scholarly journals First Report of Pseudomonas cichorii causing Bacterial Leaf Spot on Romaine lettuce (Lactuca sativa var. longifolia) and escarole (Cichorium endivia) in New Jersey.

Plant Disease ◽  
2021 ◽  
Author(s):  
Nrupali Patel ◽  
Radhika D Patel ◽  
Andrew Wyenandt ◽  
Donald Y Kobayashi
Keyword(s):  
New Jersey ◽  
Leaf Spot ◽  
Diseased Plant ◽  
Sterile Water ◽  
Bacterial Leaf Spot ◽  
Romaine Lettuce ◽  
Pseudomonas Cichorii ◽  
Single Strain ◽  
Sweet Basil ◽  
Parenchyma Tissue

We previously reported an outbreak of bacterial leaf spot (BLS) caused by Pseudomonas cichorii occurring on sweet basil in New Jersey during the summer of 2018 (Patel et al. 2019), a growing season characterized by increased leaf wetness due to high humidity and unusually high levels of summer rains. Leaf spot was also observed, as a one-time event, on older mature leaves on romaine and escarole lettuce during that same year. Symptoms on escarole were observed as grayish brown-to-black concentric lesions on leaf parenchyma tissue, ranging from 1 mm to 1-2 cm in diameter. In more severely diseased samples, lesions coalesced to form larger necrotic areas giving a blight appearance. On occasion, infection was observed in leaf midveins as brownish gray necrosis. Symptoms on romaine lettuce were observed mostly as coalesced blackened lesions on leaf parenchyma tissue near margins with a rotted consistency that spread to the midvein in severe cases. Margins of leaf lesions were excised and macerated in sterile water before streaking onto Nutrient Agar (NA) and King’s medium B agar (KMB) (Schaad et al. 2001). Growth on both NA and KMB were predominantly cream-colored circular bacterial colonies with undulated margins. Colonies on KMB fluoresced blue under 365nm UV light. Two representative colonies isolated from each host were selected for further characterization. All isolated tested negative for levan production, positive for oxidase, negative for potato rot, negative for arginine dihydrolase, and induced a strong hypersensitive response on tobacco within 24 h, consistent with LOPAT descriptions for P. cichorii (Lelliott et al. 1966). A single strain from each host (ESC6F2 and Rom1-1) was further characterized genetically to confirm species. PCR analysis using two primers sets: 16S rRNA gene universal primers 27F/1492R and Hcr1 primers used to amplify a 520 bp region of the pathogenicity gene cluster hrcRST in P. cichorii (Patel et al. 2019; Cottyn et al. 2011). Partial 16S rDNA gene sequences were deposited in the GenBank database for each isolate (ESC6F2: MT974180; and Rom1-1: MT982172). Sequence comparisons of ESC6F2 and Rom1-1 shared 99% identity with each other and several P. cichorii strains within the GenBank database, including strain B5-2-1 isolated from sweet basil in NJ the same year (MK501753). The partial hrcRST locus (strain ESC6F2: MW048775 and Rom1-1: MW048774) shared 100% identity to each other and strain B5-2-1 (MK507764), and 99% identity with P. cichorii strain P18-1 (MH396007) isolated from Ocimum basilicum in Hawaii. Koch’s postulate was performed on escarole var. Full Heart and Romaine lettuce var. Ideal Cos to confirm pathogenicity of the isolated strains. Bacterial suspensions (1x107 cfu/ml) were syringe-injected (0.1 ml) into the leaf midribs, and pressure infiltrated into leaf parenchyma tissue of 3 plants. Control plants were inoculated with sterile water. Blackened necrosis developed within 72 h around bacteria-inoculation points, which expanded beyond inoculation points within a week. In contrast, control plants remained healthy and symptomless. Although significant crop loss occurred due to BLS on escarole and romaine lettuce, P. cichorii has not been isolated from diseased plant material since 2018. This suggests inoculum sources did not persist beyond 2018, or favorable environmental conditions for disease are inconsistent to cause noticeable damage to New Jersey crops. References: Cottyn, B., et al. 2011. Plant Pathol. 60:453. Lelliott, R. A., et al. 1966. J. Appl. Bacteriol. 29:470. Patel, N., et al. 2019. Plant Disease. 103:2666

scholarly journals First Report of Pseudomonas cichorii Causing Bacterial Leaf Spot on Sweet Basil (Ocimum basilicum) in New Jersey

