First report of Powdery Mildew Caused by Golovinomyces ambrosiae on Cannabis sativa in Oregon

Oregon is the second largest producer of hemp in the United States with 25,900 ha of hemp licensed to growers in 2019, a nearly six-fold increase over the previous year (Perkowski 2019, Capital Press). Industrial hemp has a wide range of uses including textiles to nutritional supplements; in Oregon, hemp has become one of the most economically promising crops and is mainly cultivated for cannabidiol (CBD) production. Between 2018 and 2019, multiple independent greenhouse growers in western Oregon reported powdery mildew-like signs and symptoms on leaves and buds of several Cannabis sativa cultivars, including ‘Cherry Wine’. Signs of the disease started as small, white, powdery patches, typically on the adaxial sides of leaves, and progressed to coalescent colonies on leaves, stems, and buds. Fungi present on diseased tissues had unbranched hyaline conidiophores that measured 140 to 250 µm and grew erect from caulicolous and amphigenous mycelium (n = 15). Foot cells were cylindrical, often tapered at one or both ends, and measured 80 to 117 × 9.5 to 11.9 µm (n = 15). Conidia were catenescent, hyaline, ellipsoidal to barrel-shaped, lacked fibrosin bodies, and measured 24 to 34 × 12 to 18 µm (n = 50). No chasmothecia were observed. Morphological observations overlapped with several Golovinomyces spp. Including G. ambrosiae, G. cichoracearum, and G. spadiceus (Braun and Cook 2012). Identification was confirmed by bidirectional sequencing and phylogenetic analysis of 1,457 nucleotides from the concatenated internal transcribed spacer (ITS), 28S large ribosomal subunit, and beta-tubulin (TUB2) regions of two isolates using primer pairs ITS1/ITS4 and NL1/LR5, and TubF1/TubR1 respectively (Mori et al. 2000, Qiu et al. 2020, Vilgalys and Hester 1990, White et al. 1990; GenBank Acc. No.: MW248121 to MW248124, MW265971 to MW265972). The Oregon hemp isolates grouped (bootstrap value = 100) in a monophyletic clade with G. ambrosiae accessions from Qiu et al. (2020). Pathogenicity was confirmed by transferring conidia by leaf rub inoculation onto 2-to 4-week-old ‘Cherry Wine’ potted plants and incubated outdoors at 12 to 22°C. Control plants were mock-inoculated using healthy leaves. Powdery mildew symptoms developed on inoculated plants approximately 14 to 21 days later; control plants were asymptomatic. Identification was confirmed by morphological characterization and sequencing using the aforementioned primers. The hemp isolates were also able to infect detached leaves of Humulus lupulus ‘Symphony’ via similar inoculations; however, colony development on ‘Symphony’ was slow and sporulation sparse as was reported by Weldon et al. (2020). Golovinomyces spp. have also been reported on hemp in Kentucky (Szarka et al. 2019), Ohio (Farinas and Peduto Hand 2020), and New York (Weldon et al. 2020). Although reported as G. spadiceus, these reports are also likely G. ambrosiae according to new taxonomic revision of the genus (Qiu et al. 2020). This is the first known report of Golovinomyces ambrosiae causing powdery mildew on hemp in Oregon (OSC 171893). While powdery mildew on hemp currently appears most severe in protected cultivation, rapid expansion of hemp cultivation and introduction of new CBD varieties throughout Oregon could lead to increased powdery mildew risk in outdoor cultivation.

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Re-Evaluation of the Podosphaera tridactyla Species Complex in Australia

Journal of Fungi ◽

10.3390/jof7030171 ◽

2021 ◽

Vol 7 (3) ◽

pp. 171

Author(s):

Reannon L. Smith ◽

Tom W. May ◽

Jatinder Kaur ◽

Tim I. Sawbridge ◽

Ross C. Mann ◽

...

