Browsing by Subject "Herbicide resistance detection"

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From greenhouse to field practice : herbicide resistance detection using chlorophyll-fluorescence-imaging technology
(2017) Wang, Pei; Gerhards, Roland
All over the world, herbicide resistance has developed to one of the most important barriers in weed control, making the implementation of the weed control strategy more complicated. There is an intense need for a rapid, cheap and reliable method to conduct in field detection of herbicide resistant weed populations. In the current thesis with the use of chlorophyll fluorescence imaging technology, such a method is implemented and tested in field conditions. A series of experiments were designed and carried out. The data gathered from these experiments were compiled under three paper articles. Paper 1. A greenhouse experiment was conducted to verify if the parameter, Maximal Photosystem II Quantum Yield (Fv/Fm), could possibly indicate the herbicide efficacy. The chlorophyll-fluorescence-imaging sensor, Weed PAM®, was selected for the measurements. In the first part it was investigated if the Fv/Fm value could differentiate between herbicide sensitive and resistant plants. In the second part two important abiotic stress factors were tested if they affected the Fv/Fm value. I) Six herbicides were tested on herbicide sensitive and resistant Alopecurus myosuroides populations; II) Water shortage and nitrogen deficiency were applied on a herbicide sensitive population to observe their influence on the plants. The sensitive plants presented significantly lower Fv/Fm values than the resistant plants 3 days after treatment (DAT) for the ALS and ACCase inhibitors. On the same day, and for the same treatments the Fv/Fm values of the resistant plants were not affected and similar to the control. Appling a PS II inhibitor reduced the Fv/Fm values of both sensitive and resistant plants rapidly. Yet, sensitive and resistant plants could clearly be separated on 4 DAT based on the different Fv/Fm values. On the other hand, nitrogen deficiency did not influence the photosystem II measurements. Water shortage reduced rapidly the Fv/Fm value of the plants seven days after the application, yet at this point plant symptoms included the death of the plants. According to this experiment, the Weed PAM® sensor has proved its capability to identify the sensitive and resistant A. myosuroides populations shortly after the herbicide application. Paper 2. A verification of the above results was made under field conditions for different A. myosuroides populations and different locations. On the first part 50 populations in total including both sensitive and herbicide resistant populations were tested. The second part field experiments were conducted in ten locations around Germany over two years with the local field population mix. It was investigated if the Weed PAM® sensor could separate between herbicide sensitive and resistant A. myosuroides populations 5 DAT. The different populations were sown in a winter wheat field. Two ACCase- and three ALS- inhibitors were applied. In all herbicide treatments, Fv/Fm values of A. myosuroides were significantly lower than the untreated plants at the 5 DAT. For each location, measurements were conducted at 5 DAT. A visual measurement, to verify the result, was carried out at 21 DAT. In both cases, 95% of the plants were correctly identified as sensitive or resistant. This demonstrated the ability of the Weed PAM® sensor to conduct in field real time detection of herbicide resistant A. myosuroides populations shortly after treatment. Paper 3. Greenhouse and field experiments were carried out to investigate if the chlorophyll fluorescence of soybean plants was altered, under herbicide stress. Herbicide combinations including inhibitors of PS II, DOXP synthase, cell division and microtubule assembly were selected for different pre-emergence treatments. Herbicide combinations including inhibitors of PS II, ALS and ACCase were applied in post-emergence treatments. Chlorophyll fluorescence was measured from the emergence of soybeans until the three/four-leaf stage. Furthermore the stress effect of the different treatments on the soybean plants was determined by measuring their dry biomass. In the greenhouse, post-emergence treatments with ALS and ACCase inhibitors did not seem to induce stress on the soybean plants. As expected, it originally demonstrated low Fv/Fm values when stressed by PS II inhibitors. But the PS II system recovered soon, one week after emergence. Stress induced by other pre-emergence herbicides occurred one week after emergence and lasted longer than the stress induced by the PS II inhibitors. Dry biomass collaborated with the sensor result. Based on the current thesis, the Weed PAM® system can be an important tool in the identification of herbicide resistant weed populations, in a timely manner. It has proven its capabilities both in A. myosuroides as a weed and in soybean plants. This technology will help farmers to take more suitable weed control strategies, as well as less economic and environmental risks.