scholarly journals Gibberellin promotion of physiological leaf spot in detached 'Golden Delicious' apple leaves.

1975 ◽  
Vol 23 (2) ◽  
pp. 126-130
Author(s):  
W.J. Kender ◽  
H. Jonkers
Keyword(s):  
Leaf Spot ◽  
Growth Substance ◽  
Apple Leaves ◽  
Golden Delicious ◽  
Detached Leaves

The development of leaf spot, a non-pathogenic disorder specific to the cv. Golden Delicious, was accelerated in detached leaves (whether previously unmarked or showing leaf spot) when these were cultured in solutions of GA3 or GA4+7 at 10, 50 or 100 mg/l for 72 h. About 15% of the foliage on the trees exhibited leaf spot at the time selected leaves were detached for culture. In a second experiment with cultured leaves the interaction of PBA and GA4+7 applied simultaneously was highly synergistic in increasing the severity of the disorder when compared with the effect of either growth substance alone. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Improving accuracy, precision and reliability of severity estimates of Glomerella leaf spot on apple leaves using a new standard area diagram set

2018 ◽  
Vol 153 (3) ◽  
pp. 975-982 ◽  
Author(s):  
Rafaele Regina Moreira ◽  
Henrique da Silva Silveira Duarte ◽  
Louise Larissa May De Mio
Keyword(s):  
Leaf Spot ◽  
Apple Leaves ◽  
Glomerella Leaf Spot ◽  
Improving Accuracy

Assessing resistance to spring black stem and leaf spot of alfalfa caused by Phoma spp.

2004 ◽  
Vol 84 (1) ◽  
pp. 311-317 ◽  
Author(s):  
H. Wang ◽  
S. F. Hwang ◽  
K. F. Chang ◽  
B. D. Gossen ◽  
G. D. Turnbull ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Leaf Spot ◽  
Similar Pattern ◽  
Disease Incidence ◽  
Field Trials ◽  
Disease Reaction ◽  
Detached Leaf ◽  
Controlled Conditions ◽  
Detached Leaves ◽  
Phoma Sclerotioides

The disease reaction of alfalfa (Medicago sativa) cultivars to spring black stem was evaluated in field trials and greenhouse experiments. In field trials, differences in cultivar reaction to leaf spot (predominantly spring black stem) were observed in 9 of 16 station years. The reaction of certain cultivars was consistent across most trials, but other cultivars were quite variable. Under controlled conditions, one isolate each of Phoma sclerotioides and P. exigua produced symptoms on alfalfa leaves that were similar to those caused by P. medicaginis. These results indicate that P. medicaginis is not the only pathogen responsible for symptoms of spring black stem on alfalfa in the prairie region. In a detached-leaf study, one isolate each of P. medicaginis, P. sclerotioides and P. exigua produced leaf lesions on all 18 alfalfa cultivars assessed. Disease incidence in Absolute, Algonquin, Pickseed 3006 and Anik (M. sativa subsp. falcata) was lower than in 630 and AC Blue J. Inoculation of eight selected cultivars using a range of spore concentrations under controlled conditions showed a similar pattern; all three isolates produced leaf lesions on all eight cultivars. Ino culation with conidial suspensions of P. medicaginis resulted in a lower disease incidence on Absolute than on Beaver. Key words: Medicago sativa, Medicago sativa subsp. falcata, Phoma medicaginis, P. sclerotioides, P. exigua, detached leaves.

scholarly journals First Report of Leaf Spot Caused by Alternaria alternata on Kiwifruit in Italy

Plant Disease ◽  
1999 ◽  
Vol 83 (5) ◽  
pp. 487-487 ◽  
Author(s):  
L. Corazza ◽  
L. Luongo ◽  
M. Parisi
Keyword(s):  
New Zealand ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Southern Italy ◽  
Morphological Characteristics ◽  
Potato Dextrose Agar ◽  
First Report ◽  
Leaf Spots ◽  
Detached Leaves ◽  
Pathogenicity Tests

A leaf spot of kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferg.) leaves was recently observed on plants of the cultivar Hayward in an orchard near Salerno, in southern Italy. The affected plants showed early severe defoliation. The fungus isolated from the infected leaves was identified as Alternaria alternata (Fr.:Fr.) Keissl., based on conidial morphological characteristics. Pathogenicity tests were made by inoculating detached leaves of male pollinator cultivar Tomuri and the female cultivars Hayward and Bruno with a 7-mm disk taken from actively growing cultures of the fungus on potato dextrose agar (PDA). After 14 days, necrotic leaf spots developed and A. alternata was consistently isolated from the inoculated leaves. A. alternata has been observed as a pathogen on leaves and fruits in New Zealand. In the Mediterranean, it has been reported in Israel (2) and in the island of Crete (1). This is the first report of Alternaria leaf spot on kiwifruit in Italy. References: (1) V. A. Bourbos and M. T. Skoudridakis. Petria 7:111, 1997. (2) A. Sive and D. Resnizky. Alon Hanotea 41:409, 1987.

