The experimental site is geographically situated at 23° N latitude and 91° E longitudes with an elevation of 6 m from sea level at the eastern part of Bangladesh. The soil of the experimental plot was clay loam having pH 6.0, organic carbon content was moderate at 1.13%, total nitrogen 0.08%, available P (Olsen) 9 ppm, exchangeable K (meq/100 g soil) 0.20, exchangeable Ca (meq/100 g soil) 4.5, available S 14 ppm, Zn 10 ppm and Fe was 370 ppm. The research activities were conducted in the rain-fed and irrigated rice ecosystems during 1999 to 2001 at the BRRI regional station, Comilla district. A small piece of medium low land was selected for raising seedlings for field experiments of ShB and BLB. Clean and healthy matured seeds (germination rate, >85%) were pre-germinated in a moist-plastic tray in the dark at 28°C for 24 h before sowing in seedbeds. Thirty five days old rice seedlings of the varieties were transplanted in the plots using 2 to 3 seedlings/hill in 4 m long lines. The distance between hill to hill and row to row was 20 x 20 cm. Experimental plots were fertilized with the recommended doses of 124–26–60–13–4 kg/ha N–P–K–S–Zn (BRRI, 2000). For ShB, an isolate of R. solani was isolated from the susceptible variety BR11, which was collected from Gazipur district, Bangladesh. Infected samples were surfaced-sterilized by chlorox (1%) and placed on potato dextrose agar (PDA) media in the petri-dishes consisting of 39 g L-1 (Difco. Bacto®, Dicson and Co., MD USA). The petri-dishes were then incubated at 28°C for 48 h. For the preparation of inoculum in large scale, pathogen was grown and prepared on rice husk medium (30 g of rice husk in a 300 ml flask) for 10 days as described by Akter et al. (2003). In the case of BLB, an isolate of X. oryzae pv oryzae pv was collected from the susceptible variety, BRRI dhan29. Advancing lesion of the leaf tissues were cut into pieces (cal. 1.0 mm2). Surface sterilization was done by soaking the leaf pieces in 70% ethyl alcohol followed by dipping in 5% chlorox for 1 min (Vera, 1984). The surface sterilized pieces were kept for 30 min in sterile water to release the bacterium. Finally, a full loop of the suspension was streaked on a plate of MgFe medium. Observation was made after 72 h after streaking to see the appearance of the gtalies colonies. After 5 days of incubation, the bright yellow and slimy colonies were selected. The selected colonies were re-streaked on the MgFe medium. Finally, pure single colony was selected and designated as an individual isolate. The bacterium was grown on peptone semi-synthetic agar (PSA: peptone 1.2%, sucrose 1.2%, agar 2%) slants for 48 h. After that, 100 ml of sterile water was poured in a 300 ml flask. Finally, a bacterial suspension having approx. 108 to 1010 cfu ml-1 of water was made (verified by a Nikon AFX-IIA microscope, Japan). For blast, a virulent isolate of M. oryzae was collected from the susceptible variety, BRRI dhan29 which was grown on prune agar medium for a week. Finally, conidial suspension was prepared and adjusted to 1 x 105 ml-1 with sterilized deionized water (verified by Nikon AFX-IIA, Japan). For RTD, a virulent isolate of RTV was and propagated by the acquisition of viruliferous green leafhoppers in glass house. For ShB, each hill of rice plant at max. tillering stage was inoculated with 50 g inocula of 10 days old culture of R. solani as described by Akter et al. (2003). For, BLB, the plants were inoculated with the isolate of X. oryzae at max. tillering stage as described by Hossain et al. (2004). Five hybrid and 12 inbred varietie were transplanted in 2 different experimental plots and the plants of 1 plot were inoculated with BLB inoculums and the other plot was inoculated with ShB inoculums during 1999 to 2000 irrigated rice ecosystems. Again in rain-fed ecosystem during 2000 to 2001, 18 inbred and 4 hybrids were tested against BLB of rice following the aforementioned procedure. These studies were conducted in the irrigated ecosystem during 1999 to 2000. For blast, seeds of the different varieties were directly sown in 1 m long rows with approx. 100 plants. Tested varieties were replicated 3 times. Nizersail was used as susceptible variety. Twenty days old plants, with 3 or 4 fully expanded leaves, were inoculated by spraying (by hand sprayer) aqueous spore suspension at the rate of 1 x 105 spore ml-1 onto the rice leaves (Filippi and Prahbu, 2001). Inoculated nursery beds were irrigated (by sprinkler) in the evening and covered overnight with a plastic sheet to maintain high relative humidity. A total of 12 hybrids and 8 inbreds were tested against blast under artificial inoculums pressure in the irrigated rice ecosystem during 1999 to 2001. In the case of tungro, 50 seeds of each variety were seeded randomly or in rows either in tray or pot. Seven to 10 days after sowing, seedlings in excess of 30 were removed. No fertilizer was used during nursery evaluation. Initially, leafhoppers were left to feed on 45 to 60 days old infected plants (exhibiting tungro symptoms) for 2 to 3 days. The seedlings in tray were then exposed to viruliferous leafhoppers for 1 day on rate of at least 3 viruliferous green leafhoppers per seedlings. The green leafhoppers on the seedlings were disturbed for several times to ensure even distribution. Four weeks after inoculation, the seedlings were scored based on visual observation of the symptoms. A healthy check was used as a reference to measure height. Experiments were conducted in rain-fed ecosystem during 2000 to 2001 with 18 inbred and 4 hybrid varieties. Efficacy of 3 fungicides, acmecop 50 WP (copper oxychloride), adivistin 50 WP (carbendazim) and haydazim 50 WP (carbendazim) were tested for the control of blast disease of rice during 2001 to 2003. Infected seeds were treated at the rate of 0.4, 0.3 and 0.2% of each seed-treating fungicide. Seeds were collected from the previously blast infected field and the severity of panicle blast was evaluated with disease index (DI) 7 described by IRRI (1996) and fungal frequency was 25 to 30%. Two control treatments, control (healthy) and control (diseased), were maintained for comparison. 35 days old rice seedlings of BRRI dhan29 were transplanted at 25 x 15 cm spacing in 3 x 3 m unit plot. The experiments were laid out in a randomized complete block design (RCBD) with 4 replicates for each treatment. For screening, data on disease index (DI), lesion area (%), incidence (%), plant height reduction (%) and disease reaction of blast, BLB, ShB and tungro were recorded. For the management of blast disease, the incidence (%) of leaf, node and panicle blast, DI and yield were recorded. All the DI scales and disease reactions were obtained by following a standard evaluation system (IRRI, 1996), where the index values were: 0 to 1 = HR (highly resistant), 2 = R (resistant), 3 = MR (moderately resistant), 4 to 6 = MS (moderately susceptible), 7 = S (susceptible) and 8 to 9 = HR (highly susceptible). Statistical analyses were performed by analysis of variance (ANOVA) followed by protected Fisher’s least-significance difference (LSD) test at the p = 0.05 level of probability (Gomez and Gomez, 1984).