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A. Peronosclerospora ischaemi, oospores. B. Peronosclerospora jamesiae, oospores. C. Peronosclerospora maydis, sporangiophore, germinating sporangia, and oospores. D. Peronosclerospora miscanthi, sporangiophore, germinating sporangium, and oospores. E. Peronosclerospora noblei, sporangiophore, sporangia, and oospores. The top three oogonia are illustrated in surface view, including one oogonium that is one cracked open with an oospore released from oogonial wall (arrow). Illustrations were prepared from published reference images in Raciborski (1897), Weston (1929, 1942), Chu (1953), Shivas et al. (2012), Widiantini et al. (2015) and Ryley et al. (2022).
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Downy mildew pathogens of graminicolous hosts (Poaceae) are members of eight morphologically and phylogenetically distinct genera in the Peronosporaceae (Oomycota, Peronosporales). Graminicolous downy mildews (GDMs) cause severe losses in crops such as maize, millets, sorghum, and sugarcane in many parts of the world, especially in tropical climate...
Contexts in source publication
Context 1
... Oogonia highly variable shape including subglobose, ovoid and cuboid, dark golden brown, (40-)46-60(-80) μm in diam; wall smooth, rounded to flat, occasionally concave, 2-15 μm thick. Oospores sub-globose to ovoid sometimes with a flattened side, (30-)32-42(-55) μm diam, with prominent oil globule; wall hyaline, even, smooth, 1-2 μm thick (Fig. 4B). Asexual morph not observed (Ryley et al. ...
Context 2
... µm wide, with septated basal cells 60-180 µm long, dichotomously branched 2-4 times, branchlets with two or more (generally 3-6) conical sterigmata (6-9 μm long) each bearing one individual sporangium. Sporangia hyaline, oval or spherical to subspherical, non-papillate, and 15-18 μm wide, direct germination by 1-2 germ tubes (Raciborski 1897; Fig. 4C). Sexual structures rare or unknown (Semangoen 1970), that have been described from the type specimen of what was originally described as Peronosclerospora australiensis but is now accepted as a synonym of Peronosclerospora maydis (Suharjo et al. 2020); that description is as follows: Oogonia golden orange to yellowish or reddish ...
Context 3
... or reddish brown, globose, subglobose, broadly ellipsoidal to irregularly polyangular, 55-76 μm diam; exosporium 2-15 μm wide, uneven, smooth, convoluted. Oospores one per oogonium, sub-hyaline to pale yellow, globose or broadly ellipsoidal, 39-55 μm diam, often with a large vacuole; endosporium 2.5-4.0 μm wide, even, smooth (Shivas et al. 2012; Fig. ...
Context 4
... ranging from golden to rich brown; oogonial stalk fragments often retained. Oospores spherical, hyaline to pale golden, 23-28.9 (mode 25-26.9, range 20-34) μm in diam; wall 1-1.5 μm thick, contents comprising finely granular material with denser aggregations and oil drops, central to eccentric in position. Germination not observed (Weston 1929; Fig. ...
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... August 1921 collections of Saccharum spontaneum colonized by oogonia of Sclerospora spontanea are accessioned as BPI 187043 and BPI 187073 and match the published collection details; BPI 187043 is hereby used to lectotypify Peronosclerospora spontanea. One additional specimen of Sclerospora spontanea collected in December 1921, BPI 187342, consists of dried conidia scraped from the surface of diseased maize leaves that had been inoculated from conidia originally harvested from Saccharum spontaneum, and includes a typewritten note signed by Weston (Supplementary Fig. S14). Description: Conidiophores 600-1 000 μm long, with single basal compartment; 9-11.5 μm broad at the basal compartment, 20-27 μm broad at main axis branching. ...