scholarly journals First Report of Myrothecium roridum Causing Leaf Spot on Garden Hydrangea in the United States

Plant Disease ◽  
2010 ◽  
Vol 94 (10) ◽  
pp. 1266-1266 ◽  
Author(s):  
M. T. Mmbaga ◽  
Y. Li ◽  
M.-S. Kim
Keyword(s):  
United States ◽  
Leaf Spot ◽  
Incubation Temperature ◽  
Morphological Characteristics ◽  
The United States ◽  
Control Treatment ◽  
Medium Size ◽  
First Report ◽  
Detached Leaves ◽  
Myrothecium Roridum

Garden hydrangea (Hydrangea macrophylla) is a popular flowering shrub that grows well in Tennessee but foliar diseases impact their appearance, health, and market value. Leaves of garden hydrangea showed necrotic lesions with concentric rings of brown and dark brown at the Tennessee State University Research Center in McMinnville. A fungus was recovered from June and July leaf samples with 20% frequency of isolation from approximately 40 leaf pieces that were surface sterilized and plated in potato dextrose agar (PDA). Isolates developed white colonies and dark gray-to-black, spore-bearing mycelial cushions (sporodochia) that formed on older colonies (30 to 45 days old) at 25 ± 2°C. Conidia were hyaline to slightly dark, one-celled, ovoid to elongate with rounded ends, and 2.0 to 2.5 × 5.5 to 6.5 μm. These morphological characteristics were consistent with those described for Myrothecium roridum Tode ex Fr. (1). DNA sequence for three isolates of this fungus showed identical internal transcribed spacer (ITS) region sequences (GenBank Accession No. HM215150) with 99% maximum sequence identity to M. roridum isolates (GenBank Accession Nos. AJ301994.1 and AJ608978). Another close match (97%) was with M. gramineum (GenBank Accession No. FJ235084) and M. tongaense (GenBank Accession No. AY254157). Pathogenicity of M. roridum was evaluated on detached leaves from three hydrangea cultivars, Nikko Blue, All Summer Beauty, and Blue bird. Four, medium-size, detached leaves were placed in moist chambers and inoculated with 5-mm mycelial plugs from 14-day-old cultures; sterile PDA was used as the control treatment. A randomized, complete-block experimental design was used with a replication of four leaves per cultivar. Incubation temperature was 26 ± 2°C. Necrotic lesions started 4 to 5 days after inoculation in all inoculated leaves; lesions expanded to cover 10 to 25% of the leaf surface and formed concentric rings; sterile PDA plugs did not produce leaf lesions. This experiment was repeated twice and similar symptoms were produced; M. roridum was reisolated from all inoculated leaves. Spray inoculation of detached leaves of hydrangea cv. Pretty Maiden with 5 × 104 spores/ml produced similar symptoms; leaves sprayed with water remained symptom free. M. roridum has a wide host range and similar symptoms have been reported on other ornamentals including salvia (2), begonia ( http://mrec.ifas.ufl.edu/foliage/folnotes/begonias.htm ), gardenia ( http://cfextension.ifas.ufl.edu/agriculture/ nursery_production/ documents/Gardenia.pdf ), and cotton (3). To our knowledge, this is the first report of M. roridum causing leaf spot on H. macrophylla in the United States. References: (1) M. B. Ellis. Page 465 in: More Damatacous Hyphomycetes. CABI, Wallingford, UK. 1993. (2) J. A. Mangandi et al. Plant Dis. 91:772, 2007. (3) R. L. Munjal. Indian Phytopathol. New Delhi, 13:150, 1960.

scholarly journals Glomerella leaf spot in apple: validation of proposed diagrammatic scale and efficiency of fungicides

2010 ◽  
Vol 40 (7) ◽  
pp. 1502-1508 ◽  
Author(s):  
Lígia Sayko Kowata ◽  
Michele Strapasson ◽  
Márcio Alberto Challiol ◽  
Louise Larissa May-De Mio
Keyword(s):  
Leaf Spot ◽  
Scale Validation ◽  
Severity Assessment ◽  
Stimulus Response ◽  
Apple Leaves ◽  
Colletotrichum Spp ◽  
Glomerella Leaf Spot ◽  
Fruit Harvest ◽  
Diagrammatic Scale