Keyword(s):

Phylogenetic Analysis ◽

Powdery Mildew ◽

Species Complex ◽

Taxonomic Revision ◽

Stone Fruit ◽

Prunus Species ◽

Wide Range ◽

Unidentified Species ◽

The Rose ◽

Generation Sequencing

The Podosphaera tridactyla species complex is highly variable morphologically and causes powdery mildew on a wide range of Prunus species, including stone fruit. A taxonomic revision of the Po. tridactyla species complex in 2020 identified 12 species, seven of which were newly characterised. In order to clarify which species of this complex are present in Australia, next generation sequencing was used to isolate the fungal ITS+28S and host matK chloroplast gene regions from 56 powdery mildew specimens of stone fruit and ornamental Prunus species accessioned as Po. tridactyla or Oidium sp. in Australian reference collections. The specimens were collected in Australia, Switzerland, Italy and Korea and were collected from 1953 to 2018. Host species were confirmed using matK phylogenetic analysis, which identified that four had been misidentified as Prunus but were actually Malusprunifolia. Podosphaera species were identified using ITS+28S phylogenetic analysis, recognising three Podosphaera species on stone fruit and related ornamental Prunus hosts in Australia. These were Po.pannosa, the rose powdery mildew, and two species in the Po. tridactyla species complex: Po. ampla, which was the predominant species, and a previously unidentified species from peach, which we describe here as Po. cunningtonii.

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First Report of Powdery Mildew Caused by Blumeria graminis f. sp. bromi on Bromus catharticus in China

Plant Disease ◽

10.1094/pdis-09-20-1983-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Xiao Duan ◽

Wenqi Shi ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

The United States ◽

Blumeria Graminis ◽

Henan Province ◽

Width Ratio ◽

Causal Organism ◽

First Report

Bromus catharticus, rescuegrass, is a brome grass that has been cultivated for herbage production, and been widely naturalized in many provinces of China, including Henan province. During April and May 2020, powdery mildew was found on leaves of Br. catharticus on the campus of Henan Normal University, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. Abundant white or grayish irregular or coalesced circular powdery colonies were scattered on the adaxial surface of leaves and 70% of the leaf areas were affected. Some of the infected leaves either were chlorotic or senescent. About 60% of the observed plants showed powdery mildew symptoms. Conidiophores (n = 25) were 32 to 45 μm × 7 to 15 μm and composed of foot cells and conidia (mostly 6 conidia) in chains. Conidia (n = 50) were 25 to 35 μm × 10 to 15 μm, on average 30 × 13 μm, with a length/width ratio of 2.3. Chasmothecia were not found. Based on these morphologic characteristics, the pathogen was initially identified as Blumeria graminis f. sp. bromi (Braun and Cook 2012; Troch et al. 2014). B. graminis mycelia and conidia were collected, and total genomic DNA was extracted (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified with primer pairs ITS1/ITS4. The amplicon was cloned and sequenced. The sequence (574 bp) was deposited into GenBank under Accession No. MT892940. BLASTn analysis revealed that MT892940 was 100% identical to B. graminis f. sp. bromi on Br. catharticus (AB000935, 550 of 550 nucleotides) (Takamatsu et al. 1998). Phylogenetic analysis of MT892940 and ITS of other B. graminis ff. spp. clearly indicated least two phylogenetically distinct clades of B. graminis f. sp. bromi and that MT892940 clustered with the Takamatsu vouchers. Leaf surfaces of five healthy plants were fixed at the base of a settling tower and then inoculated by blowing conidia from diseased leaves using pressurized air. Five non-inoculated plants served as controls. The inoculated and non-inoculated plants were maintained separately in two growth chambers (humidity, 60%; light/dark, 16 h/8 h; temperature, 18℃). Thirteen- to fifteen-days after inoculation, B. graminis signs and symptoms were visible on inoculated leaves, whereas control plants remained asymptomatic. The pathogenicity assays were repeated twice with the same results. The observed signs and symptoms were morphologically identical to those of the originally infected leaves. Accordingly, the causal organism of the powdery mildew was confirmed as B. graminis f. sp. bromi by morphological characteristics and ITS sequence data. B. graminis has been reported on Br. catharticus in the United States (Klingeman et al. 2018), Japan (Inuma et al. 2007) and Argentina (Delhey et al. 2003). To our best knowledge, this is the first report of B. graminis on Br. catharticus in China. Since hybridization of B. graminis ff. spp. is a mechanism of adaptation to new hosts, Br. catharticus may serve as a primary inoculum reservoir of B. graminis to infect other species (Menardo et al. 2016). This report provides fundamental information for the powdery mildew that can be used to develop control management of the disease in Br. catharticus herbage production.

