Yam （Dioscorea spp.）, has been aptly described as an orphan crop. It has suffered institutional neglect from time immemorial. Until this study there were no formally released yam varieties in Ghana. The farmer parti...Yam （Dioscorea spp.）, has been aptly described as an orphan crop. It has suffered institutional neglect from time immemorial. Until this study there were no formally released yam varieties in Ghana. The farmer participatory breeding approach was adapted to fast-track the development and release of three new yam varieties in Ghana. This paper uses the breeding process as a case study and conducts a SWOT analysis to provide guidelines for breeding for crops in Low External Input Agriculture. It was faster than conventional breeding in varietal development. Scientific quality of Farmer Participatory Breeding is as good as conventional breeding. Farmer Participatory Breeding is a must for breeding yam in Ghana. Ultimately, three genotypes 2000/001, KUP2000/001 and TDr89/02665 were accepted and released as new varieties ＂CRIKukrupa＂, ＂CRIPona＂ and ＂Mankrong Pona＂ respectively in March 2005. Danger of omission of some promising genotypes in the course of varietal development and danger of opinion group cabalizing the group discussions were identified as potential threats to the approach. Effective research-extension-farmer linkage was identified as extremely vital to the success of the approach. Farmer participatory breeding process was also sustainable and more efficient than conventional breeding in varietal selection in yam breeding.展开更多
Due to industrial activities,heavy metal concentrations in aquatic systems of Mexico,are on the rise.Zooplankton,particularly rotifers,being sensitive and common components of freshwater,are widely used in ecotoxicolo...Due to industrial activities,heavy metal concentrations in aquatic systems of Mexico,are on the rise.Zooplankton,particularly rotifers,being sensitive and common components of freshwater,are widely used in ecotoxicological tests for establishing water quality criteria.Depending on the route of exposure(i.e.via medium or algal food),the toxicity of heavy metals varies.In the present study we evaluated the effect of cadmium and mercury exposed through medium and via algal food for the rotifer B.rubens.For both the heavy metals,we exposed rotifers via medium containing Chlorella at 0.5×10^(6)cells/ml or fed daily on previously exposed(1,2 and 4 h)alga to the toxicants(using 5 times the value of LC_(50)for B.rubens).For cadmium toxicity through medium,we used 3 toxicant levels(0.1,0.2 and 0.4 mg/L)and for mercury,we used 0.005,0.010 and 0.015 mg/L.Based on the LC_(50),B.rubens was 24 times more sensitive to mercury(0.035±0.002 mg/L)than cadmium.At a concentration of 0.4 mg/L,cadmium through the medium caused increased lag phase of B.rubens.When grown on Chlorella exposed for different durations to cadmium,the rotifer density decreased with the increasing duration of algal exposure to the heavy metal.When mercury was used in the medium or via algal food,the trends in the population growth of B.rubens were similar to those for cadmium.An increase in heavy metal concentration in the medium resulted in a decrease of the rate of population increase per day(r).The r varied from 0.33(in control)to 0.02 d^(-1)(in heavy metal treatment)depending on the mode of exposure though medium or via algal food.展开更多
Quantifying stoichiometry of crop N and P acquisition(i.e.removal from farmland)under different agronomic practices is essential for understanding nutrient budgets and optimizing N and P fertilizer application in agro...Quantifying stoichiometry of crop N and P acquisition(i.e.removal from farmland)under different agronomic practices is essential for understanding nutrient budgets and optimizing N and P fertilizer application in agroecosystems.It is not clear how plant N and P uptake and N:P stoichiometry vary between monoculture and intercropping throughout an entire growing season under different N fertilization and mulching practices.Here,we addressed how plant interspecific competition for nutrients have affected the temporal dynamics of crop N and P uptake(and N:P ratios)in five cropping systems(wheat,maize and barley monocultures,and wheat/maize and barley/maize intercropping),under two N levels(0 and 225 kg N ha^(−1))and two maize mulching treatments(with and without).Wheat and barley had greater N and P competitive ability than maize,leading to an increase in N and P uptake of wheat and barley and a decrease in N and P uptake of maize during co-growth stages in intercropping.N:P ratios of three crop species decreased with plant growth.Crop-level N:P ratios were either not affected by intercropping or did not change consistently with N fertilization while film mulching decreased maize N:P ratios.Community-level N:P ratios of the two intercrops were different from those of the corresponding monoculture at maturity.Because(i)the proportion of N and P removal from intercropping differs from monocultures,and(ii)N and P uptake by crops is decoupled under N fertilization and mulching,these findings may have practical implications for the nutrient budget of intercropping systems.展开更多
文摘Yam （Dioscorea spp.）, has been aptly described as an orphan crop. It has suffered institutional neglect from time immemorial. Until this study there were no formally released yam varieties in Ghana. The farmer participatory breeding approach was adapted to fast-track the development and release of three new yam varieties in Ghana. This paper uses the breeding process as a case study and conducts a SWOT analysis to provide guidelines for breeding for crops in Low External Input Agriculture. It was faster than conventional breeding in varietal development. Scientific quality of Farmer Participatory Breeding is as good as conventional breeding. Farmer Participatory Breeding is a must for breeding yam in Ghana. Ultimately, three genotypes 2000/001, KUP2000/001 and TDr89/02665 were accepted and released as new varieties ＂CRIKukrupa＂, ＂CRIPona＂ and ＂Mankrong Pona＂ respectively in March 2005. Danger of omission of some promising genotypes in the course of varietal development and danger of opinion group cabalizing the group discussions were identified as potential threats to the approach. Effective research-extension-farmer linkage was identified as extremely vital to the success of the approach. Farmer participatory breeding process was also sustainable and more efficient than conventional breeding in varietal selection in yam breeding.