A diagrammatic scale to assess Glomerella leaf spot severity (Colletotrichum spp) was developed and validated during the tryout of a fungicide efficiency experiment in the field. Apple leaves were collected for determination of minimum and maximum severity limits; intermediate levels were obtained according to "Weber-Fechner's stimulus-response law". Scale validation was performed by four raters, which estimated the severity in 100 leaves; with and without the use of the scale. An experiment was carried out in a commercial orchard in randomized blocks with 10 plants. The treatments and dosages (g 100 L-1 of water) used were: cyprodinil (15); pyrimethanil (30, 37.5, 45); propineb (140) e mancozeb (160) + tebuconazole (12.50), and a control (no spray). The incidence and severity in leaves; number of fruits, weight and incidence in fruit (harvest) and defoliation (after harvest) were evaluated. The proposed scale showed the levels of 0.08; 0.28; 0.99; 3.45; 11.23 and 30.93%. The scale was adequate for severity assessment; R2 changed from 0.68 to 0.96 with the use of the scale. Pyrimethanil treatments did not control the disease. The incidence on fruit was 30 and on leaves 63%. The incidence was reduced in 35.6% (propineb) and 33.7% (mancozeb + tebuconazole) related to the control, these treatments were efficient to control the disease. The defoliation was 44 % in the control against 9.6 and 2.5% to propineb and mancozeb + tebuconazole.

scholarly journals Biological Control of Leaf Spot and Growth Promotion of Eucalyptus Plants by Trichoderma spp.

2018 ◽  
Vol 10 (9) ◽  
pp. 459 ◽  
Author(s):  
Magno Rodrigues Carvalho Filho ◽  
Irene Martins ◽  
Gustavo Henrique Silva Peixoto ◽  
Paulo Henrique Pereira Costa Muniz ◽  
Daniel Diego Costa Carvalho ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Growth Promotion ◽  
Suppressive Effect ◽  
Growth Promoter ◽  
Trichoderma Spp ◽  
Parboiled Rice ◽  
General Terms ◽  
Detached Leaves ◽  
Trichoderma Isolates

This study aimed to evaluate the potential of twelve Trichoderma isolates on eucalyptus leaf spot control induced by Cylindrocladium scoparium and determine the sporulation capacity of the isolates on two substrates (parboiled rice and millet) for selection of potential biocontrol and growth promoter agents, in eucalypt seedlings. In the in vitro experiments, volatile and non-volatile metabolites tests showed different levels of inhibition of the pathogen mycelial growth. In tests on detached leaves, it was observed suppression of disease symptoms with all Trichoderma strains in leaves inoculated with CEN494 isolate of the pathogen, whereas with isolate CEN517 did not found the same efficiency. Sporulation of Trichoderma was higher using parboiled rice as the substrate, compared to millet. In general terms, it was obtained 3.38 × 109 and 2.84 × 109 conidia/g for the two substrates, respectively. Some of these Trichoderma isolates may be used in development of biofungicides for biocontrol of leaf spot, especially CEN262, due to its suppressive effect on C. scoparium, high sporulation, growth promotion capacity and endophytic colonization in eucalyptus seedlings.

scholarly journals A New Disease, Bacterial Leaf Spot of Rape, Caused by Atypical Pseudomonas viridiflava in South Korea

Plant Disease ◽  
2010 ◽  
Vol 94 (9) ◽  
pp. 1164-1164 ◽  
Author(s):  
I.-S. Myung ◽  
Y.-K. Lee ◽  
S. W. Lee ◽  
W. G. Kim ◽  
H. S. Shim ◽  
...  
Keyword(s):  
South Korea ◽  
Ethyl Alcohol ◽  
Leaf Spot ◽  
Pcr Primers ◽  
Bacterial Suspension ◽  
Distilled Water ◽  
Bacterial Leaf Spot ◽  
Spray Inoculation ◽  
Pseudomonas Viridiflava ◽  
Detached Leaves

