First report of a mastrevirus (Geminiviridae) transmitted by the corn leafhopper

Maize striate mosaic virus (MSMV; genus Mastrevirus), was recently reported in maize plants in Brazil, and also detected by metagenomic analyses in the corn leafhopper, Dalbulus maidis (DeLong & Wolcott). Although these findings suggested that D. maidis is a potential vector, no transmission studies have been performed. Here, we tested the transmission of MSMV by D. maidis from field-collected infected plants and plants infected with MSMV via leafhopper-mediated transmission in the laboratory; all plants were confirmed positive for MSMV by PCR. In each one of three transmission replicates, aviruliferous D. maidis nymphs and adults were confined together on a source plant during a 4-day acquisition access period (AAP), and subsequently transferred to healthy maize seedlings (10 individuals per test plant) in a series of 4-day inoculation access periods (IAPs). We also tested transmission by the corn aphid, Rhopalosiphum maidis (Fitch) and by mechanical inoculation of healthy maize seedlings. Only D. maidis transmitted MSMV, with overall transmission rates of 29.4 and 39.5% using field-collected infected plants, and 18.5% using infected plants in laboratory. D. maidis transmitted MSMV until the third (8-12 days after the AAP) or fourth successive IAP (12-16 days) with gradual loss in transmission efficiency and rate of viruliferous insects over time, suggesting a persistent, but non-propagative mode of transmission. Infected test plants showed mottling symptoms with mild chlorotic streaks and height reduction. This is the first report of transmission of a mastrevirus by D. maidis, facilitating the completion of Koch’s postulate for MSMV.

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A Graft-Based Chemotherapy Method for Screening Effective Molecules and Rescuing Huanglongbing-Affected Citrus Plants

Phytopathology ◽

10.1094/phyto-09-11-0265 ◽

2012 ◽

Vol 102 (6) ◽

pp. 567-574 ◽

Cited By ~ 35

Author(s):

Muqing Zhang ◽

Charles A. Powell ◽

Ying Guo ◽

Melissa S. Doud ◽

Yongping Duan

Keyword(s):

Survival Rate ◽

Transmission Rate ◽

High Titer ◽

Critical Factor ◽

Transmission Efficiency ◽

Pathogen Transmission ◽

Citrus Industry ◽

Chemical Treatments ◽

Bacterial Titer ◽

Transmission Studies

Huanglongbing (HLB) is the most devastating disease of citrus. The global citrus industry is in urgent need of effective chemical treatments for HLB control because of its rapid spreading worldwide. Due to the fastidious nature of the pathogens, and the poor permissibility of citrus leaf surfaces, effective screening of chemicals for the HLB control can be challenging. In this study, we developed a graft-based chemotherapy method to rapidly screen potential HLB-controlling chemical compounds. In addition, we improved transmission efficiency by using the best HLB-affected scion–rootstock combination, and demonstrated the HLB bacterial titer was the critical factor in transmission. The HLB-affected lemon scions had a high titer of HLB bacterium, survival rate (83.3%), and pathogen transmission rate (59.9%). Trifoliate, a widely used commercial rootstock, had the highest survival rate (>70.0%) compared with grapefruit (52.6%) and sour orange (50.4%). Using this method, we confirmed a mixture of penicillin and streptomycin was the most effective compounds in eliminating the HLB bacterium from the HLB-affected scions, and in successfully rescuing severely HLB-affected citrus germplasms. These findings are useful not only for chemical treatments but also for graft-based transmission studies in HLB and other Liberibacter diseases.

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First Report of Pythium Root Rot of Rau Ram (Polygonum odoratum)

Plant Disease ◽

10.1094/pd-89-0340a ◽

2005 ◽

Vol 89 (3) ◽

pp. 340-340

Author(s):

E. N. Rosskopf ◽

C. B. Yandoc ◽

B. Stange ◽

E. M. Lamb ◽

D. J. Mitchell

Keyword(s):

