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Sclerophthora rayssiae var. zeae
(brown stripe downy mildew of maize)

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Datasheet

Sclerophthora rayssiae var. zeae (brown stripe downy mildew of maize)

Summary

  • Last modified
  • 10 May 2019
  • Datasheet Type(s)
  • Documented Species
  • Pest
  • Preferred Scientific Name
  • Sclerophthora rayssiae var. zeae
  • Preferred Common Name
  • brown stripe downy mildew of maize
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Chromista
  •     Phylum: Oomycota
  •       Class: Oomycetes
  •         Order: Peronosporales
  • Summary of Invasiveness
  • The first record of brown stripe downy mildew of maize occurred in India in the early 1960s. In 1967, the pathogen was defined as Sclerophthora rayssiae var. zeae by Payak and Renfro. It spread rapidly...

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Pictures

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PictureTitleCaptionCopyright
Symptoms of S. rayssiae var. zeae on maize plant. Three leaves essentially covered by stripes.
TitleSymptoms
CaptionSymptoms of S. rayssiae var. zeae on maize plant. Three leaves essentially covered by stripes.
CopyrightM.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Three leaves essentially covered by stripes.
SymptomsSymptoms of S. rayssiae var. zeae on maize plant. Three leaves essentially covered by stripes.M.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Upper two leaves showing vein-limited elongate flecks, an early stage in stripe formation.
TitleSymptoms
CaptionSymptoms of S. rayssiae var. zeae on maize plant. Upper two leaves showing vein-limited elongate flecks, an early stage in stripe formation.
CopyrightM.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Upper two leaves showing vein-limited elongate flecks, an early stage in stripe formation.
SymptomsSymptoms of S. rayssiae var. zeae on maize plant. Upper two leaves showing vein-limited elongate flecks, an early stage in stripe formation.M.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Note that the stripes on the lower leaf are as long as the lamina.
TitleSymptoms
CaptionSymptoms of S. rayssiae var. zeae on maize plant. Note that the stripes on the lower leaf are as long as the lamina.
CopyrightM.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Note that the stripes on the lower leaf are as long as the lamina.
SymptomsSymptoms of S. rayssiae var. zeae on maize plant. Note that the stripes on the lower leaf are as long as the lamina.M.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Severe striping with blotching and tearing near leaf apices.
TitleSymptoms
CaptionSymptoms of S. rayssiae var. zeae on maize plant. Severe striping with blotching and tearing near leaf apices.
CopyrightM.M. Payak/ex. IARI
Symptoms of S. rayssiae var. zeae on maize plant. Severe striping with blotching and tearing near leaf apices.
SymptomsSymptoms of S. rayssiae var. zeae on maize plant. Severe striping with blotching and tearing near leaf apices.M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Lobulate hyphae in leaf tissue. (Scale bar equals 20 µm)
TitleLeaf section
CaptionS. rayssiae var. zeae on maize plant. Lobulate hyphae in leaf tissue. (Scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Lobulate hyphae in leaf tissue. (Scale bar equals 20 µm)
Leaf sectionS. rayssiae var. zeae on maize plant. Lobulate hyphae in leaf tissue. (Scale bar equals 20 µm)M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. A large caducous sporangium with a poroid apex and straight peduncle. (Note scale bar equals 20 µm)
TitleSporangium
CaptionS. rayssiae var. zeae on maize plant. A large caducous sporangium with a poroid apex and straight peduncle. (Note scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. A large caducous sporangium with a poroid apex and straight peduncle. (Note scale bar equals 20 µm)
SporangiumS. rayssiae var. zeae on maize plant. A large caducous sporangium with a poroid apex and straight peduncle. (Note scale bar equals 20 µm)M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Delimitation of zoospores in sporangium with a cuneate peduncle. (Note scale bar equals 20 µm)
TitleZoospores in sporangium
CaptionS. rayssiae var. zeae on maize plant. Delimitation of zoospores in sporangium with a cuneate peduncle. (Note scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Delimitation of zoospores in sporangium with a cuneate peduncle. (Note scale bar equals 20 µm)
Zoospores in sporangiumS. rayssiae var. zeae on maize plant. Delimitation of zoospores in sporangium with a cuneate peduncle. (Note scale bar equals 20 µm)M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Two oogonia in mesophyll of leaf tissue. (Note scale bar equals 20 µm)
TitleOogonia
CaptionS. rayssiae var. zeae on maize plant. Two oogonia in mesophyll of leaf tissue. (Note scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Two oogonia in mesophyll of leaf tissue. (Note scale bar equals 20 µm)
OogoniaS. rayssiae var. zeae on maize plant. Two oogonia in mesophyll of leaf tissue. (Note scale bar equals 20 µm)M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Oospores with a prominent oil globule. (Note scale bar equals 20 µm)
TitleOospores
CaptionS. rayssiae var. zeae on maize plant. Oospores with a prominent oil globule. (Note scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Oospores with a prominent oil globule. (Note scale bar equals 20 µm)
OosporesS. rayssiae var. zeae on maize plant. Oospores with a prominent oil globule. (Note scale bar equals 20 µm)M.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Two sporangia produced superstomally. (Note scale bar equals 20 µm)
TitleSporangia
CaptionS. rayssiae var. zeae on maize plant. Two sporangia produced superstomally. (Note scale bar equals 20 µm)
CopyrightM.M. Payak/ex. IARI
S. rayssiae var. zeae on maize plant. Two sporangia produced superstomally. (Note scale bar equals 20 µm)
SporangiaS. rayssiae var. zeae on maize plant. Two sporangia produced superstomally. (Note scale bar equals 20 µm)M.M. Payak/ex. IARI

