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Alternaria dauci causes leaf spots and leaf blight of coriander (Coriandrum sativum) in Brazil

Authors:
Paloma Mansur at Universidade Federal de Viçosa (UFV)
Paloma Mansur
A. L. Silva at Universidade Federal de Viçosa (UFV)
A. L. Silva
Sara Salcedo at University of Florida
Sara Salcedo
Robert W. Barreto
Robert W. Barreto
Robert W. Barreto
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Alternaria dauci is fully confirmed to cause leaf spots and leaf blight of coriander (Coriandrum sativum) in Brazil based on observations made of blighted plants at a demonstration plot (Infectarium) at Viçosa (state of Minas Gerais) Brazil. Identification was supported by a combination of morphological, cultural and molecular features. A representative herbarium sample and an isolate were deposited in public collections as well as DNA sequences. Pathogenicity tests were conducted and Koch’s postulates were fulfilled.
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Alternaria dauci causes leaf spots and leaf blight of coriander
(Coriandrum sativum)inBrazil
Paloma S. Mansur
1
&André L. Silva
1
&Sara S. Salcedo
1
&Robert W. Barreto
1
&Adans A. Colmán
1,2
Received: 18 November 2019 /Accepted: 8 October 2020
#Australasian Plant Pathology Society Inc. 2020
Abstract
Alternaria dauci is fully confirmed to cause leaf spots and leaf blight of coriander (Coriandrum sativum) in Brazil based on
observations made of blighted plants at a demonstration plot (Infectarium) at Viçosa (state of Minas Gerais) Brazil. Identification
was supported by a combination of morphological, cultural and molecular features. A representative herbarium sample and an
isolate were deposited in public collections as well as DNA sequences. Pathogenicity tests were conducted and Koch’spostulates
were fulfilled.
Keywords Etiology .Phylogeny .Section Porri .Pathogenicity .Pleosporaceae
Coriander (Coriandrum sativum), also known as cilantro
(coentro in Brazil) is an annual herb of the Apiaceae.
It is widely cultivated and used as a condiment herb
worldwide (Simpson and Connor-Ogorzaly 2001)and
also in Brazil. Several fungal pathogens have been re-
ported as causing leaf spots on coriander in Brazil (Farr
and Rossman 2019)andAlternaria leaf spot is consid-
ered an important disease of coriander in Brazil (Reis
and Lopes 2016).
In July 2018, all plants growing in a demonstration
plot in the Infectarium –theplantdiseasegarden-of
the Departamento de Fitopatologia of the Universidade
Federal de Viçosa (municipality of Viçosa, state of
Minas Gerais, Brazil) were found to be attacked by a
disease leading to severe leaf blight symptoms. Firstly
small round to oval, 3–5 mm diam., leaf spot appeared
which quickly coalesced and turned into necrotic blight
of entire leaves. Samples were collected and examined
under a dissecting microscope and a dematiaceous fun-
gus was found to be regularly associated with the ne-
crotic tissues. Under a dissecting microscope (Olympus
SZX7) conidia were taken from infected leaves with a
sterile fine pointed needle and transferred onto previous-
ly marked positions of V8 juice-agar plates. Each posi-
tion of those plates was then examined, under the high
power of the dissecting microscope, to select positions
where single conidia were deposited. Those points of
the plates were further marked, at the underside of the
plates, indicating that colonies from these positions rep-
resented single-spore isolates. After 1 week of growth in
the incubator, at 25 °C, a fragment of the margin of one
selected single spore colony was taken and transferred
to a tube containing potato carrot-agar. This representa-
tive culture was deposited in the culture collection of
the Universidade Federal de Viçosa (Acc No COAD
2594) and used in this study. Additionally, a represen-
tative specimen of diseased coriander was dried in a
plant press and deposited in the local herbarium (Acc.
No VIC 47142).