Root Rot ◽

Vascular System ◽

Pond Water ◽

Centraalbureau Voor ◽

First Report ◽

Pathogenicity Tests ◽

Symptomatic Tissue ◽

Pythium Helicoides ◽

Production House ◽

Test Plants

Polygonum odoratum (= Persicaria odorata), known as rau ram or sang hum, is native to southeastern Asia and is a common herb in Vietnamese cuisine (1). It has been studied most extensively for its aromatic compound content (2). In Florida, rau ram commonly is grown hydroponically in greenhouses using large, cement beds with recirculated water. The plants form dense mats from which new growth is trimmed for market. During January of 2002, a severe dieback was observed in one production house in Saint Lucie County, FL. Plants with less severe symptoms were yellowed and stunted. Roots of symptomatic plants were largely decayed with root symptoms beginning as a tip necrosis. The cortex of severely affected roots slipped off easily, leaving a stringy vascular system. Plating of symptomatic tissue from 20 randomly selected plant samples was performed with multiple general and selective media including potato dextrose agar, corn meal agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP) (3). All colonies produced were identified as Pythium helicoides Drechsler on the basis of sporangial, oogonial, and antheridial characteristics (4). Isolates had proliferous, obovoid, papillate sporangia, and were homothallic with smooth-walled oogonia and thick-walled, aplerotic oospores. Multiple antheridial attachments per oogonium were common with the antheridium attached along its entire length. Pathogenicity tests were conducted using P. odoratum plants grown from commercial transplants. Two tests were performed. Each test was conducted using eight inoculated and eight control plants. In the first test, plants were maintained in 10-cm pots immersed in sterilized pond water for the duration of the test. Plants were inoculated with five 7- × 70-mm sections of freshly growing mycelial culture per plant using 10-day-old cultures of Pythium helicoides grown on water agar. Chlorosis was observed at approximately 2 months after inoculation. Root necrosis was observed in inoculated plants approximately 5 months after inoculation. This test was performed in the greenhouse with temperatures ranging from 20 to 30°C. The second test was performed in growth chambers at 35 to 40°C. Plants were maintained in 10-cm pots immersed in Hoagland's solution and were inoculated with four 6-mm plugs per plant. Symptoms were observed on inoculated plants at this temperature within 1 week of inoculation. No chlorosis or root decay was observed in noninoculated, immersed plants. The pathogen was reisolated from inoculated, symptomatic tissue. To our knowledge, this is the first report of root rot of P. odoratum caused by Pythium helicoides. References: (1) R. E. Bond. Herbarist 55:34, 1989. (2) N. X. Dung et al. J. Essent. Oil Res. 7:339, 1995. (3) M. E. Kannwischer and D. J. Mitchell. Phytopathology 68:1760, 1978. (4) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcutltures, Baarn, The Netherlands, 1981.

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Use of a Biostimulant to Mitigate Salt Stress in Maize Plants

Agronomy ◽

10.3390/agronomy11091755 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1755

Author(s):

Roberto D’Amato ◽

Daniele Del Buono

Keyword(s):

Salt Stress ◽

Crop Yields ◽

Total Phenolic ◽

Maize Seedlings ◽

Fresh Weight ◽

Antioxidant Power ◽

Crop Development ◽

Ferric Reducing Antioxidant Power ◽

Maize Plants ◽

The Impact

Salinity is considered among the abiotic stresses most impacting agriculture for its ability to interfere with crop development and quality. For this reason, practices and innovations that could contain the deleterious effects of such stress are of pivotal importance for maintaining acceptable crop yields. In this context, this work has concerned the study of severe salt stress (100 mM NaCl) on maize seedlings and the effects of a plant biostimulant (Megafol–Meg) in helping plants to cope with this adversity. Biomass production, pigments, the content Na+ and K+, the accumulation of hydrogen peroxide (H2O2) and lipid peroxidation products (MDA), total phenolic compounds (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) were investigated in control samples, in samples treated with NaCl alone, and in samples treated with NaCl in combination with the biostimulant. The results showed that the biostimulant significantly mitigated the impact of the salt stress on shoot length and fresh weight, on chlorophyll and carotenoid contents, and reduced the amount of Na+ taken up by the species. Regarding the oxidative status, the biostimulated samples revealed lower amounts of H2O2 and MDA, while maize seedlings grown with NaCl alone exhibited the highest increases in the TPC, ABTS, and FRAP. The explanation for these effects is provided by highlighting the effectiveness of the biostimulant in avoiding Na+ accumulation, which resulted in a lower content of H2O2, MDA, TPC, and antioxidant activity.