Plant Disease ◽  
2019 ◽  
Vol 103 (10) ◽  
pp. 2666-2666
Author(s):  
N. Patel ◽  
D. Y. Kobayashi ◽  
A. J. Noto ◽  
A. C. Baldwin ◽  
J. E. Simon ◽  
...  
Keyword(s):  
New Jersey ◽  
Leaf Spot ◽  
Ocimum Basilicum ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report ◽  
Sweet Basil

scholarly journals First Report of Basil Leaf Spot Caused by Pseudomonas cichorii in Louisiana and Cultivar Screening Results

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1283-1283 ◽  
Author(s):  
G. E. Holcomb ◽  
P. J. Cox
Keyword(s):  
Leaf Spot ◽  
Screening Tests ◽  
Minor Importance ◽  
Bacterial Cells ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report ◽  
Sweet Basil ◽  
Leaf Spots ◽  
Cultivar Screening

A leaf spot of basil, Ocimum basilicum L., was observed on container-grown and field plantings of cultivars Aussie Sweet and Sweet Basil. The disease was of minor importance under field conditions, but was of potential economic importance in seedling production. Gray to black, watersoaked, necrotic spots commonly developed at leaf margins. Large numbers of bacteria were released from cut lesions when viewed by light microscopy. Single colony bacterial isolates were established on nutrient dextrose agar (NDA) and yeast extract-dextrose-calcium carbonate agar (YDC). Pathogencity tests were performed by misting a water suspension containing 104 bacterial cells per ml on healthy basil plants. Plants were held for 24 h in a dew chamber at 26°C and then moved to a greenhouse for observation. Typical leaf spots developed on inoculated plants in 2 days, but not on healthy control plants, and the bacterium was reisolated. The bacterium was characterized as a gram-negative, motile rod, negative for potato rot test, positive in tobacco hypersensitivity test, and oxidase positive. Isolates were identified as Pseudomonas cichorii according to the Biolog Microplate system (similarities ranged from 0.937 to 0.995). Screening tests were conducted by inoculating 15 basil cultivars, six replicates each, and rating them for disease severity based on a scale of 1 to 5 in which 1 = no disease and 5 = dead plants. Cultivars most resistant to bacterial leaf spot (ratings in parentheses are averages of two tests and those followed by the same letter are not significantly different according to Tukey's Studentized Range Test, P = 0.05) were Green Bouquet (2.0 a), Piccolo (2.2 a), Mrs. Burn's Lemon (2.2 a), Genovese (2.4 a), and Dark Opal (2.5 ab). Moderately susceptible cultivars were Bush Green (2.8 abc), Sweet Basil (2.8 abc), Large Green (2.9 abcd), Lemon (3.1 abcd), and Mexican Spice (3.6 bcd). The most susceptible cultivars were Lettuce Leaved (3.8 cd), Thai (3.8 cd), Napoletano (4.0 de), Green Ruffles (5.0 e), and Purple Ruffles (5.0 e). Bacterial leaf spot of basil caused by P. cichorii was first reported in the U.S. from Florida (1). Other bacterial diseases reported on basil include leaf blight from Egypt caused by P. syringae (2) and leaf necrosis from California caused by P. viridiflava (3). This is the first report on the occurrence of basil bacterial leaf spot in Louisiana and the first reported information on cultivar susceptibility. References: (1) S. M. Burgess et al. Proc. Fla. State Hortic. Soc. 99:249, 1986. (2) S. A. M. El-Sadek et al. Assiut J. Agric. Sci. 22:2, 1991. (3) E. L. Little et al. Plant Dis. 78:831, 1994.

scholarly journals First Report of Leaf Spot Caused by Pseudomonas cichorii on Coreopsis lanceolata in Italy

