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

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.

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

2011 ◽  
Vol 47 (No. 1) ◽  
pp. 5-12 ◽  
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.

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

Weed Science ◽  
2007 ◽  
Vol 55 (1) ◽  
pp. 1-5 ◽  
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.

Screening black gram genotypes under artificially inoculated conditions for powdery mildew resistance

2017 ◽  
Author(s):  
S. Priyanka ◽  
S. Rangaiah ◽  
R. Pavan
Keyword(s):  
Powdery Mildew ◽  
Genetic Resistance ◽  
Resistance Breeding ◽  
Cost Effective ◽  
Black Gram ◽  
Resistant Varieties ◽  
House Condition ◽  
Cent Disease

An effective and durable genetic resistance in black gram genotypes against powdery mildew provides a cost effective and reliable strategy to reduce the yield losses and save quality of the harvest. The identification of potential resistant source(s) is the most crucial step in disease resistance breeding. In the present study, out of 116 genotypes screened, genotype LBG-645 recorded lowest per cent disease severity of 0.77 and was found to be highly resistant to powdery mildew under green house condition. Under in vitro condition also, LBG-645 which was found to be highly resistant with 3.33×103 conidia colony, 0.94 per cent of leaf area covered by powdery mildew and 1.00 colony per leaflet was recorded. Hence, resistant genotype LBG-645 must be used in further breeding programme for the development of resistant varieties of black gram against powdery mildew.

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

Weed Science ◽  
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.

Interactions between Sclerotinia sclerotiorum and other fungi on the phylloplane of lettuce

1987 ◽  
Vol 65 (8) ◽  
pp. 1633-1637 ◽  
Author(s):  
J. Mercier ◽  
R. D. Reeleder
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Close Contact ◽  
Trichoderma Viride ◽  
Leaf Disc ◽  
Whole Plant ◽  
Whole Plants ◽  
Protection Against Infection ◽  
Disc Assay

Selected fungi recovered from the phylloplane of lettuce were assayed, using in vitro and in vivo techniques, to determine their effectiveness as antagonists of ascospores of the lettuce drop pathogen, Sclerotinia sclerotiorum. On leaf discs, Trichoderma viride, Alternaria alternata, and Epicoccum purpurascens significantly reduced ascospore germ-tube elongation by 34.2, 60.6, and 38.3%, respectively. On whole plants, these three fungi significantly reduced infection by 40–93.3%. Isolates of Cladosporium cladosporioides and a red yeast inhibited ascospore elongation significantly in the in vitro leaf disc assay but failed to provide significant protection against infection by S. sclerotiorum in the in vivo whole-plant assay. Observations with the scanning electron microscope indicated that hyphae of T. viride and A. alternata came into close contact with ascospores on the leaf surface, suggesting parasitic relationships. Hyphae of E. purpurascens did not come into direct contact with ascospores and inhibition may have been due to production of antifungal compounds.

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

Euphytica ◽  
2019 ◽  
Vol 215 (12) ◽  
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

scholarly journals A leaf disc assay for determining resistance of taro to Phytophthora colocasiae

2015 ◽  
Vol 68 ◽  
pp. 415-419
Author(s):  
J.L. Tyson ◽  
R.A. Fullerton
Keyword(s):  
Incubation Temperature ◽  
Leaf Age ◽  
Leaf Disc ◽  
Resistance Breeding ◽  
Leaf Blight ◽  
Phytophthora Colocasiae ◽  
Food Shortages ◽  
Taro Leaf Blight ◽  
Leaf Disc Assay ◽  
Disc Assay

Phytophthora colocasiae is a destructive fungal pathogen of taro (Colocasia esculenta) which causes taro leaf blight This disease destroyed Samoas taro export industry and led to local food shortages following introduction of the pathogen in 1993 In support of a Pacific regional taro resistance breeding programme laboratory studies in New Zealand aimed to develop a leaf disc bioassay for identifying taro genotypes with disease tolerance A medium has been developed that will retard senescence of the leaf discs for over 14 days The rate of leaf disc infection and subsequent lesion development varied with incubation temperature leaf age and taro cultivar An understanding of these factors and the variation they cause has resulted in a laboratory leaf disc assay for testing resistance of different taro cultivars to taro leaf blight

scholarly journals Occurrence and feeding preference of Diabrotica speciosa Germar and Cerotoma arcuata (Olivier) for different cultivars of cowpea Vigna unguiculata (Linnaeus) Walpers