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... Peronosclerospora philippinensis isotype BPI 187311. Fig. S9. Peronosclerospora philippinensis isotype BPI 187313. Fig. S10. Peronosclerospora sacchari lectotype BPI 187331. Fig. S11. Peronosclerospora sorghi lectotype BPI 187336. Fig. S12. Peronosclerospora spontanea lectotype BPI 187043 Fig. S13. Peronosclerospora spontanea isotype BPI 187073. Fig. S14. Peronosclerospora spontanea BPI 187342. Fig. S15. Sclerophthora cryophila holotype DAOM 20643. Fig. S16. Sclerophthora macrospora neotype BPI 187265. Fig. S17. Sclerophthora macrospora isotype BPI 187266. Fig. S18. Sclerospora farlowii lectotype BPI 187077. Fig. S19. Sclerospora farlowii isotype BPI 187076. Fig. S20. Sclerospora ...
Citations
... Downy mildew, which is caused by the oomycete Sclerospora graminicola, makes it very hard to grow pearl millet and kodo millet (Jidda and Anaso, 2017;Zoclanclounon et al., 2019). Downy mildew disease is prevalent in India, China, Japan, and Russia (Crouch et al., 2022). Several endogenous hormones, such as, salicylic acid, abscisic acid, jasmonic acid, ethylene, auxin, gibberellin, and cytokinin, are involved in regulating plant growth and development against plant disease (particularly downy mildew disease) (Berens et al., 2017). ...
Nutrient-richness, climate-resilience, and economic importance of millets are believed to ensure food security for future generations. Millets have the habit of growing against abiotic stresses (particularly drought stress). Millets show much better climate resilience and nutrient supplementation properties compared to other major cereals. Understanding the molecular mechanisms of genes that respond to stresses and nutrient transport will help understand the tolerance mechanism and improve against both stresses. Genome sequences are currently available for two major (sorghum and pearl millet) and eight minor millets (foxtail millet, finger millet, kodo millet, barnyard millet, proso millet, job’s tear, fonio millet and tef), and five minor millets (little millet, kodo millet, brown-top millet, guinea millet and raishan) have no genome sequences. Transcriptome studies help to identify differentially expressed genes (DEGs), mine genes induced in a particular stress and develop several molecular markers for all plants, including millets. Some millets have reports on transcriptome datasets for exposed to various biotic and abiotic stresses and for nutrient traits. Unfortunately, the transcriptome datasets of millets have not been adequately leveraged to explore genes associated with traits such as climate resilience, nutrient enrichment, and millet improvement. This underutilization stems from a lack of high-resolution studies and limited exploration within the field. As a result, the potential insights and genetic understanding offered by these datasets remain largely untapped. Through this review, we plan to elucidate the current status of transcriptome resources on millets and draw future insights on the utilization of these resources. This review will motivate millet researchers to utilize the available transcriptome resources for millet improvement.
... С середины 1960-х гг. были лишь единичные упоминания об обнаружении этого вида, обычно плохо задокументированные и непроверяемые (Crouch et al., 2022). ...
Despite the great attention paid to the study of barley diseases, inaccuracies in the names of diseases, their practical significance, and incorrect use of the scientific names of causal agents can be commonly found in the scientific literature. This may lead to confusion and misidentification of the pathogens that can affect this crop especially as relates to phytosanitary requirements. This review continues the series started with a publication devoted to wheat diseases. This review includes information about the main barley diseases and pathogenic organisms causing them, as well as the species emerging as a potential threat to barley. The current taxonomic status of fungal species and fungal-like organisms associated with various organs of barley is given, and the breadth of their distribution and degree of impact on the crop are summarized. The micromycetes were divided into two groups according to their phytosanitary importance. The first group is represented by fungi of great importance as the pathogens causing the 29 economically important common barley diseases. The second group consists of fungi causing 20 minor and poorly studied diseases with unconfirmed harmfulness, or potential endophytic fungi. Perceptions of their ability to cause disease remain controversial and the available data require confirmation. This dataset can be used as a reference for a more accurate description of the phytosanitary situation. The review will also be helpful for more targeted studies using molecular techniques to clarify taxonomy and areals of fungi associated with barley and to provide more detailed data on disease damage in this crop.
