Abstract
The experiments were conducted to control the foot and root rot (Fusarium oxysporum) and collar rot (Sclerotium rolfsii) of lentil (Lens culinaris Medik). F. oxysporum and S. rolfsii and their antagonist, Trichoderma were collected from nine different locations of Bangladesh. The growth and pathogenecity of F. oxysporum and S. rolfsii were studied. The highest foot and root rot and the lowest plant stand of lentil were recorded in case of using most virulent isolate, F. oxysporum (FBg-1). Among the isolates of S. rolfsii, SL-4 was found most virulent. All the isolates of Trichoderma harzianum and Trichoderma viride were fast grower and their conidia production in PDA ranged from 1.28 x 10cm2 to 3.78 x 10'/cm2. Out of 23 agro-wastes used, the highest conidia (48x10/g) and CFU (4.04x10/g) of T. harzianum (TG-2) were recorded in chickpea bran. T. harzianum and T. viride inhibited the growth of F. oxysporum (FBg-1) from 60.42 to 99.27% at 10 DAI. Overgrowth of T. harzianum and T. viride on F. oxysporum (FBg-1) was recorded, where the highest count (98.40 %) at 20 DAI was made in Tv followed by TG-2 (97 %). T. harzianum and T. viride also inhibited the growth of S. rolfsii (SL-4) from 64.07-99.41% at 7 DAI. Overgrowth of T. harzianum and T. viride on S. rolfsii (SL-4) were observed, where the highest overgrowth (98.51 %) at 20 DAI was found in TG-2 followed by Tv (92.87 %). In pot experiments, among the four different methods (i. Seed treatment, ii. Soil treatment, iii. Seed + Soil treatment and iv. Soil drenching with Trichoderma), soil treatment with Trichoderma was found best. Treatment of soil with T. viride (Tv) at 2g/kg of soil was found better against F. oxysporum, where T. harzianum (TG-2) at 20g/kg of soil was observed better for controlling S. rolfsii. T. viride (Tv) increased germination (17.86%), plant stand (171.43%), vigour index (33.27%) and yield (260.74%) over control. T. harzianum (TG-2) also increased germination (248%), plant stand (600%), vigour index (865.91%) and yield (1209.81%) of lentil over control. Soil treatment with T. harzianum (TG-2) and T. viride (Tv) was used for controlling foot and root rot (F. oxysporum) and collar rot (S. rolfsii) in the artificially inoculated field. The highest germinations, 64.87% and 73.33% were recorded in Tv and TG-2 treated plots, respectively that indicated 50.76% and 494.73% increase of germination, respectively over control. The lowest foot and root rot (16.52%) and collar rot (13.86%) were recorded in Tv and TG-2 treated plots, respectively resulting, corresponding 60.51% and 66.91% reduction of foot and root rot, and collar rot over the control. The highest grain yield (2538.8 kg/ha) was recorded when the F. oxysporum inoculated field soil was treated with T. viride which increased grain yield by 128.81 % over the control. The highest grain yield (1902.17 kg/ha) and corresponding grain yield increase by 406.57% over the control was also found when the S. rolfsii (SL-4) inoculated field soil was treated with T. harzianum (TG-2). Under natural high inoculum potential level, soil treatment with T. harzianum (TG-2) resulted the highest germinations 82.08% and 65.58% at Mymensingh and Ishurdi, respectively which showed 62.73% and 16.78% higher germination in both the locations, respectively over the control corresponding lowest disease incidence was recorded 6.88% at Mymensingh and 4.70% at Ishurdi, respectively that showed decrease of disease by 82.36% and 69.01%, respectively and resulted corresponding maximum plant stand 93.12% and 60.86% at Mymensingh and Ishurdi respectively. The highest grain yields, 3726.67 kg/ha and 3786.63 kg/ha were recorded at Mymensingh and Ishurdi, respectively and resulted 98.77% increase of grain yield at Mymensingh and 22.60% at Ishurdi over the control.