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Industrial hemp and its potential

10.32545/encyclopedia202004.0024.v4 ◽

2020 ◽

Author(s):

ARNAB BHOWMIK

Keyword(s):

Contaminated Soils ◽

Management Practices ◽

Cannabis Sativa ◽

Emerging Market ◽

The United States ◽

Future Research ◽

Research Needs ◽

Hemp Fiber ◽

Hemp Seed ◽

Wide Range

Hemp (Cannabis sativa L.) is an emerging high-value specialty crop that can be cultivated foreither fiber, seed, or cannabidiol (CBD). The demand for hemp and its products has been consistently onthe rise in the 21st century. The United States of America has reintroduced hemp and legalizedits production as an agricultural commodity through the 2018 Federal Farm Bill. Although thereis a renewed interest in the adoption of hemp due to the emerging market, its production in theUnited States remains limited partly because of unclear agronomic guidance and fertilizationrecommendations. This review article provides information on the current agronomic managementpractices that are available in the literature and identifies the future research needs for cultivating thismultipurpose crop to address the growing market demands. Hemp production could be beneficialif managed properly. Hemp fertilizer requirements vary in accordance with the type of hempgrown (seed, fiber, or CBD), soil, environmental conditions and requires a wide range of macro- andmicronutrients. Integrating management practices in hemp cultivation intended to build soil health ispromising since the hemp cropping system is suitable for crop rotation, cover cropping, and livestockintegration through animal waste applications. Hemp also has significant environmental benefitssince it has the potential to remediate contaminated soils through phytoremediation, convert highamounts of atmospheric CO2 to biomass through bio-sequestration, and hemp biomass for bioenergyproduction. This review identifies that most of the agronomic research in the past has been limitedto hemp fiber and, to some extent, hemp seed but not CBD hemp. With the increase in the globalmarkets for hemp products, more research needs to be conducted to provide agronomic guidelinesfor sustainable hemp production.

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First Report of Powdery Mildew Caused by Golovinomyces cichoracearum on Gerbera (Gerbera jamesonii) in Italy

Plant Disease ◽

10.1094/pdis-94-1-0130c ◽

2010 ◽

Vol 94 (1) ◽

pp. 130-130 ◽

Cited By ~ 4

Author(s):

