Catchweed Bedstraw (Galium aparine) is a dicot weed in the Rubiaceae family. In Iran this weed first evolved resistance to Group O/4 herbicides in 2016 and infests Wheat. Group O/4 herbicides are known as Synthetic Auxins (Synthetic auxins (action like indoleacetic acid)). Research has shown that these particular biotypes are resistant to 2,4-D, and MCPA and they may be cross-resistant to other Group O/4 herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

Greenhouse trials comparing a known susceptible Catchweed Bedstraw biotype with this Catchweed Bedstraw biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on Group O/4 resistant Catchweed Bedstraw have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group O/4 resistant Catchweed Bedstraw from Iran please update the database.

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Iran have been instrumental in providing you this information. Particular thanks is given to Bhagirath Chauhan, Iraj Nosratti, Peyman Sabeti, and Farhad Sharifi for providing detailed information.

The herbicides are very effective tools for controlling weeds but their extensive use over time has resulted in evaluation of weed resistance to herbicides with different modes of action. ACCase and ALS inhibiting herbicides have been used extensively in winter wheat and rice fields to control grass and broadleaved weeds since last two decades in Turkey. Recently, many growers in various area of Turkey complained for reduced control ofBifora radiansandGalium aparinein winter cereals, andEchinochloa spp., andCyperus difformisin water seeding rice after use of ALS and ACCase inhibitor herbicides. Therefore, the aim of this study are to understand the occurrence and frequency of resistant biotypes of these species to ACCase and ALS inhibiting herbicides; does the mechanism of resistance are target site (TSR) or non-target site resistance (NTSR), risk assessment of herbicides history in evaluation of resistance and how crop rotation reduce selection for resistance? Forty-three rice fields were sampled randomly in 2005 to confirm the existence of cross and multiple herbicide resistance ofE. oryzoides,E. crus-galliandC. difformisinvolving ALS (penoxsulam, bispyribac-sodium) and ACCase Inhibitor (cyhalofob-butyl). The same and more fields re-sampled in 2011. In addition to that, greenhouse experiments were conducted from 1995 to 2011 to monitor possible resistance populations of B. radians andG. aparineto ALS inhibitor (chlorsulfuron and tribenuron-methyl) sampled from 13 winter wheat fields. A log-logistic dose-response curve was fitted to greenhouse data ofE. oryzoidesto obtain ED90. On the basis of those data, resistance to ALS inhibitors was detected in 2 accessions in 2005. On the other hand, allE. oryzoidesaccessions were susceptible to ACCase Inhibitor in the same year. The effective dose response level of ED90resulted in 36 and 9 resistant accessions to ALS and ACCase, respectively after re-sampling from same fields in 2011. Most of E. crus-galli accessions were effectively controlled with penoxsulam and cyhalofob-butyl in 2005. But, 4 accessions did not controlled with bispyribac-sodium and these accessions were characterized as resistant. The number of resistant accession significantly increased in 2011 and reached almost 75% in both inhibitors. Of the 43 C. difformis populations tested, 11 survived after treatments of penoxsulam and bispyribac-sodium in 2005. But, the application of four times recommended rate of these herbicides resulted only 3-5% fresh weight reduction of 40 C. difformis populations in 2011. The remaining 3 population with no evidence of penoxsulam and bispyribac-sodium resistance were controlled with almost double dose of these herbicides. A significant proportion of the populations in all species were found to be non-target site resistant..

Catchweed bedstraw causes severe problems in winter wheat and other winter sown crops. Field experiments were conducted from 2005 to 2008 in wheat fields in Samsun, Turkey, to determine: (1) the response of catchweed bedstraw to chlorsulfuron, tribenuron-methyl plus thifensulfuronmethyl, dicamba plus triasulfuron and mesosulfuron-methyl plus iodosulfuron-methyl-sodium; and (2) possible resistance or tolerance to these herbicides. The herbicides were applied at the 2-4, 4-6, and 6-8 true leaf stages of biomass, there were large differences among the upper limits of the dose-response curves, and consequently, the actual response curve, an asymmetric sigmoid curve, was fitted to data to obtain 50% and 90% effective dose, ED50 and ED90, values. None of the herbicides reduced catchweed bedstraw biomass or populations satisfactorily when applied at the recommended field rate. Twice the recommended field rate was required to achieve acceptable reduction in biomass. Overall, inadequate control of this weed cannot be solely attributed to either acetolactate synthase (ALS) resistance or improper application methods. It is likely due to a slow and progressive development of ALS-tolerant populations after many years of consecutive use..

In recent years, Galium aparine L. has not been controlled by tribenuron-methyl in major Chinese winter wheat fields. The objective of this study is to understand the molecular basis of the resistance mechanism to tribenuron-methyl in G. aparine and to find the specific mutation sites in amino acid sequence of acetolactate synthase (ALS) in the resistant biotype of G. aparine. Fragments that encode the ALS were amplified and cloned from susceptible (S) and resistant (R) biotypes of G. aparine to tribenuron-methyl and sequenced subsequently. The result showed that the nucleotide sequence of R-biotype of G. aparine differed from that of the S biotype with three amino acid substitutions, of which, the amino acid substitution of Trp574 (TGG) to Gly (GGG) is located in the highly conserved region Domain B. The substitution of Trp574 might be responsible for the resistance to tribenuron-methyl in the R-biotype of G. aparine..

Objective: In recent years, Galium aparine L. in most winter wheat fields in China could not be controlled by tribenuron-methyl. The objective of this study is to understand the molecular basis of the resistance mechanism to tribenuron-methyl in G. aparine and to find the specific mutation sites in amino acid sequence of acetolactate synthase (ALS) in the resistant biotype of G. aparine. Method: Fragments encoding the ALS were amplified and cloned from G. aparine, susceptible (S) and resistant (R) biotypes to tribenuron-methyl, respectively, and sequenced subsequently. Result: The result showed that the nucleotide sequence of R-biotype of G. aparine differed from that of the S biotype with three amino acid substitutions, of which, the amino acid substitution of Trp574 (TGG) to Gly (GGG) located in the highly conserved region Domain B. Conclusion: The substitution of Trp574 might be responsible for the resistance to tribenuron-methyl in the R-biotype of G. aparine..

To evaluate the resistance of G. aparine to tribenuron-methyl [tribenuron], 14 potential resistant biotypes were collected from winter wheat fields of 14 counties or cities in Shandong, Shanxi, Henan, Hebei, Jiangsu, Shaanxi, and Anhui Provinces of China, and 14 susceptible biotypes were correspondingly collected from the nearby non-farming lands never applied with herbicides. Greenhouse pot tests and quick-test in Petri dish were conducted to detect the resistance level. The results of greenhouse pot tests showed that except for the potential resistant biotypes from the collecting sites of Shijiazhuang, Hebei, Taiyuan, Shanxi, Zhouzhi, Shaanxi and Tai'an, Shandong, all the other potential resistant biotypes had evolved resistance to tribenuron-methyl, with a resistance factor ranging from 1.6 (Xuchang, Henan) to 4.3 (Taihe, Anhui, and Huaxian, Shaanxi). The resistance in Xuchang was relatively higher than those in Taihe and Huaxian, with resistance factor of 2.2, 1.9 and 1.7, respectively. In general, the results of the quick-test in Petri-dish were in accordance with those of the greenhouse pot tests..