Several frequently occurring seed-borne mycoflora, viz., Aspergillus niger, Aspergillus flavus, Alternaria sp., Fusarium sp., Helminthosporium sp., Mucor sp., Rhizopus sp., Rhizoctonia sp., Colletotrichum sp., Macrophomina phaseolina, Penicillium sp. and Botrytis sp., are described as yield and oilseed declining factors. The role of these fungi have been documented in limiting successful cultivation of various crops in various countries including India6. Fungal and bacterial biocontrol agents viz., Trichoderma viride, T. harzianum, T. virens, Pseudomonas fluorescens and Bacillus subtilis, have been reported to manage seed-borne mycoflora of mungbean, viz., Aspergillus niger, Penicillium rubrum, Alternaria alternata and Fusarium moniliforme7. Sharma et al.8 also emphasized that T. harzianum exhibited the greatest mycelial inhibition for Alternaria sp. and Fusarium sp. The conceivable mechanisms of antagonism employed by Trichoderma spp. include antibiosis by targeting production of volatile and non-volatile antibiotics, nutrient and niche competition and mycoparasitism which possess inhibitory effect against several phyto- pathogenic fungi (Dennis and Webster9; Harman and Hadar10; Schirmbock et al.11). Stimulation of host defence response is another possible mechanism of biocontrol activity of Trichoderma spp. (Howell et al.12). Hasan et al.13 found that T. harzianum inhibited the radial growth of Fusarium graminarum by 43.33 per cent under in vitro conditions.
Anitha14 evaluated efficiency of different biopriming biocontrol agents in soybean seeds and reported that root length, shoot length and seedling length were higher in T. harzianum. Sharma et al.15 revealed that T. harzianum showed significant improvement in seed germination (88.75%), root length (13.58 cm), shoot length (14.58 cm) and seedling vigour (2501) in cucumber variety Solan Srijan.
Table 2
Effect of different biocontrol agents on seed health of artificially inoculated seeds of soybean by towel paper method
Biocontrol agents | Aspergillus niger | Colletotrichum truncatum | Alternaria alternata |
Germination (%) * | Root length (cm) | Shoot length (cm) | Seedling vigour index | Germination (%) * | Root length (cm) | Shoot length (cm) | Seedling vigour index | Germination (%) * | Root length (cm) | Shoot length (cm) | Seedling vigour index |
Trichoderma koningii (DMA-8) | 75.78 (60.50) | 7.46 | 1.50 | 679 | 81.33 (64.43) | 7.58 | 1.62 | 748 | 79.67 (63.21) | 7.53 | 1.54 | 723 |
Trichoderma harzianum (TH-11) | 85.00 (67.19) | 10.45 | 3.07 | 1149 | 89.50 (71.07) | 7.90 | 2.28 | 911 | 87.00 (68.97) | 7.87 | 2.28 | 883 |
Trichoderma harzianum (TH-4) | 80.67 (63.94) | 7.82 | 2.23 | 811 | 85.75 (67.84) | 7.86 | 2.11 | 855 | 83.00 (65.66) | 7.83 | 2.14 | 828 |
Trichoderma koningii (JMA-11) | 79.66 (63.19) | 7.72 | 1.77 | 756 | 84.20 (66.60) | 7.81 | 2.19 | 843 | 81.33 (64.38) | 7.77 | 1.78 | 776 |
Trichoderma viride (TV-1) | 78.45 (62.34) | 7.52 | 1.70 | 724 | 82.50 (65.29) | 7.62 | 1.81 | 778 | 80.67 (64.42) | 7.57 | 1.75 | 752 |
Pseudomonas fluorescens | 75.67 (60.43) | 7.45 | 1.43 | 672 | 80.44 (63.78) | 7.56 | 1.80 | 753 | 78.67 (62.48) | 7.50 | 1.43 | 702 |
Bacillus sp. | 74.00 (59.34) | 7.32 | 1.20 | 630 | 79.00 (62.74) | 7.42 | 1.69 | 720 | 76.33 (60.90) | 7.37 | 1.24 | 657 |
Negative control | 67.33 (55.12) | 5.75 | 1.00 | 454 | 60.80 (51.22) | 5.87 | 1.52 | 449 | 60.00 (56.16) | 5.97 | 0.60 | 394 |
Positive control | 72.00 (58.03) | 6.70 | 1.03 | 557 | 71.10 (57.46) | 6.63 | 1.28 | 563 | 61.00 (51.34) | 6.33 | 0.67 | 427 |
CD (P = 0.05) | 2.24 | 1.70 | 0.54 | | 3.15 | 0.37 | 0.27 | | 3.34 | 0.67 | 0.15 | |
*Figures within parentheses are arc sine transformed values |