Kansara S. S.1*and Joshi D.M.2

*1Assistant Professor, Department of Plant Pathology, N.M. College of Agriculture, Navsari Agricultural University, Navsari, Gujarat, India,E-mail: [email protected]
2Retired-Professor, Plant Pathology Department, ASPEE College of Horticulture and Forestry, Navsari  Agricultural University, Navsari, Gujarat, India

DOI: http://dx.doi.org/10.22207/JPAM.11.4.40

 

(Received: 10 May 2017; accepted: 15 July 2017)

Abstract:

Studyon leaf spot/blightDrechslera state of Trichometasphaeriaholmii(Luttrell) Subramanian & Jain. ofHeliconia(HeliconiaorthotrichaL.)under south Gujarat condition was carried out to find out suitable management strategies of this newly reported disease. Due to hazardous effect of chemical fungicides, search for safer alternative to control the pathogen is better option. This led to trials on the use of bio agents to control the pathogen. The seven known bio agents were evaluated by dual culture, pathogen atperiphery and pathogen at the centre technique to monitor antagonistic effect. Results revealed that out of all the sevenbio agents used, three bio agentsviz.,Aspergillusniger Link. (Navsari, isolate) (85.18 %, 84.67 % and 83.68 %),Pseudomonas fluorescensMigula.(Navsari isolate) (81.85%, 75.86%, and 62.76%) and TrichodermalongibrachyatumRifai.(I.A.R.I., isolate) (76.66 %, 55.93 %, 81.56 % maximum growth inhibition in dual culture, pathogen at periphery and pathogen at the centre methods respectively),showed strong antagonistic effect to inhibit the mycelia growth of thepathogen significantly.

Keywords:

Biological control, antagonists, Heliconia,Drechslera state of Trichometasphaeriaholmii

INTRODUCTION

Heliconias are grown for cut flower and landscape plants and it belongs to a morphologically diverse and species rich order Zingiberales.According to Goel (2004) Heliconias are generally known as “wild plantain” or “lobster’s claw” and are native to neotropical regions of Central and South America and some Caribbean countries. Heliconias are gaining importance and became popular among the florists and plant lovers almost round the world due to their diversity in both colour and form, and have good potential as commercial cut flower. (Janakiram& Kumar, 2011).Out of various factors responsible for successful growing of Heliconia, disease management is one of the most important factors and as the crop is newly introduce in India and Gujarat as well, not much research work is done.The leaf spot/ blight disease was observed in severe form on the floriculture farm of the Navsari Agricultural University, in the year 2009 on the Heliconiaorthotricha var. she and Drechslerastate of Trichometasphaeriaholmii (Luttrell) Subramanian and Jain, was observed to be constantly associated with the disease.The initial symptoms of disease involved small, oval or irregular, dark brown leaf spots, later resulted into severe leaf blight covering entire leaf.In the advanced stage large, distinct yellow halo around the brown spots which united with other spots to form large chlorotic and necrotic areas on blighted leaves. On the stem, several distinct black spots were observed. Disease also spreads to bracts of inflorescence as faint brown to purple red spots, results into total economic loss. The symptoms observed on Heliconia during this investigation were somewhat similar to those described earlier by Luttrell (1963).Considering the seriousness of this newly introduced problem, thepresent investigation was carried out. The hazardous effectsof chemicals used in plant disease management have divertedplant pathologists to find out the alternative techniques ofplant disease control which may cause little or no adverseeffect on environment. Now a day, the commercial formulation of some of thebiocontrol agents has already become available in the market.In the present study, attempts have been made to identifyantagonistic bio agents against Drechslera state of Trichometasphaeriaholmiiin vitrocondition to combat the battle with this newly introduced pathogen

MATERIALS AND METHODS :

Seven known fungal and bacterial bio agents (antagonists) viz.,TrichodermaviridePers, ex. Grey (Navsari, isolate), TrichodermaharzianumRifai. (Junagadh, isolate), TrichodermalongibrachyatumRifai. (I.A.R.I., isolate), TrichodermafasciculatumBissett.(Navsari, isolate), Aspergillusniger Link.(Navsari, isolate), Pseudomonas fluorescensMigula.(Navsari, isolate) and Bacillus subtilis Ell.(Navsari, isolate)were tested in vitro againstDrechslera state of Trichometasphaeriaholmii. The culture discs measuring 5mm diameter of testorganism and pathogen were cut aseptically from the colonyof pure culture grown on PDA medium and kept at differentpositions according to different techniques employed in thepresent investigation. In dual culture technique (Dennis andWebster, 1971), culture discs of test organisms and thepathogen were placed opposite to each other at 70 mm apart inthe Petri plate containing 20 ml PDA aseptically and realantagonistic properties of the test bio agents were exhibited.InPathogen at the periphery technique (Asalmol and Awasthi,1990), the culture disc of the pathogen placed aseptically 35 mm away radially at four corners keeping one disc of testorganism at centre in the plate containing 20 ml PDAaseptically. In Pathogen at the centre the culture disc of thepathogen was placed in the center and four similar discs of the test organisms were placed 35 mm away from the pathogenat the periphery in the Petri plate containing 20 ml PDAaseptically. The culture discs of the pathogens were kept atrespective places of pathogen in each technique withoutbio agentserved as control. All the treatments were incubatedat room temperature (27 ± 2ºC) and after 8 days the radialgrowth of the test organism and pathogen was measured. CRDdesign with three repetitions of each treatment was employedin the present experiment. The per cent growth inhibition (PGI)was calculated by using formula given by Vincent (1927) :

PGI = 100 (DC-DT)
DC

 

