In Niger, a landlocked country, sorghum is the second staple food cultivated over the country by smallholder farmer. The crop is important for human and animal consumption. Despite its importance, the crop is affected...In Niger, a landlocked country, sorghum is the second staple food cultivated over the country by smallholder farmer. The crop is important for human and animal consumption. Despite its importance, the crop is affected by biotic and abiotic constraints. Among those constraints, striga has a high impact on yield. In fact, to survive, farmers are growing their local preferred sorghum varieties wish is highly sensible to the weed. Striga management is a challenge that requires a permanent solution. In addition, the development of high-yielding Striga resistant genotypes will be appreciated by farmers. The development of striga resistance will be based on the breeding population performances under farmer’s diverse environmental conditions adaptation. The main objective of this study is to evaluate two breeding populations for striga resistance in two different environments at Boulke and Dibissou in Tahoua region, to identify the early and high-yielding striga tolerant genotypes under natural infestation.展开更多
Field experiments were conducted at Gore near Zebila in Bawku West District of the Upper East Region of Ghana during the 2015 and 2016 cropping season on four Striga tolerant maize varieties in maize/soybean integrati...Field experiments were conducted at Gore near Zebila in Bawku West District of the Upper East Region of Ghana during the 2015 and 2016 cropping season on four Striga tolerant maize varieties in maize/soybean integration alongside maize monocrop as a means of managing the devastating effects of Striga. The study determined the relative Striga tolerance of the maize varieties in terms of yield and yield components, as well as the most effective intercrop for the reduction of Striga seed bank. The treatment differences were not significant (p < 0.05) in affecting plant height, plant population, leaf area index (LAI), Striga count and Striga biomass. Similarly, yield components of maize such as height of cob attachment, cob length, cob weight, 100 seed weight, grain yield, as well as straw weight were not significantly affected by the treatments. There was no relativity of Striga stress tolerance in terms of yield and yield components of the four maize varieties. All the entries efficiently tolerated the biotic stress of Striga and further supported growth and grain yield equally. There was reduced S. hermonthica seed bank production in the soil in both cropping systems. The four maize varieties are proven tolerant materials to Striga infestation and are therefore recommended for long-term Striga seed bank depletion in the study area.展开更多
Sorghum (Sorghum bicolour (L.) Moench), the second most important staple crop in Sub-Saharan Africa (SSA) after maize, is well adapted to marginal environments of drought stress and high temperatures. But besides drou...Sorghum (Sorghum bicolour (L.) Moench), the second most important staple crop in Sub-Saharan Africa (SSA) after maize, is well adapted to marginal environments of drought stress and high temperatures. But besides drought stress, the obligate root-parasitic flowering plant Striga hermonthica is an equally economically important biotic stress in agro-ecological zones where soils are marginal. Notwithstanding widespread and intense Striga infestation, genetic variations in defence mechanisms against the parasite have been reported. Sorghum variants, producing low levels of chemical stimulants such as sorgolactones that deter the advance of Striga seed germination and are therefore deemed resistant to the parasite, have been also reported in a few studies. But the existence of sorghum genetic variation for this resistance especially among farmers’ landraces is yet to be demonstrated. The objective of this study was therefore to determine the levels of Striga germination stimulants in response to each of the 111 collected sorghum landraces and their progenies from Eritrea. The ability of a sorghum genotype to cause germination of a Striga seed as a measure of the amount of the germination stimulant produced was used to assess the resistance of these accessions. The data were recorded as Striga germination percentage by counting the number of germinated Striga seeds. Landraces EG47, EG1261, EG830, EG1076, EG54 and EG746 with 14.68%, 15.32%, 11.85%, 13.05%, 15.74% and 16.5% germination percentages respectively were found to stimulate low levels of Striga germination percentage compared to commercial checks, IS9830, SRN39, Framida, with 22.46%, 22.67%, 23.27% germination respectively. While these variants did not show complete resistance against Striga seed germination, the low level production of stimulant indicated their high level of resistance to Striga . These results implied that these accessions are likely potential sources of resistance against Striga infestation in SSA sorghum breeding programs.展开更多
Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fun...Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.展开更多
