Sterilisation thermique des sols et degradation des herbicides

A residual microbial population was found in sterilized soils following three autoclavings (20 min—120°C). This microorganism appeared after certain soil treatments: addition of chemical products or physical treatment. It was identified as Pseudomonas maltophilia. Degradation of two herbicides earbamates, chlorbufam and barban, was observed with a culture of P. maltophilia. This degradation was not observed in soil.     

Transformation rates of ortho-substituted thiophene and benzene carboxylic esters: Application to thifensulfuron-methyl and metsulfuron-methyl herbicides

The rate constants for soil degradation and alkaline hydrolysis of two herbicides, metsulfuron-methyl and thifensulfuron-methyl, have been determined. In order to explain the difference in behaviour of the two compounds, the chemical and enzymatic hydrolysis of some ortho-substituted methyl benzoates and methyl 3-substituted thiophene-2-carboxylates were studied. The data are consistent with a difference in polar and steric effects of the substituents in benzene and thiophene derivatives.     

Isolation from soil and growth characteristics of a cipc-degrading strain of Pseudomonas cepacia

A bacterial strain, identified as Pseudomonas cepacia, was isolated from soil and had the ability to utilize phenyl carbamates (BIPC, CIPC) as the sole source of carbon and energy. The degradation of CIPC, at various concentrations, was studied in a minimal medium. The addition of yeast extract increased bacterial growth, decreased the degradation-lag period, and increased the rate of CIPC transformation. The bacterial isolate also utilized 3-chloroaniline, the degradation product of CIPC. Its ability to degrade the herbicide was retained despite repeated growth in media without the herbicide.     

Characterization of fungal pathogens (Diaporthe angelicae and D. eres) responsible for umbel browning and stem necrosis on carrot in France

A collection of 102 Diaporthe isolates was compiled from lesions on carrot, parsley and wild Apiaceae species in France from 2010 to 2014. Molecular typing based on ITS rDNA sequences resulted in the identification of 85 D. angelicae and 17 D. eres isolates. Based on sequences of the 3′ part of the IGS rDNA, intraspecific variability was analysed for 17 D. angelicae and 13 D. eres isolates from diverse plant species, locations in France, and plant tissues. The genetic diversity was greater for D. angelicae isolates than D. eres isolates. In vitro sensitivity of five D. angelicae and four D. eres isolates to each of nine fungicides was similar for isolates of both species, with a marked variation in fungicide sensitivity depending on the active ingredient. To assess the pathogenicity of D. angelicae and D. eres isolates on carrot, one isolate of each species was inoculated onto umbels in a controlled environment. Typical lesions were observed for both isolates. Carrot crop debris collected from a seed production field in France and placed in controlled conditions produced perithecia and ascospores typical of Diaporthe, that were further characterized molecularly as belonging to D. angelicae. Detection of Diaporthe species on seed lots from three carrot production fields in France was investigated. Both species were detected on seeds by conventional PCR assay, with a greater frequency for D. angelicae than D. eres (67% vs 33%, respectively). Overall, the results highlighted that umbel browning in carrot seed crops in France was mainly caused by D. angelicae.     

A computer program for the layouts of seed orchards

A computer program has been developed, which offers the possibility of producing designs for clonal seed orchards which reduce the chance of self fertilisation and offer an equal opportunity to all cross combinations to occur with approximately the same frequency.     

Triflusulfuron-methyl dissipation in water and soil

This paper reports laboratory studies of the behavior and fate of triflusulfuron-methyl in aqueous buffer and soils. Aqueous hydrolysis was pH-dependent and fast in acidic buffer solutions. In basic buffers, the hydrolysis rate variation was low between pH 7 and pH 10. The degradation pathway in the range of pH 4-10 was via cleavage of the sulfonylurea bridge to form two transformation products: 2-amino-4-(dimethylamino)-6-(2,2,2-trifluoroethoxy)-1,3, 5-triazine (2) and 6-methyl-2-methylcarboxylate benzene sulfonamide (3). Comparison of transformation rates in sterile and nonsterile soils indicates that chemical and microbial processes are important in soil degradation. The former is more important in acidic soils, and the latter is more important in basic soils. A biphasic model fits well with dissipation of triflusulfuron-methyl in soil. The triazine formed during the first step of transformation was degraded more rapidly in basic soils than in acidic soils.     

Soil transformation of prosulfuron

The transformation of prosulfuron [1-(4-methoxy-6-methyltriazine-2-yl)-3-[2-(3,3,3-trifluropropyl)phenylsulfonyl]urea] in three soils at different pH values (sterilized and unsterilized) was studied, and it was shown that the rate of transformation was high in acidic soil. From the results obtained in sterile soils, it is shown that the mechanism of dissipation was mainly chemical in acidic soils. A new metabolite, 2-(3,3,3-trifluoropropyl)phenylsulfonic acid, was identified.