Plant Disease ◽  
2009 ◽  
Vol 93 (9) ◽  
pp. 967-967 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
C. Moretti ◽  
M. L. Gullino
Keyword(s):  
Leaf Spot ◽  
Casein Hydrolysate ◽  
Its Region ◽  
Soft Rot ◽  
Chrysanthemum Morifolium ◽  
Luria Bertani ◽  
Nutrient Broth ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report

Coreopsis lanceolata L. (Compositae), an ornamental species grown in parks and gardens, is very much appreciated for its long-lasting flowering period. In August of 2008, pot-grown plants with necrotic leaf lesions were observed in a commercial nursery located near Biella (northern Italy). Lesions were present, especially along the margin of basal leaves, and sometimes had a chlorotic halo. On infected leaves, dark brown necrosis developed. Leaf stalks were sometimes affected. In many cases, the leaves, especially those at collar level, were withered. Of 1,500 plants, 15% were infected by the disease. Microscopic examination did not reveal any fungal structures within the lesions. Small fragments of tissue from 30 affected leaves were macerated for 15 min in casein hydrolysate and 0.1-ml aliquots of the resulting suspension were spread onto Luria Bertani agar (LB) and potato dextrose agar (PDA). Plates were maintained at 22 ± 1°C for 48 h. No fungi were isolated from the leaf spots on LB or PDA. Colonies similar to those of Pseudomonas spp. were consistently isolated on LB. Colonies were fluorescent on King's medium B, levan negative, oxidase positive, potato soft rot negative, arginine dihydrolase negative, and tobacco hypersensitivity positive (LOPAT test). The bacterial colonies were identified as Pseudomonas cichorii (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers 27F and 1492R and sequenced (GenBank Accession No. FJ534557). BLAST analysis (1) of the 998-bp segment showed a 98% homology with the sequence of P. cichorii. The pathogenicity of one isolate was tested twice by growing the bacterium in nutrient broth shake cultures for 48 h at 20 ± 1°C. The suspension was centrifuged, the cell pellet resuspended in sterile water to a concentration of 107 CFU/ml, and 30 4-month-old healthy coreopsis plants were sprayed with the inoculum. The same number of plants was sprayed with sterile nutrient broth as a control. After inoculation, plants were covered with plastic bags for 48 h and placed in a growth chamber at 20 ± 1°C. Five days after inoculation, lesions similar to those seen in the field were observed on all plants inoculated with the bacterium, but not on the controls. Ten days later, 40% of the leaves were withered. Isolations were made from the lesion margins on LB and the resulting bacterial colonies were again identified as P. cichorii. The pathogen caused the same symptoms also on plants of Dendranthema frutescens (cv. Camilla), Chrysanthemum morifolium (cvs. Eleonora and Captiva), and an Osteospermum sp. (cv. Wild side) when artificially inoculated with the pathogen with the same methodology. The same bacterial leaf spot caused by P. cichorii was observed in 2005 in other nurseries in the same area on Phlox paniculata (3). To our knowledge, this is the first report of bacterial leaf spot caused by P. cichorii on C. lanceolata in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) H. Bergey et al. Bergey's Manual on Determinative Bacteriology. Williams and Wilkins, Baltimore, MD, 1994. (3) A. Garibaldi et al. Plant Dis. 89:912, 2005.

scholarly journals First Report of Bacterial Leaf Spot of Cucumber Caused by Pseudomonas cichorii in China

Plant Disease ◽  
2019 ◽  
Vol 103 (1) ◽  
pp. 147
Author(s):  
X. Y. Fu ◽  
R. Y. Zhang ◽  
Z. Q. Tan ◽  
T. Liu ◽  
Z. Q. Peng
Keyword(s):  
Leaf Spot ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report

scholarly journals First Report of Bacterial Leaf Spot Caused by Pseudomonas cichorii on Thai Basil in Hawaii

Plant Disease ◽  
2018 ◽  
Vol 102 (12) ◽  
pp. 2637-2637
Author(s):  
B. C. Luiz ◽  
W. P. Heller ◽  
E. Brill ◽  
B. C. Bushe ◽  
L. M. Keith
Keyword(s):  
Leaf Spot ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report

scholarly journals First Report of Bacterial Leaf Spot of Witloof, Caused by Pseudomonas cichorii in Korea

