Int.J.Curr.Microbiol.App.Sci (2019) 8(11): 855-862

International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 8 Number 11 (2019) Journal homepage: http://www.ijcmas.com

Review Article https://doi.org/10.20546/ijcmas.2019.811.101

Southern Disease of Corn – A Review

Srabani Debnath1*, Sanjog Chhetri1 and Sonali Biswas2

1Department of Plant pathology, 2Department of Agronomy, Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India

*Corresponding author

ABSTRACT

Maize is having a high yield potential and the problem of increasing K e yw or ds demand of food and feed for the growing population can be solved by

producing more corn in the coming years. Among the constraints faced by Biotroph, this cereal crop, one is the biotic stress. Rust is a very important disease Epidemiology, Yield Loss, problem of corn and specially the southern corn rust may pose a serious

Epidemics, threat to production. Southern Rust pathogen is a biotroph and Management cannot exist without living host. So, it is very important to study this Article Info disease thoroughly considering its mode of spread, epidemiology, yield

Accepted: loss, occurrence of epidemics in different countries and most importantly 10 October 2019 the management strategies that can be followed in minimizing the yield loss Available Online: due to this disease. In this article specially these important issues of 10 November 2019 southern corn rust is discussed in detail.

Introduction tropical rust caused by Physopellazeae (Dolezal, 2011). Severity of common and Maize (Zea mays L.) is one of the major cereal southern rust is increased when incidence crops in the world as well as in India. It is occurs earlier with a long lasting favourable used in diversified ways and known as the weather condition for the disease queen of cereals because of its highest yield development. Southern corn rust becomes potential among all the cereal crops. Maize more severe than common rust to field corn crop may be affected by 112 biotic stresses. production because of its more aggressiveness Rust disease of corn is one of the important and lack of resistance to most of the corn diseases of maize. There are three types of hybrids. Southern corn rust was not identified rusts affecting corn plant namely – common before 1941 in the western hemisphere but rust caused by Puccinia sorghi, southern corn evidences of presence of it was there in the rust (SCR) caused by Puccinia polysora and harberium specimen during 1879 (Cummins,

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1941). In 1949 Western Africa faced an Africa and Asia (Philippines) and new races outbreak of Southern corn rust which spreads were also identified in eastern Africa. In 2006 across the continent and caused a considerable Rpp9 virulent – anew race was identified. yield loss (Rhind et al., 1952). In 2000 infection of common rust was severe in the Economic damage of southern corn rust: In hybrid cornfields of Indiana (Kiersten Wise USA reported upto 45-75%, Africa more than and Esker, 2008). 50% (1950s) and Philippines more than 80% (1956). Of the three rusts that occur on corn (Zea mays L.) worldwide, southern rust of corn, Presence of southern rust of maize (Zea mays caused by Puccinia polysora. Underw, has L.) caused by Puccinia polysoraUnderw.in been reported as the most destructive among India was first confirmed in Mysore district of all the reported rusts of maize. P. ploysora Karnataka. Moderate to severe infection of differs from the common rust pathogen P. this rust was noticed in October 1999, during Sorghi Schw. Southern corn rust becomes Post-Entry Quarantine Inspection (PEQI) of progressively more severe as the plant maize crop at Bangalore (Agarwal et al., develops, resulting in premature desiccation of 2001). plant tissues. SCR is considered as minor pathogen of corn but Yield losses of 45-50% Identifying characters of southern corn rust are was found due to epidemics and destruction – pustules are mainly formed on upper leaf was greatest in late-sown corn fields in 1972, surface and occasionally some pustules are 1973, 1974 and 1979 (Leonard, 1974; Futrell, developed along the midrib of the bottom of 1975; Scott et al., 1979 and Schall et al., the leaf, on the husk, orange to reddish-orange 1983). Southern rust of corn was also reported in color, develops in warm moist conditions. from Wisconsin (Pavgi et al., 1959) and usually oblong, ellipsoid, Kansas (Sim, 1980). Sudden epidemics were mostly not round but immature round also happened in double cropping of corn in (Dolezal, 2011). lower Mississippi River Valley and on the coastal plain of the southeastern United States Sothern rust was found in corn fields of (Futrell, 1975; Widstorm and Young, 1980). southwestern part of Georgia caused by Rpp9- In this double cropping system the first crop is virulent Puccinia polysora and this was an planted in February and harvested in June, the unusual occurrence (Dolezal et al., 2009). second crop is planted in late June and harvested in October. This system provides In Georgia differential reactions was found of the scope of infection of southern rust due to Rpp resistance to an Rpp-virulent isolate of exposure of corn plants to large quantities of Puccinia polysora (Pataky et al.,). Differential inoculums at its early growth stage. races of Puccinia polysora was proposed by Favourable weather condition for southern Yeh in 1986. Variations among the isolates of corn rust prevails throughout the corn belt of Puccinia polysora was found in Brazil in 2002 United States (Hollier& King 1985). by Casela & Ferreira. Sources of resistance to Puccinia polysora was identified by Wisser et Incidences of Southern corn rust al., in 2006. Changes of races in Puccinia polysora is found in 2006. In Brazil uredial This disease was first identified in 1941, first formation of several Rpp9 lines was identified detection in Corn Belt during 1949. From in February, 2006. Widespread southern rust 1949-1950s outbreaks were documented in outbreak was happened in New York in the