Identity

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Preferred Scientific Name

  • Sclerophthora rayssiae var. zeae Payak & Renfro

Preferred Common Name

  • brown stripe downy mildew of maize

International Common Names

  • English: brown stripe: maize downy mildew
  • Spanish: estriado pardo del maiz
  • French: strie brune du mais

Local Common Names

  • India: bhooradhari mduromilphaphundi rog

EPPO code

  • SCPHRZ (Sclerophthora rayssiae var. zeae)

Summary of Invasiveness

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The first record of brown stripe downy mildew of maize occurred in India in the early 1960s. In 1967, the pathogen was defined as Sclerophthora rayssiae var. zeae by Payak and Renfro. It spread rapidly across India, especially in regions with over 100 cm of annual rainfall and into neighbouring countries, probably via seed transfer. It has been effectively controlled by the use of resistant hybrids and seed treatment. It is not reported to be an invasive species.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Chromista
  •         Phylum: Oomycota
  •             Class: Oomycetes
  •                 Order: Peronosporales
  •                     Family: Peronosporaceae
  •                         Genus: Sclerophthora
  •                             Species: Sclerophthora rayssiae var. zeae

Notes on Taxonomy and Nomenclature

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Kenneth et al. (1964) defined Sclerophthora rayssiae as the oomycete causing a form of downy mildew on barley in Israel. Payak and Renfro (1967) observed small differences in the size and colour of oospores and sporangia of the brown stripe downy mildew pathogen that they observed on maize and recognized it as a potential variant, for which they used var. zeae as a descriptor. Until DNA comparisons can be made, continuing with the Sclerophthora rayssiae var. zeae terminology is warranted.

Description

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The mycelium of S. rayssiae var. zeae permeates the mesophyll; the hyphae are irregular in shape and are lobulate rather than tubular. Sporangia are produced sympodially in groups of between two and six in a basipetal succession on sporangiophores, which arise from hyphae congregated in the substomatal cavities; sporangial production occurs superstomatally.

Sporangia are hyaline, ovate, obclavate, elliptic or cylindrical, smooth-walled, papillate, having a projecting truncate, rounded or tapering poroid apex and a persistent, straight or cuneate peduncle (caducous), 29-66.5 x 18.5-26 µm; in the apex, lens-shaped pores have been observed through which zoospores/cytoplasm may escape. Four to eight zoospores are delimited within the sporangia, which may encyst within or outside the sporangium; encysted zoospores are hyaline, spherical and 7.5-11 µm diam.

Oogonia develop in a scattered pattern in the leaf mesophyll or even in the substomatal cavities but never in the vascular bundles; they are hyaline to light, straw-coloured, subglobose, thin-walled, with one or two paragynous antheridia, 33-44.5 µm diameter; oospores plerotic, spherical or subspherical, have hyaline contents including a prominent oil globule with a smooth, glistening, uniformly 4 µm thick wall which is confluent with the oogonial wall, 29.5-37 µm diameter.