Slides were prepared by scraping fungal structures from
sporulating colonies on leaves and mounting these on a drop
*Adans A. Colmán
adan-colman@hotmail.com
Paloma S. Mansur
paloma.mansur@ufv.br
André L. Silva
als9528@gmail.com
Sara S. Salcedo
taphrina10@gmail.com
Robert W. Barreto
rbarreto@ufv.br
1
Departamento de Fitopatologia, Universidade Federal de Viçosa,
Viçosa, Minas Gerais 36570-900, Brazil
2
Present address: Facultad de Ciencias Agrarias, Universidad
Nacional de Asunción, San Lorenzo, Paraguay
https://doi.org/10.1007/s13314-020-00407-7
/ Published online: 19 October 2020
Australasian Plant Disease Notes (2020) 15: 38
of lactophenol. Observations were made under a microscope
(Olympus BX 53) equipped with differential interference
contrast (DIC) illumination and connected to an
Olympus Q-color 5™camera. The fungus on coriander
had the following morphology: conidiophores forming
loose groups, subcylindrical, straight to somewhat
sinuose, 27.5–75 × 5–10 μm, 1–4 septate, pale brown
to brown, smooth; conidiogenous cells subcylindrical,
geniculate, (7.5) 15–27.5 (37.5) × 5–10 μm,
conidiogenous loci terminal to intercalary 2.5–7.5 μm
diam.; conidia solitary, (125) 200–300 (340) × 17.5–
22 μm, 1–8 longitudinally and 8–15 transversally
septae,beakupup280μmlong,palebrown,walls
somewhat verruculose (Fig. 1).
DNA was extracted from mycelium of COAD 2594 grown
in 20 ml of potato dextrose broth at 23 ± 2 °C for 4 days.
Extraction was performed with a Wizard Genomic DNA
Purification Kit (Promega) according to the manufacturer’s
recommendations. The glyceraldehyde 3-phosphate dehydro-
genase (GAPDH) region was amplified with the primers gpd1
and gpd2 (Berbee et al. 1999), the RPB2 region with RPB2-
5F2 (Sung et al. 2007) and fRPB2–7cR (Liu et al. 1999)and
the Alt a1 region with the primers Alt-for and Alt-rev (Hong
et al. 2005). PCR was performed following the proce-
dure described in Colmán et al. (2018) and phylogenetic
analyses were performed as described in Woudenberg
et al. (2013). Bayesian inference analyses were per-
formed with the CIPRES web portal using MrBayes v.
3.2.6. (Miller et al. 2015).Thejmodeltest(Darribaetal.
2012) was used for estimation of sequence evolution.
Based on the phylogenetic analyses results combined
GAPDH, Alt 1 and RPB2 gene regions, our isolate
COAD 2594 was identified as belonging to Alternaria
dauci (Fig. 2). Sequences obtained in this work were
depositedinGenBank(Table1).
To confirm the pathogenicity of COAD 2594,
4 month old healthy coriander plants were inoculated.
Additionally, groups of four pots (one healthy plant per
pot) containing either carrot, celery or parsley were also
inoculated with COAD 2594. A conidial suspension was
prepared by flooding sporulating 7-day-old cultures
formed on V8 juice-agar plates with sterile distilled wa-
ter (SDA) and scraping their surface with a rubber spat-
ula. A haemocytometer was used to calculate the con-
centration of spores/ml which was then adjusted to 10
6
conidia/ml. Plants were sprayed until runoff and covered
with a plastic bag for 48 h to keep humidity levels
high. One healthy plant of each species treated similarly
but sprayed with SDA only served as controls. Typical
symptoms of disease were observed 2–4 days after in-
oculation. Control plants remained healthy. Alternaria
dauci sporulated abundantly on necrotic tissues and
was reisolated on V8 juice-agar plates producing sporu-
lating cultures. The morphology of the fungus reisolated
from necrotic tissues of inoculated plants was examined
under the microscope and found to have a morphology
identical to COAD 2594 fulfilling Koch’s postulates.