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Perbanyakan dan Aplikasi PGPR (Plant Growth Promoting Rhizobactheria) di Laboratorium Pengamatan Hama dan Penyakit Banyumas

Proceedings Series on Physical & Formal Sciences ◽

10.30595/pspfs.v2i.190 ◽

2021 ◽

Vol 2 ◽

pp. 234-239

Author(s):

Nada Kholifah ◽

Ardiana Kartika B ◽

Teguh Pribadi

Keyword(s):

Plant Growth ◽

Plant Height ◽

Root Length ◽

Dry Weight ◽

Test Plant ◽

Plant Growth Promoting ◽

Wet Weight ◽

Number Of Leaves ◽

Growth Promoting ◽

Test Plants

PGPR (Plant Growth Promoting Rhizobacteria) is a substance that helps plant growth with the help of rhizosphere microorganisms. PGPR propagation can be done with liquid media. This PGPR propagation needs to be done because this substance has many benefits for agricultural cultivation. The application of PGPR to the test plant, namely the pakcoy plant, proved that there was an effect of giving PGPR to the plant. Observations on the test plants were carried out by observing several observation variables such as plant height, root length, number of leaves, wet weight and dry weight. The results of these observations showed that the effect on the test plants was seen in the variables of root length, wet weight, and dry weight. Meanwhile, the variable plant height and number of leaves did not show a visible difference.

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Transmission Efficiency of Papaya ringspot virus by Three Aphid Species

Phytopathology ◽

10.1094/phyto-98-5-0541 ◽

2008 ◽

Vol 98 (5) ◽

pp. 541-546 ◽

Cited By ~ 28

Author(s):

C. M. Kalleshwaraswamy ◽

N. K. Krishna Kumar

Keyword(s):

Aphis Gossypii ◽

Transmission Efficiency ◽

Leaf Disk ◽

Ringspot Virus ◽

Test Plant ◽

Infected Leaf ◽

Papaya Ringspot Virus ◽

Access Period ◽

Virus Retention ◽

Aphid Inoculation

The transmission efficiency of Papaya ringspot virus (PRSV) by three aphid vectors (i.e., Aphis gossypii, A. craccivora, and Myzus persicae) was studied. Efficiency was measured by single-aphid inoculation, group inoculation (using five aphids), duration of virus retention, and the number of plants following a single acquisition access period (AAP) to which the aphids could successfully transmit the virus. Single-aphid inoculation studies indicated that M. persicae (56%) and A. gossypii (53%) were significantly more efficient in transmitting PRSV than A. craccivora (38%). Further, in the former two species, the time required for initiation of the first probe on the inoculation test plant was significantly shorter compared to A. craccivora. PRSV transmission efficiency was 100% in all three species when a group of five aphids were used per plant. There was a perceptible decline in transmission efficiency as the sequestration period increased, although M. persicae successfully transmitted PRSV after 30 min of sequestration. A simple leaf-disk assay technique was employed for evaluating the transmission efficiency of three species of aphids. The results of leaf-disk assays also indicated that A. gossypii (48%) and M. persicae (56%) were more efficient PRSV vectors than A. craccivora. Using leaf-disk assays, the ability of individual aphids to inoculate PRSV serially to a number of plants was studied. Following a single AAP on an infected leaf, M. persicae was more efficient than the other two species with 52.5% transmission after the first inoculation access period (IAP). However, its inoculation efficiency significantly decreased with the second and subsequent IAPs. A. gossypii was able to transmit PRSV sequentially up to four successive leaf disks, but with significantly declining efficiency. Since A. gossypii is reported to be the numerically dominant vector in south India in addition to being a more efficient vector capable of inoculating PRSV to multiple plants, it should be the target vector for control strategies.

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Effect of manganese on cadmium toxicity in maize seedlings

Plant Soil and Environment ◽

10.17221/3358-pse ◽

2011 ◽

Vol 52 (No. 4) ◽

pp. 143-149 ◽

Cited By ~ 21

Author(s):

P. Paľove-Balang ◽

A. Kisová ◽

J. Pavlovkin ◽

MistríkI

Keyword(s):

Root Growth ◽

Nitrate Uptake ◽

Reductase Activity ◽

Cadmium Toxicity ◽

Uptake System ◽

Maize Seedlings ◽

Cd Toxicity ◽

Maize Plants ◽

Pre Treatment ◽

Free Media

The interaction of manganese with cadmium (Cd) toxicity was studied on maize plants grown in hydroponics. Manganese supplied as MnSO<sub>4</sub>clearly alleviated the toxic effect of cadmium on the root growth of maize seedlings. The magnitude of alleviation was dose dependant and total abolition of 10µM Cd toxicity on root growth was observed at Mn/Cd ratio of 20:1. The 12 h pre-treatment with 10μM Cd was generally toxic for nitrate uptake and reduction (both determined in Cd-free media). The beneficial effect of 100μM Mn on this toxicity was confirmed for the low-affinity nitrate uptake system, but on the other hand, Mn alone seems to be slightly toxic for high affinity nitrate uptake system and on the nitrate reductase activity.

