Quantifying Potential Tolerance of Selected Cotton Cultivars to Belonolaimus longicaudatus

Glyphosate-tolerant cotton cultivars were evaluated for tolerance to Belonolaimus longicaudatus in field experiments conducted from 2004 to 2005. Field trials were arranged in a split-plot design that included treatment with four levels of 1, 3-dichloropropene (0.0, 13.9, 27.8, and 41.7 1 a.i./ha) to establish a range of population densities of B. longicaudatus. Six cotton cultivars (early-to-mid maturity: DP444BG/RR SG501BR, ST5242BR; mid-to late maturity: DP451B/RR, ST5599BR, DP655BRR) were planted as whole plots. Fumigation was effective in suppressing B. longicaudatus population densities at mid-season, but not at cotton harvest, and increased cotton lint yield. The cultivar × fumigation interaction for cotton lint yield was not significant for the six cultivars evaluated, indicating that tolerance did not occur in this nematode-host combination. Early-to-mid maturity cultivars yielded significantly more than mid-to-late maturity cultivars in both years. Small but significant differences in nematode final population density were observed between cultivars that may be related to relative maturity.     

Differential sensitivity of bacterial 5-enolpyruvylshikimate-3-phosphate synthases to the herbicide glyphosate

Abstract The potent inhibition of the shikimate pathway enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase by the broad-spectrum herbicide glyphosate ( N -[phosphonomethyl]glycine) was confirmed for the enzymes extracted from various bacteria, a green alga and higher plants. However, 5 out of 6 species belonging to the genus Pseudomonas were found to have EPSP synthases with a 50- to 100-fold decreased sensitivity to the inhibitor. Correspondingly, growth of these 5 species was not inhibited by 5 mM glyphosate, and the organisms did not excrete shikimate-3-phosphate in the presence of the herbicide.     

Tolerance to Hololaimus columbus in Glyphosate-Resistant,Transgenic Soybean Cultivars

Transgenic soybean cultivars, resistant to glyphosate herbicide in maturity groups V and VI, were evaluated for tolerance to the Columbia lance nematode, Hoplolaimus columbus, in field experiments conducted in 1998 and 1999. Treatment with 43 liter/ha of 1,3-dichloropropene was effective in suppressing H. columbus population densities in a split-plot design. Fumigation increased soybean yield, but a significant cultivar × fumigation interaction indicated variation in cultivar response to H. columbus. A tolerance index (yield of nontreated ÷ yield of treated × 100) was used to compare cultivar differences. Two cultivars in maturity group VI and one cultivar in maturity group V had a tolerance index greater than 90, indicating a high level of tolerance.     

The oxidative damage and inflammation caused by pesticides are reverted by lipoic acid in rat brain

We have previously demonstrated that the administration of low doses of dimethoate, glyphosate and zineb to rats (i.p. 1/250 LD50, three times a week for 5 weeks) provokes severe oxidative stress (OS) in specific brain regions: substantia nigra, cortex and hippocampus. These effects were also observed in plasma. Lipoic acid (LA) is considered an “ideal antioxidant” due to its ability to scavenge reactive species, reset antioxidant levels and cross the blood–brain barrier. To investigate its protective effect we administered LA (i.p. 25, 50 and 100 mg/kg) simultaneously with the pesticide mixture (PM) for 5 weeks. After suppression of PM administration, we evaluated the restorative effect of LA for a further 5 weeks. LA prevented OS and the production of nitrites + nitrates [NOx] caused by PM in a dose-dependent manner. The PM-induced decrease in reduced glutathione and α-tocopherol levels in all brain regions was completely restored by LA at both high doses. PM administration also caused an increase in prostaglandins E₂ and F_2α in brain that was reduced by LA in a dose-dependent fashion. Taking into account the relationship between OS, inflammation and apoptosis, we measured caspase and calpain activity. Only milli- and micro-calpain isoforms were increased in the PM-treated group and LA reduced the activities to basal levels. We also demonstrated that interrupting PM administration is not enough to restore the levels of all the parameters measured and that LA is necessary to achieve basal status. In our experimental model LA displayed a protective role against pesticide-induced damage, suggesting that LA administration is a promising therapeutic strategy to cope with disorders suspected to be caused by OS generators, especially in brain.     