The parasitic weed Striga poses a serious threat to cereal production in sub-Saharan Africa. For many years, technological packages for the control of this weed were proposed and implemented on farmers＇ fields. A sur...The parasitic weed Striga poses a serious threat to cereal production in sub-Saharan Africa. For many years, technological packages for the control of this weed were proposed and implemented on farmers＇ fields. A survey was carried out in farmers＇ fields in 2010/201l cropping season in selected dryland areas of Tanzania to： （a） determine the Striga plant counts, number of capsules/Striga plant and agronomic practices used by farmers to control Striga; and （b） evaluate the relationship between Striga reproduction, soil chemical characteristics and agronomic practices. Soil samples at 0-20 cm depth were collected from 20 different farmers＇ fields. The soil samples were analyzed for pH, organic carbon, N, P and K. Results showed that there was low adoption of recommended Striga control methods. Regression analysis of agronomic practices and soil chemical characteristics revealed a positive improvement of soil N and organic carbon and reduction of soil P and K content as one shifted from sole planting to intercropping. The results showed that potassium was highly positively related to number of capsules/Striga plant. There was a reduction in the number of capsules/plant as one moved from sole planting to intercropping. Based on these findings, K in the Striga infested in soils positively influenced Striga reproduction and seed bank replenishment, hence high soil K levels may lead to high Striga incidence.展开更多
Maximum germination distance（MGD） is an important component of Striga resistance in sorghum. The objective of this study was to determine gene action influencing MGD of Striga hermonthica and Striga asiatica among s...Maximum germination distance（MGD） is an important component of Striga resistance in sorghum. The objective of this study was to determine gene action influencing MGD of Striga hermonthica and Striga asiatica among selected sorghum lines treated with a biocontrol agent, Fusarium oxysporum f. sp. strigae（FOS） for effective breeding with Striga resistance, and FOS compatibility. Twelve sorghum genotypes were selected based on their Striga resistance, FOS compatibility, and superior agronomic performance. Selected genotypes were crossed using a bi-parental mating design to generate six families for genetic analysis. Agar-gel assays were used to determine low haustorium initiation factor（LHF） using the 12 parental lines, their F_1 progenies, backcross derivatives, and F_2 segregants in two sets. One set had S. hermonthica seed and the other one had S. asiatica seed. Both were treated with and without FOS. Genotypes were evaluated using a split-plot design with three replications and MGD data were recorded followed by generation mean analysis. FOS reduced MGD by 1cm under both S. hermonthica and S. asiatica infestations. Additive, dominance, and epistatic gene actions were involved in the control of MGD of the two Striga species in the evaluated populations. On average, the relative contribution of additive, additive×additive and dominance×dominance genetic effects on the MGD of S. hermonthica and S. asiatica, with FOS, were 20, 33, and 36%; and 21, 32, and 35%, respectively. Breeding methods exploiting these genetic effects may provide enhanced response to selection for Striga resistance and FOS compatibility in integrated Striga management（ISM） programmes.展开更多
Striga hermonthica(Del.)Benth is ranked as the number one constraint to maize productivity in Eastern Uganda.The use of trap crops is one of the control measures suggested for farmers with limited resources in Striga ...Striga hermonthica(Del.)Benth is ranked as the number one constraint to maize productivity in Eastern Uganda.The use of trap crops is one of the control measures suggested for farmers with limited resources in Striga infested areas.In this study the main focus was on the effectiveness of intercropping in reducing Striga infestation and hence overall land productivity.The major objective was to identify suitable legumes in the control of Striga.In order to achieve this,on-farm experiments were conducted in Tororo and Busia districts of Eastern Uganda where the effect of the legumes on the Striga prevalence was evaluated.Maize(Zea mays)was intercropped with common beans(Phaseolus vulgaris),soybean(Glycine max)and silver leaf desmodium(Desmodium uncinatum)with sole maize(Z.mays)as the control.Soybean,beans and desmodium decreased the infestation of Striga by 26%,40%and 72%,respectively.There was a significant(p<0.05)difference in the number of emerged Striga and maize yield attained by desmodium and the rest of the legumes.Desmodium was found to be the most effective of the legumes in the control of Striga.展开更多
Sorghum bicolor is among main staple crops of Chad but it is commonly attacked by Striga hermonthica. Assessment of sorghum varieties for resistance to this weed was carried out during three cropping seasons （2005-2...Sorghum bicolor is among main staple crops of Chad but it is commonly attacked by Striga hermonthica. Assessment of sorghum varieties for resistance to this weed was carried out during three cropping seasons （2005-2008）, in controlled conditions; promising entries （those which fulfilled at least 75% of selection criteria） were evaluated in farmer field in 2008-2009 seasons. There were five sites （Bebedjia, Deli, Bekao, Koudoti and Ndaba）. The objective was to evaluate some sorghum entries for S. hermonthica resistance in farmer field. Sorghum test was composed of four entries in Fisher blocks as experimental designs, with five replications. Among different observed variables, there were striga plant count and weight of sorghum grains. One promising entry was selected at Bebedjia and Ndaba （53）, two at Deli and Koudoti （50 and 53）. No entry was selected at Bekao. Promising entries for the whole Southern zone of Chad were composed of 50 and 53. The best entry was 53 because it was promising in all sites except Bekao.展开更多