Plant Disease ◽  
2013 ◽  
Vol 97 (10) ◽  
pp. 1376-1376 ◽  
Author(s):  
I.-S. Myung ◽  
J.-K. Choi ◽  
J. Y. Lee ◽  
M.-J. Yoon ◽  
E. Y. Hwang ◽  
...  
Keyword(s):  
16S Rrna ◽  
Economic Impact ◽  
Leaf Spot ◽  
Reference Strain ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report ◽  
Field Isolates ◽  
Original Field ◽  
Index Value

In August 2011, bacterial leaf spot was observed on witloof (Cichorium intybus L. var. foliosum) grown in a commercial field with 15% incidence in Injae, Korea. Symptoms on leaves included irregular brown to reddish brown spots in the center. Bacterial streaming from the lesions was observed microscopically. Bacterial isolates (BC3286, BC3287, and BC3308-BC3310) were recovered on Trypticase soy agar from lesions surface-sterilized in 70% ethyl alcohol for 30 s. The isolates were gram negative, urease negative, fluorescent on King's B agar, and had aerobic rods with 2 to 6 polar flagella. Pathogenicity tests were separately performed in different greenhouses located in Suwon (National Academy of Agricultural Science) and Chuncheon (Gangwondo Agricultural Research and Extension Services) in Korea. Pathogenicity was confirmed by spray inoculation of healthy, 10-day-old leaves of witloof plants (two plants/isolate) with a suspension of original field isolate (106 CFU/ml). Sterile distilled water was used as negative control. The inoculated plants were incubated in a growth chamber (25°C and 95% relative humidity [RH]) overnight, then transferred to a greenhouse at 23 to 27°C and 60 to 70% RH. Characteristic leaf spot symptoms were observed on inoculated witloof plants 8 days after inoculation. No symptoms were observed on control plants. The bacterium reisolated from the inoculated leaves was confirmed by analyzing sequence of the gyrB gene with direct sequencing method of PCR products using primers gyr-F and gyr-R (2). The sequence of reisolated bacteria shared 100% similarity with inoculated ones. In LOPAT (1) tests, all isolates and the reference strain of Pseudomonas cichorii CFBP2101T (=BC2595) were levan negative, oxidase positive, potato rot negative, arginine dihydrolase negative, and tobacco hypersensitivity positive, indicative of group III (–, +, –, –, +) of fluorescent pseudomonads. The 16S rRNA (1,408 bp), and gyrB (676 bp) regions were sequenced to aid in identification of the original field isolates as well as P. cichorii CFBP 2101T (=BC2595) using reported sets of PCR primers, fD1/rP2 and gyr-F/gyr-R, respectively (2,4). Phylogenetic analyses based on partial sequences of the gyrB and the 16S rRNA of Psudomonas spp. available in GenBank, the reference strain of P. cichorii CFBP2101T (=BC2595), and the witloof field isolates were conducted using the neighbor-joining method with Juke-Cantor model of distance calculation in MEGA version 5.1 (3). The isolates and the reference strain of P. cichorii CFBP2101T (=BC2595) was clustered in one group with P. cichorii strains in both phylogenetic trees based on the two sequences. Sequences of the 16S rRNA region had a distance index value ranging from 0.000 to 0.001 between the reference strain of P. cichori CFBP2101T (GenBank JX913784) and the field isolates (JX913785 to JX913789), and ranged from 0.000 to 0.001 within the field isolates. Sequences of the gyrB region had a distance index value ranging 0.029 to 0.033 between the reference strain (JX913790) and the field isolates (JX913791 to JX913795), and ranged from 0.000 to 0.041 within the field isolates. To our knowledge, this is the first report of bacterial leaf spot of witloof caused by P. cihorii in Korea. P. cichorii has a wide host range, and an important economic impact on vegetables. The disease is expected to result in a significant economic impact on root production of witloof in Korea. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) H. Sawada et al. J. Mol. Evol. 49:627, 1999. (3) K. Tamura et al. Mol. Biol. Evol. 28:2731, 2011. (4) W. G. Weinsburg et al. J. Bacteriol. 173, 697, 1991.

