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4792 Afr. J. Agric. Res. Table 2. Production of indole acetic acid (IAA), siderophore, HCN Lytic enzymes, fluorescein and pyocyanin by fluorescent pseudomonads. S/N PGPR isolates IAA Siderophore HCN production Lytic enzymes IAA (µg/ml of culture filtrate)* Siderophore production Siderophore (µM/ml of culture filtrate)* HCN HCN (µg/10 8 cfu/ml)* Protease Chitinase β-1, 3- glucanase Fluorescein 1 Pf1 36.00 a +++ 44.00 a +++ 74.25 a P P P +++ +++ 2 FP 7 33.00 b +++ 32.00 c ++ 40.00 b P P P +++ +++ 3 COTP- 20 29.00 de ++ 26.00 d + 12.00 c P N N - - 4 COGP -30 27.00 e ++ 25.00 d - 6.25 d P N N - - 5 TDK-1 32.00 bc +++ 38.00 b +++ 75.50 a P P P - - 6 AH-1 30.00 cd ++ 26.00 d - 8.00 d P N P - - +, Low production; ++, medium production; +++, strong production; -, no production; P, positive reaction; N, negative reaction; *Values are mean of four replications Means followed by a same letter are not significantly different at the 5% level by DMRT. Pyocyanin Table 3. In vitro screening of volatile metabolites produced by PGPR against mycelial growth of M. phaseolina. S/N PGPR isolate Mycelial growth(cm) Mycelial growth inhibition (cm) Percent inhibition over control* 1 Pf1 1.90 7.10 78.88 a (62.66) 2 FP 7 2.33 6.67 74.16 b (59.46) 3 COTP-20 3.40 5.60 62.22 d (52.08) 4 COGP-30 4.73 4.27 47.49 f (43.56) 5 TDK-1 3.75 5.25 58.32 e (49.80) 6 AH-1 2.70 6.30 69.99 c (56.80) 7 Control 9.00 - - *Values are mean of four replications; Values in parentheses are arcsine transformed; means followed by a same letter are not significantly different at the 5% level by DMRT. pre mixture fungicide (Carbendazim + Mancozeb) (stem cuttings dip + soil application) was relatively more effective and recorded maximum reduction of root rot incidence (73.52%) when compared to other treatments. The next best treatment was Pf1 (stem cuttings dip + soil application) which showed 70.19% disease reduction over control (Table 4). This study was also supported by Karthikeyan et al. (2009) in which pre-inoculation application of blackgram plants with the strains of P. fluorescens viz., Pf1 and CHAO were found to reduce ULCV infection significantly. All growth parameters viz., shoot length, root length and number of branches/plant were more in pots treated with both Pf1 (stem cuttings dip + soil application) and FP 7 (stem cuttings dip + soil application) compared to other treatments. These findings coincide with those of other scientists, Minaxi (2010) in which seed bacterization with these plant growth promoting rhizobacteria (PGPR) showed a significant increase in seed germination, shoot length, shoot fresh and dry weight, root length, root fresh and dry weight, leaf area and rhizosphere colonization in moong bean. Yield parameters viz., number of tubers/plant, tuber length, tuber diameter and tuber yield were more in pots treated with Pf1 (stem cuttings dip +
Akkim et al. 4793 Table 4. Effect of PGPR on the Coleus root rot disease and plant growth parameters under pot culture. S/N Treatment % disease Percent disease Shoot length* Root length* Number of Tuber yield* reduction over incidence* control* (cm) (cm) branches/plant* (g/plant) 1 Pf1 (SCD alone) at 0.2% 40.20 c (39.35) 50.49 40.03 c 23.37 d 21.33 c 341.30 g 2 FP 7 (SCD alone) at 0.2% 44.30 b (41.73) 45.45 39.55 c 22.13 d 21.33 c 319.00 h 3 Pre mixture fungicide (Carbendazim + Mancozeb) (SCD alone) at 0.1% 35.20 d (36.39) 56.65 37.37 c 20.27 e 19.33 e 300.70 i 4 Pf1 (SCD + SA) at 0.2% each 24.20 i (29.49) 70.19 63.33 a 33.70 a 23.33 a 501.00 a 5 FP 7 (SCD + SA) at 0.2% each 25.50 h (30.35) 68.60 62.43 a 31.27 b 23.33 a 480.30 b 6 Pre mixture fungicide (Carbendazim + Mancozeb)(SCD+SA) at 0.1% each 21.50 j (27.63) 73.52 58.50 b 30.27 bc 22.33 b 441.70 c 7 Pf1 (SA alone) at 0.2% 29.20 f (32.73) 64.03 61.13 ab 30.23 bc 23.00 ab 402.00 d 8 FP 7 (SA alone) at 0.2% 30.10 e (33.27) 62.93 58.43 b 29.47 c 21.33 c 381.00 e 9 Pre mixture fungicide (Carbendazim + Mancozeb) (SA alone) at 0.1% 27.00 g (31.31) 66.74 58.13 b 29.30 c 20.33 d 362.30 f 10 Inoculated control 81.20 a (64.31) - 30.00 d 16.57 f 10.33 f 280.00 j SCD, Stem cuttings dip; SA, soil application; Values in parentheses are arcsine transformed; *values are mean of three replications; means followed by a same letter are not significantly different at the 5% level by DMRT. soil application) compared to other treatments (Table 4). This was supported by Minaxi (2010) in which bacterization of seeds of moong bean with pseudomonads has been reported as a potential method for enhancing yield parameters such as pods, number of seeds, and grain yield per plant also enhanced significantly in comparison to control. Changes in the peroxidase (PO) and polyphenol oxidase (PPO) activity in Coleus plants treated with biocontrol agents The biotic and abiotic inducers bring about induced systemic resistance (ISR) through fortifying the physical and mechanical strength of cell wall as well as changing physiological and biochemical reaction of host leading to synthesis of defense chemicals against challenge inoculation of pathogens. Defense reaction occurs due to accumulation of peroxidse, polyphenol oxidase, PR proteins, phenylalanine ammonia lyase, phenolics, callose, lignin and phytoalexins. In the present study maximum PO and PPO activity was observed in plants treated with Pf1 (stem cuttings dip + soil application) (Figures 1 and 2). The activity of the enzyme increased up to 5 th day and declined thereafter. The next best treatment was FP 7 (Stem cuttings dip + Soil application). The control (healthy plant) recorded lesser PO and PPO activity. Similarly Karthikeyan et al. (2009) reported that soil and foliar application of P. fluorescens (Pf1) induced the accumulation of phenolics and enhanced the activities of peroxidase, phenylalanine ammonia lyase and polyphenol oxidase in black gram against Urdbean leaf crinkle virus (ULCV) in blackgram. Also, Mathiyazhagan et al. (2009) reported that application of Pseudomonas strains BSCBE4, PA23 and ENPF1 increased the defense related enzymes such as peroxidase, polyphenol oxidase, chitinase and β -1, 3 glucanase in P. amaranthus up to ten days after challenge inoculation with C. cassicola. Native gel electrophoretic analysis revealed that challenge inoculation of pathogen with PA23 induced both peroxidase and polyphnol oxidase isoforms. Similarly in the present study also many isoforms of PO were induced upon treatment with PGPR in the coleus plant (Figure 3). Field experiment Same trend was found as in pot culture experiment regarding all parameters a little
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