The production of maize is constrained by parasitic weeds, particularly Striga. A study was carried out to document farmers＇ knowledge, attitude and practices on Striga control among smallholder farmers across three ...The production of maize is constrained by parasitic weeds, particularly Striga. A study was carried out to document farmers＇ knowledge, attitude and practices on Striga control among smallholder farmers across three districts： Kisumu West, Busia and Teso South of Western Kenya. A multistage sampling technique was used to select the locations and farmers to be interviewed. A semi structured, open and closed ended questionnaire was administered leading to field experiment. Besides village meetings （39.2%）, farmers got informed on farming methods under Striga weed farms and its control technologies through neighbours （2.5%）, workshops and trainings （5.0%）, field schools （3.7%）, media （7.5%） and extension agents （10.8%）. The attitudes of farmers towards Striga control varied but frequently cited： long term viability of the Striga seed （12.5%）, difficult to control sharing of farm tools （10.8%）, expensive technologies （13.3%）, lack of adequate information （18.3%）, labour intensive （15.0%）, large farms for use of push and pull technology （1.7%） and time consuming （12.5%）. Framers used various Striga control practices but traditional methods （25%） were among the most used （25%）. Concerted effort involving researchers, extension agents and private sector are, therefore, required for wide scale dissemination and adoption of the existing modem control technologies.展开更多
This work aims to screen mutant rice lines tolerant to Striga asiatica.Two rainfed sensitive rice varieties B22 and F154 were used.Plants survival rates of the two parents were significantly lower respectively(9.74a a...This work aims to screen mutant rice lines tolerant to Striga asiatica.Two rainfed sensitive rice varieties B22 and F154 were used.Plants survival rates of the two parents were significantly lower respectively(9.74a and 11.83a)than those of mutant lines(55.36c to 74.36b);Striga plants emergence/pot were significantly higher for the parents(13.96c and14.89c)compared to the mutants(0.12a to 1.5b);the infection rate of parents(7.37b;7.86b)was higher compared to the mutants(2.27a to 2.74a);fertility rate/plant of parents was lower(20.98%b;22.29%b)but much higher than mutants(72.19%b to 78.35%b);the average panicle number/plant of parents was significantly lower(0.5a;1a)than those of mutants(1.5b to 2.4bc)and the 100 g grain weight of parents are lower(2.35a;2.56a)than those of mutants(3.19b to 3.23b).The culture of those mutant lines may increase rice production and contribute to enhancing food security in Madagascar.展开更多
The main problem of maize plantations is the attack of Striga asiatica in the poor soil,leading to the reduction of maize yield.The Arbuscular Mycorrhizal Fungi(AMF)helps the host plants to fight against the attack of...The main problem of maize plantations is the attack of Striga asiatica in the poor soil,leading to the reduction of maize yield.The Arbuscular Mycorrhizal Fungi(AMF)helps the host plants to fight against the attack of biotic stress,increasing the water and their nutrients elements.The objective of this study was to enhance maize production,particularly Plata maize variety,by restoring the AMF in soil under Striga asiatica infestation.During 3 years period from 2016 to 2019,three cropping systems were installed on an experimental field of FOFIFA station,Madagascar,using Mulch-based-Cropping System(MCS)of Stylosanthes,and Green Cover System(GCS)using Vigna unguiculata and a Control Plot(CP).A laboratory study was also conducted to determine the mycorrhizal rate in maize roots.The best results on root mycorrhization were found in MCS 16.53%and in GCS 11.65%against 2.01%for the CP.The average number of Striga asiatica plants per plot(100 m^(2) areas)emerging soil was 1 for MCS,3 for GCS,and 15 for CP.The yield production for MCS,GCS,and CP was respectively 4.43 t/ha,2.56 t/ha,and 1.40 t/ha.The high roots colonization mycorrhizal of 16.53%reduces the average Striga asiatica plants number emerging 1 per 100 m^(2) and increases maize grain production by 4.43 t/ha for MCS.The use of MCS of Stylosanthes is the best way to increase the maize yield,reduce Striga plants emerging,and improve the AMF restoration in maize culture.展开更多