... However, comprehensive taxonomic studies of grass-inhabiting fungi based on morphological and molecular approaches, especially ascomycetous fungi, have been well-investigated over the last decade. Although, these studies were restricted to some fungal genera or specific hosts (Manamgoda et al. 2011, Phookamsak et al. 2015b, Dai et al. 2017, Dayarathne et al. 2017, Marin-Felix et al. 2017, Thambugala et al. 2017, Crouch et al. 2022. Imperata (Poaceae) is considered one of the top ten most problematic weeds in the world as it causes over 62-90% yield losses of different crops (MacDonald 2004, Estrada & Flory 2015, Javaid et al. 2015, Kato-Noguchi 2022. ...
In the present study, a new species, Scolecohyalosporium thailandense, is introduced based on morphological and molecular approaches. The species was found as a saprobe occurring on Imperata sp. (Poaceae) in terrestrial habitats in Chiang Rai Province, Thailand. This species is characterized by solitary, semi-immersed to erumpent, subglobose to ampulliform, papillate ascomata, dark brown pseudoparenchymatous peridium, fissitunicate, cylindrical to subcylindrical asci embedded in a hyaline, filamentous to cellular pseudoparaphysate hamathecium, and filiform, yellowish, septate ascospores. Phylogenetic analyses based on a concatenated ITS, LSU, SSU, and TEF1-α sequence matrix demonstrated that S. thailandense formed a well-resolved clade with S. submersum (the type species of this genus) and Scolecohyalosporium sp. within the Parabambusicolaceae. Therefore, S. thailandense is introduced herein as the second species of the genus Scolecohyalosporium. Morphological characteristics, illustrations, and updated phylogenetic analyses are provided, and notes on species distinctiveness with closely related taxa are discussed.
... Moreover, in several DM genera, the determinate sporangiophores also have dilated apices on which multiple sporangia or conidia are produced. These apices are saucer-shaped in Bremia, club-shaped in Eraphthora, cone-to club-shaped in Basidiophora and broad club-shaped to cylindrical in Baobabopsis [120][121][122][123]. However, none of the known DM genera form multifurcated candelabra-like sporangiophore apices. ...
... Functionally, the synchronous production and ripening of up to more than 100 caducous sporangia per candelabra-like sporangiophore apex in S. medusiformis resembles 19 of the 20 DM genera [4,119,120,123,[125][126][127], allowing simultaneous aerial spread with high inoculum pressure. Another similarity between Synchrospora and the DMs is the small size (and hence weight) of the sporangia increasing their aerial dispersibility, whereas the unusually long, curved and twisted pedicels most likely facilitate sporangial clustering and adherence to plant surfaces as recently suggested for aerial long-pedicellate Phytophthora species [16]. ...
... Synchrospora medusiformis, 75% of the eight described Nothophytophthora species, 26.7% of the 210 described Phytophthora species and all ca 900 DM species have caducous sporangia (or conidia) connected to an aerial or partially aerial lifestyle [4,6,13,14,16,31,34,36,123], whereas the other Peronosporaceae genera Calycofera, Halophytophthora and Phytopythium completely lack sporangial caducity [5,9,22,33]. Significant differences in sporangiophore growth and sporangial caducity between Synchrospora (determinate sporangiophores, synchronous production of up to >100 pedicellate caducous sporangia per candelabra-like sporangiophore apex); Nothophytophthora (indeterminate sporangiophores forming sympodia of non-pedicellate sporangia that mature non-synchronously; caducity by breaking off below a conspicuous opaque plug); Phytophthora (indeterminate sporangiophores forming sympodia of pedicellate sporangia that mature non-synchronously; caducity in airborne species); Viennotia (indeterminate sporangiophores, non-pedicellate caducous sporangia that mature non-synchronously); and the other 19 DM genera (determinate sporangiophores forming non-pedicellate or rarely pedicellate (cf. ...