Distribution

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S. rayssiae var. zeae has been identified on leaves of Zea mays subsp. mays in India, Myanmar, Nepal, Pakistan and Thailand; on leaves of Z. mays subsp. mexicanna in Iltis, Delhi, in experimental fields only; and Digitaria sanguinalis in Pantnagar (Uttar Pradesh) and Punjab.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

IndiaWidespreadFrederiksen and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014
-Andhra PradeshPresentPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-BiharWidespreadPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-DelhiPresent, few occurrencesSingh et al., 1970; CABI/EPPO, 2009; EPPO, 2014
-GujaratWidespreadPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-HaryanaPresentPayak, 1975; Payak and Sharma, 1985; CABI/EPPO, 2009; EPPO, 2014
-Himachal PradeshWidespreadPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-Indian PunjabWidespreadMalhotra et al., 1986; CABI/EPPO, 2009; EPPO, 2014
-Jammu and KashmirPresentPayak, 1975; CABI/EPPO, 2009; EPPO, 2014
-KarnatakaPresentPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-Madhya PradeshWidespreadPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-MeghalayaPresentPayak and Sharma, 1985; CABI/EPPO, 2009; EPPO, 2014
-RajasthanWidespreadPayak and Renfro, 1967; Payak, 1975; CABI/EPPO, 2009; EPPO, 2014
-SikkimPresentFrederiksen and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014
-Uttar PradeshWidespreadPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
-West BengalPresentPayak and Renfro, 1967; CABI/EPPO, 2009; EPPO, 2014
MyanmarPresentFrederikson and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014
NepalPresentSplitter, 1975; Frederiksen and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014
PakistanPresentFrederiksen and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014
ThailandPresentSenanarong, 1975; Frederiksen and Renfro, 1977; CABI/EPPO, 2009; EPPO, 2014

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
India 1960s Yes No Payak and Renfro (1967) No reports of recurrent epidemics or new races

Risk of Introduction

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Risk Criteria Category

Economic Importance Low
Distribution India, Nepal, Pakistan, Sikkim, Thailand
Seedborne Incidence Low
Seed Transmitted Yes
Seed Treatment Yes

Overall Risk Low

Notes on Phytosanitary Risk

While it is generally considered that drying seeds to below 14% water content and storage over several months will render downy mildew pathogens inviable (Frederiksen and Renfro,1977; CAPS, 2010) that is not a 100% reliable preventative. For example, Adenle and Cardwell (2000) found that some seeds from small ears taken from Peronosclerospora sorghi-infected plants produced infected plants even though the moisture content was 8.5% after nine months storage. Seed treatment with metalaxyl provides additional insurance against introductions by infected seeds (Lal et al., 1980).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial – ManagedCultivated / agricultural land Present, no further details Harmful (pest or invasive)
Freshwater
Irrigation channels Present, no further details

Hosts/Species Affected

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Singh et al. (1970) found Digitaria sanguinalis at Pantnagar, Uttar Pradesh, India to be infected with a downy mildew, which was identified as Sclerophthora rayssiae var. zeae. Cross inoculations confirmed that the pathogen from the grass was able to produce infection on maize similar to that incited by the maize isolate; reciprocal inoculations were also successful. However, field observations indicated that, in terms of epidemiology, it constituted a minor infection source in comparison to the oosporic stage present in leaf debris on the soil surface. In Punjab, however, Bains et al. (1978) found D. sanguinalis instrumental in causing infections in a one-month-old maize crop as early as the month of June (the regular planting season begins a month later, mid-June to the beginning of July). Disease incidence was higher in the maize crop on the northern and southern side of irrigation channels where there was a high density of infected D. sanguinalis plants (Bains et al., 1978). In laboratory studies, cross inoculations between the grass host and maize plants were successful.

A downy mildew found on Digitaria bicornis in Thailand, although identified as S. rayssiae var. zeae, was not able to infect maize or rice (Chamswarng et al., 1976). It is possibly a specialized strain and may need a status of an independent variety. Thus, this pathogen would have no role in causing infection on maize, but only further work in Thailand can clarify this aspect.

A downy mildew on zoysia grass (Zoysia japonica) in Korea was classified as a Scleropthora based on morphology. DNA sequences within the cox2 mitochondrial gene and nuclear ribosomal 28s subunit differed 1%-2% from the equivalent sequences in isolates from S. macrospora from various hosts. This is the only other Scleropthora for which sequences are available and therefore no species designation was assigned (Lee et al., 2017). 

Growth Stages

Top of page Flowering stage, Seedling stage, Vegetative growing stage

Symptoms

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The characteristic feature of brown stripe downy mildew, as its name suggests, is the vein-limited striping of the foliage. Other parts of the plant including husk leaves, ears or tassels, do not show symptoms even though all of the leaves including the flag leaf may be affected by the disease.

