Physiological basis for cotton tolerance to flumioxazin applied postemergence directed

Abstract

Previous research has shown that flumioxazin, a herbicide being developed as a postemergence-directed spray (PDS) in cotton, has the potential to injure cotton less than 30 cm tall if the herbicide contacts green stem tissue by rain splash or misapplication. In response to this concern, five-leaf cotton plants with chlorophyllous stems and older cotton, 16-leaf cotton plants, with bark on the lower stem were treated with a PDS containing flumioxazin plus crop oil concentrate (COC) or nonionic surfactant (NIS). Stems of treated plants and untreated plants at the respective growth stage were cross-sectioned and then magnified and photographed using bright-field microscopy techniques. More visible injury consisting of necrosis and desiccation was evident in younger cotton. Also, there was a decrease in treated-stem diameter and an increase in visible injury with COC compared with NIS in younger cotton. The effects of plant growth stage and harvest time on absorption, translocation, and metabolism of14C-flumioxazin in cotton were also investigated. Total14C absorbed at 72 h after treatment (HAT) was 77, 76, and 94% of applied at 4-, 8-, and 12-leaf growth stages, respectively. Cotton at the 12-leaf stage absorbed more14C within 48 HAT than was absorbed by four- or eight-leaf cotton by 72 HAT. A majority (31 to 57%) of applied14C remained in the treated stem for all growth stages and harvest times. Treated cotton stems at all growth stages and harvest times contained higher concentrations (Bq g−1) of14C than any other tissues. Flumioxazin metabolites made up less than 5% of the radioactivity found in the treated stem. Because of the undetectable levels of metabolites in other tissues when flumioxazin was applied PDS, flumioxazin was foliar applied to determine whether flumioxazin transported to the leaves may have been metabolized. In foliar-treated cotton, flumioxazin metabolites in the treated leaf of four-leaf cotton totaled 4% of the recovered14C 72 HAT. Flumioxazin metabolites in the treated leaf of 12-leaf cotton totaled 35% of the recovered14C 48 HAT. These data suggest that differential absorption, translocation, and metabolism at various growth stages, as well as the development of a bark layer, are the bases for differential tolerances of cotton to flumioxazin applied PDS.

Effect of Winter Herbicide Applications on Bald Cypress (Taxodium distichum) and Giant Salvinia (Salvinia molesta)

“…Franco] seedlings were not affected by over-the-top spring applications of flumioxazin at 850 g ai ha − 1 , which is approximately four times greater than the rate tested in the current study. Flumioxazin tolerance in cotton (Gossypium hirsutum L.) has been associated with plant age and restricted herbicide uptake in mature barked stems compared with immature chlorophyllus stems (Ferrell and Vencill 2003;Price et al 2004). The trees used in the current study would be classified as young (2 to 3 yr old) considering the longevity of bald cypress; however, all had fully developed bark.…”

Seletividade do flumioxazin ao trigo

“…The tolerance of cotton to flumioxazin applied in post-emergence was observed and related with the absorption, translocations and differential metabolism of the product on the plant (Price et al, 2004). In addition to these selectivity mechanisms, wheat's response to the herbicide may be involved with the superexpression of the PROTOX enzyme or the compartmentalization of the molecule, which must be investigated.…”

Identification of Resistance to Insect Pests Infestations in Cotton (Gossypium hirsutum L.) Varieties Evaluated in the Field Experiment

“…Both dominant and recessive genes control the inheritance of resistance to insect pests, while polygenic resistance also exists in many genotypes (Khush and Brar, 1991;Katiyar et al, 2001). Previous research has also shown that differential absorption, translocation and metabolism at various growth stages, as well as the development of a bark layer, are the basis for differential tolerances of cotton (Price et al, 2004). In other trials, cotton pest's density was significantly correlated with the density of trichomes (unicellular outgrowths from the epidermis of leaves, shoots and roots, their cover of a plant surface is collectively called pubescence) on leaves, bracts and stems.…”