RHIZOCTONIA AND PYTHIUM UNDER CONTROLLED GREENHOUSE CONDITIONS
4.3 RESULTS
4.3.1 Effects of treatments on damping-off caused by Rhizoctonia solani
4.2.6 Variables of seedlings
Assessment of pre- and post-emergence damping-off caused by a Pythium sp. and R. so/ani was conducted by counting the number of emerged seedlings two weeks after planting and the percentage of seedlings that survived four (for tef) and six (for sorghum) weeks of growth. All surviving seedlings in each tray were cut at their base, oven dried for two days at 70DC and then weighed.
4.2.7 Statistical analysis
Each treatment had four replicates, each plot having 24 seedlings hence, 96 seedlings per treatment. Treatments were arranged in a randomized complete block design. The experiment was conducted twice. Data obtained from the two trials were analysed three times using Genstat'" Statistical Analysis Software (Genstat, 2002). Firstly, data of the two trials were analyzed separately to determine Analysis of Variance (ANOVA), to make contrasts between infected and uninfected controls, to determine the effect of the sticker on seedling emergence and to separated treatment means using Fisher's Protected LSD. Secondly, data0 f t he two trials were combined and analysed together to determine the effect of season on treatments.
Thirdly, data of the two trials containing only results of BCAs were combined together and analysed to determine interactive effects between season, application method and BCAs and to compare the two application methods. In each analysis, transformation of data using square root transformations was performed where CV of the original data was >20% and the statistical results generated from the transformed data were used to meet the objectives.
seedling stands recorded in the pathogen-infestedcontrol were 52% and 51% for sorghum and tef, respectively. This means that stands of sorghum and tef were reduced by >50%. On both crops most B CAs provided a higher percentage0 f emergence a nd stand of seedlings when compared to the plot treated only withR. so/ani(Tables 4.1 and 4.2).
Treatment effect was also statistically significant (P<O.OO 1) on plot weight of sorghum and tef (Table 4.5). With sorghum, mean plot weights of untreated controls declined up to 44%, when soils were inoculated with R. so/ani. On average, treatments with H44, Eco-T, SY3 and SY4 and B enlate resulted in increased plot weight of sorghum when compared to the pathogen- infested control (Table 4.1). Compared to the non-infested control; significant reduction (P<0.05) in plot weights (up to 45%) were observed in tef as a result of inoculation by R.
so/ani. Treatments with H44, H51, Eco-T, SY3, SY4 and Benlate®significantly increased dry weight of plots inoculated withR. so/aniin at least one season (Table 4.2).
Stand reduction, as a result of post-emergence damping-off caused by R. so/ani, was in the range of 5-15% for both crops. For plots containing R. so/ani, it appears that plot weights were the product of final seedling stand. Overall performance of antagonistic fungi were relatively better than that of bacteria (Tables 4.1 and 4.2).
Table 4.1 Percentage seedling emergence, final stand and plot weights of greenhouse grown sorghum seedlings inoculated with Rhizoctonia solaniand treated with biocontrol agents applied as seed coating or drenching
Application Season 1 Season 2
Treatment method Emergence Final stand Plot weight Emergence Final stand Plot weight
lli) (~ ~ ~ (~ ~
Bacillussp. H44 Seed coating 74.0 ab 72.9ab 7.7 (2.78) b 82.3 a 78.1 a 5.5(2.33) ab Bacillussp. H44 Drenching 62.5 bc 60.4 bc 8.5 (2.92) ab 79.2 ab 74.0 ab 5.4 (2.31) ab Bacillussp. H51 Seed coating 62.5 be 60.4 be 5.4 2.28) c 82.3 a 77.1 a 5.2 (2.28) ab
Bacillussp. H51 Drenching 60.4 bc 59.4 bc 5.0 (2.20) c 83.3 a 82.3 a 5.9(2.41) ab
Bacillussp. B81 Seed coating 54.1be 50.0 be 5.1 (2.22)c 64.6 b 60.4 b 5.9 (2.40) ab
Bacillussp. B81 Drenching 56.3be 60.4 be 6.62.55) c 74.0ab 74.0 ab 5.9 (2.42) a
