Pattern of disease spread provides improved knowledge on how the pathogen introduces itself and interacts with environment in fields and expresses as a disease. It is especially significant when epidemiology of a disease, such as Rice False Smut (RFSm), is unclearly understood. Not reported before, this study attempted an analysis of spatial pattern of natural spread of RFSm in nine fields in an intensive rice ecosystem in Bangladesh. Both conventional and specialized statistical methods were applied in the analysis. Results show that the spread of the disease was not similar between and within the fields and even some fields were almost disease free. RFSm recorded aggregation in spaces in most of the fields, but the location of this aggregation differed between the fields. Symptom recorded on panicles in regenerated tillers from harvested main crop (otherwise known as ratoons). The disease tended to be prominent towards proximity of drainage channels. The probability of occurring one diseased tiller per hill was calculated as 73% and cumulative probability of four or less smut balls per diseased panicle as little over 60%. This study establishes soil as the absolute dominant source of initiation of the epidemic. The analysis did not find evidence of any long-or short-distance primary and/or secondary sources of infection. It is concluded that the disease management be directed specific to the fields at risk. It suggests development of a soil testing tool for quantifying inoculum potential in a field to ascertain the risk. With the discovery of symptom on ratoons, this study highlights the need for fresh thinking on identifying the pathway of entry of the pathogen into the plant.
Twenty-six rice hybrids were evaluated at three locations. Data were normally distributed after running the Shapiro–Wilk test. Plant height and effective tillers/hills showed leptokurtic distribution, indicating these traits were controlled by fewer genes, whereas the rest of the attributes had platykurtic distribution, indicating these traits were controlled by many genes. Most of the traits were significant for variety, locations, and variety × locations. For yield stability, the data were analyzed using additive main effect and multiplicative interaction (AMMI), genotype and genotype–environment interaction (GGE), and Eberhart and Russell’s model. Among 26 hybrids, BRRI99A × BRRI38R and BRRI hybrid dhan5 exhibited high yields at three locations. BRRI99A × BRRI45R, BRRI99A × BRRI31R, IR79156A × BRRI38R, and BRRI hybrid dhan3 were selected for mega-environments: Gazipur and Ishwardi. Among the tested locations, Gazipur (E2) and Ishwardi (E3) were identified as mega-environments for the hybrid combinations, including BRRI99A × BRRI36R, BRRI99A × BRRI49R, IR79156A × BRRI31R, IR79156A × BRRI38R, BRRI hybrid dhan5, BRRI99A × BRRI38R, BRRI99A × BRRI45R, and BRRI99A × BRRI31R based on their average action and fixity. Gazipur and Ishwardi were the best environments because their discriminative and representative ability was remarkable. The hybrid assessment, as well as area selection for hybrid rice breeding in Bangladesh, were revealed in this study. The hybrid BRRI99A × BRRI38R, BRRI99A × BRRI36R, and IR79156A × Rline7 belonged to medium-to-long slender grain types. Nowadays, the citizens of Bangladesh prefer fine-grain rice. Therefore, these fine-grain hybrids can be cultivated as preferable commercial varieties at three locations, such as Barisal, Gazipur, and Ishwardi in Bangladesh. The stable hybrids identified in the current study can be recommended for cultivation throughout the whole country without compromising the loss of grain yield of rice.
An experiment was conducted to study the effect of crop establishment methods and time of nitrogen application in Boro rice at the Bangladesh Rice Research Institute (BRRI) experimental farm, Gazipur during Boro season . Five establishment methods viz; line sowing in zero tilled, broadcasting in zero tilled, line sowing in tilled, broadcasting in tilled wet soil and transplanting method and three times of nitrogen application viz; three splits of nitrogen application at 20, 40 and 85 DAS, four splits of nitrogen application at 20, 40, 60 and 85 DAS and leaf colour chart based nitrogen application methods were investigated. Line sowing in tilled wet soil gave the highest number of tiller m -2 , panicles m -2 , grains m -2 , grain yield, straw yield, gross return, gross margin and less variable cost compared to other direct seeding and transplanting methods. In case of time of nitrogen application, four splits of nitrogen application gave the highest number of tiller m -2 , panicles m -2 , grains m -2 , grain yield, straw yield, gross return, gross margin compared to other nitrogen application techniques.
A study was conducted from June to December 2003 to assess weed dynamics and yield performance of transplanted aman rice (cv. BRRI Dhan39) in different weed control treatments e.g. two hand weedings at 15 and 40 DAT; Weeding by BRRI Weeder at 20 and 40 DAT; Rifit 500EC @ 1L/ha at 7 DAT; Rifit 500EC @ 1 L/ha at 7 DAT and one hand weeding at 40 DAT; Butachlor 5G @ 2 kg/ha at 7 DAT; Butachlor 5G @ 2 kg/ha at 7 DAT and one hand weeding at 40 DAT along with weed free and unweeded check under both good and poor water management practices. Weed density, weed biomass and weed control efficiency were significantly influenced by different weed control treatments under both water management practices. Other than weed free treatment, Butachlor 5G @ 2 kg/ha applied at 7 DAT along with one hand weeding at 40 DAT showed the best performance under good water management with minimum weed density (16 g/m 2 ) as well as weed biomass (9.27 g/m 2 ) and the highest weed control efficiency (82.57%). Yield and yield components were also significantly influenced by different weed control treatments and water management. The highest grain yield (5.22 t/ha) was obtained under good water management in weed free treatment followed by Butachlor 5G @ 2 kg/ ha and one hand weeding (4.96 t/ha) under same water management. Results revealed that integration of approaches, particularly Butachlor application along with one manual weeding accompanied by proper water management might be the best option to combat weed problems as well as to obtain satisfactory grain yield in transplanted aman rice.
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