1,344,204 research outputs found

    Genetic variation and possible origins of weedy rice found in California.

    Get PDF
    Control of weeds in cultivated crops is a pivotal component in successful crop production allowing higher yield and higher quality. In rice-growing regions worldwide, weedy rice (Oryza sativa f. spontanea Rosh.) is a weed related to cultivated rice which infests rice fields. With populations across the globe evolving a suite of phenotypic traits characteristic of weeds and of cultivated rice, varying hypotheses exist on the origin of weedy rice. Here, we investigated the genetic diversity and possible origin of weedy rice in California using 98 simple sequence repeat (SSR) markers and an Rc gene-specific marker. By employing phylogenetic clustering analysis, we show that four to five genetically distinct biotypes of weedy rice exist in California. Analysis of population structure and genetic distance among individuals reveals diverse evolutionary origins of California weedy rice biotypes, with ancestry derived from indica, aus, and japonica cultivated rice as well as possible contributions from weedy rice from the southern United States and wild rice. Because this diverse parentage primarily consists of weedy, wild, and cultivated rice not found in California, most existing weedy rice biotypes likely originated outside California

    Drying of post-harvest rough rice with silica gel: A preliminary investigation

    Get PDF
    Rice drying operations can encounter problems of over drying and losses in head rice yield (HRY) through the formation of fissures. Typical rice drying methods also utilize large volumes of expensive fossil fuels to dry the kernels. Drying of rice with a solid desiccant such as silica gel has several potential advantages that avoid some of these problems. Two cultivars of long-grain rough rice, ‘Cheniere’ and ‘Wells’ with harvest moisture contents of 17.8% and 22.0%, respectively, were dried over a 48-h period with various ratios of rough rice-to-silica gel. It was found that an intimate mixture of 3:1 rough rice to silica gel was sufficient to dry these rice lots to 12.5% and 14.3% within 12 h, respectively. Head rice yields of desiccant-dried rice showed no considerable differences from the control. Rough-rice drying curves for all rough rice-to-silica gel mixtures followed exponential relationships

    Effect of Nitrogen Fertilizer Dose and Application Timing on Yield and Nitrogen Use Efficiency of Irrigated Hybrid Rice under Semi-Arid Conditions

    Get PDF
    Nitrogen fertilizer is the major input in rice production and the optimum rate and application timing management assure profitability and sustainability of the production system. This study aims to investigate hybrid rice response to different nitrogen fertilizer levels and the timing of application and quantify hybrid rice nitrogen use efficiency. Field experiments were conducted during the dry and the wet seasons 2016 at the research station of Africa Rice at Ndiaye in Senegal. Six nitrogen rates (0, 60, 90, 120, 150 and 180 kg N/ha) and three hybrid rice varieties (AR031H, AR032H, AR033H) and one inbred variety (Sahel108) and two nitrogen fertilizer application timings (three split and four split) were combined within a split-split plot design. The results showed significant effect of nitrogen rate and timing on rice grain yield that varied from 4.10 to 11.58 tons/ha and most the yield components. Rice grain yield exhibited curvilinear relationship with the applied nitrogen rates during the dry season under both nitrogen application timings and a linear relationship during the wet season under three splits. Nitrogen rate of 150 kg/ha was revealed optimum with best performance achieved by the Hybrid rice AR033H. Hybrid rice genotypes achieved greater nitrogen use efficiency compared to the inbred rice Sahel108. Hence, hybrid rice genotypes, and nitrogen rate of 150 kg/ha applied in four splits could be recommended to improve rice production and food security for achieving self-sufficiency in rice as targeted by Senegal and the neighboring countries

    Effectiveness of botanical preparations for the control of rice weevil (Sitophilus oryzae) during rice seed storage and their impact on the rice seed viability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Seed Technology at Massey University, Palmerston North, New Zealand

