African Cassava mosaic disease (ACMD) is the most severe and widespread disease caused by viruses limiting production of the crop in sub-Saharan Africa. The objective of the present study was to evaluate CMD incidence...African Cassava mosaic disease (ACMD) is the most severe and widespread disease caused by viruses limiting production of the crop in sub-Saharan Africa. The objective of the present study was to evaluate CMD incidence, severity, and gravity under different agro-environmental conditions. A total of 222 fields were surveyed in 23 different locations. All the farmers grow only local cassava varieties without applications of fertilizers. Overall, mean CMD incidences for all sites surveyed were 58.2% and 51.7%, in 2009 and 2010, respectively. Disease severity ranged from 2.4 to 3.1 on a scale of 1 to 5. Mean disease gravity varied from 29.7% to 62%, in 2010, and 2009, respectively. Detailed analysis of agronomic and environmental revealed no significant association between cassava stand locations, age, land topography and the development of CMD. Likewise intercropping practices and field topping did not affect the development of CMD in all the fields surveyed. There were significant differences in the number of white flies (Bemisia tabaci) per plant in 2009 and 2010, but no significant correlations between the number of B. tabaci per plant and CMD incidence, severity, and gravity was found. In most fields, CMD appears to originate mostly from unhealthy cassava cuttings used for planting.展开更多
The agro-environmental fragility of 31 provinces and regions (except Hong Kong,Macao and Taiwan) of our country during the years 1978-2004 is measured by adopting the method of principal component analysis.With the su...The agro-environmental fragility of 31 provinces and regions (except Hong Kong,Macao and Taiwan) of our country during the years 1978-2004 is measured by adopting the method of principal component analysis.With the support of analytical model of panel data,regressive analysis is achieved from the aspects of introducing regional differences,not introducing regional differences,existing industrial differences and not existing industrial differences respectively.The conclusion points out that there are both industrial and regional differences in the economic growth effect on the environmental fragility;these differences are reflected on the industrial or regional development levels.The higher the development level it is,the less the effect it is when the economic growth effect on the environmental fragility is negative,the more when the effect is positive,and it will change from being negative to positive when on the critical point;and vice versa.展开更多
文摘African Cassava mosaic disease (ACMD) is the most severe and widespread disease caused by viruses limiting production of the crop in sub-Saharan Africa. The objective of the present study was to evaluate CMD incidence, severity, and gravity under different agro-environmental conditions. A total of 222 fields were surveyed in 23 different locations. All the farmers grow only local cassava varieties without applications of fertilizers. Overall, mean CMD incidences for all sites surveyed were 58.2% and 51.7%, in 2009 and 2010, respectively. Disease severity ranged from 2.4 to 3.1 on a scale of 1 to 5. Mean disease gravity varied from 29.7% to 62%, in 2010, and 2009, respectively. Detailed analysis of agronomic and environmental revealed no significant association between cassava stand locations, age, land topography and the development of CMD. Likewise intercropping practices and field topping did not affect the development of CMD in all the fields surveyed. There were significant differences in the number of white flies (Bemisia tabaci) per plant in 2009 and 2010, but no significant correlations between the number of B. tabaci per plant and CMD incidence, severity, and gravity was found. In most fields, CMD appears to originate mostly from unhealthy cassava cuttings used for planting.
文摘The agro-environmental fragility of 31 provinces and regions (except Hong Kong,Macao and Taiwan) of our country during the years 1978-2004 is measured by adopting the method of principal component analysis.With the support of analytical model of panel data,regressive analysis is achieved from the aspects of introducing regional differences,not introducing regional differences,existing industrial differences and not existing industrial differences respectively.The conclusion points out that there are both industrial and regional differences in the economic growth effect on the environmental fragility;these differences are reflected on the industrial or regional development levels.The higher the development level it is,the less the effect it is when the economic growth effect on the environmental fragility is negative,the more when the effect is positive,and it will change from being negative to positive when on the critical point;and vice versa.