Several species of Alternaria have been reported on
C. sativum (Farr and Rossman 2019). Of these
(A. poonensis) was originally described by Raghunath
Fig. 1 Alternaria dauci on coriander (Coriandrum sativum). aLeaf spot
and some blight symptoms on coriander; bGroup of conidiophores of
A. dauci;cConidia with long septate beaks, dColony of A. dauci on V8
juice-agar; e-f Pathogenicity test on coriander plants, control (e) and in-
oculated plants (f) 4 days after inoculation. Scale bars 20 μm
38 Page 2 of 5 Australasian Plant Dis. Notes (2020) 15: 38
(1963) based on a sample of diseased coriander from
India. This was based on morphological features and
supposed host-specificity. Morphology of COAD 2594
was found to be rather similar to that described by
Raghunath (1963)forA. poonensis, including for the
absence of bifurcated beaks, thought to be typical for
A. dauci but not seen in COAD 2594 (either from in
planta or in vitro materials). Nevertheless, based on
their molecular phylogenetic analysis Woudenberg
et al. (2014), placed A. poonensis as a synonym of
A. dauci. Results of our phylogenetic analysis of
COAD 2594 were in agreement with Woudenberg
et al. (2014)(Fig.2). COAD 2594 grouped with the
type strain of A. dauci (CBS 111.38) and other
A. dauci strains isolated from coriander in the United
States US-FL-1 (Poudel and Zhang 2018) and Algeria
NB622 (Bessadat et al. 2019). Alternaria dauci is now
recognized to be a polyphagous pathogen infecting sev-
eral plants in the Apiaceae. COAD 2594 was also prov-
en to be capable of infecting carrots, parsley and celery
in our inoculation studies, further confirming the po-
lyphagous status (within the Apiaceae) of A. dauci.In
Brazil this species has already been reported in associ-
ation with coriander seeds and plants (Reis et al. 2006).
Nevertheless these reports were never supported by mo-
lecular data and no voucher specimens were deposited
in herbaria or culture collections. Here the identity of
Alternaria dauci as the ethiological agent of leaf spots
and blight of coriander in Brazil is fully confirmed for
the first time.
Table 1 GenBank accession number of sequences obtained in this study and other Alternaria spp. used for phylogenetic analysis
Species Name Host Strain number Country GenBank accession number
Alt 1 GPDH RPB2
Alternaria anagallidis Anagallis arvensis CBS 117128 New Zealand KJ718628 KJ717961 KJ718282
Alternaria anagallidis Anagallis arvensis CBS 117129 New Zealand KJ718629 KJ717962 KJ718283
Alternaria argyroxiphii Argyroxiphium sp CBS 117122 USA KJ71863 JQ646350 KJ718286
Alternaria argyroxiphii Ipomoea batatas PPRI 11848 South Africa KJ718633 KJ717965 KJ718287
Alternaria argyroxiphii Ipomoea batatas PPRI 11971 South Africa KJ718634 KJ717966 KJ718288
Alternaria bataticola Ipomoea batatas CBS 531.63 Japan JQ646433 JQ646349 KJ718291
Alternaria bataticola Ipomoea batatas CBS 532.63 Japan KJ718637 KJ717969 KJ718292
Alternaria bataticola Ipomoea batatas CBS 117095 Australia KJ718638 KJ717970 KJ718293
Alternaria bataticola Ipomoea batatas CBS 117096 Australia KJ718639 KJ717971 KJ718294
Alternaria dauci Daucus carota CBS 111.38 Italy KJ718673 KJ718005 KJ718331
Alternaria dauci Daucus carota CBS 345.79 New Zealand KJ718675 KJ718007 KJ718333
A. dauci (syn. A. poonensis)Coriadrum sativum CBS 117.100 Puerto Rico KJ718680 JQ646348 KJ718338
Alternaria dauci Coriadrum sativum USFL-3 USA MF595071 MF595072 –
Alternaria dauci Coriadrum sativum NB625 Algeria –MK513412 MK513423
Alternaria dauci Coriadrum sativum NB622 Algeria –MK513409 MK513420
Alternaria dauci Coriadrum sativum COAD 2594 Brazil MN433697 MT050451 MN433698
Alternaria echinaceae Echinaceae sp. CBS 116117 New Zealand KJ718684 KJ718015 KJ718343
Alternaria echinaceae Echinaceae sp. CBS116118 New Zealand KJ718685 KJ718016 KJ718344
Alternaria euphorbiicola Euphorbia hyssopifolia CBS 133874 USA KJ718019 KJ718687 KJ718347
Alternaria euphorbiicola Euphorbia pulcherrima CBS 19886 USA KJ718017 KJ718686 KJ718345
Alternaria ipomeae Ipomoea batatas CBS 219.79 Ethiopia KJ718689 KJ718020 KJ718348
Alternaria ipomeae Ipomoea batatas PPRI 8988 South Africa KJ718690 KJ718021 KJ718349
Alternaria neoipomeae Ipomoea batatas PPRI 8990 South Africa KJ718706 KJ718035 KJ718370
Alternaria neoipomeae Ipomoea batatas PPRI 13903 South Africa KJ718709 KJ718038 KJ718373
Alternaria tagetica Tagetes sp. CBS 297.79 UK KJ718759 KJ718080 KJ718428
Alternaria tagetica Tagetes sp. CBS 298.79 UK KJ718760 KJ718081 KJ718429
Alternaria tagetica Tagetes erecta CBS 479.81 UK KJ718761 KC584143 KC584434
Alternaria tropica Passiflora edulis CBS 631.93 USA KJ718768 KJ718088 KJ718436
Alternaria tropica Passiflora edulis CBS 117216 USA KJ718769 KJ718089 KJ718437
Page 3 of 5 38Australasian Plant Dis. Notes (2020) 15: 38
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Page 5 of 5 38Australasian Plant Dis. Notes (2020) 15: 38
... A total of 100 plants (pots experiment, two plants/pot) were inoculated. The plants were then observed for 20 days [24]. ...