Where,

PGI = Per cent growth inhibition

DC = Average diameter of mycelial colony of control plate (mm)

DT = Average diameter of mycelial colony of treated plate (mm)

 RESULT AND DISCUSSSION

All the antagonists under test were significantly superior overcontrol in all the techniques against Drechslera state of Trichometasphaeriaholmii. In dual culture technique, out of seven antagonists testedAspergillusniger Link. (85.18%) and Pseudomonas fluorescensMigula. (81.85 %) showed maximum growth inhibition of the pathogen and appeared to be the most superior over all the antagonists tested. Next best in order of merit was TrichodermalongibrachyatumRifai. (76.66 %), T. viridePers, ex. grey.(42.22 %) and T. harzianumRifai.(35.55 %). Rest of the antagonists showed comparatively and significantly least growth inhibition (Table 1). In pathogen at periphery technique,AspergillusnigerLink. gave maximum growth inhibition (84.67 %) and appeared to be the most superior antagonists among all the antagonists tested. It was followed by Pseudomonas fluorescensMigula. (75.86 %), T. longibrachyatumRifai.(55.93 %), T. harzianumRifai.(44.06 %) and TrichodermaviridePers, ex. Grey.(41.01 %).While, rest of the antagonists showed comparatively least growth inhibition (Table 2). In pathogen at centre, AspergillusnigerLink. showed maximum inhibition (83.68 %)  and appeared to be the most superior antagonists among all the antagonists tested which was statistically a par with T. longibrachyatumRifai.(81.56 %) followed by Pseudomonas fluorescensMigula. (62.76 %)which in turn was statistically at par with T. harzianumRifai.(62.05 %), followed by T. viridePers, ex. Grey. (48.93%). The rest of the antagonists showed comparatively least growth inhibition (Table 3).

Table 1 :   Effect of different antagonists against Drechslerastate ofTrichometasphaeriaholmiiin vitro condition under dual culture method.

Sr. No.
 

Test organism
Average colony diameter of pathogen(mm)
Growth inhibition

(%)
1.
Trichodermaviride
26.00
42.22
2.
Trichoderma harzianum
29.00
35.55
3.
Trichoderma fasciculatum
38.33
14.81
4.
Trichoderma longibrachyatum
10.50
76.66
5.
Aspergillus niger
6.66
85.18
6.
Pseudomonas fluroscens
8.16
81.85
7.
Bacillus subtilis
34.00
24.44
8.
Control
45
0
S.Em. +
0.4208
C.D. at 5 %
1.2614
C.V. %
2.94

 

Table 2 :   Effect of different antagonists against Drechslerastate ofTrichometasphaeriaholmiiin vitro condition under  pathogen at periphery method.

Sr. No.
Test organism
Average colony diameter of pathogen

(mm)
Growth inhibition

(%)
1
Trichodermaviride
25.66
41.01
2
Trichoderma harzianum
24.33
44.06
3
Trichoderma fasciculatum
33.33
23.37
4
Trichoderma longibrachyatum
19.16
55.95
5
Aspergillus niger
6.66
84.68
6
Pseudomonas fluroscens
10.50
75.86
7
Bacillus subtilis
28.00
35.63
8
Control
43.5
0
S.Em. +
0.4639
C.D. at 5 %
1.3908
C.V. %
3.36

 

Table 3 :   Effect of different antagonists against Drechslerastate  ofTrichometasphaeriaholmiiin vitro condition under pathogen at centre

 

Sr. No.

 
 

 

Test organism

 
Average colony diameter of pathogen(mm)
 

Growth inhibition

(%)
1
Trichodermaviride
24.00
48.93
2
Trichoderma  harzianum
28.16
62.05
3
Trichoderma fasciculatum
17.83
40.07
4
Trichoderma longibrachyatum
8.66
81.56
5
Aspergillus niger
7.66
83.70
6
Pseudomonas fluroscens
34
62.76
7
Bacillus subtilis
17.5
27.65
8
Control
47
0
S.Em. +
0.3908
C.D. at 5 %
1.1716
C.V. %
2.93

 

DISCUSSION

It appeared from this study that all the antagonists tested by three methods proved effective against Drechslera state of Trichometasphaeriaholmii and were proved to be very useful as potential biological control agents.Among them, AspergillusnigerLink.,Pseudomonas fluorescensMigula., T. longibrachyatumRifai.andT. harzianumRifai.proved to be very effective antagonist against Drechslera state of Trichometasphaeriaholmii. This may be due to undeniably its mode of actionlike competition, antibiosis and mycoparasitim and it possesssome important secondary metabolites and antibiotics likeharzianiol and so many. The results of the present investigation are analogous to the previous findings published by several workers.Biswaset al. (2008) showed that in dual culture test, TrichodermaharzianumRifai. and its bio-formulation reduced mycelium growth of DrechsleraoryzaeSubram. & Jain, by 55.3 % and 58.1 %, respectively.Mandalet al. (1999) reported inhibitory effect of Trichoderma spp., Talaromycesflavus(Klocker) Stolk and Samson. andChaetomiumglobosumKunz., on mycelial growth ofDrechslerasorokiniana(Sacc.) Subram. & Jain with upto 92 % inhibition of conidial germination. The results of present investigation indicated Aspergillusniger, Pseudomonas fluorescensandTrichodermalongibrachyatumwere found as a strong antagonists against Drechslera state of Trichometasphaeriaholmii was somewhat similar to those findings of Mandalet al. (1999). Hence it can berecommended after rigorous testing in the pot and fieldcondition against the pathogen for management of Heliconia leafspot/blight disease.

REFERENCES

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