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Transmission of Xylella fastidiosa, Causal Agent of Citrus Variegated Chlorosis, by the Glassy-Winged Sharpshooter, Homalodisca coagulata

Plant Disease ◽

10.1094/pd-90-0567 ◽

2006 ◽

Vol 90 (5) ◽

pp. 567-570 ◽

Cited By ~ 20

Author(s):

V. D. Damsteegt ◽

R. H. Brlansky ◽

P. A. Phillips ◽

Avijit Roy

Keyword(s):

Xylella Fastidiosa ◽

The United States ◽

Citrus Variegated Chlorosis ◽

Homalodisca Coagulata ◽

Causal Pathogen ◽

Polymerase Chain ◽

Species Specific ◽

Transmission Studies ◽

Test Plants ◽

Important Disease

Citrus variegated chlorosis (CVC) is an economically important disease of citrus in Brazil and Argentina. The causal pathogen is a strain of Xylella fastidiosa transmitted by several sharpshooter species. The glassy-winged sharpshooter (GWSS), Homalodisca coagulata, has become an important new pest of citrus and grapevines in California, where it transmits X. fastidiosa strains to several crops including grapes, oleander, and almonds. Transmission studies over a 3-year period at the USDA BSL3-P containment facility at Fort Detrick, MD, utilizing California field-collected GWSS, a Brazilian strain of CVC, and Madam Vinous sweet orange seedlings, have shown a consistent although low level of transmission of CVC. Test plants were observed for CVC symptoms, analyzed by polymerase chain reaction using species-specific primers for X. fastidiosa, membrane entrapment immunofluorescence, and scanning electron microscopy. X. fastidiosa was not detected in field-collected GWSS but was detected in GWSS following feeding on CVC-infected source plants. Transmission of the CVC strain of X. fastidiosa by GWSS increases the risk of establishment of CVC in the United States if it were introduced.

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First Report of Bacterial Fruit Blotch of Watermelon in Oregon

Plant Disease ◽

10.1094/pdis.1997.81.1.113a ◽

1997 ◽

Vol 81 (1) ◽

pp. 113-113 ◽

Cited By ~ 9

Author(s):

P. B. Hamm ◽

D. S. Spink ◽

G. H. Clough ◽

K. S. Mohan

Keyword(s):

Citrullus Lanatus ◽

Nutrient Agar ◽

Green Water ◽

Hypodermic Needle ◽

Identification System ◽

Columbia Basin ◽

Plastic Mulch ◽

First Report ◽

Bacterial Fruit Blotch ◽

Test Plants

Most of the watermelons, Citrullus lanatus (Thunb.) Matsum. & Nakai, consumed in the Pacific Northwest during the summer months are grown in the southern Columbia Basin under dry (<5 cm rainfall), low relative humidity (46 to 57%), and high temperature (29 to 41°C) conditions, using transplants, plastic mulch, and drip irrigation. During May 1996, irregularly shaped, water-soaked lesions were observed on cotyledons and first true leaves of watermelon cv. Sangria transplants growing in a greenhouse. Similar lesions were observed later on older leaves in a commercial field of cv. Millionaire. Microscopic examination of symptomatic tissue revealed bacterial streaming, and isolation on nutrient agar consistently yielded numerous creamy to off-white bacterial colonies. Bacteria from purified, single colonies were Gram negative and rod shaped. Physiological characterization by the Biolog GN Bacterial Identification System (version 3.5) showed a similarity of 0.971 to the Biolog description for Acidovorax avenae subsp. citrulli. Pathogenicity of two strains was confirmed in three separate tests by hypodermic needle infiltration of cotyledons or by stab inoculation into hypocotyls of 12 to 24 21-day-old cv. Crimson Sweet seedlings with aqueous suspensions of bacteria containing approximately 6.0 × 108 CFU/ml. Inoculum was prepared from 48-h-old nutrient agar cultures. Test plants were incubated in the greenhouse at 21°C, under a 16-h photoperiod. Hypocotyl and cotyledon inoculations produced water-soaked lesions within 24 to 48 h on both the hypocotyl and cotyledons or just the cotyledon, respectively, on plants inoculated by either method. No symptoms developed on control plants infiltrated or stabbed with sterile water only. Isolations from three symptomatic seedlings yielded colonies similar in morphology to those used for inoculation. Tests of two purified cultures by Biolog indicated the bacteria were A. avenae subsp. citrulli. The symptomatic test plants were transplanted to fields, and the maturing melons developed large, dark green, water-soaked lesions with irregular margins. Similar fruit symptoms were seen in commercial fields. Labels on seed used in commercial production and in our tests warned of risks related to fruit blotch. This is the first report of bacterial fruit blotch of watermelon in Oregon. This disease may have a significant impact on watermelon production in the Columbia Basin.

