Okumu, Martha NelimaRobbertse, P.J. (Petrus Johannes), 1932-Vorster, Barend JuanReinhardt, Carl Frederick (Charlie)2022-12-122022-12-122022-10-24Okumu, M.N.; Robbertse, P.J.; Vorster, B.J.; Reinhardt, C.F. The Molecular, Morphological and Genetic Characterization of Glyphosate Resistance in Conyza bonariensis from South Africa. Plants 2022, 11, 2830. https://doi.org/10.3390/plants11212830.2223-7747 (online)10.3390/plants11212830https://repository.up.ac.za/handle/2263/88737SUPPLEMENTARY MATERIAL : FIGURE S1. Transmission electron micrographs of outer epidermis cell wall of C. bonariensis showing cuticular membrane. FIGURE S2. Transmission electron micrographs of outer epidermis cell wall of C. bonariensis showing cuticular undulations. FIGURE S3. Scanning electron micrographs of C. bonariensis trichomes on leaf surface (A and B) and on cross section of leaf (C) showing trichomes on both adaxial and abaxial sides. FIGURE S4. Light microscope images of C. bonariensis leaf surface showing numerous trichomes on the adaxial (‘A’) and fewer trichomes on the abaxial (‘B’) leaf surfaces. Figure S5. Melting curves for the EPSPS and Actin genes of C. bonariensis. TABLE S1. qRT-PCR primer sets used in the study.Six Conyza bonariensis (L.) Cronquist populations were screened in a pot experiment at the University of Pretoria’s Hatfield experimental farm to evaluate and confirm the degree of glyphosate response. Resistance factors ranged from 2.7- to 24.8-fold compared to the most susceptible biotype. Partial sequencing of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene found no mutation at the Thr102, Ala103 or Pro106 positions. EPSPS mRNA expression levels in glyphosate-resistant biotypes (Swellendam and Piketberg seed sampling sites) were comparable or lower than those in susceptible biotypes (George and Fauresmith sites). Additionally, the highest expression level was reported in the susceptible Fauresmith biotype. These results indicate that glyphosate resistance in the tested resistant biotypes is not caused by target-site mutations and EPSPS gene amplification. Leaf surface characteristics can influence the spread and subsequent absorption of glyphosate. The study established non-significant results in the amount of leaf wax and insufficient mean separations in cuticle thickness and trichome density data. Therefore, the observed differences in response of biotypes to glyphosate treatment could not be attributed conclusively to differences in the leaf morphological characteristics investigated. Results from the inheritance study were consistent with glyphosate resistance being inherited in an incompletely dominant manner when plants were treated with glyphosate herbicide at 900 g ae ha−1 .en© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).Herbicide resistanceDose–responseLeaf morphologyEPSP synthaseHeredity of resistanceConyza bonariensis5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)Article