<div style="text-align:justify;"> <i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> species affect the potenti...<div style="text-align:justify;"> <i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> species affect the potential productivity of cereals in sub-Saharian Africa due to the lack of durable </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;">-resistance in host crops. This study aimed at inducing the new source of resistance in sorghum using gamma irradiation. Dry seeds of three Sorghum varieties;Grinkan, ICV1049 and Sariaso14 were gamma-irradiated with 200 Gy, 300 Gy, 400 Gy and 500 Gy. Screening strategies involved a 2-year field and greenhouse experiments, where mutant Sorghum families, their parents and resistant control were artificially infected with </span><i><span style="font-family:Verdana;">Striga hermonthica</span></i><span style="font-family:Verdana;"> seeds. Field screenings revealed induced genetic variability among them, forty families significantly reduced the number of emerged </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> plants or showed good Sorghum grain yield performance despite the infection by S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype from Burkina Faso. The induced putative resistant mutants were identified across the four applied gamma-irradiation doses. Greenhouse experiment confirmed </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> resistance in seven mutant Sorghum families leading to no emergence of Burkina’s S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype along with high resistance index (RI) and low </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> damage score. Among them, two mutants SA38M5 and IC47M5 withstood S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype from Sudan. The induced mutants will be evaluated for the release to farmers for commercial production. Further studies are ongoing on confirmed mutants to highlight their </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> resistance mechanisms and explore the potential of pyramiding different mechanisms to produce durable resistance to S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> in sorghum.</span> </div>展开更多
Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic we...Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic weeds comprise Alectra vogelii,Striga spp.,Orobanche spp.,Rafflesia spp.,and Phoradendron spp.Parasitic attachment is successful when three necessary conditions have been fulfilled namely the compatible host,suitable environment,and parasitic weed.These species parasite plant species through special attachment features such as modified leaves,suckers,haustoria,or modified roots.In Africa,the variability of parasitic weeds is largely driven by environmental factors such as temperature,rainfall,soil type,and crop husbandry practices.Warmer temperatures create more hospitable conditions for certain parasitic weeds,and allowing them to spread to new areas.Parasitic weed control is vital for effective crop production and the control strategies can be achieved through integrated weed control method that embraces mechanical,cultural,chemical,and biological methods.However,the most effective and crucial method is the cultivation of resistant varieties that provide long-term protection against parasitic weeds.Studies have been done on host-parasite attachment where dodder can send out new roots to infected neighbouring plants and spread their parasitic behaviour.More insight and knowledge should offer new goals for control within the life cycle of the parasitic weeds and their metabolic activities.Lastly,disciplines such as agronomy,plant breeding,nutrition,economics,and IT should play their roles effectively in combating parasitic weeds.展开更多
文摘In Niger, a landlocked country, sorghum is the second staple food cultivated over the country by smallholder farmer. The crop is important for human and animal consumption. Despite its importance, the crop is affected by biotic and abiotic constraints. Among those constraints, striga has a high impact on yield. In fact, to survive, farmers are growing their local preferred sorghum varieties wish is highly sensible to the weed. Striga management is a challenge that requires a permanent solution. In addition, the development of high-yielding Striga resistant genotypes will be appreciated by farmers. The development of striga resistance will be based on the breeding population performances under farmer’s diverse environmental conditions adaptation. The main objective of this study is to evaluate two breeding populations for striga resistance in two different environments at Boulke and Dibissou in Tahoua region, to identify the early and high-yielding striga tolerant genotypes under natural infestation.
文摘Field experiments were conducted at Gore near Zebila in Bawku West District of the Upper East Region of Ghana during the 2015 and 2016 cropping season on four Striga tolerant maize varieties in maize/soybean integration alongside maize monocrop as a means of managing the devastating effects of Striga. The study determined the relative Striga tolerance of the maize varieties in terms of yield and yield components, as well as the most effective intercrop for the reduction of Striga seed bank. The treatment differences were not significant (p < 0.05) in affecting plant height, plant population, leaf area index (LAI), Striga count and Striga biomass. Similarly, yield components of maize such as height of cob attachment, cob length, cob weight, 100 seed weight, grain yield, as well as straw weight were not significantly affected by the treatments. There was no relativity of Striga stress tolerance in terms of yield and yield components of the four maize varieties. All the entries efficiently tolerated the biotic stress of Striga and further supported growth and grain yield equally. There was reduced S. hermonthica seed bank production in the soil in both cropping systems. The four maize varieties are proven tolerant materials to Striga infestation and are therefore recommended for long-term Striga seed bank depletion in the study area.