... Alternaria dauci has been reported as a causal pathogen of cultivated and wild carrots and it has also been claimed that it can infect wild parsnip, celery, and parsley [12,24]. The suitability of other alternate hosts, such as Ridolfia segetum (corn parsley) and Caucalis tenet (hedge parsley), to be infected by A. dauci below controlled environment conditions was reported [40]. ...
... 2-170 µm (average; 81.8), a width of 5-10 µm (average; 7.2), and the body size of mature conidia of 45.2-92.9 × 12.5-30.1 (average; 68.3 × 18.4) µm with a beak up 301.4 µm long, further the transverse-septa and longitudinal-septa of conidia measuring 10-18 and 0-4 µm, respectively[23].Similar approximate results[24] on coriander reported some differences in conidiophores measurements of A. dauci, being 27.5-75 × 5-10 µm in length and 1-4 µm septate, and conidia solitary with a body size of 200-300 × 17.5-22 µm, longitudinally 1-8 and 8transversally 15 µm septa, with a beak up to 280 µm long. The pathogens were identified as A. dauci based on their morphological characteristics[27]. ...
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This puts the genera Allewia, Brachycladium, Chalastospora, Chmelia, Crivellia, Embellisia, Lewia, Nimbya, Sinomyces, Teretispora, Ulocladium, Undifilum and Ybotromyces in synonymy with Alternaria. In this study, we treat the 24 internal clades in the Alternaria complex as sections, which is a continuation of a recent proposal for the taxonomic treatment of lineages in Alternaria. Embellisia annulata is synonymised with Dendryphiella salina, and together with Dendryphiella arenariae, are placed in the new genus Paradendryphiella. The sexual genera Clathrospora and Comoclathris, which were previously associated with Alternaria, cluster within the Pleosporaceae, outside Alternaria s. str., whereas Alternariaster, a genus formerly seen as part of Alternaria, clusters within the Leptosphaeriaceae. Paradendryphiella is newly described, the generic circumscription of Alternaria is emended, and 32 new combinations and 10 new names are proposed. A further 10 names are resurrected, while descriptions are provided for 16 new Alternaria sections. Taxonomic novelties: New combinations - Alternaria abundans (E.G. Simmons) Woudenb. & Crous, Alternaria alternariae (Cooke) Woudenb. & Crous, Alternaria atra (Preuss) Woudenb. & Crous, Alternaria bornmuelleri (Magnus) Woudenb. & Crous, Alternaria botrytis (Preuss) Woudenb. & Crous, Alternaria caespitosa (de Hoog & C. Rubio) Woudenb. & Crous, Alternaria cantlous (Yong Wang bis & X.G. Zhang) Woudenb. & Crous, Alternaria caricis (E.G. Simmons) Woudenb. & Crous, Alternaria cinerea (Baucom & Creamer) Woudenb. & Crous, Alternaria didymospora (Munt.-Cvetk.) Woudenb. & Crous, Alternaria fulva (Baucom & Creamer) Woudenb. & Crous, Alternaria hyacinthi (de Hoog & P.J. Mull. bis) Woudenb. & Crous, Alternaria indefessa (E.G. Simmons) Woudenberg & Crous, Alternaria leptinellae (E.G. Simmons & C.F. Hill) Woudenb. & Crous, Alternaria lolii (E.G. Simmons & C.F. Hill) Woudenb. & Crous, Alternaria multiformis (E.G. Simmons) Woudenb. & Crous, Alternaria obclavata (Crous & U. Braun) Woudenb. & Crous, Alternaria obovoidea (E.G. Simmons) Woudenb. & Crous, Alternaria oudemansii (E.G. Simmons) Woudenb. & Crous, Alternaria oxytropis (Q. Wang, Nagao & Kakish.) Woudenb. & Crous, Alternaria penicillata (Corda) Woudenb. & Crous, Alternaria planifunda (E.G. Simmons) Woudenb. & Crous, Alternaria proteae (E.G. Simmons) Woudenb. & Crous, Alternaria scirpinfestans (E.G. Simmons & D.A. Johnson) Woudenb. & Crous, Alternaria scirpivora (E.G. Simmons & D.A. Johnson) Woudenb. & Crous, Alternaria septospora (Preuss) Woudenb. & Crous, Alternaria slovaca (Svob.