chlorophyll-a and metamitron

Sugar beet growers in Europe are more often confronted with an unsatisfactory control of Chenopodium album L. (fat-hen), possibly due to the presence of a triazinone resistant biotype. So far, two mutations on the psbA-gene, i.e. Ser264-Gly and Ala251-Val, are known to cause resistance in C. album to the photosystem II-inhibiting triazinones metamitron, a key herbicide in sugar beet, and metribuzin. The Ser264-Gly biotype, cross-resistant to many other photosystem II-inhibitors like the triazines atrazine and terbuthylazine, is most common. The second resistant C. album biotype, recorded in Sweden, is highly resistant to triazinones but only slightly cross-resistant to terbuthylazine. Since farmers should adapt their weed control strategy when a resistant biotype is present, a quick and cheap detection method is needed. Therefore, through trial and error, a protocol for detection with chlorophyll fluorescence measurements was developed and put to the test. First, C. album leaves were incubated in herbicide solution (i.e. 0 microM, 25 microM metribuzin, 200 microM metamitron or 25 microM terbuthylazine) during three hours under natural light. After 30 minutes of dark adaptation, photosynthesis yield was measured with Pocket PEA (Hansatech Instruments). In Leaves from sensitive C. album, herbicide treatment reduces photosynthesis yield due to inhibition of photosynthesis at photosystem II. This results in a difference of photosynthesis yield between the untreated control and herbicide treatment. Based on the relative photosynthesis yield (as a percentage of untreated), a classification rule was formulated: C. album is classified as sensitive when its relative photosynthesis yield is less than 90%, otherwise it is resistant. While metribuzin, and to a lesser extent, metamitron treatment allowed a quick detection of triazinone resistant C. album, terbuthylazine treatment was able to distinguish the Ser264-Gly from the Ala251-Val biotype. As a final test, 265 plants were classified with the protocol. Simultaneously, a CLeaved Amplified Polymorphic Sequence (CAPS)-analysis was conducted on the same plants to verify the presence of the Ser264-Gly mutation. Only one mismatch was found when results of both detection methods were compared. The test results illustrate that this protocol provides a reliable, quick and cheap alternative for DNA-analysis and bio-assays to detect the triazinone resistant C. album biotypes.

Topics: Beta vulgaris; Chenopodium album; Chlorophyll; Fluorescence; Herbicide Resistance; Herbicides; Mutation; Photosynthesis; Photosystem II Protein Complex; Triazines; Weed Control

Recently, fat-hen (Chenopodium album L.) biotypes resistant to metamitron, a key herbicide in sugar beet, were recorded. Pot experiments revealed that these biotypes showed cross-resistance to metribuzin, a triazinone used in potato. Greenhouse and laboratory experiments were performed to develop resistance monitoring tests, so that resistant biotypes can be detected quickly and farmers may adapt their weed management. Resistant and susceptible biotypes were grown in a greenhouse under conditions of natural and artificial light at an intensity of 100 micromol photons m(-2) s(-1). Leaves were collected and, immersed in a solution of 1000 microM metamitron and 500 microM metribuzin, exposed to natural and artificial light (1000, 750 and 100 micromol photons m(-2) s(-1) respectively). After this, chlorophyll fluorescence measurements were carried out. The results revealed that the photosynthetic electron transport of metamitron- and metribuzin-incubated leaves of resistant biotypes decreased less than that of the incubated Leaves of susceptible biotypes. The differences between the metribuzin-incubated leaves of the susceptible and resistant biotypes were larger than those observed with the metamitron-incubated leaves. The aim of the experiments was to optimise the chlorophyll fluorescence test and to find a sufficiently high correlation between the results of the pot experiments and the chlorophyll fluorescence measurements.

Topics: Chenopodium album; Chlorophyll; Fluorescence; Herbicide Resistance; Herbicides; Pest Control; Triazines

This paper presents a quick chlorophyll fluorescence method for the estimation of the influence of some adjuvants applied with Azoprim 50WP (a.s. atrazine) or Buramet 70WG (a.s. metamitron) on oat plants. These herbicides inhibit photosynthetic electron transport in photosystem II, which was measured by means of a pulse PAM-210 chlorophyll fluorometer. Results of the ETR measurements show differences between the efficacies of the studied adjuvants. Olemix 84EC, Atpolan 80EC, Adpros 85 SL and Break-Thru S-240 were the most effective in the mixture with Azoprim, and the last two--also in the mixture with Buramet. Olejan 85 EC did not change the biological action of Azoprim nor Buramet. Moreover, the most effective adjuvants showed relatively good stability.

Topics: Adjuvants, Pharmaceutic; Atrazine; Avena; Chlorophyll; Fluorescence; Fluorometry; Herbicides; Photosynthesis; Photosystem II Protein Complex; Triazines