectively. At the population level, the assay clearly separated susceptible from highly resistant populations. However, the assay showed lower sensitivity in distinguishing populations of different resistance levels or separating low resistance from susceptible populations. At the individual plant level, results from the leaf disc assay and whole plant spray tests were concordant in 85.5%, 92.3%, and 71.7% of the plants tested for fomesafen-Amaranthus, glyphosate-Eleusine and dicamba-Bassia, respectively. The assay yielded 1-15% false positive and 6-13% false negative results across herbicides. The current study demonstrated that the leaf disc assay is a useful tool to identify weed resistance. Optimization is needed to improve its sensitivities and expand its usage to more diverse herbicide-weed species combinations.

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Exogenous applied defense hormones regulate broad mite population growth in an azalea leaf disc assay

Acta Horticulturae ◽

10.17660/actahortic.2020.1283.12 ◽

2020 ◽

pp. 83-88

Author(s):

G. Luypaert ◽

L. Leus ◽

J. Van Huylenbroeck

Keyword(s):

Population Growth ◽

Leaf Disc ◽

Mite Population ◽

Broad Mite ◽

Leaf Disc Assay ◽

Disc Assay

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Assessment of grapevine germoplasm collection for resistance to grape leaf rust (Phakopsora euvitis) using a leaf disc assay

Euphytica ◽

10.1007/s10681-019-2514-2 ◽

2019 ◽

Vol 215 (12) ◽

Cited By ~ 1

Author(s):

Beatriz Ribeiro Gomes ◽

Amauri Bogo ◽

Andrio Copatti ◽

Claudia Aparecida Guginski-Piva ◽

Andriele Caroline de Morais ◽

...

Keyword(s):

Leaf Rust ◽

Leaf Disc ◽

Phakopsora Euvitis ◽

Grape Leaf ◽

Leaf Disc Assay ◽

Disc Assay

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Sensitivity to fungicides in the isolates of Phytophthora infestans (Mont.) de Bary in the Czech Republic from 2003 to 2008

Plant Protection Science ◽

10.17221/16/2010-pps ◽

2011 ◽

Vol 47 (No. 1) ◽

pp. 5-12 ◽

Cited By ~ 3

Author(s):

J. Mazáková ◽

M. Zouhar ◽

P. Ryšánek ◽

V. Táborský ◽

E. Hausvater ◽

...

Keyword(s):

Czech Republic ◽

Phytophthora Infestans ◽

Mycelial Growth ◽

Leaf Disc ◽

The Czech Republic ◽

Growing Seasons ◽

Leaf Disc Assay ◽

Disc Assay ◽

Floating Leaf

In the growing seasons from 2003 to 2008, 547 isolates of Phytophthora infestans from five regions in the Czech Republic were collected and examined for their sensitivity to the active ingredients (metalaxyl, dimethomorph and propamocarb-HCl) of frequently used fungicides. The response of the isolates to each of these substances was examined using the in vitro amended-agar method; in 352 of these isolates, the sensitivity to metalaxyl was also assessed by the floating leaf-disc assay. The majority of the isolates were sensitive (89.8%) to metalaxyl. Resistant isolates were found only in two of the sample years (2003 and 2008); they represented 58% of the samples in 2003 and only 29% in 2008. Four isolates from 2004 were found to be intermediate for their level of resistance. All the isolates that were tested were sensitive to dimethomorph and propamocarb-HCl; these particular substances completely suppressed mycelial growth at 1 µg a.i. per ml.

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