文摘Sorghum (Sorghum bicolour (L.) Moench), the second most important staple crop in Sub-Saharan Africa (SSA) after maize, is well adapted to marginal environments of drought stress and high temperatures. But besides drought stress, the obligate root-parasitic flowering plant Striga hermonthica is an equally economically important biotic stress in agro-ecological zones where soils are marginal. Notwithstanding widespread and intense Striga infestation, genetic variations in defence mechanisms against the parasite have been reported. Sorghum variants, producing low levels of chemical stimulants such as sorgolactones that deter the advance of Striga seed germination and are therefore deemed resistant to the parasite, have been also reported in a few studies. But the existence of sorghum genetic variation for this resistance especially among farmers’ landraces is yet to be demonstrated. The objective of this study was therefore to determine the levels of Striga germination stimulants in response to each of the 111 collected sorghum landraces and their progenies from Eritrea. The ability of a sorghum genotype to cause germination of a Striga seed as a measure of the amount of the germination stimulant produced was used to assess the resistance of these accessions. The data were recorded as Striga germination percentage by counting the number of germinated Striga seeds. Landraces EG47, EG1261, EG830, EG1076, EG54 and EG746 with 14.68%, 15.32%, 11.85%, 13.05%, 15.74% and 16.5% germination percentages respectively were found to stimulate low levels of Striga germination percentage compared to commercial checks, IS9830, SRN39, Framida, with 22.46%, 22.67%, 23.27% germination respectively. While these variants did not show complete resistance against Striga seed germination, the low level production of stimulant indicated their high level of resistance to Striga . These results implied that these accessions are likely potential sources of resistance against Striga infestation in SSA sorghum breeding programs.
文摘Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.
文摘The parasitic weed Striga poses a serious threat to cereal production in sub-Saharan Africa. For many years, technological packages for the control of this weed were proposed and implemented on farmers＇ fields. A survey was carried out in farmers＇ fields in 2010/201l cropping season in selected dryland areas of Tanzania to： （a） determine the Striga plant counts, number of capsules/Striga plant and agronomic practices used by farmers to control Striga; and （b） evaluate the relationship between Striga reproduction, soil chemical characteristics and agronomic practices. Soil samples at 0-20 cm depth were collected from 20 different farmers＇ fields. The soil samples were analyzed for pH, organic carbon, N, P and K. Results showed that there was low adoption of recommended Striga control methods. Regression analysis of agronomic practices and soil chemical characteristics revealed a positive improvement of soil N and organic carbon and reduction of soil P and K content as one shifted from sole planting to intercropping. The results showed that potassium was highly positively related to number of capsules/Striga plant. There was a reduction in the number of capsules/plant as one moved from sole planting to intercropping. Based on these findings, K in the Striga infested in soils positively influenced Striga reproduction and seed bank replenishment, hence high soil K levels may lead to high Striga incidence.
基金The Alliance for a Green Revolution in Africa(AGRA)is gratefully acknowledged for financial support of the study through the African Centre for Crop Improvement(ACCI)
文摘Maximum germination distance（MGD） is an important component of Striga resistance in sorghum. The objective of this study was to determine gene action influencing MGD of Striga hermonthica and Striga asiatica among selected sorghum lines treated with a biocontrol agent, Fusarium oxysporum f. sp. strigae（FOS） for effective breeding with Striga resistance, and FOS compatibility. Twelve sorghum genotypes were selected based on their Striga resistance, FOS compatibility, and superior agronomic performance. Selected genotypes were crossed using a bi-parental mating design to generate six families for genetic analysis. Agar-gel assays were used to determine low haustorium initiation factor（LHF） using the 12 parental lines, their F_1 progenies, backcross derivatives, and F_2 segregants in two sets. One set had S. hermonthica seed and the other one had S. asiatica seed. Both were treated with and without FOS. Genotypes were evaluated using a split-plot design with three replications and MGD data were recorded followed by generation mean analysis. FOS reduced MGD by 1cm under both S. hermonthica and S. asiatica infestations. Additive, dominance, and epistatic gene actions were involved in the control of MGD of the two Striga species in the evaluated populations. On average, the relative contribution of additive, additive×additive and dominance×dominance genetic effects on the MGD of S. hermonthica and S. asiatica, with FOS, were 20, 33, and 36%; and 21, 32, and 35%, respectively. Breeding methods exploiting these genetic effects may provide enhanced response to selection for Striga resistance and FOS compatibility in integrated Striga management（ISM） programmes.
