Occurrence of diseases on medicinal plants in Vidarbha region and correlation of weather factors with leaf blight of coleus  

Aparna Tekade , Koche Mina D. , Mohod Y.N.
Department of Plant Pathology Shri Shivaji Agriculture College, Amravati
Author    Correspondence author
Medicinal Plant Research, 2015, Vol. 5, No. 2   doi: 10.5376/mpr.2015.05.0002
Received: 08 Apr., 2015    Accepted: 10 Jun., 2015    Published: 19 Jun., 2015
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Aparna Tekade, Koche Mina D. and Mohod Y.N., 2015, Occurrence of diseases on medicinal plants in Vidarbha region and correlation of weather factors with leaf blight of coleus, Medicinal Plant Research, 5(2) 1-4 (doi: 10.5376/mpr.2015.05.0002)

Abstract

Different medicinal plants were observed for occurrence of fungal diseases in Vidarbha region. Piper longum was infected by Colletotrichum gloesporiodes, Datura (Datura innoxia) and Behada (Terminalia bellerica) were proned by leaf spot caused by Alternaria alternata and kidmar (Aristolochia bracteata) infected by leaf blight caused by Colletotrichum dematium. The leaf blight disease of coleus (Coleus forskolii) caused by Curvularia lunata was recorded and its intensity was observed to the extent of 24.26% during 4th week of November. The maximum temperature and both (morning and evening) humidity exhibited negatively significant correlation with the disease.

Keywords
Medicinal plant; Fungal pathogens; Correlation

India has about 2000 species of medicinal plants on a vast geographical area with high production potential. India is considered as the land of medicinal plants. These plants can be cultivated or grown as wild under diversified geographical environmental situation and proned with different diseases.
Among the medicinal and aromatic plants Datura, kidmar, Lendipimpali, Behada and Coleus were mainly proned with the pathogen causing severe losses in yield. The pathogens are responsible for causing predominant foliar diseases viz., Colletotrichum gloeosporiodies causing leaf blight and leaf spot by Alternaria alternata in Piper longum. During recent days commercial cultivation of medicinal plant has increased their pathological problems. The disease of plants and their occurrence at higher intensity may occur in near future due to monocropping.
Among the medicinal and aromatic plant Coleus forskolii was mainly proned with the pathogens causing severe losses in yield. The predominant foliar pathogen is Curvularia lunata causing leaf blight. To know the role of weather parameters on the development of disease was also studied.
1 Materials and methods
Fungal diseases of medicinal and aromatic plant cause severe reduction in yield and qualitative losses. The present studies deals with recording of different diseases of some medicinal and aromatic plants. Infected parts of medicinal/aromatic plant i.e. leaves, stem, branches roots were collected from the field of Nagaarjun, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola and examined in the laboratory for external symptoms and for isolation of disease causing pathogen (Table 1).


