The gene sequence encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzymatic target site of the herbicide glyphosate, was determined for several purple nutsedge (Cyperus rotundus L.) accessions from g...The gene sequence encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzymatic target site of the herbicide glyphosate, was determined for several purple nutsedge (Cyperus rotundus L.) accessions from geographically distant locations and these were aligned to generate a consensus sequence. The EPSPS sequences each had single nucleotide polymorphisms (SNPs) only a few of which were predicted to cause an amino acid change in the EPSP synthase. None had the proline to serine substitution or other substitutions responsible for glyphosate resistance reported in other species. A dendrogram generated from the cluster analysis of the EPSPS gene sequences indicated similarities between accessions from Tanzania, Indonesia, California-2, Greece, Brazil, Argentina and Iran much like cluster analysis previously reported based on RAPD scores and morphological traits possibly indicating a common genetic background or origin. Considering the differences in EPSPS sequences, the response of these purple nutsedge accessions to 0.84 kg·ae·ha-1 of glyphosate was assessed to determine whether differential tolerance was present. At 7 days after the first application control ranged from 9% for the accession from Greece to 73% for the accession from Tanzania. Control of these accessions increased to 45% and 93% respectively by 14 days after the second application. The I50’s for glyphosate inhibition of growth for four accessions from geographically distant countries (Mississippi, Brazil, Indonesia and Tanzania) were 0.21, 0.10, 0.25 and 0.06 kg·ha-1, respectively, which represented a 4-fold difference. The difference in sensitivity to glyphosate may be a result of a non-target site mechanism such as differences in sequestration, translocation or cuticle thickness rather than alterations in EPSPS.展开更多
The diversity of globally distributed populations of purple nutsedge was assessed using molecular marker data and morphological traits. Cluster analysis of binary random amplified polymorphic DNA (RAPD) data and morph...The diversity of globally distributed populations of purple nutsedge was assessed using molecular marker data and morphological traits. Cluster analysis of binary random amplified polymorphic DNA (RAPD) data and morphological traits indicated that the global population of purple nutsedge consisted of two clades. Cluster analysis of the RAPD data supported separation of the purple nutsedge accessions evaluated into two distinct clades of 11 and 33 accessions. Except for accessions identified as California* and Arizona, all USA accessions were clustered with accessions from Taiwan, Western Samoa, New Zealand, Malaysia, Japan, El Salvador, Columbia, Australia, Thailand and West Indies. A second cluster included accessions from Sudan, Greece, Iran, California*, Arizona, Brazil, Argentina, Mauritius, Philippines, Indonesia and Tanzania. The accessions from Sudan, Greece, Iran, Mauritius, and Tanzania were distributed along a similar longitudinal axis. Cluster analysis based on morphological traits though not identical to that based on RAPD data also supported separation into two clades and perhaps a third. The lack of genetic diversity among accessions supported the hypothesis that spread and propagation into new environments were largely by tubers which preserved genetic identity. The lack of diversity particularly among New World and USA accessions may also reflect a relatively recent introduction of the species into the Americas and a low level of outcrossing.展开更多
文摘The gene sequence encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzymatic target site of the herbicide glyphosate, was determined for several purple nutsedge (Cyperus rotundus L.) accessions from geographically distant locations and these were aligned to generate a consensus sequence. The EPSPS sequences each had single nucleotide polymorphisms (SNPs) only a few of which were predicted to cause an amino acid change in the EPSP synthase. None had the proline to serine substitution or other substitutions responsible for glyphosate resistance reported in other species. A dendrogram generated from the cluster analysis of the EPSPS gene sequences indicated similarities between accessions from Tanzania, Indonesia, California-2, Greece, Brazil, Argentina and Iran much like cluster analysis previously reported based on RAPD scores and morphological traits possibly indicating a common genetic background or origin. Considering the differences in EPSPS sequences, the response of these purple nutsedge accessions to 0.84 kg·ae·ha-1 of glyphosate was assessed to determine whether differential tolerance was present. At 7 days after the first application control ranged from 9% for the accession from Greece to 73% for the accession from Tanzania. Control of these accessions increased to 45% and 93% respectively by 14 days after the second application. The I50’s for glyphosate inhibition of growth for four accessions from geographically distant countries (Mississippi, Brazil, Indonesia and Tanzania) were 0.21, 0.10, 0.25 and 0.06 kg·ha-1, respectively, which represented a 4-fold difference. The difference in sensitivity to glyphosate may be a result of a non-target site mechanism such as differences in sequestration, translocation or cuticle thickness rather than alterations in EPSPS.
文摘The diversity of globally distributed populations of purple nutsedge was assessed using molecular marker data and morphological traits. Cluster analysis of binary random amplified polymorphic DNA (RAPD) data and morphological traits indicated that the global population of purple nutsedge consisted of two clades. Cluster analysis of the RAPD data supported separation of the purple nutsedge accessions evaluated into two distinct clades of 11 and 33 accessions. Except for accessions identified as California* and Arizona, all USA accessions were clustered with accessions from Taiwan, Western Samoa, New Zealand, Malaysia, Japan, El Salvador, Columbia, Australia, Thailand and West Indies. A second cluster included accessions from Sudan, Greece, Iran, California*, Arizona, Brazil, Argentina, Mauritius, Philippines, Indonesia and Tanzania. The accessions from Sudan, Greece, Iran, Mauritius, and Tanzania were distributed along a similar longitudinal axis. Cluster analysis based on morphological traits though not identical to that based on RAPD data also supported separation into two clades and perhaps a third. The lack of genetic diversity among accessions supported the hypothesis that spread and propagation into new environments were largely by tubers which preserved genetic identity. The lack of diversity particularly among New World and USA accessions may also reflect a relatively recent introduction of the species into the Americas and a low level of outcrossing.