Effects of Herbicide on the Invasive Biennial Alliaria petiolata (Garlic Mustard) and Initial Responses of Native Plants in a Southwestern Ohio Forest

Restoration often includes control of invasive plants, but little is known about how native plant communities respond to this control. The biennial Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard) is one of the most prevalent invasive plants in forests of eastern North America. We investigated the effects of the herbicide Round‐up (glyphosate) on Alliaria and the response of the forest floor plant community to the herbicide and the subsequent decline of Alliaria. In an old‐growth Acer–Fagus stand and a second‐growth Liriodendron‐dominated stand in Hueston Woods State Nature Preserve, Ohio, United States, we spot applied Round‐up in November 2000 and 2001 in 25 1 × 1–m plots and maintained 25 control plots. Herbicide decreased Alliaria density in both stands and reduced the density of other species in leaf during treatment (mostly exotic winter annuals) in the old‐growth stand. Treatment did not affect the initial density of the Alliaria cohort that germinated in the spring of 2001, but decreased the 2002 cohort. Community differences were found in the old‐growth stand after Alliaria reduction, specifically greater cover of spring ephemerals in the herbicide treatment. In the second‐growth stand, herbicide treatment increased reproduction of the late‐summer perennial, Phryma leptostachya. These results indicate that glyphosate reduces Alliaria without negatively impacting native species and that some native species respond positively to a single‐year reduction in this invasive biennial.     

Carrier-mediated uptake of glyphosate in broad bean (Vicia faba) via a phosphate transporter

The possibility that the herbicide glyphosate (N-phosphonomethylglycine) may be taken up in plant cells via a phosphate transporter of the plasma membrane was investigated using protoplasts of broad bean leaves ( Vicia faba L.). Phosphonoformic acid, a powerful inhibitor of phosphate transport in animal cells, was first demonstrated to be a competitive inhibitor of phosphate uptake inbroad bean protoplasts. Glyphosate was able to inhibit phosphate uptake into the protoplasts, and to protect partially the phosphate transporter from inhibition by phosphonoformic acid. Concentration dependence studies showed that glyphosate uptake exhibited a saturable phase at low glyphosate concentrations (0. 5 to 3 μ M ), superimposed by a linear uptake at higher concentrations (up to 100 μ M ). Inhibition of glyphosate uptake by para -chloromercuribenzene sulphonic acid, sodium azide and carbonyl-cyanide- m -chlorophenylhydrazone was much stronger at 1 than at 100 μ M glyphosate. Kinetics indicated that the saturable component of glyphosate transport was competitively inhibited by either phosphate or phosphonoformic acid. It is concluded that glyphosate can be absorbed via a phosphate transporter of the plasma membrane     

Isolation from sugarcane cultures of variants resistant to antimetabolites

Variants resistant to antimetabolites are useful for investigating metabolic regulation and biochemical genetics in organisms. In this study, suspensions of mutagenized sugarcane ( Saccharum sp.) cells, originating from a stalk parenchyma explain of the Hawaiian variety 50–7209, were used to investigate the feasibility of isolating variants resistant to l -canavanine, glyphosate [N-(phosphonomethyl)glycine], ophiobolin A and orthovanadate. Rigorous retesting of clones which grew on selection media led to the identification of three cell lines, two of which were resistant to glyphosate and one to orthovanadate. No variants were isolated which showed a persistent resistance either to l -canavanine or ophiobolin A.
The results demonstrate that resistant variants do occur, or can be induced, in sugarcane cell suspensions and that they can be rescued and cultivated.