The early zoosporic infections appear as vein-limited chlorotic flecks or blobs, which enlarge lengthwise and coalesce. The merger of the flecks leads to the formation of rudimentary stripes in the inter-veinal areas. The stripes range in width from 3-7 mm. In length, however, they may extend to the full length of the lamina and also on either side of the midrib. At first the stripes are chlorotic or yellowish but with age they turn yellowish-tan to purple ferrugineous and necrotic. In some maize genotypes, the pathogen induces stripes, which have reddish to reddish-purple borders with bleached centres. This process of stripes becoming necrotic coincides with the development of the teleomorphic stage (antheridia and oogonia) and heralds the cessation of sporangial prodution.

The disease first appears on the lowermost leaves, which are proximate to ground level. These leaves show the highest level of striping; as a result they present a pale-brown, burnt appearance and severely affected leaves may be shed prematurely. Leaves around the ear shoot show a lesser amount of striping and the leaves above it (near the tassel) show the least striping. Occasional infections through localized rain-splashing or a similar kind of disturbance may alter this pattern of disease appearance to some extent. Infections leading to severe striping result in blotching of extensive areas of leaf laminae. In the early stages, zoosporic infections en masse in large patches lead to rapid coalescencence, which produces the blotching effect. The damage becomes more severe and premature defoliation may result. As the veins are not affected, laminar shredding is uncommon. However, when severe infection occurs, leaves tear apart near the apices and hang in tatters.

Vegetative or floral malformations of any kind are completely absent. What differentiates this disease from crazy top, caused by Sclerophthora macrospora, is the absence of malformation, stunting, leaf thickening, leaves becoming strap-like, etc. Greatest damage due to the brown stripe disease occurs when the disease severity is high in the pre-flowering stage. It suppresses emergence of the ear or at best a rudimentary ear of no consequence may peep out of the sheath of the ear shoot.

On the under surfaces of the chlorotic stripes, a greyish-white, downy growth develops, which has a fine granular rather than fibrous appearance. It is not restricted to the adaxial surfaces of the stripes on the leaf though it is more commonly found there. On the upper leaf surfaces a downy growth is also quite often encountered. Thus, in a strict sense, it is amphigenous rather than hypophyllous. The downy growth has been observed even in the afternoons and so it is not so evanescent as is the case with other downy mildews affecting poaceous crops (Payak and Renfro, 1967; Payak et al., 1970). As the stripes lose their chlorotic appearance and turn necrotic, the downy growth disappears. Oospores appear to be produced only in necrotic tissues. Striping of maize leaves can occur due to a variety of causes: genetic, nutritional or pathological. However, the presence of granular downy growth on the undersides of vein-limited stripes without any malformation is a diagnostic feature of brown stripe downy mildew.

List of Symptoms/Signs

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SignLife StagesType
Leaves / abnormal colours
Leaves / fungal growth
Leaves / necrotic areas
Leaves / shredding
Leaves / yellowed or dead

Biology and Ecology

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Life Cycle

In S. rayssiae var. zeae the diurnal rhythm does not resemble that observed in species of Sclerospora in that the peak sporangial germination occurs in material collected at 16:00 h rather than in collections made in night time (Singh et al., 1970). Accordingly, inoculations in the afternoon lead to adequate infection.

Epidemiology

Once through primary infection the disease becomes established, then the sporangial stage takes over producing a cyclical chain of secondary infections (in a favourable environment one generation of sporangia requires no more than 10 days) which leads to plant-to-plant infections and ultimately the rapid spread of the disease throughout the entire crop.

The seedling stage is ordinarily the most vulnerable stage. Experimental work has shown that in 10-day-old plants, zoosporic inoculations led to as much as 87% infection while in 60-day-old plants it was hardly 9% (Singh et al., 1970).

It is obvious that the disease requires a high level of ambient moisture in the crop canopy for infection and disease spread.

