Influence of application volume on the efficacy of clodinafop-propargyl and fenoxaprop-P-ethyl on oats

The influence of application volume on the efficacy of clodinafop‐propargyl and fenoxaprop‐P‐ethyl on cultivated oats (Avena sativa) was studied in the glasshouse. Both herbicides were more efficacious when applied in 75 L ha^?1 than in 300 L ha^?1, with 11002 and 11006 nozzles respectively. However, when the same two volume rates were created by varying the speed of a 11003 nozzle, clodinafop‐propargyl efficacy was not affected by application volume, whereas fenoxaprop‐P‐ethyl remained more efficacious at 75 L ha^?1. This suggests that in the first experiment, fenoxaprop‐P‐ethyl efficacy was affected by changes in both spray quality and concentration, whereas only the former influenced clodinafop‐propargyl efficacy. The hypothesis that the fenoxaprop‐P‐ethyl formulation was more influenced by concentration than clodinafop‐propargyl was supported by dynamic surface tension studies and measures of active ingredient retention by oat plants. Within the practically relevant concentration range considered, surface activity of clodinafop‐propargyl remained low, with little influence on herbicide retention. In contrast, depending on the concentration, surface activity of fenoxaprop‐P‐ethyl was below or above levels that were critical for its retention. Although these differences may not be as apparent in the field as in the glasshouse, our study certainly indicates that both clodinafop‐propargyl and fenoxaprop‐P‐ethyl are herbicides favoured by low application volumes.     

Genetic diversity of sulfonylurea-resistant and -susceptible Monochoria vaginalis populations in Japan

Monochoria vaginalis is one of the most serious weeds of rice fields in Asia. The species is predominantly selfing. To reveal the potential for multiple mutational events, outcrossing and gene flow in the sulfonylurea‐resistant (SU‐R) M. vaginalis populations, we investigated (i) if each SU‐R population was a single SU‐R biotype or a mixture of several SU‐R biotypes using restriction analysis or direct sequencing of acetolacatate synthase (ALS) genes and (ii) genetic diversity of SU‐R and ‐susceptible (S) populations using amplified fragment length polymorphism (AFLP) analysis. Nineteen or 20 individuals were sampled from four SU‐R and five SU‐S populations respectively. Amino acid substitutions conferring resistance in the SU‐R populations were Pro₁₉₇Ser in the ALS1 or ALS3, or Asp₃₇₆Glu in the ALS1 and each SU‐R population was composed of a single SU‐R biotype. In cluster analysis each SU‐R individual formed a cluster, whereas the individuals from a SU‐S population belonged to different clusters. Some SU‐R populations showed polymorphic AFLP loci. The results indicated that these SU‐R biotypes emerged from a single mutational event and any gene flow of SU‐R genes from adjacent populations did not occur. A low level of outcrossing and recombinations of SU‐R genes occurred within some SU‐R populations of M. vaginalis.     

Evaluation of herbicides for selective weed control in grafted watermelons

Grafted watermelon is a combination of two plants, aCucurbita rootstock and a watermelon scion. Therefore, weed control for this crop faces a unique problem: the safety of the selected herbicide has to be tested for both plants that make up the grafted plant. In the current study, we evaluated the usage safety of selected herbicides forCucurbita rootstocks as well as for non-grafted and grafted watermelons, and the control ofAmaranthus retroflexus by the same herbicides. In addition, the residual effect of the herbicides was tested for seeded and transplanted melons representing the next crop following cultivation of the grafted watermelons. The herbicides ethalfluralin, pendimethalin, ethalfluralin, sulfentrazone, oxyfluorfen, chlorsulfuron and clomazone were chosen for their potential to controlA. retroflexus. Pendimethalin and trifluralin were less effective than the other herbicides in controllingA. retroflexus; sulfentrazone, chlorsulfuron and clomazone were not safe for use on the tested cucurbits and thus cannot be recommended for weed control in grafted watermelons. Therefore, by eliminating the herbicides that are toxic to cucurbits and those that are ineffective forA. retroflexus control, it was concluded that the herbicides ethalfluralin and oxyfluorfen can be considered effective and safe for weed control in grafted watermelons. It was shown that trifluralin and oxyfluorfen have the potential to be applied effectively through the drip irrigation system. http://www.phytoparasitica.org posting Jan. 10, 2008.     

Virulence characteristics of a new race of the parasitic angiosperm,Striga gesnerioides,from southern Benin on cowpea (Vigna unguiculata)

An in vitro growth system was used to determine the virulence of two samples of Striga gesnerioides from Zakpota in southern Benin. Cowpea variety B301, previously considered resistant to all races of S. gesnerioides, was susceptible to both samples of the parasite. Two other cowpea varieties, 58–57 and IT81D-994, were totally resistant. Resistance in 58–57 was associated with a hypersensitive necrosis of infected roots, whilst IT81D-994 supported production of small S. gesnerioides tubercles with stems which failed to develop. Striga gesnerioides from southern Benin is the fourth race of the parasite to be identified, and the first with virulence on variety B301. The implications for breeding cowpeas with resistance to S. gesnerioides are discussed.Abbreviations IITA International Institute of Tropical Agriculture - LARS Long Ashton Research Station - SAFGRAD Semi-Arid Food Grain Research and Development     

Protein Phosphorylation and Protein Patterns in Developing Endosperms of Barley

The SDS-soluble protein-fractions of barley endosperms (2 and 3 weeks after anthesis) were compared using 1-D SDS-PAGE and 2-D IEF/SDS-PAGE. Similar procedures have been followed after in vivo phosphorylation of isolated endosperm with ³²PO₄.Protein patterns were similar when 1-D SDS-PAGE was used. On the other hand, 2-D IEF/SDS-PAGE revealed several major differences, the most important being the appearance of a major protein of Mr about 40,000 in the 3-weeks old endosperm. By contrast, the patterns of phosphorylated proteins, with both methods, were relatively simple. Only two phosphorylated bands showed up in the 3-weeks old endosperm: a highly labelled band of Mr about 65,000, and a band of about 75,000. In the case of 2-weeks old endosperm, where the phosphorylation was more active, these and several others were also labelled, but the Mr 75,000 band was labelled more intensely.