During a survey of Phytophthora diversity in Panama, fast-growing oomycete isolates were obtained from naturally fallen leaves of an unidentified tree species in a tropical cloud forest. Phylogenetic analyses of sequences from the nuclear ITS, LSU and ßtub loci and the mitochondrial cox1 and cox2 genes revealed that they belong to a new species of a new genus, officially described here as Synchrospora gen. nov., which resided as a basal genus within the Peronosporaceae. The type species S. medusiformis has unique morphological characteristics. The sporangiophores show determinate growth, multifurcating at the end, forming a stunted, candelabra-like apex from which multiple (8 to >100) long, curved pedicels are growing simultaneously in a medusa-like way. The caducous papillate sporangia mature and are shed synchronously. The breeding system is homothallic, hence more inbreeding than outcrossing, with smooth-walled oogonia, plerotic oospores and paragynous antheridia. Optimum and maximum temperatures for growth are 22.5 and 25–27.5 °C, consistent with its natural cloud forest habitat. It is concluded that S. medusiformis as adapted to a lifestyle as a canopy-dwelling leaf pathogen in tropical cloud forests. More oomycete explorations in the canopies of tropical rainforests and cloud forests are needed to elucidate the diversity, host associations and ecological roles of oomycetes and, in particular, S. medusiformis and possibly other Synchrospora taxa in this as yet under-explored habitat.
... Downy mildew of corn caused by Peronosclerospora spp. has been reported in many countries in South-East Asia and Australasia (Sharma et al. 1993;Spencer and Dick 2002;Suharjo et al. 2020;Crouch et al. 2022). The native grass species that serve as the primary host for most of the Peronosclerospora species that infect corn are known. ...
... However, due to the absence of specimens, the species could not be morphologically compared to the known species of Peronosclerospora and was not formally introduced. More recently, extype sequences of additional Peronosclerospora species have been made available (Crouch et al. 2022), but none of them matched the new lineage found in Indonesia. It was the aim of the current study to clarify the identity of this Peronosclerospora species using the cox2 gene sequence barcode (Choi et al. 2015) and specimen morphology. ...
Downy mildew is a serious threat to corn (maize) production in the tropics and subtropics. Corn is native to Central America, and was introduced into South-East Asia by the Spanish colonisers in the 1700s. Corn is evolutionarily naïve to downy mildews of the genus Peronosclerospora . Consequently, corn monocultures are particularly susceptible to a variety of Peronosclerospora species, which spread to the crop from local grasses. Globally, corn is one of the most important crops for both humans and livestock. Several downy mildews of corn have been identified as potential threats to global food security, and trade with corn seeds is strictly regulated to avoid spreading the pathogens. Despite their importance, little is known about the biodiversity of graminicolous downy mildews, because their identification has often relied on variable morphological features, such as conidial dimensions. DNA barcodes for most species have become available only recently. During surveys for downy mildews on corn in Indonesia, a previously unrecognised species of Peronosclerospora was found and investigated using a combination of morphological characters and molecular phylogenetic analyses. The new species, introduced here as Peronosclerospora neglecta , is widely distributed in South-East Asia from Thailand to eastern Indonesia. The impact of this downy mildew can be severe, with complete crop losses in heavily affected fields. Given the aggressiveness of the species, close surveillance is warranted to restrict its further spread.
Maize is the second staple food commodity in Indonesia. Apart from being the main source of carbohydrates and protein, the production of maize continues to increase along with the escalation of population growth and animal feed requirements in the last few years. The potential to increase the national production of maize is still feasible because of the yield gap between the potential yields of new superior varieties and the level of yields obtained by farmers. The yield gap caused by biotic stress in maize is mainly caused by pathogens such as downy mildew due to Peronosclerospora spp. Downy mildew distribution is sporadic that can infect a wide area. In Indonesia, it spreads widely and significantly reduces yields in the areas of maize production centres in East Java, Central Java, South Sulawesi, North Sulawesi, Gorontalo, Lampung, and Sumatera. These obstacles can be overcome by integrated pest and disease control technology. One strategy is to discover downy mildew-resistant varieties that can be combined with other control treatments. The phenomenon of resistance to downy mildew infection of several hybrid maize strains began to be detected in the vegetative growth phase, with symptoms beginning at 14 days after planting (DAP), increasing with plant age, and reaching its peak after 28-35 DAP and then the symptoms will gradually disappear until no infection after 42 HST. This study analyses the resistant maize varieties from 2020 to 2022. The data showed the susceptible comparison variety (Anoman) was infected with 88.94% to 100%. In 2020, BMD73 showed a resistant reaction to Philippinensis species, other strains were classified as susceptible in P. maydis except BMD 76. All strains showed highly susceptible and susceptible reactions. In 2021, in P. philippinensis all strains FCP10-FCP16 showed a resistant reaction, but line FCP10-FCP16 had a resistance response that was classified as moderately resistant to P. maydis . The incidence of genetic response in 2022, except BMD86, strains BMD81-BMD85 were classified as resistant, as well as in the P. maydis endemic area all strains showed the same reaction.