M. Troisi ◽

D. Bertetti ◽

A. Garibaldi ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Signs And Symptoms ◽

Its Region ◽

The United States ◽

Plant Diseases ◽

Gerbera Jamesonii ◽

First Report ◽

Potted Plants ◽

Golovinomyces Cichoracearum ◽

Blastn Analysis

Gerbera (Gerbera jamesonii) is one of the top 10 economically important flower crops in Europe as well as the United States. The acreage devoted to this crop continues to increase especially for use in landscape typologies. Abundant flowering from spring until autumn allows the use of this plant to decorate gardens, terraces, and borders. During the summer of 2009, an outbreak of a previously unknown powdery mildew was observed on potted gerbera ‘Mini Yellow’ growing in a private garden in Turin (northern Italy). Adaxial leaf surfaces were covered with white mycelium and conidia, and as the disease progressed, infected leaves turned yellow and died. Conidia were hyaline, ellipsoid, borne in chains (three conidia per chain), and measured 16 to 45 × 10 to 30 μm. Conidiophores measured 109 to 117 × 11 to 13 μm and had a foot cell measuring 72 to 80 × 11 to 12 μm followed by two shorter cells measuring 19 to 29 × 11 to 14 and 20 to 32 × 12 to 14 μm. Fibrosin bodies were absent and chasmothecia were not observed in the collected samples. On the basis of its morphology, the pathogen was identified as Golovinomyces cichoracearum. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and sequenced. BLASTn analysis of the 548-bp fragment showed an E-value of 0.0 and a percentage homology of 99% with G. cichoracearum isolated from Coreopsis leavenworthii (Accession No. DQ871605) confirming diagnosis inferred by morphological analysis. The nucleotide sequence has been assigned GenBank Accession No. GQ870342. Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of three healthy potted plants of Gerbera ‘Mini Yellow’. Three noninoculated plants served as the control. Plants were maintained in a greenhouse at temperatures ranging between 20 and 30°C. Inoculated plants developed signs and symptoms after 8 days, whereas control plants remained healthy. The fungus present on inoculated plants was morphologically identical to that originally observed on diseased plants. To our knowledge, this is the first report of the presence of powdery mildew caused by G. cichoracearum on gerbera in Italy. Specimens are available at the Agroinnova Collection at the University of Torino. Gerbera is also susceptible to different powdery mildews. Powdery mildew of Gerbera jamesonii caused by Sphaerotheca fusca was reported in Italy (4). G. cichoracearum on Gerbera jamesonii was reported in North America (2), Argentina (3), and Switzerland (1). References: (1) A. Bolay. Cryptogam. Helv. 20:1, 2005. (2) M. Daughtrey et al. Page 39 in: Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society, St Paul, MN, 1995. (3) R. Delhey et al. Schlechtendalia 10:79, 2003. (4) F. Zaccaria et al. Ann. Fac. Agrar. Univ. Stud. di Napoli Federico II 34:44, 2000.

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First Report of Powdery Mildew Caused by Erysiphe heraclei on Chervil in Korea

Plant Disease ◽

10.1094/pdis-07-13-0797-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 426-426

Author(s):

K. S. Han ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

The United States ◽

Control Treatment ◽

Width Ratio ◽

Anethum Graveolens ◽

First Report ◽

Powdery Mildews

Chervil (Anthriscus cerefolium (L.) Hoffm.), belonging to the family Apiaceae, is an aromatic annual herb that is native to the Caucasus. It is widely used as a flavoring agent for culinary purposes. This herb was recently introduced in Korea. In April 2013, plants showing typical symptoms of powdery mildew disease were observed in a polyethylene film-covered greenhouse in Seoul, Korea. White mycelium bearing conidia formed irregular patches on leaves and stems. Mycelial growth was amphigenous. Severe infections caused leaf withering and premature senescence. Voucher specimens were deposited in the Korea University Herbarium (KUS). Hyphae were septate, branched, with moderately lobed appressoria. Conidiophores presented 3 to 4 cells and measured 85 to 148 × 7 to 9 μm. Foot-cells of conidiophores were 37 to 50 μm long. Conidia were produced singly, oblong-elliptical to oblong, measured 30 to 50 × 13 to 18 μm with a length/width ratio of 2.0 to 3.3, lacked conspicuous fibrosin bodies, and with angular/rectangular wrinkling of the outer walls. Germ tubes were produced in the subterminal position of conidia. Chasmothecia were not found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and morphological characteristics were consistent with those of E. heraclei DC. (1). To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F27279 was amplified with primers ITS5 and P3 (4) and sequenced directly. The resulting 561-bp sequence was deposited in GenBank (Accession No. KF111807). A GenBank BLAST search of this sequence showed >99% similarity with those of many E. heraclei isolates, e.g., Pimpinella affinis (AB104513), Anethum graveolens (JN603995), and Daucus carota (EU371725). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted chervil plants. Five non-inoculated plants served as a control treatment. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated plants developed signs and symptoms after 6 days, whereas the control plants remained healthy. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Chervil powdery mildews caused by E. heraclei have been reported in Europe (Bulgaria, France, Germany, Hungary, Italy, Romania, Switzerland, and the former Soviet Union) and the United States (2,3). To our knowledge, this is the first report of powdery mildew caused by E. heraclei on chervil in Asia as well as in Korea. The plant is cultivated in commercial farms for its edible leaves in Korea. Occurrence of powdery mildew is a threat to quality and marketability of this herb, especially those grown in organic farming where chemical control options are limited. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11, CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., Online publication. ARS, USDA. Retrieved July 29, 2013. (3) S. T. Koike and G. S. Saenz. Plant Dis. 88:1163, 2004. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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Outbreak of Powdery Mildew on Common Sage in Argentina

