Pythium aphanidermatum is one of the most important pathogens to cause damping off disease in nurseries and a major constraint in the production of tomato.
J.Pl.Dis.Sci.Vol 8(2) 2013 : 200-203 MANAGEMENT OF TOMATO DAMPING OFF BY USING PLANT GROWTH PROMOTING MICROORGANISMS Archana Zalte, R. M. Gade, A. V. Shitole and Y.K.Belkar Department of Plant Pathology, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola-444104 (M.S.) India ABSTRACT Pythium aphanidermatum is one of the most important pathogens to cause damping off disease in nurseries and a major constraint in the production of tomato. Considering integrated control system for damping off, fungicides were tested alone and in combination with Pseudomonas fluorescens and Bacillus subtilis. The fungicides were also tested in vitro for their efficacy against Pythium aphanidermatum and for compatibility with P. fluorescens and Bacillus subtilis. Bioagent, P. fluorescens and Bacillus subtilis were effective against Pythium aphanidermatum. Maximum per cent growth inhibition was recorded by P. fluorescens (35.37%). It was also observed that growth of P. fluorescens and B. subtilis did not affect due to fungicides except propiconazole @ 0.1%. Amongst fungicides Thiram, Metalaxyl, Fosetyl-AL, Propeconazole were cent percent effective against pathogen at all tests concentrations (0.1%, 0.2% and 0.3%). The lowest per cent growth inhibition was observed in Carbendazim at 24 hr (18.86%) and 36 hr (20.25%). The disease was reduced by the seed treatment of P. fluorescens @ 10g/kg + Metalaxyl @ 2g/kg seed. Combination of antagonists P. fluorescens and B. subtilis were found effective to increase seed emergence (73.78%), shoot length (4.5cm), root length (7.02cm) and vigour index (894.21).
Keywords: Tomato, Pseudomonas fluorescens, Bacillus subtilis, Pythium aphanidermatum. MATERIAL AND METHODS The present investigation on in vitro P. fluorescens and B. subtilis isolates were tested for their antagonistic ability against soil borne plant pathogens i.e Pythium sp. The bacterial isolates were screened by dual culture test as followed by (Morton and Stroube, 1955 and Ramanathan et al., 2002). Compatibility of P. fluorescens and B. subtilis with fungicides by disc diffusion method. Compatibility of fungi by poisoned food technique. Effect of P. fluorescens and B. subtilis on seed germination and seedling vigor index by Roll paper towel method.
Tomato (Lycopersicon esculentum) is an important vegetable crop and suffers from many diseases leading to severe crop losses. Among fungal di se ase s, dampi ng o ff inc ite d by Pyth ium aphanidermatum in nurseries is a major constraint in production of tomato. Pythium spp. viz., P. aphanidermatum, P. debaryanum, P. butleri and P. ultimum are essentially soil borne and pose a greater problem in disease management. The most common means to manage dise ase in nurse rie s is by using fungicide s, but with incre asing awareness of the e nvironmental implications of the use of large quantities of fungicides, alternative strategies for management of plant disease are being sought (Weller,1988; Elli s et al .,199 9). Biol ogical c ontrol u sing antagonistic microbes alone or as supplements to minimize the use of chemical pesticides in a system of integrated plant disease management has become more important in recent years. Integrated approach consisting combinations of biological agents such as P. fluorescens and B. subtilis (Pal and Gardener, 2006) have been successfully used as a bio control agents and chemicals could provide a solution to the problem of ind ivi dual ap pli cati on of f ung ici de s or bioagents (Whipps, 2001). The aim of the studies work was to evaluate fungicides and antagonist alone and in combination for control of the disease. The work focused on combination of biological and chemical tools for compatibility and also efficacy to manage disease in order to mi nimi ze e nv ironme ntal pol lut ion whi le maximizing plant health with long term protection of seedlings.
RESULTS AND DISCUSSION The data on efficacy of P. fluorescens and B. subtilis against P. aphanidermatum presented in Table 1 showed that both bioagents have enough po te nt ial to che ck m yce lial growt h of P. aphanidermatum at 24 and 36 hr. P. fluorescens gave maximum inhibition of mycelial growth 27.46 and 35.37% at 24 and 36 hr after incubation (Table 1). Salman and Abasamsha (2012) reported that the genus P. fluorescens has the ability to antagonize fungal phytopathogens and show great promise to restrict the plant diseases. P. fluorescens was also found effective in reduction of oospore activities of P. ultimum in vitro. The data regarding compatibility of P. fluorescens and B. subtilis are presented in Table 2. The fungicides viz., Thiram, Carbendazim, Metalaxyl, Fo se ty l-A L, Prop ico naz ole we re t e ste d f or tole rance and se nsitivity by poisoned food technique. Among this P. fluorescens was found to tolerate all fungicide at all test concentrations i.e. 0.1%, 0.2% and 0.3% (Table 2). Similarly, B.
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J.Pl.Dis.Sci.Vol 8(2) 2013 : 200-203 Table 1. Efficacy of Pseudomonas fluorescens and Bacillus subtilis on growth of P. aphanidermatum (mm).
Mycelium Growth (mm)
Growth inhibition (%)
Biological agent P. fluorescens B. subtilis Control SE (m)± CD p=0.01
24 hr.
36 hr.
24 hr.
36 hr.
40.94 45.55 56.44 0.82 3.44
58.16 60.44 90.00 0.23 0.95
27.46 19.29
35.37 32.84
Table 2. Compatibility of Pseudomonas fluorescens and Bacillus subtilis with different fungicides
Treatment No.