scholarly journals Occurrence of Bacterial Leaf Spot of Escarole Caused by Pseudomonas cichorii in the Everglades Agricultural Area of Southern Florida

Plant Disease ◽  
2001 ◽  
Vol 85 (11) ◽  
pp. 1208-1208 ◽  
Author(s):  
K. Pernezny ◽  
R. N. Raid
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Agricultural Area ◽  
Leaf Spot Disease ◽  
Bacterial Strains ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
Everglades Agricultural Area ◽  
Leaf Spots ◽  
Pure Cultures

In the fall of 1997, 1998, and 2000, a leaf spot disease of escarole (Cichorium endivia L.) was widespread among commercial plantings in the Everglades Agricultural Area (EAA), south and east of Lake Okeechobee, FL. Symptoms consisted of dry, dark gray-to-black lesions that expanded to ≈4 cm in diameter. Concentric rings were often observed in mature lesions. Growers and scouts in the area consistently identified this disease as Alternaria leaf spot, because the symptoms closely resembled Alternaria leaf spots seen on a number of other vegetables. Prolific bacterial streaming occurred when cut portions of lesions were observed microscopically. A fluorescent bacterium was consistently isolated when a sterile inoculation needle was pushed through lesions. Eight bacterial strains were isolated, restreaked to obtain pure cultures, and characterized. All strains were aerobic, gram-negative rods that were oxidase positive and arginine dihydrolase negative. Negative reactions were recorded for levan formation and rotting of potato slices. All strains utilized glucose, mannitol, and m-tartrate and were negative for sucrose, sorbitol, benzoate, d-arabinose, l-rhamnose, and cellobiose. Results for utilization of D-aspartate were variable. Based on these results, the causal agent of bacterial leaf spot of escarole was identified as Pseudomonas cichorii. Greenhouse-grown plants of escarole, cv. Full Heart, and Cos lettuce, cv. Tall Guzmaine, were mistinoculated with a suspension (107 CFU/ml) of each test strain from escarole and P. cichorii strain Pc28, originally isolated from celery (1). Plants were bagged for 3 days after inoculation. Symptoms characteristic of this disease were evident on escarole inoculated with all test strains and Pc28 6 days after inoculation. Pure cultures of P. cichorii were recovered from lesions on King's B medium. Three test strains produced mild leaf spot symptoms in Cos lettuce, but the symptoms were distinctly different from those associated with the common bacterial leaf spot of lettuce in Florida caused by Xanthomonas campestris pv. vitians (2). To our knowledge, this is the first report of P. cichorii causing this unusual target spot symptom on escarole in the EAA. References: (1) K. Pernezny et al. Plant Dis. 78:917, 1994. (2) K. Pernezny et al. Plant Dis. 79:359, 1995.

scholarly journals First Report of Bacterial Leaf Spot on Cichorium intybus Caused by Pseudomonas cichorii in Florida

Plant Disease ◽  
2013 ◽  
Vol 97 (6) ◽  
pp. 837-837 ◽  
Author(s):  
S. Zhang ◽  
Y. Fu
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Leaf Spot ◽  
South Florida ◽  
Cichorium Intybus ◽  
Rrna Gene ◽  
Fluorescent Pseudomonad ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
First Report

