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Physiological Studies on Colletotrichum gloeosporioides Penz. Causing Anthracnose of Mango and its Chemical Control



Khalid P. Akhtar, M. J. Jaskani, M. Asif and I. A. Khan
 
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ABSTRACT

Colletotrichum gloeosporioides Penz. produced excellent mycelial growth with maximum acervuli and spores on PDA with least on water agar. The best temperature was 25±2°C and pH between 7 to 8 under continuous light. Growth and acervuli production of pathogen was excellent when basal medium was supplemented with glucose as carbon source. Te 60 showed the maximum inhibition on mycelial growth and acervuli production at all concentrations.

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  How to cite this article:

Khalid P. Akhtar, M. J. Jaskani, M. Asif and I. A. Khan, 1999. Physiological Studies on Colletotrichum gloeosporioides Penz. Causing Anthracnose of Mango and its Chemical Control. Pakistan Journal of Biological Sciences, 2: 382-385.

DOI: 10.3923/pjbs.1999.382.385

URL: https://scialert.net/abstract/?doi=pjbs.1999.382.385

Introduction

Anthracnose caused by Colletotrichum gloeosporioides Penz. is prevalent in all the mango growing regions of the world (Ploetz et al., 1994). It has been noted that disease attacks leaves, petioles, twigs and fruits at pre and post harvest stages (McGuire and Campbell, 1993). It produces oval to irregular brown coloured spots on leaves, sometimes forming concentric rings on fresh leaves. Under damp conditions, the spots grow rapidly, producing elongated necrotic areas on the affected tissues. They turn black or brown on petioles and cause leaf drop after drying. Elongated black necrotic areas develop on twigs that start drying from tip to downward. In severe cases, affected areas show black small bodies named as acervuli. Sunken black spots develop on the fruits that later cause rottening on the fruits (Hafiz, 1986).

Little work has been reported on the physiology of this pathogen from mango in Pakistan. The present study was carried out to investigate the effect of different physiological factors on the mycelial growth and acervuli production of C. gloeosporioides.

Materials and Methods

C. gloeosporioides was isolated from diseased specimens and after purification it was tested for pathogenicity (Akhtar et al., 1998). Mycelial growth and acervuli production was studied in basal medium (BM), corn meal dextrose peptone agar (CMDPA), Richards agar (RA), czapeks dox agar (CA), corn meal peptone agar (CMPA), malt extract agar (MEA), malt extract glucose agar (MEGA), water agar (WA), potato starch agar (PSA) and potato dextrose agar (PDA) medium, as described by Saleem and Nasir (1991). The effect of different temperatures, light periods, and pH were also checked by growing the fungus on PDA medium.

Different carbon sources such as Sucrose (4.75 g), D-Glucose, Fructose, Mannitol (5.00 g), Starch, Adenine (4.50 g), Glycine (6.25 g), L-Asparagine (5.50 g), L-Glutamine (4.25 g), Inosit (4.76 g), Nicotinic acid (3.42 g) and L-Tyrosine (3.02 g) were studied for the growth and acervuli production of fungus. The quantity of these sources were adjusted to give an amount of carbon equivalent to 5.0 g of dextrose for 250 ml of basal medium (Saleem and Nasir, 1991).

Potato dextrose agar medium was amended with different concentrations of mold inhibitors; Thiabendazole, Borax and Boric acid (Ilyas et al., 1982). Petri plates poured with potato dextrose agar medium without mold inhibitors serve as control.

All media in the above studies were autoclaved for 2 minutes at 15 lb/inch2 pressure and 121°C. Petri plate with 20 ml medium, were inoculated in the centre with mm plugs of 7 days old culture obtained with the help sterilized cork borer into four replicates.

Cultural characters of C. gloeosporioides were also noted. The acervuli were counted under stereoscope by taking a 2 mm diameter disc of 7 days old culture from the centre each petri plate by the help of cork borer. Data were analyzed statistically by using the CRD two factor design (Steel and Torrie, 1960).

