Using 2009/2010 cropping season survey data from 181 randomly selected smallholder tobacco farmers, this study provides baseline information on tobacco farming in Mara region. Both descriptive and inferential statisti...Using 2009/2010 cropping season survey data from 181 randomly selected smallholder tobacco farmers, this study provides baseline information on tobacco farming in Mara region. Both descriptive and inferential statistics were employed in data analysis. Result indicates that farmers adopted tobacco farming from tobacco farmers in Kenya. Drought and inadequate supply of inputs were identified as the major production constraints. Others were incidence of pests and diseases, shortage of fire woods, poor extension services and hailstones. Low selling price and contradicting grading systems were the major tobacco marketing constraints. The study also revealed that access to extension services was similar across study districts with over 65.7% of the respondents accessing technical expertise mainly from Alliance One Tanzania employees. Given the positive and negative impacts of tobacco farming, majority of the respondents （95.6%） still were willing to proceed with tobacco farming as their main source of income. However, watermelon, maize and sunflower were ranked as first priority alternative cash crops to tobacco in Serengeti, Tarime and Rorya districts, respectively. This study concludes that tobacco farming still is the main household income source; hence, more investment is required to ensure sustainable economic develooment of rural communities in Mara reeion.展开更多
Plant height and tillering are crucial factors determining rice plant architecture and influencing rice grain production. In this study, rnulti-tillering dwarf1 （mtdl）, a stable multi-tiller and dwarf mutant, was sc...Plant height and tillering are crucial factors determining rice plant architecture and influencing rice grain production. In this study, rnulti-tillering dwarf1 （mtdl）, a stable multi-tiller and dwarf mutant, was screened from the ethylmethane sulfonate-treated japonica rice variety Wuyunging7. Compared with the wild type, mtdl mutant exhibited pleiotropic phenotypes, including dwarf- ism, more tillers, brittle culms and delayed heading date. By employing map-based cloning strategy, the gene MTD1 was finally mapped to an approximately 66-kb region on the short arm of chromosome 9. Sequencing results showed that the gene LOCOsO9g02650 （BC12） in mtdl mutant had a single nucleotide substitution （G to A）, which gen- erated a premature translation stop. Over-expressing MTD1/BC12 coding sequ（nce rescued all the phenotypes of mtdl mutants including plant height and tillers, which confirms that BC12 is the mutated gene in mtdl mutant. Quantitative reverse tran,-eription-PCR analysis showed that MTDI/BCI2 could negatively regulate the expression of MONOCULM 1, IDEAL PLANT ARCHITECTURE1 and Tillering and Dwarf 1, and control rice tillering. Remark- ably, a-amylase activity analysis and gibberellic acid （GA） treatment showed that the dwarf phenotype of mtdl mutant was dependent on GA biosynthesis pathway. These results facilitated to further uncover the molecular mechanism of the growth and development in rice.展开更多
When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The rel...When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.展开更多
文摘Using 2009/2010 cropping season survey data from 181 randomly selected smallholder tobacco farmers, this study provides baseline information on tobacco farming in Mara region. Both descriptive and inferential statistics were employed in data analysis. Result indicates that farmers adopted tobacco farming from tobacco farmers in Kenya. Drought and inadequate supply of inputs were identified as the major production constraints. Others were incidence of pests and diseases, shortage of fire woods, poor extension services and hailstones. Low selling price and contradicting grading systems were the major tobacco marketing constraints. The study also revealed that access to extension services was similar across study districts with over 65.7% of the respondents accessing technical expertise mainly from Alliance One Tanzania employees. Given the positive and negative impacts of tobacco farming, majority of the respondents （95.6%） still were willing to proceed with tobacco farming as their main source of income. However, watermelon, maize and sunflower were ranked as first priority alternative cash crops to tobacco in Serengeti, Tarime and Rorya districts, respectively. This study concludes that tobacco farming still is the main household income source; hence, more investment is required to ensure sustainable economic develooment of rural communities in Mara reeion.
基金supported by the National Natural Science Foundation of China (31401464, 31201183)Zhejiang Provincial Natural Science Foundation of China (Y3110194, LY16C130001)+1 种基金China Postdoctoral Science Foundation (2014M561108)the Open Foundation from Zhejiang Provincial Top Key Discipline of Biology (KFJJ2014006)
文摘Plant height and tillering are crucial factors determining rice plant architecture and influencing rice grain production. In this study, rnulti-tillering dwarf1 （mtdl）, a stable multi-tiller and dwarf mutant, was screened from the ethylmethane sulfonate-treated japonica rice variety Wuyunging7. Compared with the wild type, mtdl mutant exhibited pleiotropic phenotypes, including dwarf- ism, more tillers, brittle culms and delayed heading date. By employing map-based cloning strategy, the gene MTD1 was finally mapped to an approximately 66-kb region on the short arm of chromosome 9. Sequencing results showed that the gene LOCOsO9g02650 （BC12） in mtdl mutant had a single nucleotide substitution （G to A）, which gen- erated a premature translation stop. Over-expressing MTD1/BC12 coding sequ（nce rescued all the phenotypes of mtdl mutants including plant height and tillers, which confirms that BC12 is the mutated gene in mtdl mutant. Quantitative reverse tran,-eription-PCR analysis showed that MTDI/BCI2 could negatively regulate the expression of MONOCULM 1, IDEAL PLANT ARCHITECTURE1 and Tillering and Dwarf 1, and control rice tillering. Remark- ably, a-amylase activity analysis and gibberellic acid （GA） treatment showed that the dwarf phenotype of mtdl mutant was dependent on GA biosynthesis pathway. These results facilitated to further uncover the molecular mechanism of the growth and development in rice.
基金supported by the Hundred Talent Project(s) of Chinese Academy of Sciencesthe National Natural Science Foundation of China (Grant Nos.11073048 and 11073047)+1 种基金the Pujiang Project of Shanghai (Grant No.10PJ1411700)Shanghai Key Laboratory of Space Navigation and Position Techniques (Grant No.Y054262001)
文摘When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.