Italian dandelion (Cichorium intybus L.) is a leafy chicory plant grown as a fresh vegetable in salads. In August 2011, necrotic lesions were observed on leaves of about 20% of the Italian dandelion plants in an experimental field at the Tropical Research and Education Center (TREC) of the University of Florida in Homestead, FL. The lesions were dark brown with a yellow halo and most were irregular in shape. Some lesions formed along the leaf edge and developed into large lesions up to 20 to 30 mm long. Symptomatic leaf tissues were cut into small pieces (2 to 3 mm), sterilized in 10% Clorox (0.6% sodium hypochlorite) for 2 min following surface disinfection in 70% ethanol for 30 s, placed on nutrient agar (NA), and incubated at 28°C in the dark for 4 to 5 days. A bacterium was consistently isolated from the leaf lesions. Colonies of these bacteria were raised, opaque, and round with a slightly irregular, colorless margin while the center was light brown. The colonies were gram-negative with yellow fluorescence appearance on Pseudomonas F agar (Becton, Dickinson and Company, Sparks, MD). LOPAT tests were carried out to further identify the species of this fluorescent pseudomonad (2). The bacterium was levan negative, oxidase positive, potato rot negative, arginine dihydrolase negative, and tobacco hypersensitivity positive. Results from this test indicated that the bacterium belongs to LOPAT group III of fluorescent pseudomonads. Bacterial identity was further confirmed as Pseudomonas cichorii by amplifying the 16S rRNA gene with the universal bacterial primers 8F and 1492R (1) and sequence analysis (GenBank Accession No. KC311733). The partial 1,361-bp 16S rRNA gene sequences had 100% identity with P. cichorii (JF951725.1), which was isolated from infected soybean plants. Pathogenicity of the isolate was tested twice by spraying a suspension of the bacterium (107 CFU/ml) onto three 4-week-old plants until runoff. The control plants were sprayed with sterile distilled water. All plants were covered with plastic bags to maintain moisture for 48 h in an air-conditioned greenhouse (22 ± 1°C). Similar lesions were observed on the inoculated plant leaves 5 to 7 days after inoculation, whereas no lesions were developed on the control plants. Bacterial colonies with same morphology were recovered from the lesions, fulfilling Koch's postulates. P. cichorii is widespread worldwide with an important economic impact on celery, chrysanthemum, and lettuce. In South Florida, P. cichorii was reported as the causal agent of bacterial leaf spot on escarole (Cichorium endivia L.) (3). To our knowledge, this is the first report of bacterial leaf spot on Italian dandelion caused by P. cichorii in Florida. References: (1) J. P. Galkiewicz and C. A. Kellogg. Appl. Environ. Microbiol. 74:7828, 2008. (2) T. Goszczynska et al. Introduction to Practical Phytobacteriology. Isteg Scientific Publications, Irene, South Africa, 2000. (3) K. Pernezny and R. N. Raid. Plant Dis. 85:1208, 2001.

scholarly journals Sugar maple autumn-shed leaf extract: a potential antibacterial agent for the management of lettuce bacterial leaf spot (Xanthomonas campestris pv. vitians) and varnish spot (Pseudomonas cichorii)

2020 ◽  
Vol 100 (1) ◽  
pp. 78-85 ◽  
Author(s):  
M. Delisle-Houde ◽  
R.J. Tweddell
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Sugar Maple ◽  
Foliar Application ◽  
Antibacterial Activities ◽  
Northern Red Oak ◽  
Bacterial Leaf Spot ◽  
Pseudomonas Cichorii ◽  
Bacterial Diseases

Different extracts prepared from wastes (barks, branches, needles, or leaves) of different trees (grey alder, balsam fir, American larch, red maple, sugar maple, white spruce, black spruce, jack pine, white pine, quaking aspen, sweet cherry, and northern red oak) were investigated for their potential use as antibacterial agents for the management of lettuce varnish spot and bacterial leaf spot caused by Pseudomonas cichorii (Swingle) Stapp and Xanthomonas campestris pv. vitians (Brown) Dye, respectively. Extracts were first screened for their antibacterial activities against P. cichorii and X. campestris pv. vitians using the in vitro disk diffusion assay. Based on the diameter of the inhibition zone, ethanol (95%) extract prepared from sugar maple autumn-shed leaves (SMASL) and aqueous ethanol (50%, v/v) extracts prepared from SMASL and from sugar maple green leaves showed the strongest antibacterial activities. Ethanol (95%) SMASL extract was further investigated for its efficacy to manage bacterial diseases when applied on lettuce plants grown in the greenhouse. Foliar application of ethanol (95%) SMASL extract at a concentration of 3.2 g L−1 was shown to significantly (P ≤ 0.05) reduce bacterial leaf spot severity compared with the control without causing phytotoxicity symptoms that could prevent the commercial marketing of the lettuce. Ethanol (95%) SMASL extract (1.6 and 3.2 g L−1) was also shown to significantly reduce varnish spot severity in one experiment out of two. This study identifies for the first time the possibility of exploiting SMASL to manage bacterial diseases affecting horticultural crops.

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