An attempt was made by Payak and Renfro (1970) to correlate rainfall with the geographical distribution and severity of the disease in India. The areas in which the disease has been recorded fall, in respect of rainfall, into three distinct regions. In region I, the average annual rainfall varies from 40 to 60 cm; in region II, 60-100 cm; and in region III, 100-200 cm. Kalimpong in West Bengal is one station where the rainfall is slightly higher (218 cm). In region I, the disease has been recorded from Ludhiana, Punjab (69 cm), Ajmer, Rajasthan (53 cm), Godhra, Gujarat (71 cm) and Arbhavi, Karnataka (51 cm). The disease ratings recorded have been from low to trace level but occasionally in Ludhiana, the incidence may be higher. In region II, at Mandsaur, Jhabua and Dhar in Madhya Pradesh and Hyderabad in Andhra Pradesh, the disease intensity has been moderate. In region III, maximum incidence has been observed. In 1965 and 1966 Kharif season (June-July to September-October) there was an epidemic at Pantnagar, Uttar Pradesh and also in 1966 Kharif at Solan, Himachal Pradesh. The other locations within this region are Almora, Uttar Pradesh, and Dholi, Pusa and Messina in Bihar. Disease intensities of a higher order are possible in regions I and II in localized areas only where brief spells of heavy rain occur in a short period accompanied by temperatures up to 25°C. Sporangia development is optimal at 22-25°C and zoospores at 18-30°C.

Climate

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ClimateStatusDescriptionRemark
Cfb - Maritime temperate climate Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year, warmest month average temp. < 22°C
Dfb - Warm summer continental or hemiboreal climate Preferred Warm summer continental or hemiboreal climate (Warm average temp. > 10°C, coldest month < 0°C, wet all year, warmest month average temp. < 22°C)

Rainfall

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ParameterLower limitUpper limitDescription
Mean annual rainfall100-200mm; lower/upper limits

Means of Movement and Dispersal

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Primary dispersal of S. rayssiae var. zeae is via oospores in soil, though it is also dispersed through wind-blown infected leaf debris, contact, seed contamination and rain splash.

The pathogen survives in the soil in the form of oospores, which fall with the infected leaf debris of the previous crop. Initially, this was surmised by noting the mode of first disease expression; the lower leaves show greater disease intensity than the upper leaves (Payak and Renfro, 1967). Singh et al. (1970) demonstrated experimentally that the highest number of seedlings were infected (94%) when powdered infected leaf debris was placed in the uppermost 3.75 cm layer of the soil. It was also demonstrated that the oosporic inoculum was viable for up to three years and when 2 g of powdered leaf debris was placed around each seed at the time of sowing, heavy infection resulted in the emerging seedlings.

Circumstantial evidence suggests that the oospores of S. rayssiae var. zeae germinate in an indirect way, i.e. an oospore produces a single germ sporangium, as has been shown to occur in Sclerophthora macrospora by Semeniuk and Mankin (1964). This in turn produces the zoospores which infect the maize crop. Thus whether it is oospores or sporangia, the propagule which actually infects the plants is the zoospore or rarely the sporangial germ tube (Payak et al., 1970).

As is the case with other pathogens, moisture is a crucial factor for infection to occur. Singh et al. (1970) found that a 12-h wetting period (the availability of a free film of moisture on the leaf surface) is necessary for infection to take place; longer wetting periods increased the amount of infection and a 6-h wetting period failed to produce any infection.

Seedborne Aspects

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Incidence

S. rayssiae var. zeae has been found in embryos of maize seeds (Singh et al., 1967, Singh et al., 1968). Sangam et al. (1989) reported viable oospores on the seed surface and mycelium was found within seed tissues.

Effect on Seed Quality

S. rayssiae var. zeae infection has been associated with smaller seed size (Sangam et al., 1989).

Pathogen Transmission

Brown stripe downy mildew developed on seedlings grown in sterilized soil from seeds taken from infected plants (Singh et al., 1968). Other attempts to demonstrate seed transmission of S. rayssiae var. zeae were unsuccessful (Singh et al., 1970).

Soilborne oospores (Singh et al., 1970) and infected Digitaria sanguinalis (Bains et al., 1978) are sources of inoculum. The pathogen is transmitted by wind and rain (Singh and Renfro, 1971).

Seed Treatment

Seed treatment with metalaxyl gave control of the disease up to 30 days after planting; when followed by a foliar application of metalaxyl, control was improved and yield increased (Lal et al., 1980; Sangam et al., 1989). A high rate application of metalaxyl to seeds was phytotoxic (Lal et al., 1980).