Millets are cereal crops that are grown in tropical and subtropical regions of the world most popular in China, India, and Africa. The millet rhizosphere refers to the area in the soil surrounding millet roots, and it can be quite helpful in managing some pest problems and encouraging healthy growth. One reason it grows so well in these areas is that it can thrive in high temperatures and low humidity. This chapter outlines what we need to know about the millet rhizosphere, from its structure to its microorganisms and more. Soil biodiversity can be restored by using millet crops as their rhizosphere has a variety of microbial populations which can only be seen in the areas/soil where millet crops are grown. The rhizosphere is an area of soil that surrounds plant roots and is shaped by their biological responses. In millet crops, it has been shown that the rhizosphere influences root growth, influencing nutrient uptake and stress resistance. Several microbes have been found in millet rhizospheres, some of which are only found in this environment. This is important as it can help us understand how these microbes affect plants in terms of plant nutrition and plant health. The rhizosphere of millets is a habitat for bacteria, fungi, and other microorganisms. These organisms play an important role in soil quality through their interaction with plants. Some organisms help plants from getting resistance to various soil-borne diseases. There is not much information/research available on millet rhizosphere due to its less consumption. This chapter concentrates on the benefits of microbial populations in the millet rhizosphere and their importance with all the available information.KeywordsMillet cropsPlant biomassPlant nutritionRhizosphereRhizospheric microbesRhizospheric pHSoil-borne diseasesStress-resistance
While it is increasingly well understood how plants and animals spread around the world, and how they diversify and occupy new niches, such knowledge is fairly limited for fungi and oomycetes. As is true for animals and plants, many plant pathogenic fungi have been spread anthropogenically, but, in contrast to them, only rarely as a deliberate introduction. In addition, the occupation of new niches for plant pathogenic fungi is less defined by the abiotic environment, but more by the biotic environment, as the interaction with the host plant is the major ecological determinant of fitness, especially for biotrophic and hemibiotrophic pathogens. Thus, host switches are a major driver in the diversification of pathogens, which can have an effect similar to the arrival of animals or plants on a previously uninhabited archipelago. This chapter summarises the current state of knowledge on range expansions and host jumps in plant pathogens, focusing on (hemi-)biotrophic fungi and oomycetes.KeywordsAnthropogenic spreadEvolutionHost jumps
Erysiphaceae
Oomycota
Pucciniales
Ustilaginomycotina
Oomycetes that cause downy mildew diseases are highly specialized, obligately biotrophic phytopathogens that can have major impacts on agriculture and natural ecosystems. Deciphering the genome sequence of these organisms provides foundational tools to study and deploy control strategies against downy mildew pathogens (DMPs). The recent telomere-to-telomere genome assembly of the DMP Peronospora effusa revealed high levels of synteny with distantly related DMPs, higher than expected repeat content, and previously undescribed architectures. This provides a road map for generating similar high-quality genome assemblies for other oomycetes. This review discusses biological insights made using this and other assemblies, including ancestral chromosome architecture, modes of sexual and asexual variation, the occurrence of heterokaryosis, candidate gene identification, functional validation, and population dynamics. We also discuss future avenues of research likely to be fruitful in studies of DMPs and highlight resources necessary for advancing our understanding and ability to forecast and control disease outbreaks.
Expected final online publication date for the Annual Review of Phytopathology, Volume 61 is September 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