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First Report of Sclerotinia sclerotiorum on Common Ragweed (Ambrosia artemisiifolia) in Europe

Plant Disease ◽

10.1094/pdis.1999.83.3.302c ◽

1999 ◽

Vol 83 (3) ◽

pp. 302-302 ◽

Cited By ~ 1

Author(s):

Gy. Bohár ◽

L. Kiss

Keyword(s):

Sclerotinia Sclerotiorum ◽

Aerial Mycelium ◽

The United States ◽

Ambrosia Artemisiifolia ◽

American Phytopathological Society ◽

Common Ragweed ◽

First Report ◽

Sclerotinia Rot ◽

Stem Lesions ◽

Test Plants

Common ragweed (Ambrosia artemisiifolia L.) is reported as a host of Sclerotinia sclerotiorum (Lib.) de Bary in North America (2,4), but not in Europe. A Hungarian survey of fungal diseases of ragweed in 1994 did not find sclerotinia rot of common ragweed (A. artemisiifolia var. elatior (L.) Descourt.) (1). In autumn 1998, mature ragweed plants, 1 to 1.5 m tall, were collected from the borders of four sunflower (Helianthus annuus L.) fields in which sclerotinia rot of sunflower was frequently observed during the season, and also from six other roadside sites in Hungary. Ragweed plants exhibiting symptoms characteristic of sclerotinia rot, i.e., wilting foliage and light brown, dry lesions on the stems, were found only near two sunflower fields. Black, round to irregular or oblong sclerotia were also observed on the infected ragweed plants both externally on the stem lesions and internally, in the pith cavity. Sclerotia measured up to 5 mm in diameter and were 5 to 14 mm long. After isolation on potato dextrose agar, the pathogen produced abundant aerial mycelium and large sclerotia characteristic of S. sclerotiorum. To confirm pathogenicity, potted seedlings and mature plants of ragweed were inoculated in the greenhouse with autoclaved wheat grains colonized with mycelia of S. sclerotiorum placed 0.5 to 1 cm from the collar of the test plants. Seedlings were killed in 2 to 3 days while mature plants wilted after 5 to 6 days. In a field test, six mature plants were inoculated by attaching mycelial disks to their stems with Parafilm. These plants wilted 12 to 14 days after inoculation. The pathogen was reisolated from all diseased plants. This is the first report of S. sclerotiorum on common ragweed in Europe. Nonsclerotial mutants of the fungus (3) are being produced to be tested as potential biocontrol agents of common ragweed, which has become not only the most widespread, but also the most important allergenic plant species in Hungary since the early 1990s. References: (1) Gy. Bohár and L. Vajna. Nōvényvédelem 32:527, 1996. (2) G. J. Boland and R. Hall. Can. J. Plant Pathol. 16:93, 1994. (3) G. J. Boland and E. A. Smith. Phytopathology 81:766, 1991.(4) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

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Contribution to the knowledge of diversity of Fusarium associated with maize in Malaysia

Plant Protection Science ◽

10.17221/52/2008-pps ◽

2011 ◽

Vol 47 (No. 1) ◽

pp. 20-24 ◽

Cited By ~ 4

Author(s):

M.Z. Nur Ain Izzati ◽

A.R. Azmi ◽

M.S. Siti Nordahliawate ◽

J. Norazlina

Keyword(s):

Growth Rates ◽

Fusarium Species ◽

First Report ◽

Maize Plants ◽

Mode Of Production

The Fusarium species associated with maize are widely distributed in Malaysia. Eight Fusarium species were obtained in this country. A series of field samplings was conducted from 2006 to 2008, when 167 Fusarium isolates were obtained from maize plants in seven locations throughout Malaysia. The determination was based on micro- and macromorphological features (growth rates, colony features, mode of production of microconidia, macroconidia, conidiophores, and chlamydospores). F. proliferatum (29.9% isolates), F. semitectum (22.2% isolates), F. verticillioides (13.7% isolates), and F. subglutinans (12.6% isolates) were found out most frequently. F. equiseti, F. pseudograminearum, F. oxysporum, and F. solani were also isolated. This is the first report on the occurrence of F. equiseti, F. pseudograminearum, and F. subglutinans associated with maize plants in Malaysia.

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