Seed Health Tests

Embryo test:
Seed is digested in 2% sodium or potassium hydroxide for 15 min to 12 h (depending on seed hardness) at 45-50°C, then washed several times in distilled water, stained in 0.1% cotton blue in lactic acid or glycerol for 15-20 min, squashed under a coverslip and examined microscopically (Singh et al., 1967, 1968).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Crop productionUnless seed is contaminated with mycelium or oospores Yes Singh et al., 1967; Singh and Renfro, 1971
HitchhikerAccidental, potentially on farm equipment Yes Yes
Seed trade Yes Yes Singh and Renfro, 1971

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
GermplasmNot documented, but likely Yes Yes Singh et al., 1967
Machinery and equipmentLikely since oospores in soil could be transferred Yes ,
Soil, sand and gravel Yes Singh and Renfro, 1971
Water Yes Singh and Renfro, 1971
Wind Yes Singh and Renfro, 1971

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Flowers/Inflorescences/Cones/Calyx hyphae; spores Yes Yes Pest or symptoms usually invisible
Growing medium accompanying plants spores Yes Pest or symptoms usually invisible
Leaves hyphae; spores Yes Yes Pest or symptoms usually visible to the naked eye
Stems (above ground)/Shoots/Trunks/Branches hyphae; spores Yes Pest or symptoms usually invisible
True seeds (inc. grain) hyphae; spores Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Fruits (inc. pods)
Wood

Impact Summary

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CategoryImpact
Economic/livelihood Negative

Impact

Top of page The disease was observed in India in 1962, but not described until 1967 (Payak and Renfro, 1967). It is a common and destructive disease in India, with losses ranging from 20 to 90% (Payak, 1975). It tends to be most severe in areas with 100 to 200 cm rainfall, declining in severity as rainfall declines (Frederiksen and Renfro, 1977).

The losses that the disease may inflict on a crop in a given area varies in a complex way. In general, if three-quarters or more of the foliage is affected prior to flowering, then the loss may be total, ear formation is either totally suppressed or markedly attenuated. Grain yield reductions may vary from 20 to 90%. Losses above 70% occur only in highly susceptible cultivars grown in conditions favourable for the disease (Payak, 1975). Yield losses of up to 63% have been recorded in the tarai area of Uttar Pradesh (Sharma et al., 1993).

McGregor (1978) established the parameter designated as Expected Economic Impact (EEI), which formed the basis for listing '49 top-ranking exotic pathogens' from a total of 551 that pose a significant threat to agriculture in the USA. S. rayssiae var. zeae was ranked 43rd with the EEI standing at US$ 53 million at 1978 prices.

Impact: Economic

Top of page

The disease was observed in India in 1962, but not described until 1967 (Payak and Renfro, 1967). It is a common and destructive disease in India, with losses ranging from 20 to 90% (Payak, 1975). It tends to be most severe in areas with 100 to 200 cm rainfall, declining in severity as rainfall declines (Frederiksen and Renfro, 1977).

The losses that the disease may inflict on a crop in a given area varies in a complex way. In general, if three-quarters or more of the foliage is affected prior to flowering, then the loss may be total, ear formation is either totally suppressed or markedly attenuated. Grain yield reductions may vary from 20 to 90%. Losses above 70% occur only in highly susceptible cultivars grown in conditions favourable for the disease (Payak, 1975). Yield losses of up to 63% have been recorded in the tarai area of Uttar Pradesh (Sharma et al., 1993).

McGregor (1978) established the parameter designated as Expected Economic Impact (EEI), which formed the basis for listing '49 top-ranking exotic pathogens' from a total of 551 that pose a significant threat to agriculture in the USA. S. rayssiae var. zeae was ranked 43rd with the EEI standing at US$ 53 million at 1978 prices.

Impact: Social

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The development and use of resistant maize varieties and chemical control have greatly lowered the risk of crop loss and food shortages caused by the disease.

Risk and Impact Factors

Top of page Invasiveness
  • Long lived
  • Has propagules that can remain viable for more than one year
Impact outcomes
  • Host damage
  • Negatively impacts agriculture
  • Negatively impacts livelihoods
  • Negatively impacts animal/plant collections
  • Negatively impacts trade/international relations
Impact mechanisms
  • Antagonistic (micro-organisms)
  • Pest and disease transmission
  • Pathogenic
Likelihood of entry/control
  • Difficult to identify/detect as a commodity contaminant

Uses List

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General

  • Laboratory use

Genetic importance

  • Test organisms (for pests and diseases)

Ornamental

  • Seed trade

Diagnosis

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As the disease is restricted in its development to the foliage, the crop in the field has to be inspected to determine its occurrence. The disease is easily distinguishable from crazy top disease, caused by Sclerophthora macrospora, in that no malformation/deformation of vegetative or floral parts occurs (Payak and Renfro, 1967). Microscopic examination to determine the occurrence of sporangia and oogonia/oospores will confirm the identity of the disease. Striping of maize leaves can occur due to a variey of causes: genetic, nutritional or pathological. However, the presence of granular downy growth on the underside of vein-limited stripes without any malformation is a diagnostic feature of brown stripe downy mildew.

