Yazar "Zandstra, Bernard H." seçeneğine göre listele

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    Investigating glyphosate resistance in Amaranthus palmeri biotypes from Turkey
    (Springer, 2021) Mennan, Husrev; Kaya-Altop, Emine; Belvaux, Xavier; Brants, Ivo; Zandstra, Bernard H.; Jabran, Khawar; Uysal, Meral Sahin
    Amaranthus palmeri is a troublesome weed which is growing in importance worldwide. It causes serious competition in many crops. A. palmeri was introduced into Turkey 4-5 years ago and appears to adapt to different environmental conditions. Monoculture cropping systems and repeated use of the same herbicides have led to development of herbicide resistance in A. palmeri to several active ingredients including glyphosate, in USA and in South America. This study was conducted to investigate the evolution of glyphosate resistance in A. palmeri in Turkey. Seeds of 21 A. palmeri populations were collected in Turkish citrus fields where control problems with glyphosate were reported. A potentially glyphosate susceptible A. palmeri population was collected from a maize field (GS1 biotype). Seeds of putatively resistant and potentially susceptible (GS) biotypes were germinated and transplanted into large pots, and then allowed to grow in separate greenhouse chambers to obtain F2 generations. After carrying out a preliminary test experiment to exclude the most susceptible populations, a dose-response experiment was conducted in which glyphosate was applied at the 3-4 true leaf stage at 0, 332.5, 665, 1330, 2660, 5320, 10,640 and 21,280 g a.i. ha(-1). Plants were harvested 21 days after treatment and dry weight was determined. Glyphosate applied at the recommended rate (1330 g a.i ha(-1)) controlled GS A. palmeri biotypes by more than 95% while controlling the GR biotypes at about 45%. Among those biotypes, GR1 and GR2 biotypes were confirmed to have an incipient resistance to glyphosate. The effect of glyphosate on shikimic acid accumulation was determined. Results showed that the GS2 biotype accumulated 3.1 and 1.56 times more shikimic acid than GR2 and GR1 biotypes which demonstrates that there is a lower accumulation of shikimic acid in the alleged resistant biotypes than in GS1. These findings demonstrate some increased tolerance of A. palmeri biotypes to glyphosate, which reinforces the need to implement integrated weed management to control this invasive plant in Turkey.
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    Non-Chemical Weed Management in Vegetables by Using Cover Crops: A Review
    (Mdpi, 2020) Mennan, Husrev; Jabran, Khawar; Zandstra, Bernard H.; Pala, Firat
    Vegetables are a substantial part of our lives and possess great commercial and nutritional value. Weeds not only decrease vegetable yield but also reduce their quality. Non-chemical weed control is important both for the organic production of vegetables and achieving ecologically sustainable weed management. Estimates have shown that the yield of vegetables may be decreased by 45%-95% in the case of weed-vegetable competition. Non-chemical weed control in vegetables is desired for several reasons. For example, there are greater chances of contamination of vegetables by herbicide residue compared to cereals or pulse crops. Non-chemical weed control in vegetables is also needed due to environmental pollution, the evolution of herbicide resistance in weeds and a strong desire for organic vegetable cultivation. Although there are several ways to control weeds without the use of herbicides, cover crops are an attractive choice because these have a number of additional benefits (such as soil and water conservation) along with the provision of satisfactory and sustainable weed control. Several cover crops are available that may provide excellent weed control in vegetable production systems. Cover crops such as rye, vetch, or Brassicaceae plants can suppress weeds in rotations, including vegetables crops such as tomato, cabbage, or pumpkin. Growers should also consider the negative effects of using cover crops for weed control, such as the negative allelopathic effects of some cover crop residues on the main vegetable crop.