2019 ◽  
Vol 12 (3) ◽  
pp. 103-107
Author(s):  
Danival José De Souza ◽  
Julner Pachoute
Keyword(s):  
Vigna Unguiculata ◽  
Leaf Disc ◽  
Feeding Preference ◽  
Environmental Costs ◽  
Cowpea Cultivars ◽  
Significant Difference ◽  
Diabrotica Speciosa ◽  
Species Being ◽  
Leaf Disc Assay ◽  
Disc Assay

Abstract. Chrysomelid pests are not only known as leaf-feeding in beans but as vectors of viruses too. Chemical control is most commonly used but has high economic and environmental costs. This study aimed to report the occurrence of chrysomelid pests on cowpea area in the State of Tocantins and compare the feeding preference of the species collected in different cowpea cultivars. Weekly monitoring was carried out in cowpea stand at the experimental station of the Federal University of Tocantins, in Gurupi-TO. Insect feeding preference was evaluated under laboratory conditions (25 ± 2 °C, 60 ± 5% R.H.). A total of 1,542 adults of two species of chrysomelid pests was recorded: Cerotoma arcuata (Olivier) presented 71.49% and Diabrotica speciosa Germar, 28.51%. Leaf discs of the cultivars BRS "Tumucumaque"," BRS "Nova Era", BRS "Sempre Verde", and "Pingo de Ouro", were offered to adult beetles. It was observed a significant difference in no-choice leaf disc assays and four-choice leaf disc assays for the D. speciosa species, being BRS "Tumucumaque" the most consumed. In the no-choice leaf disc assay "Pingo de Ouro" was less consumed and showed non-preference type resistance. In the four-choice leaf disc assay, BRS Sempre Verde was more resistant to D. speciosa consumption. In both tests, C. arcuata did not show a significant difference among the tested cultivars, but mathematically, BRS "Nova Era" was the most consumed, while "Pingo de Ouro" the lowest consumed and showed non-preferred resistance in both tests. Cerotoma arcuata stood out as greater defoliant than D. speciosa in all cultivars tested.Ocorrência e preferência alimentar de Diabrotica speciosa Germar e Cerotoma arcuata (Olivier) por diferentes cultivares de feijão caupi Vigna unguiculata (Linnaeus) WalpersResumo. Crisomelídeos pragas não são apenas desfolhadores do feijoeiro, mas atuam também como vetores de viroses. O método de controle mais utilizado é o químico, o que acarreta altos custos econômicos e ambientais. Este trabalho objetivou registrar a ocorrência de crisomelídeos pragas em cultivo de feijão-caupi no estado do Tocantins, bem como comparar a preferência alimentar das espécies coletadas por diferentes cultivares. Foi realizado monitoramento semanal na área de feijão-caupi da estação experimental da Universidade Federal do Tocantins em Gurupi-TO. Foram registrados 1.542 adultos de duas espécies de crisomelídeos pragas: Cerotoma arcuata (Olivier)apresentou 71,49% e Diabrotica speciosa Germar, 28,51%. Em condições de laboratório, discos foliares das cultivares BRS "Tumucumaque", BRS "Nova Era", BRS "Sempre Verde" e "Pingo de Ouro" foram oferecidos a insetos adultos para testar sua preferência alimentar. Foi observada diferença significativa nos ensaios sem chance e com chance de escolha para espécie de D. speciosa, sendo o BRS "Tumucumaque" o mais consumido. Nos ensaios sem chance de escolha, "Pingo de Ouro" foi menos consumido e apresentou resistência do tipo não preferência. Nos ensaios com chance de escolha, o cultivar BRS "Sempre Verde" foi mais resistente ao consumo de D. speciosa. Em ambos os testes, C. arcuata não apresentou diferença significativa na preferência pelos quatro cultivares, embora BRS "Nova Era" tenha sido mais consumido em valores absolutos, enquanto "Pingo de Ouro" foi menos desfolhado apresentando resistência de tipo não preferência nos dois testes. Cerotoma arcuata destacou-se como maior desfolhador do que D. speciosa em todas os cultivares testados.

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