    Get PDF
    Food security and the maintenance of seed quality from harvest to planting are key issues for peasant farmers. In Sierra Leone, up to 28% of rice seed can be damaged by rice weevil in the six months storage period. The use of chemical insecticides to control this insect is not practical for traditional farmers. Some tribes use pepper powder (Capsicum spp.) as a seed protectant. In this study, I have compared the effects of neem (Azadirachta indica) oil, neem powder, pepper (Capsicum frutescens cv. "Habanero") powder and lentil (Lens culinaris cv. "Raja") powder on the survival of adult rice weevil (Sitophilus oryzae) and weevil offspring during rice (Oryza spp.) seed storage, and on the germination of the rice. Treatment of stored rice with neem oil, neem powder and lentil powder gave some protection from rice weevil damage. Neem oil at the rate of 0.005ml/kg rice seed effectively controlled weevil damage without reducing the seed germination. Lentil and neem powders at the rate of 0.02g/kg rice seed gave effective protection against rice weevil damage with no reduction in viability of the seeds. Pepper powder did not kill adult rice weevil. Neem oil reduced the development of weevil offspring in rice seed, but the powders of neem, lentil and pepper did not. Low relative humidity of 42.5% in seed storage environment and a reduction in seed moisture content below 10% enhanced the mortality of adult rice weevils on rice seed

    Characterization of Jasmine Rice Cultivars Grown in the United States

    Get PDF
    Jasmine rice from Thailand accounts for about 60-70% of U.S. imported rice, primarily due to its preference by ethnic Asians as well as general American population. Recently new U.S. jasmine rice cultivars have been developed independently at three rice research stations in Arkansas, California, and Louisiana, but their properties have not been characterized. The objective of this research was to characterize and compare the physical appearance, chemical composition, thermal and pasting properties, cooked rice texture and starch structures of the newly-developed U.S. jasmine rice from Arkansas, California and Louisiana, to be compared with jasmine rice samples from Thailand. In general, the U.S. varieties had smaller length/width ratios, darker color, and greater ash and lipid contents than the Thai controls. The Arkansas samples were similar to each other as well as one Louisiana sample, CLJ01 2017, and the other Louisiana samples were similar to each other, but rice of both origins were different from Thai jasmine. Calaroma-201 was found to be the most similar to the Thai jasmine rice out of the U.S. varieties from Ward’s hierarchical cluster analysis of all attributes. These findings can help the U.S. rice industry to develop U.S. jasmine rice cultivars closer to Thai jasmine rice

    Rice monitoring using ENVISAT-ASAR data: preliminary results of a case study in the Mekong River Delta, Vietnam

    Get PDF
    Vietnam is one of the world’s largest rice exporting countries, and the fertile Mekong River Delta at the southern tip of Vietnam accounts for more than half of the country’s rice production. Unfortunately, a large part of rice crop growing time coincides with a rainy season, resulting in a limited number of cloud-free optical remote sensing images for rice monitoring. Synthetic aperture radar (SAR) data allows for observations independent of weather conditions and solar illumination, and is potentially well suited for rice crop monitoring. The aim of the study was to apply new generation Envisat ASAR data with dual polarization (HH and VV) to rice cropping system mapping and monitoring in An Giang province, Mekong River Delta. Several sample areas were established on the ground, where selected rice parameters (e.g. rice height and biomass) are periodically being measured over a period of 12 months. A correlation analysis of rice parameters and radar imagery values is then being conducted to determine the significance and magnitude of the relationships. This paper describes a review of the previous research studies on rice monitoring using SAR data, the context of this on-going study, and some preliminary results that provide insights on how ASAR imagery could be useful for rice crop monitoring. More work is being done to develop algorithms for mapping and monitoring rice cropping systems, and to validate a rice yield prediction model for one year cycle using time-series SAR imagery

    Metal Chelating Activity Of Rice Bran And Rice Husk

    Get PDF
    Free radical-induced oxidative stress is the root cause for many human diseases. Naturally occurring antioxidant supplements from plants are vital to counter the oxidative damage in cells. The main objective of the present study was to explore and compare the antioxidant activity of rice bran and rice husk extracted from rice milling waste. N-hexane extracts of rice bran and rice husk were used to study their in vitro antioxidant activities using metal chelating activity (iron (II)-phenanthroline complex). Vitamin E was used as standard material. The ability of the sample to chelate metal ion (ferrous ion) was calculated relative to the control and expressed as % inhibition. % inhibition of two samples were analyzed with student test (P=0.05). The results have shown that at the same concentration (10 ppm), rice husk extract, rice bran extract and vitamin E have the different activity, i.e.: 0.51%, 2.27% and 5.55% in inhibition of chelat formation, respectively. In conclusion, metal chelating activity of rice husk extract is smaller than rice bran extract. Activity of rice bran extract is almost a half from vitamin E, so thi
    • …