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Int.J.Curr.Microbiol.App.Sci (2019) 8(11): 855-862 month of August, 2006. Significant uredial Difference between common rust and development was observed in hybrids southern rust containing the Rpp9 gene in Goias of Brazil during February, Puerto Vallarta of Mexico Cool, warm and moist weather (15-250C) is during March, in Victoria of Texas during favorable for common rust but for southern June of 2007. Again detection of southern rust rust hot, warm and moist weather (250C) is by using PCR was done in 2011 by Crouch suitable. Pustules of common rust are large and Szabo. circular to elongated, brown to cinnamon brown but that of southern rust are small, Symptoms of southern cornrust circular, pinheaded and reddish orange.

Southern rust is caused by the Puccinia Pustules are formed both on upper and lower polysora. Symptoms of southern rust are surface and sparsely scattered in common rust different from common rust in that they are and pustules are formed only on upper surface typically smaller in size and are often a in densely cluster form in southern rust. brighter orange color. Pustules of southern Puccinia polysora differs from the common rust also typically only develop on Southern rust pathogen Puccinia sorghischw. SCR rust pustules on a corn leaf. The upper surface becomes more severe as the plant develops, of the leaf becomes more affected. Southern resulting in premature desiccation of plant rust is microcyclic in nature and believed to be tissues (Scott et al., 1984). autoecioushemiform. This type of rust is distributed worldwide in tropical and Conditions favoring disease development subtropical regions. Orange to tan circular or oval pustules commonly form in dense These fungi require living plant tissue to clusters on the upper leaf surface (Fig. 1). As survive, so once the corn plant dies, the fungus the season progresses, the pustules can change loses its host. Most rust fungi are biologically to brown or black. Southern rust can be easily complex (with many stages) and require confused with other leaf diseases of corn such more than one host species to complete their as common rust or Physoderma brown spot. life cycles, which includes sexual repro- Proper diagnosis helps to avoid unnecessary duction. However, the spores produced on and costly fungicide applications (Geist, corn (urediniospores) are capable of indefinite 2018). Sometimes this disease may come in asexual reproduction, as long as living corn is later stage of crop and can cause major stalk available to be infected. Each year, lodging. Urediniospores of Puccinia polysora urediniospores of both rusts are blown north usually oblong, ellipsoid but most are not from tropical areas. round and the teleutospores are having short pedicels which are ¼th in length of spore. They are carried on wind currents and are usually found in the field only deposited into cornfields of USA. Favorable late in season as the tissue starts to die and conditions for southern rust development common in tropical regions. Sometimes they include high humidity and temperatures show a semicircular / horseshoe type or around 8ºF. However, very little free moisture completely circular pattern. Optimum is need for infection to occur. Southern rust is temperature for the germination of typically a rare occurrence in Wisconsin but is 23 – 280C and 16 hrsdew its occurrence is found usually in the southern period is required for optimal infection and south-western portions of the state, (Dolezal et al., 2009). epidemics initiating late in the season and in

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Int.J.Curr.Microbiol.App.Sci (2019) 8(11): 855-862 southern Wisconsin epidemic was happened in Yield loss due to SCR is significant when the 2016 (Damon L. Smith, 2017). disease appears early in the growing season or in case of corn planted late during the growing Southern corn rust fungi require short periods season. Critical yield loss is observed when of leaf wetness to cause infection. infection occurred by early grain fill stages Approximately six hours of dew is usually (Storey and Howland 1957, Futrell, 1975). enough moisture for infection and disease Historic outbreaks of SCR occurred in Africa development. Temperature plays a critical role in 1949 and yield loss of around 50% was in the life cycle of this rust. reported (Rhind et al., 1952, Hemmingway, 1955 and Cammack, 1958). In Philippines, Southern rust prefers warmer weather — during 1953, Yield losses of 80 to 84% were fungal infection occurs between 77-82°F. This observed on susceptible cultivars (Reyes, disease usually appears in Indiana of USA in 1953) and substantial yield loss of 42 to 53% late August or September. When conditions was first reported in northern China in 1998 are favorable for rust development, the (Chen et al., 2004). Losses upto 18 and 39% infection cycle will continually repeat and in SCR inoculated field trials conducted in result in secondary infections. Each pustule Pennsylvania and Maryland (Raid, 1988). In produces thousands of spores that can infect Florida, yields reduction of corn planted in a the plant and produce additional pustules double-cropped field was upto 45% due to within seven days. With continuation of these SCR (Pernenzy, 1999). cycles, disease intensity can reach epidemic levels very quickly. Extent of yield loss depends on the timing of disease development and severity. Upto 45% Corn rust can reach damaging levels at high yield loss is reported from Florida due to speed and it is necessary to pay careful severe outbreak of southern corn rust. For attention to the level and timing of initial 10% leaf area infection, 6% yield loss was disease infection in susceptible hybrids. recorded in Illinois sweet corn (Tamra and Young leaves are more susceptible to southern Jackson, 2014). rust infection than mature leaves, and late- planted corn may be at greater risk for Rust diseases are parasites and divert nutrients infection if rust spores reach to corn fields and for fungal growth that would normally be used weather conditions favour disease by the plant. This process can lead to yield development. loss during grain filling stage when plant resources are needed to contribute to the Disease impact developing ear.