Plant Disease ◽

10.1094/pd-89-0911c ◽

2005 ◽

Vol 89 (8) ◽

pp. 911-911 ◽

Cited By ~ 1

Author(s):

M. Madia ◽

S. Gaetán

Keyword(s):

United States ◽

Powdery Mildew ◽

Disease Incidence ◽

Signs And Symptoms ◽

The United States ◽

Erysiphe Cichoracearum ◽

Leaf Surfaces ◽

Pathogenicity Tests ◽

Salvia Officinalis L ◽

Autumn And Winter

Common sage, Salvia officinalis L., is produced primarily in greenhouses for the culinary herb market in Argentina. Since 2003 during autumn and winter, powdery mildew symptoms have been repeatedly observed on potted common sage plants in commercial greenhouses located on the outskirts of Buenos Aires. The average disease incidence during this period was 85 to 90%. Circular, white, powdery patches developed on leaf surfaces and stems. Heavily infected leaves turned brown and died. Hyaline mycelium and nonlobed appressoria were observed. Conidiophores were simple with straight foot cells measuring 53.0 to 80.0 × 10.0 to 12.3 μm. Conidia were aseptate, hyaline, cylindrical to ovoid, measured 33.0 to 40.5 × 15.0 to 18.5 μm, did not contain fibrosine bodies, and were produced in chains. Cleistothecia were not observed. The pathogen was identified as Erysiphe cichoracearum DC (1). Pathogenicity was confirmed by gently pressing leaves displaying abundant sporulation onto the adaxial surface of healthy leaves. After 10 to 12 days, typical signs and symptoms of powdery mildew appeared on all inoculated plants. Pathogenicity tests were conducted in a greenhouse at 20 to 23°C and included 10 sage plants (five inoculated and five noninoculated). The experiment was performed twice, each time with the same result. Control plants did not show any signs or symptoms. E. cichoracearum DC was previously reported in the United States on Salvia sp. (2).To our knowledge, this is the first report of an outbreak of powdery mildew caused by E. cichoracearun on potted common sage plants produced in greenhouses in Argentina. References: (1) H. J. Boesewinkel. Rev. Mycol. Tome 41:493, 1977. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.

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Industrial Hemp Knowledge and Interest among North Carolina Organic Farmers in the United States

Sustainability ◽

10.3390/su11092691 ◽

2019 ◽

Vol 11 (9) ◽

pp. 2691 ◽

Cited By ~ 7

Author(s):

Beatrice Dingha ◽

Leah Sandler ◽

Arnab Bhowmik ◽

Clement Akotsen-Mensah ◽

Louis Jackai ◽

...

Keyword(s):

United States ◽

North Carolina ◽

Crop Production ◽

Cannabis Sativa ◽

The United States ◽

Online Questionnaire ◽

Wide Range ◽

Organic Farmers ◽

Certified Organic ◽

Industrial Hemp

Industrial hemp (Cannabis sativa), has been proposed as a new crop that might be of interest to organic farmers in the North Carolina and other states in the United States. However, little is known about how organic farmers view this crop. We conducted a survey among North Carolina certified organic growers to ascertain their knowledge of, and willingness to adopt, industrial hemp. Contact information was obtained from a database of certified organic farmers in North Carolina and the growers were contacted by email and directed to complete an online questionnaire. Growers were asked a wide range of questions about farm characteristics, technology adoption, interest toward industrial hemp, and policy issues regarding hemp adoption. A total of 245 farmers were contacted; 64 started the survey and 35 responded to all questions. Our results indicate that 85% of North Carolina organic growers are interested in growing hemp on their farms and the majority wanted to learn more about the crop production practices, adapted cultivars, and legality of growing it. Seventy-five percent expressed interest in being certified growers while 52% wanted to grow industrial hemp primarily for cannabidiol (CBD) oil. Most (65%) respondents indicate they aspired to be among the first farmers in their area to grow and sell hemp. Growers who have tried new crops or new farming technology in the last three years were more likely to adopt industrial hemp production. These findings will help decision-makers understand the critical concerns of growers who are willing to adopt industrial hemp as an alternative income-generating enterprise.