T. harzianumEco-T Seed coating 62.5 be 53.1 be 8.4 (2.89) b 74.0 ab 68.8 ab 5.2 (2.27) ab T. harzianumEco-T Drenching 63.5 be 62.5 be 7.2 (2.68) be 76.0ab 74.0 ab 4.9(2.21) ab Trichodermasp.SY3 Seed coating 71.9 ab 71.9 ab 8.92.98) ab 84.4 a 81.3 a 5.7(2.38) ab Trichodermasp. SY3 Drenching 69.8 b 67.7 ab 7.7(2.77)b 83.3 a 83.3 a 5.1 (2.23) ab Trichodermasp. SY4 Seed coating 53.1 c 51.0 be 8.5(2.91) ab 81.3 a 77.1 a 6.2 (2.46) a Trichodermasp. SY4 Drenching 59.4 bc 59.4 bc 6.4 (2.53) bc 63.5 b 58.3 b 4.1 (2.01) b
Benlate® Nil 69.8 ab 65.6 b 8.4 (2.89) b 79.2 ab 67.7 ab 5.0(2.23) ab
Rsolanionly Nil 50.0c 45.8 c 5.2 (2.24) c 60.4 b 57.3 b 4.2 (2.05) b
Control (only sticker) Nil 89.6 a 89.6 a 9.7 (3.09) ab 82.3 a 81.3 a 6.3 (2.51) a
Control (only water) Nil 92.7 a 92.7 a 11.0 (3.31) a 83.3 a 82.3 a 5.9 (2.41) ab
Effects P-values P-values P-values P-values P-values P-values
Treatment <.001 *** <.001 *** <.001 *** 0.029* 0.013* 0.360
Pathogen vs.control <.001*** <.001 *** <.001 *** 0.005** 0.003** 0.056
Sticker 0.704 0.733 0.322 0.893 0.897 0.596
%CV 17.6 20.2 11.7 14.1 15.4 11.4
MSE 133.5 166.0 0.099 118.3 128.8 0.069
LSD 16.43 18.32 0.45 15.46 16.13 0.37
1.* = significant at P<0.05; **= significant at P<O.OI;*** = significant at P<O.OOI
2. Means within column followed by a common letter were not significantly different according to Fisher's protected least significant difference (P<0.05) 3. Values in brackets are means of data transformed using square root transformations
Table 4.2 Percentage seedling emergence, final stand and plot weights of greenhouse grown tef seedlings inoculated with Rhizoctonia solani and treated with biocontrol agents applied as seed coating or drenching
Treatment
Season 1
Application Emergence Final stand Plot weight
method (%) (%) (g)
Emergence (%)
Season 2 Final stand
(%)
Plot weight (g)
1.4 (1.20) ab 1.3 (1.15) ab
1.1 (1.04) b 1.4 (1.13) ab 1.4 (1.20) ab 1.4 (1.16) ab
1.5 (1.23) ab 1.1 (1.06) b 1.6 (1.26) a 1.9 (1.37) a 1.1 (1.05) b 1.5 (1.22) ab 1.2 (1.08) ab 1.3 (1.14) ab 1.4 (1.17) ab 1.2 (1.12) ab
50.0 b 59.4 ab 53.1 ab 61.5 ab
62.5 ab 54.2 b 72.9 a 75.0 a 56.3 ab 59.4 ab 62.5 ab 56.3 ab 60.4 ab 66.7a 66.7 a SLOb 61.5 ab
67.7 a 62.5 ab 56.3 ab
57.3 ab 59.4 ab 50.0 b 59.4 ab 66.7 a 51.0 b
64.6 a 54.2b 72.9 a 76.0 a 53.1 ab 61.5 ab
Trichodermasp. SY4 Seed coating 74.0(8.53) ab 62.5 (7.84) ab 1.5 (1.23) ab Trichodermasp.SY4 Drenching 79.2 (8.84) ab 66.6 (8.12) ab 1.7(1.13) ab
Benlatef Nil 64.6 (7.97) b 53.1 (7.25)b 1.3 (1.07) b
R. solani. only Nil 55.2 (7.41) b 46.8 (6.82)b 1.1 (1.04) b Control (only sticker) Nil 82.3 (9.06) ab 69.7 (8.35) ab 1.4 (1.16) ab Control(only water) Nil 89.6 (9.45) a 76.0 (8.71) a 1.7 (1.29) ab Trichodermasp.SY3 Seed coating 72.9(8.49) ab 61.5 (7.79) ab 1.5 (1.21) ab Trichodermasp. SY3 Drenching 69.8 (8.35) ab 58.3 (7.63) ab 1.6 (1.31) ab Bacillussp. H44 Seed coating 55.2 (7.40) b 45.8 (6.75) b 1.2 (1.11) b Bacillussp. H44 Drenching 69.8 (8.31) ab 56.3 (7.45) b 1.5 (1.01) b
Bacillussp. B81 Seed coating 59.4 (7.67) b 48.9 (6.97) b 1.1 (1.21) ab Bacillussp. B81 Drenching 54.2 (7.35) b 43.7 (6.60) b 1.0 (1.36) a Bacillussp. H51 Seed coating 61.4 (7.74) b 49.0 (6.91) b 1.3 (1.06) b Bacillussp. H51 Drenching 57.3(7.56) b 46.8 (6.84) b 1.0 (1.01) b
T harzianumEco-T Seed coating 59.4 (7.68) b 50.0 (7.04) b 1.5 (1.23) ab T harzianum Eco-T Drenching 77.1 (8.72) ab 62.5 (7.86) ab 1.9 (1.26) ab
Effects P-values P-values P-values P-values P-values P-values
Treatment 0.027* 0.011 * 0.051
Pathogen vs. control 0.002** 0.002** 0.035*
Sticker 0.540 0.533 0.287
0.025*
0.013*
0.668
0.035*
0.012*
0.774
0.221 0.005**
0.278
%CV 11.1 11.0 13.7
MSE 0.817 0.665 0.026
LSD 1.29 1.16 0.23
16.8 104.8 14.56
16.9 104.1 14.50
12.9 0.022 0.21 1. *= significant at P<0.05;**=significant at P<O.Ol; ***=significant at P<O.OOl
2. Means within column followed by a common letter were not significantly different according to Fisher's protected least significant difference (P<0.05).
3. Values in brackets are means of data transformed using square root transformations