Results and Discussion

Effect of Different Culture Media: Maximum growth of gloeosporioides was observed on potato dextrose age (51.32 mm) and malt extract glucose agar (50.67 mm) after 168 hours of incubation followed by Richards agar, malt extract agar, czapeks dox agar, basal medium, corn meal peptone agar and corn meal dextrose agar, while least on potato starch agar (13.25 mm). Maximum number of acervuli of fungus was found on potato dextrose agar (56.75), followed by potato starch agar (54.50), while corn meal dextrose agar and czapeks dox agar were unable to produce any acervulus (Table 2).

Spore production was excellent in the case of potato dextrose agar, potato starch agar, malt extract agar and malt extract glucose agar. Colour of mycelium a substrate also gave varying responses. Colonies on potato dextrose agar, malt extract agar and malt extract glucose agar were greyish-white while on other media except water agar they were white. Conidia were orange coloured masses forming concentric rings on PDA (Table 1). Same results were presented by Jeffries et al. (1990) and Fitzell (1979) they reported that colonies on potato dextrose agar are greyish white to dark grey with salmon coloured masses of spores formed usually in concentric rings on such media.

Effect of Temperature: Maximum growth of fungus was observed between 25±2°C (52.21 mm) while a little growth was observed at 10°C (3.57 mm) but no growth was observed below 7°C.

Table 1: Effect of culture media on Colletotrichum gloeosporiodes

Table 2:
Studies on the mycelial growth and acervuli production of Colletotrichum gloeosporioides pent.

Best acervuli production (29.00) was observed at 25 - 32°C but no acervulus was found below 17°C. Fitzell (1979) also reported that fungus grows well and sporulates profusely between temperature of 25- 32°C. Similarly Hafiz (1986) noticed that the optimum range of temperature for the growth of fungus was 25- 29°C, while maximum and minimum ranges of temperature for the mycelial growth are, 35-40°C and 10-15°C, respectively.

Table 3:
Effect of different mold inhibitors on mycelial growth (mm) and acervuli production of Colletotrichum gloeosporioides Penz.

Effect of Different Light Intensities: Continuous light was found to be the most suitable for the maximum mycelia' (44.82 mm) growth and best acervuli production (31.0) of the fungus. Continuous darkness resulted in the least mycelial growth (37.29 mm) and 8 h light alternated with 12 h darkness for least acervuli production (22.50).

Effect of pH: The best mycelial growth was found at pH 7 but less was found in case of pH 10 (Table 2). Maximum number of acervuli were found in the case of pH 6 (46.50) but poor at pH 10 (8.75). It is also clear from Table 2 that fungus prefers acidic range over alkaline range for both mycelial growth and acervuli production. These results are in conformity with the results of Hafiz (1986) who concluded that the growth was same at pH 4 and pH 9 but it fells considerably at pH 3.5 on the acidic side and at pH 8.2 on the alkaline side. These results are supported by Verma (1969), Singh (1971), Ahmed (1973) and Nusrullah (1983).

Effect of Different Carbon Sources: Maximum growth (44.2 mm) was observed when glucose was added as a carbon source (Table 2). The growth of fungus was not found on nicotinic acid even after 168 hours. From Table 2 it is evident that treatment means differed statistically from media added with glucose and also among themselves. But the response of starch, L-Asparagine, inosit, mannitol, fructose and sucrose was almost similar.

The fungus produced maximum number of acervuli (47 on glucose medium while minimum number were observed in case of L-Asparagine (4.50). Glycine, glutamine, and nicotinic acid were unable to produce any acer (Table 2). Glucose, sucrose, fructose , mannitol ands exerted almost similar response but showed stati difference from other carbon sources. Tandon and Chandra (1962), also reported that C. gloeosporiodies show poor response to sorbitol (the reduction product of glucose when supplemented as carbon source in artificial material.

Effect of Different Mold Inhibitors: Thiabendazole (Te 60) completely inhibited the growth of fungus ahove ppm and was found effective even at 5 ppm on the my growth and the acervuli production of the fungus. Boron 50 ppm checked the acervuli production. Spalding and Reeder (1972), Jacobs et al. (1973) and Feng et al. (1991) also reported that anthracnose on mango can be count dipping the fruits in thiabendazole (1000 ppm). Boric was found inefficient against mycelial growth and formation of the fungus (Table 3).

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