Molecular basis of natural tolerance to glyphosate in Convolvulus arvensis.

Convolvulus arvensis is a troublesome weed that is naturally tolerant to glyphosate. This weed tolerates glyphosate at a rate 5.1 times higher than that of glyphosate-susceptible Calystegia hederacea. Glyphosate-treated C. arvensis plants accumulated less shikimic acid than C. hederacea plants. The overexpression of EPSPS genes from the two species in transgenic Arabidopsis thaliana resulted in similar glyphosate tolerance levels. qPCR of genomic DNA revealed that the EPSPS copy number in C. arvensis was approximately 2 times higher than that in C. hederacea. Moreover, glyphosate treatment caused a marked increase in EPSPS mRNA in C. arvensis compared to C. hederacea. GUS activity analysis showed that the promoter of CaEPSPS (CaEPSPS-P) highly improved GUS expression after glyphosate treatment, while no obvious differential GUS expression was observed in ChEPSPS-P transgenic A. thaliana in the presence or absence of glyphosate. Based on the obtained results, two coexisting mechanisms may explain the natural glyphosate tolerance in C. arvensis: (i) high EPSPS copy number and (ii) specific promoter-mediated overexpression of EPSPS after glyphosate treatment.

Phoma crystallifera with phytotoxic effects and pathogenic potential against field bindweed (Convolvulus arvensis L.) in Iran.

AIMS: To identify a potential pathogenic isolate of fungus on Convolvulus arvensis and to determine its phytotoxic activity, which revealed the presence of toxic metabolites responsible for the toxicity against the target weed. METHODS AND RESULTS: A high virulent isolate of the fungus, Phoma crystallifera was isolated from symptomatic field bindweed in the west of Iran and was screened for the production of phytotoxins, which promoted necrosis on the detached leaves and seedlings of field bindweed in the bioassays. The isolate was distinct from other isolates of the fungi on the basis of morphological characteristics and the combined sequence database of the ITS region, partial LSU rDNA and ß-tubulin gene. Isolate P. crystalifera P6 produced the highest amount of phytotoxins after 21 days in a shacked culture of Richard's broth. The active metabolites were isolated from a cell-free culture filtrate by ethyl-acetate and purified by thin layer chromatography. The result indicated that six out of nine spots had phytotoxic activity in the bioassays, with Rf values of 0·16, 0·30, 0·36, 0·43, 0·57 and 0·81. CONCLUSIONS: Phoma crystallifera P6 and its active metabolites showed significant phytotoxic effects on the detached leaves of C. arvensis. SIGNIFICANCE AND IMPACT OF THE STUDY: To date, there are no reports of possible biocontrol agent(s) on C. arvensis in Iran. Thus, P. crystallifera P6 is introduced here as a severe pathogenic fungus and which can be used as a biocontrol agent against C. arvensis.

Biochemical and spectroscopic studies of the response of Convolvulus arvensis L. to chromium(III) and chromium(VI) stress.

The objective of the present study was to determine the oxidative stress caused by hexavalent chromium (Cr[VI]), the chromium (Cr) uptake, and the Cr speciation in Convolvulus arvensis L. plants grown in hydroponics media containing either Cr(VI) or Cr(III). The results demonstrated that C. arvensis plants exposed to Cr(VI) concentrations ranging from 0 to 40 mg/L expressed higher ascorbate peroxidase specific activity in roots than in shoots. On the other hand, catalase activity monitored in plants exposed to 2 mg/L of Cr(VI) for 24 h increased in roots after a few hours of exposure. However, catalase activity in shoots revealed a decrement almost immediately after treatment was initiated. The results from x-ray absorption spectroscopic studies indicated that the oxidation state of the supplied Cr(III) remained the same in plant tissues. The supplied Cr(VI), however, was reduced to the trivalent form in plant tissues. The results of inductively coupled plasma/optical emission spectroscopy demonstrated that after 5 d, the roots of plants exposed to 40 mg/L of Cr(III) or Cr(VI) accumulated approximately 25,000 and 3,500 mg/kg dry weight of Cr, respectively. Nevertheless, shoots concentrated 1,500 and 2,000 mg/kg dry weight of Cr from Cr(III) and Cr(VI), respectively, which indicated that Cr moved faster into C. arvensis plants when supplied as Cr(VI).

Vegetative reproduction and chemical control with post-emergent herbicides of field bindweed (Convolvulus arvensis L.).

It is clearly seen from data that roots of Convolvulus arvensis L. have more and less intensive regenerative period during growing season. The more intensive period is in autumn, because in that time roots culminate nutrients, carbohydrate as starch and sugar. The less intensive regenerative or shoot-growing period is in spring, called "late spring bud dormancy". Experiments were conducted to get more information and further details about the regenerative capacity of roots close to and far from the collar of Convolvulus arvensis L. Root segments closer to collar have an intensive regenerative capacity than those ones further to collar. By data of Bakke et al. (1939) is well known, roots exhumed from deep soil layers are able to create shoots with low intensity. So finally we can exclaim that regenerative capacity is decreasing further to collar. Using mechanical weed control it is sufficient to till the upper layer of soil, but many times. Chemical treatments are most effective in the integrated weed control. It is clearly seen that auxin-type herbicide such as 2,4-D, fluroxipir, MCPA. dicamba give the best result. They gave 95% weed control effect used them separately or in combination with other herbicides. Combination of Banvel 480 S (dicamba) and Logran 75 WG (triasulfuron) introduced 95% weed control effect. Only one time got absolutely 100% weed control effect, in the case of Glyphosate active substance. Caused total plant destruction. Excellent result was given with the application of Pledge 50WP (flumioxazin). Herbicides mentioned above are absolutely allowed to take an important and significant part in chemical plant protection against Convolvulus arvensis L. Other herbicides like Granstar 75DF (tribenuron-methyl), Basis 75DF (rimsulfuron + tifensulfuron-methyl) and Huszár (jodosulfuron-methyl-sodium + mefenpir-diethyl) are not so effective against Convolvulus arvensis L., as compared to the previous ones.

Efficacy of Phomopsis convolvulus as a mycoherbicide for Convolvulus arvensis.

The purpose of the investigations was to determine the efficacy of different conidia concentrations of Phomopsis convolvulus Ormeno on different leaf stages of Convolvulus arvensis seedlings and regrowth potential of C. arvensis 25 days after inoculation. Furthermore, the potential of P. convolvulus on the growth of C. arvensis derived from different root lengths was studied. The results showed a great reduction in dry weight of above-ground biomass with more than 80% irrespective of the conidia concentration (1 x 10(6), 10(7) and 10(8) conidia/ml) on plants of the leaf stage 1-3 and 5-7 and gave more than 80% reduction of root biomass with an exception in case of 1 x 10(6) conidia/ml on plants of the leaf stage 9-11. Mortality was reached complete only with 1 x 10(8) conidia/ml on plants of the leaf stage 1-3. Regrowth potential of C. arvensis at more developed leaf stages was higher than at early leaf stages. Within the 3 categories of root lengths tested (5, 10 and 15 cm), the 1-3 leaf stage shoots showed the highest susceptibility to P. convolvulus. Obtained results illustrate that the application of P. convolvulus with 1 x 10(8) conidia/ml at the young leaf stage (1-3 leaf stage) on all treatments give a great reduction of biomass and adversely affects regeneration of the plants.