Table 1 Fungal disease and botanical name of medicinal plant

Field observation was recorded on the plants grown in Nagarjun Garden of Dr. PDKV, Akola (M.S.). The initiation of diseases and its intensity was recorded on the basis of infection grades. All disease were recorded on the basis of percent leaf area covered by the disease by selecting six leaves/plant. Periodical observations were recorded and the correlations with leaf blight of Coleus and weather parameter are analyzed with simple correlation method.
The symptoms were studied in detail and the diseased samples were subjected to isolation and pathogenicity was proved under net house condition.
2 Results and discussion
2.1 Lendi Pimpli (Piper longum)
Piper longum, Datura innoxia, Terminalia bellerica, Aristolochi bracteata and Curvularia lunata are important medicinal plants besides being useful in treatment of other diseases of living beings as an ayurvedic treatment.
2.2 Lendi Pimpli (Piper longum)
2.2.1 Leaf blight (Colletotrichum gloeosporioides)
The disease was observed in the form of small dull pale pin head spots with yellowish brown, dots at initial stage on leaves. All the aerial parts were observed to be infected including berries. The spots were circular to irregular dark brown in colour, later coalesced to each other and form necrotic areas on leaves and stem. Necrotic are were observed to be extended on stem. The disease was appeared soon after the rains. Severely infected leaves turned yellow and shed prematurely. The incidence was more on older leaves.
2.3 Pathogenicity
The fungus was isolated in pure form and identified as Colletotrichum gloeosporioides. The pathogenicity was also proved on excised leaves. The symptoms were observed after 3 days of inoculation. The pathogen was reisolated from inoculated tissues. Sathyarajan and Naseema (1985) recorded new host i.e. Piper longum for C. gloeosporioides the pathogenicity by spraying spore suspension. Kuch (1990) reported that Colletotrichum capsci and C. gloeosporioides are harmful pathogens resulting in blackening of berries.
2.4 Datura (Datura innoxia)
2.4.1 Leaf spot (Alternaria alternata)
Characteristic symptoms were initially water soaked minute spot, on leaves and at advance stages spots became larger in size and coalesced together and brightening of leaves. The spots were dark brown; round to oval or slightly irregular with necrotic areas resulted in defoliation. The fungal pathogen was isolated in pure form and identified as Alternaria alternata. The fungus was proved to be pathogenic and developed the symptoms as under natural condition.
Ganguly and Pandotra (1962) stated that Alternaria tenuissima causes severe defoliation. Early infection due to Alternaria alternata in the form of circular spots on leaves finally death of the tissue with concentric rings were reported by Janardhan et al. (1972). The pathogenicity was tested on three months old potted plant by spray of spore and mycelial suspension. The plants showed symptoms after 4 days. Early development of disease may be due to the high virulence of the isolates prevailed in this area resulting in necrosis within three days of inoculation.
2.5 Behada (Terminalia bellerica)
2.5.1 Leaf spot (Alternaria alternata)
Under natural conditions foliage were found to infect with fungal pathogen. Initially small water soaked lesions were developed on the foliage, later spots become dark brown in colour. The spots enlarged, coalesced together resulting in blightening of complete leaves, under severe condition defoliation was recorded. The pathogen was isolated and identified as Alternaria alternata on the basis of morphology. The intensity was ranged between 37 to 52 %.
2.6 Kidmar (Aristolochia bracteata)
2.6.1 Leaf blight (Colletotrichum dematium)
The first symptoms were noted on foliage in the form of water soaked lesions. The disease spread down the petiole to main stalk. The stalks were brake off with slight touch. The leaflets were infected severely under wet condition. The symptoms developed in the form of blackish irregular of circular spots with concentric rings having dot like acervuli. The spots subsequently increased and shot holes were observed on leaves. With an intensity of 32 to 43%. Petioles and stems also infected and developed the spots and become necrotic.
2.7 Coleus (Coleus forskolii)
2.7.1 Leaf blight (Curvularia lunata)
Initially water soaked leaf spots were observed, later increased rapidly in size and become light and then turned to brown in colour. The spots coalesced together result in blight symptoms. The causal fungus isolated in pure form was Curvularia lunata. The identity was confirmed on the basis of published literature. The pathogencity was inoculating the culture artificially. The symptoms were developed within 3 days of inoculation and similar observed under natural condition on reisolation the same pathogen was observed which leads to confirm the pathogenicity.
Naseema and Wilson (1991) observed that the leaf blight of coleus was caused due to number of pathogens including Curvularia sp. In the present studies Curvularia leaf blight was recorded with (24.26%) maximum intensity.
2.8 Seasonal incidence
A medicinal plant coleus was infected with blight disease caused by Curvularia lunata under natural field condition. The initiation of blight symptoms was recorded during 32nd met week i.e. 2nd week of August. The higher intensity was observed during 4th week of November i.e. 24.26% and later it was at decreasing trend and reached to 14.25% in 1st week of January. Weather factors prevailed during 47th met week i.e. maximum temperature 32.2°C, minimum 13.7°C RH I (81%) and RH II (20%) were responsible for increase in the disease intensity which exhibited in 45th met week i.e. 24.26% (Table 2).
Relative humidity Ist, IInd and maximum temperature exhibited significant and negative correlation with disease, while positive and significant correlation was established with rainfall (Table 3).


Table 2 Effect of weather parameters on leaf blight (Curvularia lunata) of coleus (Coleus foreskolii)


Table 3 Correlation of leaf blight (Curvularia lunata) of coleus (Coleus forsklii) with weather parameter

References
Ganguly D, and Pandotra V. R., 1962, Some commonly occurring diseases of important medicinal and aromatic plants in Jummu and Kashmir, Indian Phytopathology 15: 50-54
Janardhanan K. K., Gupta, M. L. and Akhtar Husain, 1972, Pythium die back a new disease of Catharanthus roseus, Indian Phytopathology, 30 : 427-428
Kuch T. K., 1990, Diseases of black paper and their management, Malayasian plant protection society. Proc. 3rd International conference on plant protection in the Trapics. 4: 114
Naseema A., and Wilson K. I., 1991, New record of fungi on some medicinal plants from India, Indian Phytopathology, 43: 595

Sathyarajan P. K., and Naseema A., 1985, Piper longum a new host record for Colletotrichum gloeosporioides. Current Science. 54 : 637

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