-Pol., L. Chmel & Bojan.) Woudenb. & Crous, Alternaria subcucurbitae (Yong Wang bis & X.G. Zhang) Woudenb. & Crous, Alternaria tellustris (E.G. Simmons) Woudenb. & Crous, Alternaria tumida (E.G. Simmons) Woudenb. & Crous, Paradendryphiella salina (G.K. Sutherl.) Woudenb. & Crous, Paradendryphiella arenariae (Nicot) Woudenb. & Crous. New names - Alternaria aspera Woudenb. & Crous, Alternaria botryospora Woudenb. & Crous, Alternaria brassicae-pekinensis Woudenb. & Crous, Alternaria breviramosa Woudenb. & Crous, Alternaria chlamydosporigena Woudenb. & Crous, Alternaria concatenata Woudenb. & Crous, Alternaria embellisia Woudenb. & Crous, Alternaria heterospora Woudenb. & Crous, Alternaria papavericola Woudenb. & Crous, Alternaria terricola Woudenb. & Crous. Resurrected names - Alternaria cetera E.G. Simmons, Alternaria chartarum Preuss, Alternaria consortialis (Thüm.) J.W. Groves & S. Hughes, Alternaria cucurbitae Letendre & Roum., Alternaria dennisii M.B. Ellis, Alternaria eureka E.G. Simmons, Alternaria gomphrenae Togashi, Alternaria malorum (Ruehle) U. Braun, Crous & Dugan, Alternaria phragmospora Emden, Alternaria scirpicola (Fuckel) Sivan. New sections, all in Alternaria - sect. Chalastospora Woudenb. & Crous, sect. Cheiranthus Woudenb. & Crous, sect. Crivellia Woudenb. & Crous, sect. Dianthicola Woudenb. & Crous, sect. Embellisia Woudenb. & Crous, sect. Embellisioides Woudenb. & Crous, sect. Eureka Woudenb. & Crous, sect. Infectoriae Woudenb. & Crous, sect. Japonicae Woudenb. & Crous, sect. Nimbya Woudenb. & Crous, sect. Phragmosporae Woudenb. & Crous, sect. Pseudoulocladium Woudenb. & Crous, sect. Teretispora Woudenb. & Crous, sect. Ulocladioides Woudenb. & Crous, sect. Ulocladium Woudenb. & Crous, sect. Undifilum Woudenb. & Crous. New genus - Paradendryphiella Woudenb. & Crous.
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Associação de Alternaria dauci e A. alternata com sementes de coentro e eficiência do tratamento químico
Article
Full-text available
  • Mar 2006
  • HORTIC BRAS
Association of Alternaria dauci and A. alternata with coriander seeds and efficiency of chemical treatments Twelve lots of coriander seeds were evaluated for the presence of Alternaria spp., using 600 seeds per lot in the blotter test. Two Alternaria species were detected, A. dauci (AD) in eight lots and A. alternata (AA) in six lots. A sample of 400 seeds was sown in styrofoam trays and the incidence of spots on cotyledons was evaluated 21 days after sowing. Only lesions caused by AD were observed on leaves. The seed lot with higher incidence of AA and AD was treated with fungicides (thiram, benomyl, captam and iprodione) and 400 seeds in each treatment were placed in four gerbox boxes with sterilized wet filter paper. Seeds were observed under stereoscopic microscope for presence of AD and AA. The best treatment was the mixture of thiram + iprodione resulting in 0.5% and 0% incidence of AA and AD, respectively. Treated seed samples were sown in styrofoam trays to verify transmission of Alternaria spp. from seeds to seedlings. Plants resulting from non treated seeds presented 13% of infection with AD. Plants from seeds treated with the mixture thiram + iprodione were not infected by AD. The results demonstrated the efficacy of thiram + iprodione mixture for treatment of coriander seeds against A. dauci and A. alternata.