+
Treatment
T1
Thiram
T2
Carbendazim
T3
Metalaxyl
T4
Fosetyl-AL
T5
Propiconazole
Compatible,
Concentration (per cent) 0.1 0.2 0.3 0.1 0.2 0.3 0.1 0.2 0.3 0.1 0.2 0.3 0.1 0.2 0.3
Compatibility of biocontrol agent P. fluorescens B. subtilis + + + + + + + + + + + + + + + + + + + + + + + + + + + + + -
- Not Compatible
Table 3. Effect of fungicides on growth of Pythium sp.(In vitro) Treat.
Treatment
Conc. (%)
No.
Mean
%
Mean
%
colony
growth
colony
growth
diameter
inhibi tion
diameter
inhibition
(mm)
(mm) at
at 24 hr.
36 hr.
T1
Thiram
0.20
0.00
100
0.00
100
T2
Metalaxyl
0.20
0.00
100
0.00
100
T3
Fosetyl-AL
0.20
0.00
100
0.00
100
T4
Propiconazole
0.05
0.00
100
0.00
100
T5
Propiconazole
0.10
0.00
100
0.00
100
T6
Carbendazim
0.25
43.00
18.86
71.77
20.25
T7
Control
53.00
0.00
90
0.00
SE (m)±
1.20
0.18
CD p=0.01
5.07
0.76
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J.Pl.Dis.Sci.Vol 8(2) 2013 : 200-203
*Values in parenthesis are arcsine transformed
Table 4. Effect of Pseudomonas fluorescens and Bacillus subtilis on P. aphanidermatum population, pre and damping off and growth promotion
post emergence
subtilis have also shown adaptation to their fu ngic ide s at al l co nce ntratio ns e xce pt Propiconazole @ 0.3% recorded 25 mm growth. In vitro studies clearly established that both biocontrol agents were able to tole rate the recommended fungicidal dose. Yildiz et al. (2007) observed no decline in the colonial growth of P. fluores cens wi th l ow dose of fungici de Mallikarjuniah (1995) tested the compatibility of different fungicides with rhizobacteria showed stimulatory action against rhizobacteria. The data regarding in vitro effect of fungicides on growth of Pythium sp. are presented in Table 3. It was found that fungicides were fungitoxic to P. aphanidermatum. All fungicides under test were effective to record cent per cent inhibition of P. aphanidermatum. However Carbendazim @ 0.25% was found to achieve 20 and 25% inhibition. Many workers have tested Metalaxyl against Pythium sp. and found highly effective against pathogen (Zagade et al., 2012 and Deshpande, 1986). The data presented in Table 4. showed that the highest germination was found in combination of P. fluorescens and B. subtilis @ 10g/kg seed (73.78%). It statistically significant over control and at par with all other treatments with highest shoot 4.5 cm and root 7.02 cm in addition to maximum vigor index 894.21. Lowest germination was in control (53.15%), shoot (2.48 cm) and root length (4.44 cm) with vigor index 367.82. The data on pre and post emergence damping off of tomato are presented in Table 4 showed that minimum pre and post damping off of 21.83 and 36.60% was registered by combination of seed treatment of P. fluorescens and B. subtilis @ 10 g/kg seed each. It was statistically significant over control (34 .40 and 71.5 7% ) b ut at par wi th s e e d treatment with P. fluorescens @ 10g/kg seed. Whereas minimum cfu/g soil was recorded in P. fluorescens ( 2.8 5x1 0 2 cf u/g soil ). It w as st atis tic all y lo we r as agains t c ontrol (12.76x102cfu/g soil) but at par with T2 and T3. These results are in accordance with Salman and Abasamsha (2012). The reduction in population of P. aphanidermatum might be the reason for lesser incidence of pre and post emergence damping off of tomato in seed treatment with biological control agents. This clearly indicated that antagonist highly competes with pathogen and bring down the inoculums of the pathogen there by reducing the disease incidence LITERATURE CITED Deshpande, G. D., 1986: Susceptible stages of Cucumber post emergence damping off and fungicidal e ffi cie ncy against P. ultimum., Trow. India J. Mycol. Pl. Pathol., 16: 326-328. Ellis, R. J., 1998: Basis for the biocontrol of
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J.Pl.Dis.Sci.Vol 8(2) 2013 : 200-203 Pythium by Fluorescent pseudomonads. D Phil Thesis, University of Oxford. Mallikarjuniah, R. R., 1995: Effect of some fungicides and insecticides on gro wth and nitrog e n fix ation in Azo tobact e r. Mysore J. Agric. Sci., 29: 36-42. Mo rton, D . J . and W . H . St rou be , 195 5: Antagonistic and stimulatory effect of soil microorganism upon Sclerotium rolfsii. Phytopathology. 45: 417-420. Pal, K. K. and B. Mc. Spadder Gardner, 2006: Biological control of plant pathogens. The Plant Health Instructor. pp. 1117-02. Ramanathan, A., 1989: Biocontrol of damping off of chilli due to Pythium aphanidermatum (Edson) Fitz. M. Sc. (Ag) Thesis, TNAU, Coimbatore., pp. 99. Ramanathan, A ., V. Shanmug am, T. Raghuchander and R. Samiyappan, 2002: Induction of systemic resistance in ragi against blast disease by Pseudomonas fluorescens. Ann. Pl. Protec. Soc., 10(2): 313318. Salman, M. and R. Abnamsha, 2012: Potential
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