文摘Striga hermonthica(Del.)Benth is ranked as the number one constraint to maize productivity in Eastern Uganda.The use of trap crops is one of the control measures suggested for farmers with limited resources in Striga infested areas.In this study the main focus was on the effectiveness of intercropping in reducing Striga infestation and hence overall land productivity.The major objective was to identify suitable legumes in the control of Striga.In order to achieve this,on-farm experiments were conducted in Tororo and Busia districts of Eastern Uganda where the effect of the legumes on the Striga prevalence was evaluated.Maize(Zea mays)was intercropped with common beans(Phaseolus vulgaris),soybean(Glycine max)and silver leaf desmodium(Desmodium uncinatum)with sole maize(Z.mays)as the control.Soybean,beans and desmodium decreased the infestation of Striga by 26%,40%and 72%,respectively.There was a significant(p<0.05)difference in the number of emerged Striga and maize yield attained by desmodium and the rest of the legumes.Desmodium was found to be the most effective of the legumes in the control of Striga.
文摘Sorghum bicolor is among main staple crops of Chad but it is commonly attacked by Striga hermonthica. Assessment of sorghum varieties for resistance to this weed was carried out during three cropping seasons （2005-2008）, in controlled conditions; promising entries （those which fulfilled at least 75% of selection criteria） were evaluated in farmer field in 2008-2009 seasons. There were five sites （Bebedjia, Deli, Bekao, Koudoti and Ndaba）. The objective was to evaluate some sorghum entries for S. hermonthica resistance in farmer field. Sorghum test was composed of four entries in Fisher blocks as experimental designs, with five replications. Among different observed variables, there were striga plant count and weight of sorghum grains. One promising entry was selected at Bebedjia and Ndaba （53）, two at Deli and Koudoti （50 and 53）. No entry was selected at Bekao. Promising entries for the whole Southern zone of Chad were composed of 50 and 53. The best entry was 53 because it was promising in all sites except Bekao.
文摘The production of maize is constrained by parasitic weeds, particularly Striga. A study was carried out to document farmers＇ knowledge, attitude and practices on Striga control among smallholder farmers across three districts： Kisumu West, Busia and Teso South of Western Kenya. A multistage sampling technique was used to select the locations and farmers to be interviewed. A semi structured, open and closed ended questionnaire was administered leading to field experiment. Besides village meetings （39.2%）, farmers got informed on farming methods under Striga weed farms and its control technologies through neighbours （2.5%）, workshops and trainings （5.0%）, field schools （3.7%）, media （7.5%） and extension agents （10.8%）. The attitudes of farmers towards Striga control varied but frequently cited： long term viability of the Striga seed （12.5%）, difficult to control sharing of farm tools （10.8%）, expensive technologies （13.3%）, lack of adequate information （18.3%）, labour intensive （15.0%）, large farms for use of push and pull technology （1.7%） and time consuming （12.5%）. Framers used various Striga control practices but traditional methods （25%） were among the most used （25%）. Concerted effort involving researchers, extension agents and private sector are, therefore, required for wide scale dissemination and adoption of the existing modem control technologies.
文摘This work aims to screen mutant rice lines tolerant to Striga asiatica.Two rainfed sensitive rice varieties B22 and F154 were used.Plants survival rates of the two parents were significantly lower respectively(9.74a and 11.83a)than those of mutant lines(55.36c to 74.36b);Striga plants emergence/pot were significantly higher for the parents(13.96c and14.89c)compared to the mutants(0.12a to 1.5b);the infection rate of parents(7.37b;7.86b)was higher compared to the mutants(2.27a to 2.74a);fertility rate/plant of parents was lower(20.98%b;22.29%b)but much higher than mutants(72.19%b to 78.35%b);the average panicle number/plant of parents was significantly lower(0.5a;1a)than those of mutants(1.5b to 2.4bc)and the 100 g grain weight of parents are lower(2.35a;2.56a)than those of mutants(3.19b to 3.23b).The culture of those mutant lines may increase rice production and contribute to enhancing food security in Madagascar.