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Cochliobolus phylogenetics and the origin of known, highly virulent pathogens, inferred from ITS and glyceraldehyde-3-phosphate dehydrogenase gene sequences
Article
  • Nov 1999
We evaluate the phylogenetic distribution of known, highly virulent plant pathogens in the genus Cochliobolus (sexually reproducing species in the Ascomycota, Pleosporaceae) and assess the relationship between Cochliobolus species and species of Curvularia and Bipolaris (asexual states of fungi in the Ascomycota, Pleosporaceae). To infer a phylogeny, we have used two sequence regions: (i) the complete ITS 1, ITS 2, and 5.8S rDNA sequences for 65 fungal isolates and (ii) a 600 bp fragment of the housekeeping gene gpd, coding for glyceraldehyde-3-phosphate dehydrogenase, for 54 isolates. We combined ITS, 5.8S and gpd sequence data from 41 species. In the Cochliobolus clade, 31 out of 32 species fit clearly into one of two groups. One species, Cochliobolus homomorphus, did not fit clearly into either group. The 13 species in Cochliobolus Group 1 grouped together with 100% bootstrap support from the combined ITS/gpd data. This group included Cochliobolus and Bipolaris species that cause serious crop losses, such as Co. sativus, Co. miyabeanus, Co. carbonum and Co. heterostrophus. However, within Group 1, the known, highly virulent pathogens did not form a monophyletic group of species. Average substitution levels between pairs of species in the Group 1 were low, about 1.7% in the ITS region, suggesting that these species had radiated rapidly and recently. The 18 species in Cochliobolus Group 2 formed a monophyletic group in 96% of parsimony bootstrap replicates of the combined ITS and gpd data. The Cochliobolus species that were transferred into the segregate genus Pseudocochliobolus were in this second group. This study included 9 Curvularia and Bipolaris species without known sexual states and they all appear to be recently derived from among sexual species of Cochliobolus. Both Curvularia and Bipolaris were polyphyletic, but only Bipolaris states were associated with Group 1 Cochliobolus species. Both Curvularia and Bipolaris states were associated with species in Cochliobolus Group 2.
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First report of Seimatosporium hypericinum causing leaf spots on the ornamental shrub Hypericum × inodorum and in Brazil
Article
  • Dec 2018
  • Australas Plant Dis Notes
Hypericum ×inodorum is an ornamental plant that has become popular for the cut flower industry in Brazil, in recent years. No pathogen has been reported on this plant in Brazil. A coelomycete asexual morph was found associated with leaf spot and severe foliage blight on this host and is reported here for the first time. A combination of morphological and molecular features allowed it to be identified as Seimatosporium hypericinum. Koch’s postulates were performed and demonstrated, for the first time, that S. hypericinum is pathogenic to H. × inodorum.
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A new species of Alternaria causing blight of coriandrum sativum L.
Article
  • Dec 1963
A crop of Coriander (Coriandrum sativum L.) growing in an experimental area ill Poona was found to be badly affected by a blight disease during September-October 1962, a preliminary account of which has been already reported by the writer (1963). The disease is a new outbreak, not previously reported in literature and has been proved to be incited by an undescribed species of Alternaria under artificial inoculation experiments. Plants of Daucas carota L. and Cuminum cyminum L. both belonging to the family Umbelliferae and growing in the vicinity were found to be free from infection. Since three species of Alternaria have been previously reported on hosts belonging to this family, it was considered necessary to undertake comparative studies into these species, with a view to determine the exact identity of the Coriander Alternaria, the results of which are presented in the following table I. A critical study of the results obtained show that the Coriander Alternaria is distinct from the other three species both in respect of morphological characters as well as dimensions of conidia and conidiophores and justify accommodation of the Coriander fungus as a new species. It is also noteworthy that the Coriander species of Alternaria was found incapable of infecting the other two hosts under artificial inoculation experiments thus proving its distinctive and specific nature.
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