Late leaf spot caused by Cercosporidium personatum is one of the most widespread groundnut leaf diseases. Along with early leaf spot and rust, it is one of the main fungal diseases hampering groundnut production world...Late leaf spot caused by Cercosporidium personatum is one of the most widespread groundnut leaf diseases. Along with early leaf spot and rust, it is one of the main fungal diseases hampering groundnut production worldwide. Late leaf spot accounts for significant yield losses throughout the world where groundnuts are grown. This reduction in yield caused by the disease could result in yield losses of between 50% and 70%. In Burkina Faso, the disease is present throughout the country, with incidence varying according to region and season. Could the variability in the incidence of the disease be linked to the nature of the isolates or to the conditions from each agro-ecological zone? In this study, the aim was to assess the capacity of three isolates from three agroclimatic zones of the country to defoliate and reduce groundnut yield. To this end, three isolates of Cercosporidium personatum (Berk. Et M.A Curt.) were collected in these zones and evaluated on three contrasting groundnut varieties. A split-splot design was used for the experiment. Isolates were prepared from samples collected in farmers’ fields. After incubation in the laboratory, leaf spots showing good sporulation were scraped off with a scalpel after immersing the leaves in distilled water. Inoculations were carried out under controlled environment. After inoculation with the isolate, the percentage of defoliation and the reduction in yield of these varieties were then evaluated. Inoculation was carried out from the 30th day after sowing with Cercosporidium personatum spore suspensions at 10<sup>5</sup> spores/ml. The study showed that the percentage of defoliation (P = 0.0001) and the reduction in yield (P = 0.0001) were significant. The study revealed that, whatever the variety, isolate I3TF from the Upper Basins region in the South Sudanese zone caused the greatest defoliation and the greatest reduction in yield. The variety TS32-1, regardless of the isolate used for the treatment, recorded the best yield. The variety PC79-79, regardless of the isolate used for the treatment, recorded the lowest percentage of defoliation. The highest defoliation recorded under the effect of the isolates was of the order of 72.20%;the highest yield reduction was of the order of 87.20% compared with the water control.展开更多
The essential oil was extracted from fresh leaf and defoliation of Bischofia polycarpa(Lévl.) Airy Shaw using steam distillation,and the chemical components and relative content of essential oil were analyzed by ...The essential oil was extracted from fresh leaf and defoliation of Bischofia polycarpa(Lévl.) Airy Shaw using steam distillation,and the chemical components and relative content of essential oil were analyzed by GC-MS and peak area normalization.The results show that the yields of crude extracts of essential oil from fresh leaf and defoliation are 0.114% and 0.105% respectively,and 114 and 15 peaks have been obtained respectively.Forty-seven compounds have been identified from the essential oil of fresh leaf,and the main compounds are camphor,2-hexenoic acid,heptacosane,dibutylphthalate,diethyladipate,2,6,10-trimethyl tetradecaneanddiisobutyladipatewith relativecontents of 10.416%,8.078%,7.627%,7.463%,5.171%,4.411% and 4.144%,respectively.Fourteen compounds have been identified from the essential oil of defoliation,and the main compounds are camphor,2-carboxymethyl-3-n-hexylmaleic acid anhydride and eucalyptol with relative contents of 33.070%,12.670% and 8.620%,respectively.The relative content of camphor in essential oil from fresh leaf and defoliation is the highest.展开更多
