Crosstalk between cytokinin and ethylene signaling pathways regulates leaf abscission in cotton in response to chemical defoliants.

Abscission is a process that allows plants to shed tissues or organs via cell separation, and occurs throughout the life cycle. Removal of leaves through the use of chemical defoliants is very important for mechanical harvesting of cotton (Gossypium hirsutum). However, our knowledge of the molecular mechanisms of the defoliation response involved is limited. In this study, RNA-seq was conducted in order to profile the differentially expressed genes (DEGs) between cultivars X50 (sensitive to chemical defoliants) and X33 (relatively insensitive) at different time points after treatment with thidiazuron and ethephon (TE). A total of 2434 DEGs were identified between the two cultivars across the different time-points. Functional categories according to GO and KEGG analyses revealed that plant hormone signal transduction and zeatin biosynthesis were involved in the response to TE. Cytokinin oxidase/dehydrogenase (CKX) genes and ethylene-related genes were up-regulated following TE treatment, and were associated with increased level of ethylene, especially in cultivar X50. Down-regulation of GhCKX3 resulted in delayed defoliation and a reduced ethylene response. The results show that crosstalk between cytokinin and ethylene regulates cotton defoliation, and provide new insights into the molecular mechanisms underlying the mode of action of defoliants in cotton.

Dose and time dependent efficacy alteration of different defoliants on seed cotton yield.

Field experiments were conducted during 2012 and 2013 to determine the effect of select defoliants i.e dropp ultra and ethrel, their optimal dose and suitable time of application on earliness and seed cotton yield in 3 American cotton cultivars. MRC7361BGII (3055.2 kg ha(-1)) and MRC7017BGII (2913.0 kg ha(-1)) resulted in significantly improved seed cotton yield as compared to F1 861 (2346.0 kg ha(-1)). Dropp ultra? @ 200 ml ha(-1) revealed highest yield (3018.7 kg ha(-1)) followed by ethrel @ 2000 ppm (2820.1 kg ha(-1)) and control (2730.0 kg ha(-1)) , while statistically least yield (2516.9 kg ha(-1)) was observed with higher dose of dropp ultra @ 225 ml ha(-1). Defoliants applied 150 days after sowing (DAS) resulted in significantly better yield (2853.3 kg ha(-1)) as compared to the early application at 140 DAS (2689.5 kg ha(-1) owing to improvement in open bolls and boll weight. Pooled data indicated that dropp ultra @ 200 ml ha(-1) has potential to promote crop earliness, better boll opening and their retention by keeping vegetative and reproductive growth in harmony to enhance seed cotton yield.

Spray droplet size, drift potential, and risks to nontarget organisms from aerially applied glyphosate for coca control in Colombia.

A wind tunnel atomization study was conducted to measure the emission droplet size spectra for water and Glyphos (a glyphosate formulation sold in Colombia) + Cosmo-flux sprays for aerial application to control coca and poppy crops in Colombia. The droplet size spectra were measured in a wind tunnel for an Accu-Flo nozzle (with 16 size 0.085 [2.16 mm] orifices), under appropriate simulated aircraft speeds (up to 333 km/h), using a laser diffraction instrument covering a dynamic size range for droplets of 0.5 to 3,500 microm. The spray drift potential of the glyphosate was modeled using the AGDISP spray application and drift model, using input parameters representative of those occurring in Colombia for typical aerial application operations. The droplet size spectra for tank mixes containing glyphosate and Cosmo-Flux were considerably finer than water and became finer with higher aircraft speeds. The tank mix with 44% glyphosate had a D(v0.5) of 128 microm, while the value at the 4.9% glyphosate rate was 140 microm. These are classified as very fine to fine sprays. Despite being relatively fine, modeling showed that the droplets would not evaporate as rapidly as most similarly sized agricultural sprays because the nonvolatile proportion of the tank mix (active and inert adjuvant ingredients) was large. Thus, longer range drift is small and most drift that does occur will deposit relatively close to the application area. Drift will only occur downwind and, with winds of velocity less than the modeled maximum of 9 km/h, the drift distance would be substantially reduced. Spray drift potential might be additionally reduced through various practices such as the selection of nozzles, tank mix adjuvants, aircraft speeds, and spray pressures that would produce coarser sprays. Species sensitivity distributions to glyphosate were constructed for plants and amphibians. Based on modeled drift and 5th centile concentrations, appropriate no-spray buffer zones (distance from the end of the spray boom as recorded electronically +/-5%) for protection of sensitive plants were 50-120 m for coca spray scenarios and considerably lower for poppy spray scenarios. The equivalent buffer zone for amphibia was 5 m. The low toxicity of glyphosate to humans suggests that these aerial applications are not a concern for human health.

Vaginally applied diquat intoxication.

CASE REPORT: We report the case of a woman who introduced 20 mL of diquat concentrate intravaginally. Abdominal pain, vomiting, diarrhea, burning chest pains, and somnolence appeared within the first 24 hours. The vulva and vagina were corrosively inflamed. Acute renal failure appeared on the third day and was treated by 6 hemodialyses over 6 days. The patient was dysarthric with spastic tetraparesis for 3 months. The electroencephalogram, diffusely slow on day 3, was normal on day 28. The electromyoneurogram was normal at all times. Biopsy of a peripheral nerve performed on day 57 following intoxication showed no myelin or axonal alterations.