Exposure of Gambian children to Anopheles gambiae malaria vectors in an irrigated rice production area

Abstract. Variation in exposure of children to malaria vectors of the Anopheles gambiae complex was recorded in a Gambian village situated near an irrigated area of rice cultivation. Observations were made in 1987 and 1988 during two dry seasons, when pumped water was used to grow rice, and two rainy seasons, when rice was produced using a combination of irrigated and rainfed paddies. Routine collections of mosquitoes were made from under bednets. Most of these specimens were assumed to have fed on the occupants of the net and thus represented a crude measure of exposure to malaria. Most nets in the village were in good condition, but even these were a poor defence against blood-seeking mosquitoes. Two annual peaks in the numbers of An. gambiae s.l. corresponded with the irrigation of rice paddies in the dry and wet seasons. When there were few vectors in the village the frequency distribution of mosquitoes caught under nets was described best by a Poisson process. When high numbers were present the daily distributions were over-dispersed and fitted a negative binomial model. The spatial distribution of mosquitoes varied between dry and wet seasons and was related to the predominant wind direction at night, suggesting that wind assisted the dispersal of mosquitoes from their breeding sites. For individual children in the rainy season, increased exposure to malaria vectors was associated with living adjacent to a mosquito breeding site, being resident in larger compounds, having open eaves in the house, a store-room adjacent to the bedroom, the absence of a ceiling in the bedroom, the absence of wood smoke indoors and leaving the bednet untucked at night. In the dry season a high level of exposure was associated with living close to a mosquito breeding site, having an unfenced compound, sleeping in a room without a ceiling and using insecticide aerosols. These observations demonstrate that within a village there are systematic and persistent differences in the level of exposure to malaria parasites experienced by individual children.     

Alcohol fermentation of enzymatic hydrolysate of exploded rice straw by Pichia stipitis

The xylose in an enzymatic hydrolysate of steam-exploded rice straw was not consumed by Pichia stipitis until the glucose was almost exhausted. A diauxic lag of 2 to 3 h in both cell growth and ethanol production occurred as metabolism switched from glucose to xylose utilization. Ethanol production was maximal [6 g ethano/l from 15 g reducing sugars/l (78% theoretical yield)] at an aeration rate of 0.2 vol/vol. min.The author was with the Department of Chemical Engineering, Kanazawa University, Kanazawa 920, Japan, but is now with the Engineering Biosciences Research Center, Cater-Mattil Hall, The Texas A&M University System, College Station, Texas 77843-2476, USA.     

Neck blast disease influences grain yield and quality traits of aromatic rice

A critical investigation was conducted to find out the effect of neck blast disease on yield-contributing characters, and seed quality traits of aromatic rice in Bangladesh. Both healthy and neck-blast-infected panicles of three aromatic rice cultivars (high-yielding and local) were collected and investigated at Plant Pathology Division, Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh. All of the tested varieties were highly susceptible to neck blast disease under natural conditions, though no leaf blast symptoms appear on leaves. Neck blast disease increased grain sterility percentages, reduced grain size, yield and quality traits of seeds. The degrees of yield and seed quality reduction depended on disease severity and variety's genetic make-up. Unfilled grains were the main source of seed-borne pathogen, especially for blast in the seed lot. Transmission of blast pathogen from neck (panicle base) to seed was very poor. These findings are important, especially concerning the seed certification programme in which seed lots are certified on the basis of field inspection. Finally, controlled experiments are needed to draw more critical conclusions.     

Rice G protein γ subunit qPE9-1 modulates root elongation for phosphorus uptake by involving 14-3-3 protein OsGF14b and plasma membrane H+-ATPase

Heterotrimeric G protein is involved in plant growth and development, while the role of rice (Oryza sativa) G protein γ subunit qPE9-1 in response to low-phosphorus (LP) conditions remains unclear. The gene expression of qPE9-1 was significantly induced in rice roots under LP conditions. Rice varieties carrying the qPE9-1 allele showed a stronger primary root response to LP than the varieties carrying the qpe9-1 allele (mutant of the qPE9-1 allele). Transgenic rice plants with the qPE9-1 allele had longer primary roots and higher P concentrations than those with the qpe9-1 allele under LP conditions. The plasma membrane (PM) H⁺-ATPase was important for the qPE9-1-mediated response to LP. Furthermore, OsGF14b, a 14-3-3 protein that acts as a key component in activating PM H⁺-ATPase for root elongation, is also involved in the qPE9-1 mediation. Moreover, the overexpression of OsGF14b in WYJ8 (carrying the qpe9-1 allele) partially increased primary root length under LP conditions. Experiments using R18 peptide (a 14-3-3 protein inhibitor) showed that qPE9-1 is important for primary root elongation and H⁺ efflux under LP conditions by involving the 14-3-3 protein. In addition, rhizosheath weight, total P content, and the rhizosheath soil Olsen-P concentration of qPE9-1 lines were higher than those of qpe9-1 lines under soil drying and LP conditions. These results suggest that the G protein γ subunit qPE9-1 in rice plants modulates root elongation for phosphorus uptake by involving the 14-3-3 protein OsGF14b and PM H⁺-ATPase, which is required for rice P use.     