Prevention and Control

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Prevention

As the disease was recorded in the 1960s, the need for control through host resistance was deemed to be a priority for the All India Coordinated Maize Improvement Project. In the hybrid development programme a large number of inbred lines were evaluated to this disease and many promising lines were soon identified so that it was possible to release a resistant hybrid as early as 1968. This was one of the fastest answers to a disease problem identified in 1965. Multiple sources of genetic resistance were identified and have proven to be effective in that no reports of epidemics have occurred since resistant hybrids were introduced. This may reflect that quantitative inheritance rather than single gene resistance has been the norm (Singh and Asnani, 1975a; Singh and Asnani, 1975b). Cooperative work in the Asian region under the aegis of the Inter Asian Corn Programme, identified very promising resistance to all the prevailing downy mildews of maize in the region in Philippine germplasm; Taiwan had already released hybrids resistant to sugarcane downy mildew (Peronosclerospora sacchari). Materials identified as resistant in the Philippines and Thailand to the prevailing downy mildews in those locations have also shown a high level of resistance to S. rayssiae var. zeae (Payak and Sharma, 1978). Identification of sources of maize resistant to brown stripe downy mildew is continuing (Singh and Singh, 2011; Singh and Singh, 2012).

Chemical Control

Coordinated work at a national level has been carried out to determine dosage, formulations, etc., for the systemic fungicide metalaxyl, which is specifically active as a seed treatment against oomycetous fungi including the downy mildews. Lal et al. (1980) found that seed treatment with the fungicide controlled brown stripe downy mildew for up to 30 days after planting, at which time a second foliar application was found to be effective in season-long control. To date, no reports of S. rayssiae var. zeae showing metalaxl resistance have been published, but effective application of other chemicals after symptoms has been described (Lal et al., 1980).

Gaps in Knowledge/Research Needs

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A lack of DNA sequence information for species-conserved sequences, such as the internal transcribed spacers between ribosomal DNA subunits, parts of the rDNA itself and cox2 mitochondrial DNA along with variable markers such as simple sequence repeats (SSRs) that provide a measure of variability among isolates of the same species, makes it especially difficult to assess relationships of the maize brown stripe downy mildew with downy mildews of other crops. So far, only limited sequence information is available in GenBank for Sclerophthora macrospora, the prototype for this genus, which infects a number of plant hosts.

References

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Adenle, V. O., Cardwell, K. F., 2000. Seed transmission of maize downy mildew (Peronosclerospora sorghi) in Nigeria. Plant Pathology, 49(5), 628-634. doi: 10.1046/j.1365-3059.2000.00484.x

Bains SS, Jhooty JS, Sokhi SS, Rewal AS, 1978. Role of Digitaria sanguinalis in outbreaks of brown stripe downy mildew of maize. Plant Disease Reporter, 62(2):143

CABI/EPPO, 2009. Sclerophthora rayssiae. [Distribution map]. Distribution Maps of Plant Diseases, No.April. Wallingford, UK: CABI, Map 1057 (Edition 1)

CAPS, 2010. Sclerophthora rayssiae var. zeae. In: CPHST Pest Datasheet , USA: Cooperative Agricultural Pest Survey.http://download.ceris.purdue.edu/file/3118

Chamswarng C, Pupipat U, Sommartaya T, Renfro BL, 1976. A downy mildew on white birdfoot grass (Digitaria bicornis (Lamk.) Roem. & Schult. ex Loud.). Kasetsart Journal, 10(1):14-24

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Frederiksen RA, Renfro BL, 1977. Global status of maize downy mildew. Annual Review of Phytopathology, 15:249-275

Kenneth R, Koltin Y, Wahl I, 1964. Barley diseases newly found in Israel. Bulletin Torrey Botanical Club, 91:185-193

Lal S, Saxena SC, Upadhyay RN, 1980. Control of brown stripe downy mildew of maize by metalaxyl. Plant Disease, 64(9):874-876

Lee JS, Kim K, Tae H, Choi Y-J, 2017. First report of downy mildewcaused by Sclerophthora sp. on Zoysia grass (Zoysia japonica) in Korea. Plant Disease, 101(10), 1826.