In March 2007, a bacterial leaf spot of rape (Brassica napus var. oleifera) was observed in fields near Seogwipo City, Jeju Province, South Korea. Symptoms on leaves included white and corky-brown spots and sometimes water-soaked spots on the lower leaf surface. Seven bacterial isolates (BC2495–BC2497 and BC2506–BC2509) were recovered on trypticase soy agar (TSA) from leaf spot lesions surface sterilized in 70% ethyl alcohol for 1 min. Isolates were gram-negative, aerobic rods with one to three flagella. Pathogenicity was evaluated on 2-week-old rape plants by spot and spray inoculation. Bacteria were grown on TSA for 48 h at 25°C. Five microliters of bacterial suspension in sterile distilled water (1 × 105 CFU/ml) were spot inoculated on pinpricked positions of five detached leaves for each isolate. The detached leaves were incubated in a plastic box with high humidity at 20°C. Spot-inoculated surfaces turned white 48 h after inoculation followed by a brownish discoloration. A bacterial suspension in sterile distilled water (100 ml at 1 × 105 CFU/ml) was sprayed onto three plants for each isolate. Plants were maintained in a growth chamber at 20°C and 90% relative humidity. Isolates induced identical symptoms 2 weeks after spray inoculation as those originally observed on rape in the fields. Bacteria were reisolated 18 days after inoculation from diseased lesions surface sterilized in 70% ethyl alcohol for 1 min. Pathogenicity of the reisolated bacteria was confirmed by spot inoculation as described above. No symptoms were noted on detached leaves and intact plants inoculated with sterilized distilled water. Using the Biolog Microbial Identification System, Version 4.2 (Biolog Inc., Hayward, CA), the isolates were identified as Pseudomonas viridiflava with a Biolog similarity index range of 0.52 to 0.72 after 24 h. Results of LOPAT tests (2) of isolates were identical to that of atypical P. viridiflava reported by Gonzalez et al. (1). Levan production and pectolytic activity of the isolates were variable. All isolates were positive for tobacco hypersensitivity and negative for oxidase reaction and arginine dihydrolase production. The 16S rDNA region (1,442 bp) of the isolates (GenBank Accession Nos. HM190218-HM190224; P. viridiflava CFBP2107T = HM190229), amplified by using universal PCR primers, shared 100% sequence identity with atypical P. viridiflava (GenBank Accession No. AM182934) (1). The gyrB sequence (638 bp) from the isolates (GenBank Accession Nos. HM190232-HM190238; P. viridiflava CFBP2107T = HM190239), amplified by using previously reported PCR primers (3), had a distance index value range of 0.029 to 0.031 with that of the P. viridiflava CFBP2107T (=BC2597) as determined by Jukes-Cantor model using MEGA Version 4.1 (4). On the basis of phenotypic characteristics and the sequences, the seven isolates were identified as atypical P. viridiflava. The disease is named “bacterial leaf spot”. To our knowledge, this is the first report of bacterial leaf spot of rape caused by atypical P. viridiflava. References: (1) A. J. Gonzalez et al. Appl. Environ. Microbiol. 69:2936, 2003. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (3) H. Sawada et al. J. Mol. Evol. 49:627, 1999. (4) K. Tamura et al. Mol. Biol. Evol. 24:1596, 2007.

scholarly journals FOLIAR APPLICATION OF BENZYLADENINE INCREASES ENDOGENOUS LEAF CYTOKININ IN APPLE

HortScience ◽  
1991 ◽  
Vol 26 (5) ◽  
pp. 480d-480 ◽  
Author(s):  
Robin A. Cohen ◽  
Duane W. Greene
Keyword(s):  
Growth Regulator ◽  
Foliar Application ◽  
Foliar Spray ◽  
Application Rate ◽  
Endogenous Cytokinin ◽  
Full Bloom ◽  
Apple Leaves ◽  
Golden Delicious

Two experiments were conducted to examine the effects of growth regulator application on cytokinin levels in developing apple leaves. In experiment 1, gibberellin GA4/7 (100 mg·liter-1) and benzyladenine (BA, 100 mg·liter-1) were applied alone or in combination as a foliar spray to `Golden Delicious' 7 days after full bloom. In experiment 2, BA was applied at 50 or 100 mg·liter-1 as a foliar spray to `Morespur McIntosh' 18 days after full bloom. Trans-zeatin ribosidelike (t-ZR) levels were determined by immunoassay. In experiment 1, GA1/7 had no effect and BA increased t-ZR-like levels. In experiment 2, BA increased t-ZR levels quadratically with application rate. The increase in endogenous cytokinin levels with BA treatment occured within 2 hours. Initially, t-ZR-like levels were 47 times higher in the BA (100 mg·liter-1) treated leaves as compared to check leaves. Over the next 8 days, t-ZR-like content in treated leaves decreased in a cubic manner.

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