【目的】探讨不同配方落叶剂对榕树冬季集中落叶的效应及对其生理变化的影响,为有效防治榕树叶部病虫害提供参考依据。【方法】以5年生榕树为试验材料,采用经正交试验筛选获得的5种由不同浓度乙烯利、碘化钾和尿素配成的落叶剂,对榕树...【目的】探讨不同配方落叶剂对榕树冬季集中落叶的效应及对其生理变化的影响,为有效防治榕树叶部病虫害提供参考依据。【方法】以5年生榕树为试验材料,采用经正交试验筛选获得的5种由不同浓度乙烯利、碘化钾和尿素配成的落叶剂,对榕树进行叶面喷施处理(T1～T5),以喷施清水为对照(CK),统计分析各处理的落叶率、萌发率和病情指数,并测定若干生理指标。【结果】T1～T5处理榕树的落叶率均显著高于CK(P<0.05),叶片病情指数极显著低于CK(P<0.01),其中,喷药后第14 d T5处理的落叶率最高,为90.33%,其次为T4处理,为84.67%,T3处理的落叶率为72.67%。各落叶剂处理榕树叶片的叶绿素和可溶性蛋白含量呈先下降后上升的变化趋势,相对电导率和丙二醛(MDA)含量呈先上升后下降的变化趋势。落叶剂处理7 d后,榕树树体均恢复生长,其中T5处理对榕树树体的胁迫较小,对榕树后期发芽影响较小,萌发率达72.36%。【结论】以0.8%乙烯利+0.2%碘化钾+2.0%尿素配成的落叶剂对榕树的落叶效果最佳且生理胁迫小,对其后期叶片萌发影响小,是最佳的榕树落叶剂配方。展开更多
【目的】脱叶率是评价机采棉脱叶催熟效果的重要依据。以无人机RGB图像为基础数据源,通过从RGB图像中提取14种可见光植被指数,建立快速、准确监测棉花脱叶率的模型,为机采棉适时采收提供理论和技术支持。【方法】设置不同棉花品种,通过...【目的】脱叶率是评价机采棉脱叶催熟效果的重要依据。以无人机RGB图像为基础数据源,通过从RGB图像中提取14种可见光植被指数,建立快速、准确监测棉花脱叶率的模型,为机采棉适时采收提供理论和技术支持。【方法】设置不同棉花品种,通过采集不同脱叶剂浓度及喷施时间处理下的棉花脱叶率数据,并利用无人机采集冠层RGB图像,提取可见光植被指数,分析其与棉花脱叶率的相关关系,进而采用一元线性回归(Simple linear regression,SLR)、多元线性回归(Multivariate linear regression,MLR)和偏最小二乘法回归(Partial least square regression,PLSR)构建棉花脱叶率监测模型,并进行模型评价。【结果】不同处理下的棉花脱叶率有明显差异,脱叶率与不同可见光植被指数存在较好相关性,其中三角形绿度值(Triangular greenness index,TGI)与棉花脱叶率的相关性最高(r=0.81)。建模结果表明,SLR模型中,以TGI指数建模效果最好(决定系数0.66,均方根误差10.44%,相对均方根误差12.87%);MLR模型中,以过蓝指数(Excess blue index,ExB)、绿叶指数(Green leaf index,GLI)、TGI和过绿指数(Excess green index,ExG)4个植被指数组合建立的模型效果最好,其决定系数为0.70,均方根误差为10.26%,相对均方根误差为12.65%。PLSR模型中,以ExB、GLI、TGI、ExG、综合植被指数2和综合植被指数1建立的模型精度更高,其决定系数为0.70,均方根误差为10.02%,相对均方根误差为12.22%。外部验证表明,各模型实测值与预测值间有较好的拟合关系。【结论】以MLR和PLSR方法建立的模型精度较高,拟合程度较好。从计算量及模型复杂程度角度考虑,通过MLR方法以ExB、GLI、TGI、ExG建立的棉花脱叶率监测模型,能够更好地监测棉花脱叶率。展开更多
文摘Late leaf spot caused by Cercosporidium personatum is one of the most widespread groundnut leaf diseases. Along with early leaf spot and rust, it is one of the main fungal diseases hampering groundnut production worldwide. Late leaf spot accounts for significant yield losses throughout the world where groundnuts are grown. This reduction in yield caused by the disease could result in yield losses of between 50% and 70%. In Burkina Faso, the disease is present throughout the country, with incidence varying according to region and season. Could the variability in the incidence of the disease be linked to the nature of the isolates or to the conditions from each agro-ecological zone? In this study, the aim was to assess the capacity of three isolates from three agroclimatic zones of the country to defoliate and reduce groundnut yield. To this end, three isolates of Cercosporidium personatum (Berk. Et M.A Curt.) were collected in these zones and evaluated on three contrasting groundnut varieties. A split-splot design was used for the experiment. Isolates were prepared from samples collected in farmers’ fields. After incubation in the laboratory, leaf spots showing good sporulation were scraped off with a scalpel after immersing the leaves in distilled water. Inoculations were carried out under controlled environment. After inoculation with the isolate, the percentage of defoliation and the reduction in yield of these varieties were then evaluated. Inoculation was carried out from the 30th day after sowing with Cercosporidium personatum spore suspensions at 10<sup>5</sup> spores/ml. The study showed that the percentage of defoliation (P = 0.0001) and the reduction in yield (P = 0.0001) were significant. The study revealed that, whatever the variety, isolate I3TF from the Upper Basins region in the South Sudanese zone caused the greatest defoliation and the greatest reduction in yield. The variety TS32-1, regardless of the isolate used for the treatment, recorded the best yield. The variety PC79-79, regardless of the isolate used for the treatment, recorded the lowest percentage of defoliation. The highest defoliation recorded under the effect of the isolates was of the order of 72.20%;the highest yield reduction was of the order of 87.20% compared with the water control.