文摘The main problem of maize plantations is the attack of Striga asiatica in the poor soil,leading to the reduction of maize yield.The Arbuscular Mycorrhizal Fungi(AMF)helps the host plants to fight against the attack of biotic stress,increasing the water and their nutrients elements.The objective of this study was to enhance maize production,particularly Plata maize variety,by restoring the AMF in soil under Striga asiatica infestation.During 3 years period from 2016 to 2019,three cropping systems were installed on an experimental field of FOFIFA station,Madagascar,using Mulch-based-Cropping System(MCS)of Stylosanthes,and Green Cover System(GCS)using Vigna unguiculata and a Control Plot(CP).A laboratory study was also conducted to determine the mycorrhizal rate in maize roots.The best results on root mycorrhization were found in MCS 16.53%and in GCS 11.65%against 2.01%for the CP.The average number of Striga asiatica plants per plot(100 m^(2) areas)emerging soil was 1 for MCS,3 for GCS,and 15 for CP.The yield production for MCS,GCS,and CP was respectively 4.43 t/ha,2.56 t/ha,and 1.40 t/ha.The high roots colonization mycorrhizal of 16.53%reduces the average Striga asiatica plants number emerging 1 per 100 m^(2) and increases maize grain production by 4.43 t/ha for MCS.The use of MCS of Stylosanthes is the best way to increase the maize yield,reduce Striga plants emerging,and improve the AMF restoration in maize culture.
文摘<div style="text-align:justify;"> <i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> species affect the potential productivity of cereals in sub-Saharian Africa due to the lack of durable </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;">-resistance in host crops. This study aimed at inducing the new source of resistance in sorghum using gamma irradiation. Dry seeds of three Sorghum varieties;Grinkan, ICV1049 and Sariaso14 were gamma-irradiated with 200 Gy, 300 Gy, 400 Gy and 500 Gy. Screening strategies involved a 2-year field and greenhouse experiments, where mutant Sorghum families, their parents and resistant control were artificially infected with </span><i><span style="font-family:Verdana;">Striga hermonthica</span></i><span style="font-family:Verdana;"> seeds. Field screenings revealed induced genetic variability among them, forty families significantly reduced the number of emerged </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> plants or showed good Sorghum grain yield performance despite the infection by S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype from Burkina Faso. The induced putative resistant mutants were identified across the four applied gamma-irradiation doses. Greenhouse experiment confirmed </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> resistance in seven mutant Sorghum families leading to no emergence of Burkina’s S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype along with high resistance index (RI) and low </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> damage score. Among them, two mutants SA38M5 and IC47M5 withstood S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> ecotype from Sudan. The induced mutants will be evaluated for the release to farmers for commercial production. Further studies are ongoing on confirmed mutants to highlight their </span><i><span style="font-family:Verdana;">Striga</span></i><span style="font-family:Verdana;"> resistance mechanisms and explore the potential of pyramiding different mechanisms to produce durable resistance to S. </span><i><span style="font-family:Verdana;">hermonthica</span></i><span style="font-family:Verdana;"> in sorghum.</span> </div>
文摘Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic weeds comprise Alectra vogelii,Striga spp.,Orobanche spp.,Rafflesia spp.,and Phoradendron spp.Parasitic attachment is successful when three necessary conditions have been fulfilled namely the compatible host,suitable environment,and parasitic weed.These species parasite plant species through special attachment features such as modified leaves,suckers,haustoria,or modified roots.In Africa,the variability of parasitic weeds is largely driven by environmental factors such as temperature,rainfall,soil type,and crop husbandry practices.Warmer temperatures create more hospitable conditions for certain parasitic weeds,and allowing them to spread to new areas.Parasitic weed control is vital for effective crop production and the control strategies can be achieved through integrated weed control method that embraces mechanical,cultural,chemical,and biological methods.However,the most effective and crucial method is the cultivation of resistant varieties that provide long-term protection against parasitic weeds.Studies have been done on host-parasite attachment where dodder can send out new roots to infected neighbouring plants and spread their parasitic behaviour.More insight and knowledge should offer new goals for control within the life cycle of the parasitic weeds and their metabolic activities.Lastly,disciplines such as agronomy,plant breeding,nutrition,economics,and IT should play their roles effectively in combating parasitic weeds.