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Powdery Mildew Caused by Golovinomyces biocellatus on Spearmint (Mentha spicata) in Italy

Plant Disease ◽

10.1094/pdis-94-9-1171a ◽

2010 ◽

Vol 94 (9) ◽

pp. 1171-1171 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

M. L. Gullino

Keyword(s):

United States ◽

Powdery Mildew ◽

Signs And Symptoms ◽

Its Region ◽

The United States ◽

Pathogenicity Test ◽

Aromatic Plants ◽

Mentha Spicata ◽

Leaf Surfaces ◽

Voucher Specimens

Spearmint (Mentha spicata) is grown for its aromatic and carminative oil and as an ornamental. During the fall of 2009, 4-month-old plants grown on a commercial farm located near Albenga (northern Italy) showed signs and symptoms of an unknown powdery mildew. The adaxial leaf surfaces were covered with white mycelia and conidia, while the abaxial surfaces were less infected. As the disease progressed, infected leaves turned yellow and wilted. Mycelia were also observed on stems. Conidia were hyaline, elliptical to doliform, borne in short chains (two to three conidia per chain), and measured 35 × 21 μm (30 to 43 × 18 to 26 μm). Conidiophores measured 86 × 11 μm (76 to 97 × 9 to 13 μm) followed by one to three shorter cells, measuring, respectively, 22 × 11 μm (13 to 28 × 9 to 15 μm). Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced (1) (GenBank Accession No. HM053470). The 567-bp amplicon had 100% homology with the sequence of Golovinomyces biocellatus (GenBank Accession No. AB307675). Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of healthy M. spicata plants. Three plants were inoculated, while the same number of noninoculated plants served as a control. Plants were maintained at temperatures from 18 to 25°C. Twelve days after inoculation, typical symptoms of powdery mildew developed on inoculated plants. The fungus observed on inoculated plants was morphologically identical to that originally observed. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. G. biocellatus has been reported on Mentha spp. in Australia (3) and the United States (4) and the pathogen is present on other plant genera in Italy. A similar powdery mildew of M. spicata was attributed to Erysiphe orontii in the United States (2). The economic importance of this disease is currently limited in Italy because of the limited planting of this host, but potted aromatic plants represent a steadily increasing crop in Italy. Voucher specimens are available at the Agroinnova Collection, University of Torino. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) S. T. Koike and G. S. Saenz. Plant Dis. 83:399, 1999. (3) J. R. Liberato and J. H. Cunnington. Australas. Plant Dis. Notes 2:83, 2007. (4) D. B. Marcum et al. Plant Dis. 94:276, 2010.

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Genome-wide characterization of the MLO gene family in Cannabis sativa reveals two genes as strong candidates for powdery mildew susceptibility

10.1101/2021.07.16.452661 ◽

2021 ◽

Author(s):

Noémi Pépin ◽

Francois Olivier Hebert ◽

David L Joly

Keyword(s):