文摘The essential oil was extracted from fresh leaf and defoliation of Bischofia polycarpa(Lévl.) Airy Shaw using steam distillation,and the chemical components and relative content of essential oil were analyzed by GC-MS and peak area normalization.The results show that the yields of crude extracts of essential oil from fresh leaf and defoliation are 0.114% and 0.105% respectively,and 114 and 15 peaks have been obtained respectively.Forty-seven compounds have been identified from the essential oil of fresh leaf,and the main compounds are camphor,2-hexenoic acid,heptacosane,dibutylphthalate,diethyladipate,2,6,10-trimethyl tetradecaneanddiisobutyladipatewith relativecontents of 10.416%,8.078%,7.627%,7.463%,5.171%,4.411% and 4.144%,respectively.Fourteen compounds have been identified from the essential oil of defoliation,and the main compounds are camphor,2-carboxymethyl-3-n-hexylmaleic acid anhydride and eucalyptol with relative contents of 33.070%,12.670% and 8.620%,respectively.The relative content of camphor in essential oil from fresh leaf and defoliation is the highest.
文摘【目的】探讨不同配方落叶剂对榕树冬季集中落叶的效应及对其生理变化的影响,为有效防治榕树叶部病虫害提供参考依据。【方法】以5年生榕树为试验材料,采用经正交试验筛选获得的5种由不同浓度乙烯利、碘化钾和尿素配成的落叶剂,对榕树进行叶面喷施处理(T1～T5),以喷施清水为对照(CK),统计分析各处理的落叶率、萌发率和病情指数,并测定若干生理指标。【结果】T1～T5处理榕树的落叶率均显著高于CK(P<0.05),叶片病情指数极显著低于CK(P<0.01),其中,喷药后第14 d T5处理的落叶率最高,为90.33%,其次为T4处理,为84.67%,T3处理的落叶率为72.67%。各落叶剂处理榕树叶片的叶绿素和可溶性蛋白含量呈先下降后上升的变化趋势,相对电导率和丙二醛(MDA)含量呈先上升后下降的变化趋势。落叶剂处理7 d后,榕树树体均恢复生长,其中T5处理对榕树树体的胁迫较小,对榕树后期发芽影响较小,萌发率达72.36%。【结论】以0.8%乙烯利+0.2%碘化钾+2.0%尿素配成的落叶剂对榕树的落叶效果最佳且生理胁迫小,对其后期叶片萌发影响小,是最佳的榕树落叶剂配方。
文摘【目的】脱叶率是评价机采棉脱叶催熟效果的重要依据。以无人机RGB图像为基础数据源,通过从RGB图像中提取14种可见光植被指数,建立快速、准确监测棉花脱叶率的模型,为机采棉适时采收提供理论和技术支持。【方法】设置不同棉花品种,通过采集不同脱叶剂浓度及喷施时间处理下的棉花脱叶率数据,并利用无人机采集冠层RGB图像,提取可见光植被指数,分析其与棉花脱叶率的相关关系,进而采用一元线性回归(Simple linear regression,SLR)、多元线性回归(Multivariate linear regression,MLR)和偏最小二乘法回归(Partial least square regression,PLSR)构建棉花脱叶率监测模型,并进行模型评价。【结果】不同处理下的棉花脱叶率有明显差异,脱叶率与不同可见光植被指数存在较好相关性,其中三角形绿度值(Triangular greenness index,TGI)与棉花脱叶率的相关性最高(r=0.81)。建模结果表明,SLR模型中,以TGI指数建模效果最好(决定系数0.66,均方根误差10.44%,相对均方根误差12.87%);MLR模型中,以过蓝指数(Excess blue index,ExB)、绿叶指数(Green leaf index,GLI)、TGI和过绿指数(Excess green index,ExG)4个植被指数组合建立的模型效果最好,其决定系数为0.70,均方根误差为10.26%,相对均方根误差为12.65%。PLSR模型中,以ExB、GLI、TGI、ExG、综合植被指数2和综合植被指数1建立的模型精度更高,其决定系数为0.70,均方根误差为10.02%,相对均方根误差为12.22%。外部验证表明,各模型实测值与预测值间有较好的拟合关系。【结论】以MLR和PLSR方法建立的模型精度较高,拟合程度较好。从计算量及模型复杂程度角度考虑,通过MLR方法以ExB、GLI、TGI、ExG建立的棉花脱叶率监测模型,能够更好地监测棉花脱叶率。
