Browsing by Author "Ali, Md. Ansar"

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Biological Characterization and Management of Rhizoctonia oryzae-sativae Causal Agent of Aggregate Sheath Spot Disease of Rice
(University of Rajshahi, 2014) Jahan, Suriya Bilkis; Alam, Mohammad Shahidul; Ali, Md. Ansar
Plant pathogenic fungus Rhizoctonia oryzae-sativae (teleomorph Ceratbasidium oryzae-sativae) caused aggregate sheath spot disease of rice. The disease is considered as minor on rice. However, in rice–wheat/potato cropping system the disease has emerged in higher incidence in North-West region of Bangladesh. Research studies of R. oryzae-sativae in particular are still limited hence very little information concerning the fungus is available in Bangladesh. Therefore, the present study was undertaken with aims to generate preliminary information on the population biology and structure of R. oryzae-sativae. Perhaps this is the first comprehensive report in which thirty isolates of R. oryzae-sativae collected from rice fields of ten different districts of Bangladesh. Multidisciplinary characterization approach or technique viz. culture morphology, virulence test, somatic compatibility groups (SCGs) and DNA fingerprinting were adopted. Isolates were confirmed using R. oryzae-sativae specific diagnostic markers in which a single band of 1200 bp was amplified. Data analysis of the mycelial growth rate separated the isolates into two distinct groups relatively slow and faster. Pathogenicity test on cultivar BR11 revealed that all the tested isolates were pathogenic and found significant correlation between mycelial growth rate and relative lesion height (RLH). There were 27 SCGs from 30 isolates indicated 90% diversity among the isolates. Variable number tandem repeat (VNTR) and Repetitive-element Polymerase Chain Reaction (Rep-PCR) were conducted using MR, RY, GF and BOXA1R primers respectively. DNA bands of four primers ranged from 0.25 to 2.21 kb. A combined dendrogram was constructed by NTSYS-pc software (2.20 e) which separated the isolates into three groups at 69.6% similarity level. Among them, all isolates placed in two major clusters except isolate RA-1, which placed in cluster group III. Fast growing isolates have been placed in Group II, while slow growing isolates in cluster group I. The similarity coefficient values of the dendrogram profile ranged from 0.36 to 0.98 with an average of 0.67. The effects of eight fungicides with six concentrations were tested in vitro on mycelial growth of R. oryzae-sativae. R. oryzae-sativae found sensitive to all the fungicides tested. Carbendazim showed strong activity against the pathogen with the lowest LD (lethal dose) 90 values (0.8 ppm) and LD50 (0.1 ppm) in vitro. All the fungicides significantly reduced disease development in field trials but only Carbendazim, Tebuconazole and Trifloxystroin-tebuconazole increased rice yield. However, aggregate sheath spot reduced yields by up to 14.74% under Bangladeshi conditions. The maximum growth of the pathogen on PDA measured at 6.0-9.0 pH level. The highest mycelial growth was recorded in dextrose (0.47 mm/hr) followed by sucrose (0.44 mm/hr). The best mycelial growth rate of R. oryzae-sativae found in peptone (0.43 mm/hr) followed by yeast (0.37 mm/hr). Among the tested phytoextracts, garlic and henna found most effective against R. oryzae-sativae. None of the tested germplasm or cultivars found immune to aggregate sheath spot disease. T. Aus germplasm Akuee, Kalosoti and T. Aman varieties Kurchi jira, Kurchi binni, Shabichi dhan, BRRI dhan39, BRRI dhan40, BRRI dhan46 found moderately susceptible while no susceptible variety found in Boro season. Multidisciplinary characterization of R. oryzae-sativae revealed that isolates of Bangladesh origin is not genetically identical.
Sustainable use of Water for Some Selected Hybrid and Inbred Rice Cultivation in the Floodplain Areas (AEZ 26 and AEZ 28) of Bangladesh
(University of Rajshahi, 2013) Bulbul, Sheikh Helena; Rahman, Md. Safinur; Sattar, M.A.; Rahman, Md. Redwanur; Ali, Md. Ansar; Masuduzzaman, A.S.M.
The water crisis is threatening the sustainability of the irrigated rice system and food security in Asia. Our challenge is to promote novel technology and production systems that allow rice cultivation to be maintained in the declining water availability. This paper introduces principles for sustainable water use and water saving technology for reducing water inputs and increasing water productivity, and assesses the opportunities of such technologies and systems at spatial scale levels from plant to field, to irrigation system, and to agro-ecological zones. The rapid growth of world population has resulted in significantly increased global water demand. According to a recent repo1t on limited water supply, conservation techniques and water use policies are needed to preserve water resources. Worldwide agriculture is the largest consumer of water, particularly for growing rice. Water use for rice production was chosen because rice will continue to be a staple crop for the majority of the world's population and because of its pervasive use of water. Traditional lowland rice production in Asia requires much water: it consumes more than 50% of all irrigation water used in Asia. Water resources are, however, increasingly getting scarce and expensive. The supply of water for irrigation is endangered by declining water quality, declining resource availability, increased competition from other users, and increasing costs. During the past decades, rice production in Bangladesh experienced an impressive intensification. The change to dry season rice, constituting about 60% of national rice production, was largely due to groundwater irrigation by shallow tube wells (STW) and deep tube wells (DTW). This practice led to the massive extraction of groundwater, an overexploitation of groundwater, locally manifested by declining groundwater tables in Rajshahi. Co1Tespondingly to the expansion of i1Tigation, demand for energy increased, as electricity or fuel are needed to lift groundwater to the surface. This also touches on the chronically deficient energy situation of Bangladesh. To address problems of water scarcity, researchers have studied and developed a number of water-saving i1Tigation technologies such as saturated soil culture and alternate wetting and drying (A WD) that can drastically diminish these losses. Under these technologies, yields may decline, but they have demonstrated that they save water and increase water productivity. Hence, this thesis was designed to investigate water conservation possibilities for rice production in two water management regimes: alternate wetting and drying and continuous standing (the latter is the traditional water management technique in iITigated rice culture). The study revealed that the alternate wetting and drying treatment reduced water use and increased rice grain yield than continuous standing water. Among the results of the study, it was found that BRRJ hybrid2 gave better performance than other inbred varieties. Logistic regression model used to estimate the contribution of key variables of adoption of A WD. Boro rice, it was suggested that farm size, education of household head, and contact with extension agents, water scarcity and dissemination through demonstration were the variables that had significant impact on the adoption of A WD. It was also evident that water conservation benefits can potentially be realized if local government agencies (e.g., Phil- Rice and NIA), as well as international agencies ( e.g., IRRI), continue to provide education and training about the latest research on A WD and other water-conserving technologies to local extension personnel, field technicians, and as well as farmers. With calls for re-orientation of sustainable water use, the implications of the findings of this research suggest that alternate wetting and drying water saving technology is making a positive contribution towards sustainability. It should be a valuable approach that should not be trivialized, stigmatized or ignored because of its potential to bring long-lasting impacts.