Amino Acid ◽

Powdery Mildew ◽

Gene Family ◽

Cannabis Sativa ◽

Protein Sequences ◽

Cultivated Plants ◽

Economic Losses ◽

Functional Domain ◽

Wide Range

Cannabis sativa is increasingly being grown around the world for medicinal, industrial, and recreational purposes. As in all cultivated plants, cannabis is exposed to a wide range of pathogens, including powdery mildew (PM). This fungal disease stresses cannabis plants and reduces flower bud quality, resulting in significant economic losses for licensed producers. The Mildew Locus O (MLO) gene family encodes plant-specific proteins distributed among conserved clades, of which clades IV and V are known to be involved in susceptibility to PM in monocots and dicots, respectively. In several studies, the inactivation of those genes resulted in durable resistance to the disease. In this study, we identified and characterized the MLO gene family members in five different cannabis genomes. Fifteen Cannabis sativa MLO (CsMLO) genes were manually curated in cannabis, with numbers varying between 14, 17, 19, 18, and 18 for CBDRx, Jamaican Lion female, Jamaican Lion male, Purple Kush, and Finola, respectively (when considering paralogs and incomplete genes). Further analysis of the CsMLO genes and their deduced protein sequences revealed that many characteristics of the gene family, such as the presence of 7 transmembrane domains, the MLO functional domain, and particular amino acid positions, were present and well conserved. Phylogenetic analysis of the MLO protein sequences from all five cannabis genomes and other plant species indicated seven distinct clades (I through VII), as reported in other crops. Expression analysis revealed that the CsMLOs from clade V, CsMLO1 and CsMLO4, were significantly upregulated following Golovinomyces ambrosiae infection, providing preliminary evidence that they could be involved in PM susceptibility. Finally, the examination of variation within CsMLO1 and CsMLO4 in 32 cannabis cultivars revealed several amino acid changes, which could affect their function. Altogether, cannabis MLO genes were identified and characterized, among which candidates potentially involved in PM susceptibility were noted. The results of this study will lay the foundation for further investigations, such as the functional characterization of clade V MLOs as well as the potential impact of the amino acid changes reported. Those will be useful for breeding purposes in order to develop resistant cultivars.

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Genome-Wide Characterization of the MLO Gene Family in Cannabis sativa Reveals Two Genes as Strong Candidates for Powdery Mildew Susceptibility

Frontiers in Plant Science ◽

10.3389/fpls.2021.729261 ◽

2021 ◽

Vol 12 ◽

Author(s):

Noémi Pépin ◽

Francois Olivier Hebert ◽

David L. Joly

Keyword(s):

Amino Acid ◽

Powdery Mildew ◽

Gene Family ◽

Cannabis Sativa ◽

Protein Sequences ◽

Cultivated Plants ◽

Economic Losses ◽

Functional Domain ◽

Wide Range

Cannabis sativa is increasingly being grown around the world for medicinal, industrial, and recreational purposes. As in all cultivated plants, cannabis is exposed to a wide range of pathogens, including powdery mildew (PM). This fungal disease stresses cannabis plants and reduces flower bud quality, resulting in significant economic losses for licensed producers. The Mildew Locus O (MLO) gene family encodes plant-specific proteins distributed among conserved clades, of which clades IV and V are known to be involved in susceptibility to PM in monocots and dicots, respectively. In several studies, the inactivation of those genes resulted in durable resistance to the disease. In this study, we identified and characterized the MLO gene family members in five different cannabis genomes. Fifteen Cannabis sativa MLO (CsMLO) genes were manually curated in cannabis, with numbers varying between 14, 17, 19, 18, and 18 for CBDRx, Jamaican Lion female, Jamaican Lion male, Purple Kush, and Finola, respectively (when considering paralogs and incomplete genes). Further analysis of the CsMLO genes and their deduced protein sequences revealed that many characteristics of the gene family, such as the presence of seven transmembrane domains, the MLO functional domain, and particular amino acid positions, were present and well conserved. Phylogenetic analysis of the MLO protein sequences from all five cannabis genomes and other plant species indicated seven distinct clades (I through VII), as reported in other crops. Expression analysis revealed that the CsMLOs from clade V, CsMLO1 and CsMLO4, were significantly upregulated following Golovinomyces ambrosiae infection, providing preliminary evidence that they could be involved in PM susceptibility. Finally, the examination of variation within CsMLO1 and CsMLO4 in 32 cannabis cultivars revealed several amino acid changes, which could affect their function. Altogether, cannabis MLO genes were identified and characterized, among which candidates potentially involved in PM susceptibility were noted. The results of this study will lay the foundation for further investigations, such as the functional characterization of clade V MLOs as well as the potential impact of the amino acid changes reported. Those will be useful for breeding purposes in order to develop resistant cultivars.

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