Rust disease is responsible for economic loss Rust pustules also rupture leaf epidermal in seed corn, sweet corn, and pop corn tissue, which can interfere with the regulation production. Among the three rusts affecting of water loss by stomata on the leaf surface. corn southern rust caused by Puccinia polysora Undrew. has been reported as the Severe rust outbreaks may reduce the plant’s most destructive (Melching, 1975). Due to this water use efficiency and symptoms of mild disease attack, yield loss may be upto 45% - drought stress are found in infected plants 50 % (Rodriguez et al., 1980). Destruction due which may also help to the development of to the attack of southern corn rust is more stalk rot and lodging. Southern rust has great severe in late sown corn fields (Scott et al., impact on seed corn, sweet corn, and popcorn 1976). 858

Int.J.Curr.Microbiol.App.Sci (2019) 8(11): 855-862 because of the inherent susceptibility of inbred on identifying phenotypic virulence and and specialty hybrids. genetic diversity of P. polysora.

Southern rust has the greatest potential to Management of Southern Corn Rust (SCR) in damage yield of corn in Indiana of USA at a Georgia by using fungicides is recommended critical point in the growing season. The since 2004 (Kemerait, 2012). It was started in importance of this disease has increased in response to the serious damages caused by southern states of USA and routinely reducing severe outbreaks of Southern Corn Rust in yields on susceptible hybrids without any 2003(Woodward, 2012). Fungicide fungicide application. applications are expected to be effective upto the dough stage of the corn crop, after that Southern rust of corn epidemic caused by crop becomes safe from southern rust. Puccinia polysora was initiated in Maryland Application of fungicides at the tasselling and Pennsylvania. The rust was more severe stage was effective to manage SCR and in on lower leaves and the severity generally protecting the yield of corn (Kemerait, 2012). decreased with successive leaf positions. Susceptible hybrids must be protected with Grain yields were reduced 17.7% to 39.1% fungicides, especially when the environment is respectively at Pennsylvania and Maryland favorable for disease development. Southern field sites. This maximum reduction occurred corn rust is a destructive disease in maize. The during 1984 at a 3m distance from the inbred line Qi319 is highly resistant to inoculum source. The yield reduction was southern corn rust. The inheritance of significantly related to the area under the resistance to southern rust in Qi319 was disease progress curves as calculated from investigated (Chen et al., 2002) and time 10 to 35 days after anthesis. considered that Qi319 carries one dominant Environmental data suggest temperature may gene for resistance to southern corn rust. be the factor most limiting to development of southern rust of corn in northern areas of the Traditionally resistance was used to manage United States. southern rust of corn. In 2008 a resistance- breaking race of the southern rust fungus was In 2008, a new genetic variant (race) of the confirmed in Georgia. Thus most modern southern rust fungus was discovered in hybrids are considered susceptible to southern Georgia that was able to cause disease on rust. Rotation and residue management have formerly resistant hybrids. This has increased no effect on the occurrence of southern rust. the importance of the disease in southern areas The southern rust fungus has to have living of USA. corn tissue in order to survive and cannot overwinter in Wisconsin. Fungicides are Management typically used to control southern rust in parts of the U.S. where this is a consistent problem By utilizing the Rpp9 gene and other sources (Damon L. Smith, 2017). of Rpp resistance have been successful for management of Southern Corn Rust in the Biological control of SCR can be done by United States for more than two decades Sphaerellopsis sp. Which is a mycoparasite. (Pataky et al., 2010). Puccinia polysora is Some Sphaerellopsis sp. isolates were assayed known to have multiple races to overcome in vitro and inhibition of uredospore single, dominant resistance genes (Hooker, germination of P. polysora by 69 to 92% was 1985) but there are few recent studies focusing found. In pot experiment, Sphaerellopsis sp.

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Int.J.Curr.Microbiol.App.Sci (2019) 8(11): 855-862 reduced the infection efficiency of P. polysora significant reduction of rust severity from 46% from 75-82% with the most virulent isolates. to 25% was obtained. Yield of dehusked green Uredospore production was reduced by 69%. corn ears was increased from 4.688 ton/ha to Sphaerellopsis sp. when applied in the field 7.262 tons/ha (Paningbatan et al., 2000).

Fig.1 Symptoms, uredospores and teliospores of southern corn rust [(a) infected leaf in the field, (b)infected corn stalk in the field, (c) close up view of pustules on leaves), (d) uredospores, and (e-f)horseshoe ]

a b c

d e f

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How to cite this article:

Srabani Debnath, Sanjog Chhetri and Sonali Biswas. 2019. Southern Rust Disease of Corn – A Review. Int.J.Curr.Microbiol.App.Sci. 8(11): 855-862. doi: https://doi.org/10.20546/ijcmas.2019.811.101

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