[Show abstract][Hide abstract] ABSTRACT: In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with 14C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from 14C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with 14C-diclofop-methyl-treated ryegrass was observed. The study with 14C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of 14C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation.
Weed Research 01/2007; 47(1):25 - 33. · 2.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and a semi-random PCR system were used to analyze
the genetic diversity of 16 Italian common bean landraces and their relationship to four commercial cultivars. Of the primers
tested, 8 ISSR, 6 RAPD and 7 semi-random primers produced polymorphic and reproducible DNA fragments. A higher proportion
of polymorphic bands were observed using ISSR (85%) and semi-random (90%) primers than RAPD (69%) method. The combination
of any two semi-random markers allowed the identification of all 20 bean genotypes. In contrast ISSR (except for primer (CAC)3GC) and RAPD markers appeared to be less informative as more than two markers were necessary to achieve the same diagnostic
level. Moreover, 7 ISSR, 2 RAPD and 8 semi-random exclusive bands were identified as putative population-specific markers.
Semi-random and ISSR derived dendrograms showed similar tendencies in terms of genetic relatedness, whereas clustering of
genotypes within groups was not similar when compared with the RAPD technique. Despite the different ability to resolve genetic
variation among the investigated landraces, two major clusters with less than 60% (ISSR) and 40% (RAPD and semi-random) genetic
similarity were formed with all three marker systems. The two groups were correlated with the phaseolin patterns and seed
size of the landraces. The analysis showed that the cultivar ȁ8Lingua di Fuocoȁ9 and most of the landraces (13 out of 16)
collected in Italy belong to the Andean gene pool, whereas only the three populations from Pratomagno belong to the Middle
American gene pool.
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to develop a quantitative-competitive PCR (QC-PCR) method to detect DNA from transgenic herbicide-resistant (roundup ready, RR) soybean and maize. Since no QC-PCR system for the quantification of RR maize had been published at the time of writing, a specific competitor DNA for transgenic event was developed. For the QC-PCR of RR-soybean, a commercially available competitor was employed. These internal standards were calibrated by coamplifying with mixtures containing RR-soybean and maize DNAs. The calibrated QC-PCR systems were applied to certified RR-soybean and maize flour mixtures in order to demonstrate their suitability not only for the quantification of the glyphosate resistance traits in DNA matrices, but also in practically relevant samples. In addition, a special focus of the present work was to compare the detection of QC-PCR products by slab gel and CGE with UV detection. CGE permitted the precise detection of transgenic events also below the equivalence points; while in slab gel electrophoresis, due to the low sensitivity the quantification of genetically modified DNA was allowed only at the equivalence point.
[Show abstract][Hide abstract] ABSTRACT: The physiological and molecular basis of glyphosate resistance in susceptible (S) and resistant (R) horseweed (Conyza canadensis (L.) Cronq.) populations collected from regions across the USA (Arkansas, Delaware, Ohio, Virginia, Washington) was investigated. At two-leaf stage approximately the same ED50 values were observed for the S and R populations, while at the rosette stage the R biotypes were approximately three times more resistant than the S biotypes. After treatment with severe glyphosate doses (more than 1× the recommended field rate), different morphological responses in R and S biotypes were observed. In S biotypes, the first phytotoxic effects were found in the meristematic tissues, while in the R biotypes the first phytotoxic effects were observed in leaves. At 2 to 4 weeks after the treatment, R plants recovered by emitting new leaves and/or new branches from the center of the rosette. A significant increase of the mean number of branches per surviving R plants as a function of glyphosate-applied dose was observed. As regards the physiological mechanism of resistance, the main difference between R and S biotypes was the dissimilar mobility of glyphosate in the whole plant. In the R biotypes the herbicide was less translocated in the downward direction (from leaves to roots) and more translocated in the upward direction (from culm to leaves) with respect to the S biotypes. Finally, in R biotypes the relative level of EPSPS mRNA was from 1.8 to 3.1 times higher than that found in S biotypes. On the basis of obtained results three factors may concur to glyphosate resistance in the investigated R biotypes: impaired translocation of the herbicide, increase in EPSP synthase transcript levels, and enhanced ramification.
Pesticide Biochemistry and Physiology 09/2006; · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Methanol extracts of seeds from 23 accessions of 3 Phaseolus vulgaris ecotypes (''Sarconi'', ''Lamon'', ''Zolfino del Prato-magno''), grown in different Italian regions (Basilicata, Veneto, Tuscany) were analyzed for their flavonoid content. Flavonoid gly-cosides were found in the seed coat from ten accessions of the ''Zolfino'' ecotype and in one accession of the ''Sarconi'' ecotype. From highest to lowest concentration these compounds were kaempferol 3-O-glucoside (compound 2), kaempferol 3-O-xylosylg-lucoside (compound 1) and a not completely identified kaempferol monoglucoside (compound 3). Total flavonol content varied from 0.19 to 0.84 g/kg of seed fresh weight. A great variability in the total flavonol content, being between 18% and 50%, and in the relative abundance of different kaempferol derivatives was observed for the same genotypes sampled in the original locations in the 2001–2003 period. Fluctuation in flavonol content suggests that further researches are necessary for an exhaustive compre-hension of physiological mechanisms influencing the expression of these phenolic compounds. Obtained results evidenced that some Italian bean ecotypes may be an important source of functional compounds as kaempferol glycosides.
[Show abstract][Hide abstract] ABSTRACT: The mechanism of resistance to diclofop-methyl in three Italian populations of Lolium spp. (two resistant and one susceptible) was investigated. The major proportion of R-1 (Tuscania 1997) and R-2 (Roma 1994) plants (approximately 80%) survived after herbicide treatment by emitting new tillers from the crown. Both resistant (R-1 and R-2) and susceptible (Vetralla 1994) Lolium spp. populations were target-site sensitive. No difference in diclofop-methyl absorption by shoots of resistant and susceptible biotypes was observed. At the dose corresponding to 1× the recommended field rate, a relatively higher metabolism was found in R-2 biotype. In contrast, at the doses 2× and 10× the field rate no difference in herbicide metabolism between susceptible and resistant biotypes was observed. At all the three herbicide doses (1×, 2×, and 10× the field rate) 48h after the treatment (HAT), the total amount of metabolites produced by wheat was more than three times higher than that produced by resistant and susceptible ryegrass biotypes. At the doses 1× and 2× the field rate, the herbicide translocation was different in the susceptible biotypes compared to resistant biotypes. The total amount of the radiolabel found 48 HAT in culm and root was approximately twice in susceptible biotype than in resistant biotypes. Susceptible and resistant ryegrass biotypes differed in the capability of their roots to acidify the external medium. Susceptible biotype acidified the external solution at approximately 6 times the rates of the resistant biotypes. In the present study, the mechanism responsible for resistance in the investigated resistant biotypes was not univocally identified. Indirect evidence supports the possible involvement of herbicide sequestration or immobilization.
Pesticide Biochemistry and Physiology - PESTIC BIOCHEM PHYSIOL. 01/2005; 81(1):1-12.