Elicitor(s) in Sogatella furcifera (Horváth) Causing the Japanese Rice Plant (Oryza sativa L.) to Induce the Ovicidal Substance,Benzyl Benzoate

We elucidate the mechanism for inducing the production of ovicidal benzyl benzoate by Japonica rice varieties to kill eggs of the whitebacked planthopper, Sogatella furcifera (Horváth), lying in the rice plant. Even when subjected to physical damage by a needle or damage with water, the rice plant produced no benzyl benzoate. However, significant benzyl benzoate was produced when the plant was damaged with a methanol extract or homogenate of S. furcifera. The extract of the male did not induce the production of benzyl benzoate, but that of the female did. We concluded from these results that benzyl benzoate was induced by some elicitor(s) in the female of S. furcifera.     

低温下水稻幼苗形态生理应变研究

低温下水稻幼苗形态生理应变研究李太贵王磊（中国水稻研究所，杭州３１０００６）ＳｔｕｄｙｏｆＭｏｒｐｈｏＰｈｙｓｉｏｌｏｇｉｃａｌＳｔｒａｉｎｏｆＲｉｃｅＳｅｅｄｌｉｎｇＵｎｄｅｒＬｏｗＴｅｍｐｅｒａｔｕｒｅ．ＬｉＴａｉｇｕｉ，ＷａｎｇＬｅｉ（Ｃｈｉ...     

Single-nucleus sequencing deciphers developmental trajectories in rice pistils

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Profiling of selected indigenous rice (Oryza sativa L.) landraces of Rarh Bengal in relation to osmotic stress tolerance

A total of ten rare indigenous rice landraces of West Bengal were screened for germination potential and seedling growth under varying concentrations of sodium chloride (NaCl) and polyethylene glycol (PEG) solutions as osmotic stress inducing agents. Among the studied rice landraces Kelas and Bhut Moori showed highest degree of tolerance to induced osmotic stresses. Proline content of the studied lines was also determined. Genetic relationship among the studied rice landraces was assessed with 22 previously reported osmotic stress tolerance linked Simple Sequence Repeat (SSR) markers. The identified allelic variants in form of amplified products size (molecular weight) for each SSR marker were documented to find out allele mining set for the linked markers of the studied genotypes in relation to osmotic stress tolerance. A Microsatellite Panel was constructed for the different allelic forms (size of amplified products) of each used marker. Among 22 SSR markers, ten showed unique alleles in form of single specific amplified product for the studied four genotypes which can be used for varietal identification. Genetic relationship among the studied rice lines was determined and a dendrogram was constructed to reveal their genetic inter-relationship. Polymorphism Information Content (PIC) for each used marker was also calculated for the studied rice lines.     

CH4 emission with differences in atmospheric CO2 enrichment and rice cultivars in a Japanese paddy soil

A pot experiment was conducted to investigate CH₄ emissions from a sandy paddy soil as influenced by rice cultivars and atmospheric CO₂ elevation. The experiment with two CO₂ levels, 370 μL L⁻¹ (ambient) and 570 μL L⁻¹ (elevated), was performed in a climatron, located at the National Institute for Agro‐Environmental Sciences, Tsukuba, Japan. Four rice cultivars were tested in this experiment, including IR65598, IR72, Dular and Koshihikari. Tiller number, root length and grain yield were clearly larger under elevated CO₂ than under ambient CO₂. IR72 and Dular showed significantly higher tiller number, root length and grain yield than Koshihikari and IR65598. Average daily CH₄ fluxes under elevated CO₂ were significantly larger by 10.9–23.8% than those under ambient CO₂, and varied with the cultivars in the sequence Dular ≧ IR72>IR65598 ≧ Koshihikari. Dissolved organic C (DOC) content in the soil was obviously higher under elevated CO₂ than under ambient CO₂ and differed among the cultivars, in the sequence IR72>Dular>Koshihikari>IR65598. The differences in average daily CH₄ fluxes between CO₂ levels and among the cultivars were related to different root exudation as DOC content, root length and tiller number. This study indicated that Koshihikari should be a potential cultivar for mitigating CH₄ emission and simultaneously keeping stable grain yield, because this cultivar emitted lowest CH₄ emission and produced medium grain yield.