Malhotra VV, Khehra AS, Dhillon BS, 1986. Variability in resistance of local maize germplasm to brown-stripe downy-mildew and its relationship with rainfall in the areas of their adaptation. Indian Journal of Agricultural Sciences, 56(5):387-389

McGregor RC, 1978. People-placed pathogens: the emigrant pests. In: Horsfall JG, Cowling EB, ed. Plant disease. An advanced treatise. Volume II. How disease develops in populations. Academic Press Inc. New York, USA & London UK, 383-396

Payak MM, 1975. Downy mildews of maize in India. Tropical Agriculture Research Series, 8:13-18

Payak MM, 1975. Epidemiology of maize downy mildews with special reference to those occurring in Asia. Trop. Agric. Res. Ser. No. 8, 81-91

Payak MM, Lal S, Renfro BL, 1970. Downy Mildew diseases incited by Sclerophthora. Indian Phytopathology, 23:183-193

Payak MM, Renfro BL, 1967. A new downy mildew disease of maize. Phytopathology, 57:394-397

Payak MM, Renfro BL, 1970. The Biology, Distribution and differential response of Maize to Sclerophthora rayssiae var. zeae In: Raychaudhuri, SP et al., eds, Plant Disease Problems, New Delhi, India: Indian Phytopathological Society, 383-387

Payak MM, Sharma RC, 1978. Research on diseases of maize. In: PL-480 Project Final Technical Report (April 1969-March 1975) . New Delhi, India: Indian Council of Agricultural Research.pp. 228.

Payak MM, Sharma RC, 1985. Maize diseases and approaches to their management in India. Tropical Pest Management, 31(4):302-310

Sangam Lal, Thakur Prasad, 1989. Detection and management of seed-borne nature of downy mildew diseases of maize. Seeds & Farms, 15(6):35-40

Semeniuk G, Mankin CJ, 1964. Occurrence and development of Sclerophthora macrospora on cereals and grasses in South Dakota. Phytopathology, 54:409-416

Senanarong A, 1975. Present corn production status. Symposium on downy mildew of maize, Tokyo, Japan, September, 1974. Tropical Agriculture Research Series, No. 8, 31-34

Sharma RC, Deleon C, Payak MM, 1993. Diseases of Maize in South and South-East Asia : Problems and progress Crop Protection, 12:414-422

Singh A, Singh D, 2011. Sources of resistance in maize (Zea mays L) against erwinia stalk rot and brown stripe downy mildew. Plant disease Research, 26, 187.

Singh A, Singh D, 2012. Screening of maize genotypes for resistance to bacterial stalk rot and brown stripe downy mildew. Maize Journal, 1, 134-135.

Singh JP, Renfro BL, 1971. Studies on spore dispersal in Sclerophthora rayssiae var. zeae. Indian Phytopathology, 24(3):457-461

Singh JP, Renfro BL, Payak MM, 1970. Studies on the epidemiology and control of brown stripe downy mildew of maize (Sclerophthora rayssiae var. zeae). Indian Phytopathology, 23:194-208

SINGH RS, CHAUBE HS, KHANNA RN, JOSHI HM, 1967. Internally seedborne nature of two downy mildews on Corn. Plant Disease Reporter, 51(12):1010-1012

Singh, I. S., Asnani, V. L., 1975. Combining ability for resistance to brown stripe downy mildew in maize. Indian Journal of Genetics and Plant Breeding, 35(1), 128-130.

Singh, I. S., Asnani, V. L., 1975. Gene effect for resistance to brown stripe downy mildew in maize. Indian Journal of Genetics and Plant Breeding, 35(1), 123-127.

Splitter MV, 1975. Downy mildew disease in Nepal. Symposium on downy mildew of maize jointly held by Tropical Agriculture Research Center and Inter-Asian Corn Program. Session I. Tropical Agricultural Research Series, No. 8:19-20

Telle S, Thines M, 2012. Reclassification of an enigmatic downy mildew species on lovegrass (Eragrostis) to the new genus Eraphthora, with a key to the genera of the Peronosporaceae. Mycological Progress, 11, 121-129.

Links to Websites

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WebsiteURLComment
Center for Environmental and Regulatory Information Systems (CERIS)http://pest.ceris.purdue.edu/services/approvedmethods/sheet.php?v=12
Phytosanitary information from CGIARhttp://cropgenebank.sgrp.cgiar.org/images/file/management/quarantine%20requirements%20maize%20jun%2009.pdfCountries that verify absence of S. rayssiae var. zeae for maize imports
Plant Management Networkhttps://www.plantmanagementnetwork.org/pub/php/diagnosticguide/2007/stripe/

Contributors

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01/08/17 Updated by:

Clint Magill, Department of Plant Pathology and Microbiology, Texas A&M University, Texas, USA

Distribution Maps

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