基金This research was funded by a grant from PAPIIT—IN204101.SSSS and SN also thank National System of Investigators(SNI一18723&20520)
文摘Due to industrial activities,heavy metal concentrations in aquatic systems of Mexico,are on the rise.Zooplankton,particularly rotifers,being sensitive and common components of freshwater,are widely used in ecotoxicological tests for establishing water quality criteria.Depending on the route of exposure(i.e.via medium or algal food),the toxicity of heavy metals varies.In the present study we evaluated the effect of cadmium and mercury exposed through medium and via algal food for the rotifer B.rubens.For both the heavy metals,we exposed rotifers via medium containing Chlorella at 0.5×10^(6)cells/ml or fed daily on previously exposed(1,2 and 4 h)alga to the toxicants(using 5 times the value of LC_(50)for B.rubens).For cadmium toxicity through medium,we used 3 toxicant levels(0.1,0.2 and 0.4 mg/L)and for mercury,we used 0.005,0.010 and 0.015 mg/L.Based on the LC_(50),B.rubens was 24 times more sensitive to mercury(0.035±0.002 mg/L)than cadmium.At a concentration of 0.4 mg/L,cadmium through the medium caused increased lag phase of B.rubens.When grown on Chlorella exposed for different durations to cadmium,the rotifer density decreased with the increasing duration of algal exposure to the heavy metal.When mercury was used in the medium or via algal food,the trends in the population growth of B.rubens were similar to those for cadmium.An increase in heavy metal concentration in the medium resulted in a decrease of the rate of population increase per day(r).The r varied from 0.33(in control)to 0.02 d^(-1)(in heavy metal treatment)depending on the mode of exposure though medium or via algal food.
基金funded by the National Key Research and Development Program of China(2016YFD0300202)the Natural Science Foundation of China(31971450,31500348,31430014)Chinese Universities Scientific Fund(2020TC051)and the European Research Council Synergy grant(ERC-SyG-2013-610028,IMBALANCE-P).
文摘Quantifying stoichiometry of crop N and P acquisition(i.e.removal from farmland)under different agronomic practices is essential for understanding nutrient budgets and optimizing N and P fertilizer application in agroecosystems.It is not clear how plant N and P uptake and N:P stoichiometry vary between monoculture and intercropping throughout an entire growing season under different N fertilization and mulching practices.Here,we addressed how plant interspecific competition for nutrients have affected the temporal dynamics of crop N and P uptake(and N:P ratios)in five cropping systems(wheat,maize and barley monocultures,and wheat/maize and barley/maize intercropping),under two N levels(0 and 225 kg N ha^(−1))and two maize mulching treatments(with and without).Wheat and barley had greater N and P competitive ability than maize,leading to an increase in N and P uptake of wheat and barley and a decrease in N and P uptake of maize during co-growth stages in intercropping.N:P ratios of three crop species decreased with plant growth.Crop-level N:P ratios were either not affected by intercropping or did not change consistently with N fertilization while film mulching decreased maize N:P ratios.Community-level N:P ratios of the two intercrops were different from those of the corresponding monoculture at maturity.Because(i)the proportion of N and P removal from intercropping differs from monocultures,and(ii)N and P uptake by crops is decoupled under N fertilization and mulching,these findings may have practical implications for the nutrient budget of intercropping systems.
