Alfalfa (Medicago sativa L.), beans (Phaseolus vulgaris L.), corn (Zea mays L.), potatoes (Solanum tuberosum L.), spring wheat (Triticum aestivum L.), and sugarbeets (Beta vulgaris L.) were severely injured and had reduced foliage dry weights when grown in soil containing 0.10 ppmw or more terbacil (3-tert-butyl-5-chloro-6-methyluracil). Activated carbon at 150 kg/ha prevented a significant loss in weight of beans and corn in soil containing 0.10 ppmw terbacil and fully protected potatoes in soil containing 0.19 ppmw terbacil. Carbon at 300 kg/ha fully protected sugarbeets and prevented a significant weight loss in alfalfa in soil containing 0.19 ppmw terbacil. Carbon at 600 kg/ha did not protect wheat from 0.19 ppmw terbacil.

Characteristics of glyphosate [N-(phosphonomethyl)glycine] uptake for as long as 3 days by plant cells were studied using suspension-cultured potato (Solanum tuberosum L. cv. ‘Red Pontiac’ and S. brevidens Phil.) cells. An experimental system was developed wherein uptake was assayed in a reduced salt medium that minimized cell growth yet maintained cell viability. Glyphosate uptake was nonlinear over time; an immediate rapid uptake phase was followed by uptake at a decreased rate that continued through 72 h. Glyphosate uptake was the same in both an experimental uptake medium (reduced salt and sucrose, no hormones) and in the complete growth medium used for routine cell growth. The pattern of glyphosate uptake was similar with both Red Pontiac and S. brevidens cells, though uptake was greater in Red Pontiac cells. Glyphosate uptake was not inhibited by 1 mM CaSO4, MgSO4, MnSO4, or ZnSO4. Rather, uptake was inhibited by the absence of salts at 8 h, and ZnSO4 and MnSO4 increased uptake. Similarly, increasing concentrations (0 to 5 mM) of CaSO4 and CaCl2 did not inhibit uptake, whereas the absence of either salt of Ca2+ decreased uptake. Increasing concentrations of (NH4)2 SO4 (0 to 150 mM) did not affect glyphosate uptake, but (NH4)2 SO4 at 50 mM and above was toxic to the cells.

Six cropping/weed control systems were evaluated from 1978 to 1980 for the control of yellow nutsedge (Cyperus esculentus L.). Supplementing cultivation of cotton (Gossypium hirsutum L. ‘Acala SJ-2′) with either preplant applications of fluridone {1 - methyl - 3 - phenyl - 5 - [3 - (trifluoromethyl)phenyl] -4(1H-pyridinone} or two hoeings for 2 yr preceding cotton treated with DSMA (disodium methanearsonate) and MSMA (monosodium methanearsonate) reduced populations of viable yellow nutsedge tubers 98 to 99% within 3 yr. Dry- or wet - fallowing plus tillage after barley (Hordeum vulgare L. ‘Kombyne’), and double cropping potatoes (Solanum tuberosum L. ‘White Rose’) treated with EPTC (S-ethyl dipropylthiocarbamate) with soybeans [Glycine max (L.) Merr. ‘Williams’] treated with alachlor [2-chloro - 2′, 6’ - diethyl - N - (methoxymethyl)acetanilide] for 2 yr preceding cotton, reduced populations of tubers 98 to 99% within 3 yr. A similar reduction of tubers (97%) was obtained by double cropping potatoes with milo [Sorghum bicolor (L.) Moench. ‘NK- 265′] for 2 yr preceding cotton.

Ten herbicide treatments were evaluated for early season control of three broadleaf weeds and effects on marketable potato yields in low-organic, coarse-textured soil. All treatments controlled prostrate pigweed 100%. Trifluralin with metolachlor or with EPTC did not control kochia well. Pendimethalin alone or with EPTC controlled Russian thistle poorly, and produced the lowest marketable tuber yields. Fluorochloridone at 0.6 kg ai/ha caused chlorosis and reduced potato yield 11%. Treatments with metribuzin tended to have high potato yields.

Sublethal amounts of 2,4-D [(2,4-dichlorophenoxy) acetic acid] were applied to several vegetable crops in order to determine effect on yield and quality in a simulated drift experiment. Tomato (Lycopersicon esculentum Mill.) and root crops were most sensitive to 2,4-D; as little as 2.1 g/ha of acid distorted tomato fruit shape and elongated radish (Raphanus sativus L.) roots. All root crops were rendered unmarketable by 10.4 g/ha and gross yields were reduced by exposure to 104 g/ha. Yield of peppers (Capsicum frutescens L. var. grossum) was increased by exposure to 2.1 g/ha and severely depressed by 104 g/ha. Cucumber (Cucumis sativus L.) fruit shape was distorted at 11 g/ha and yield was reduced slightly. Lettuce (Lactuca sativa L.), onion (Allium cepa L.), and cabbage (Brassica oleracea L. var. capitata) were least sensitive to 2,4-D. Exposure to 20.8 g/ha did not reduce yields of lettuce or cabbage. Onion yields were reduced by application of 104 g/ha. Bush bean (Phaseolus vulgaris L.) yield was decreased by exposure to 22 g/ha, but potato (Solarium tuberosum L.) yield increased at 16 g/ha. Herbicide residues in the crop foliage were proportional to the degree of exposure. Residue analysis combined with foliar symptoms may be useful in predicting crop damage following 2,4-D drift.

Five sulfonylurea herbicides were applied to Typic Boroll soil with pH 8.0 and 2% organic matter in the field and growth chamber to assess their residual effects on following crops. Under irrigated conditions, triasulfuron at 22 g/ha reduced the growth of alfalfa, canola, corn, lentil, pea, potato, and sugarbeet the year after application but caused no injury after two years. Alfalfa GR50 (rate required to reduce growth by 50%) values immediately after application of chlorsulfuron, triasulfuron, and metsulfuron were < 2.2 g/ha and similar in the growth chamber and field. Alfalfa and canola GR50 values immediately after thifensulfuron application in the growth chamber were ≥ 90 g/ha. Alfalfa, canola, flax, and sugarbeet GR50 for tribenuron in the growth chamber were < 4 g/ha. Crop response curves developed by growth chamber experiments could replace many of the multiple site and crop field experiments now required to develop recropping guidelines for residual herbicides.

In greenhouse replacement series experiments, ‘Atlantic’ and ‘Russet Burbank’ potatoes and barnyardgrass were more competitive than redroot pigweed as measured by relative competitive ability. In additive design field studies, four redroot pigweed or barnyardgrass per meter of row did not reduce Atlantic tuber yield when planted between the row following hilling (6 to 7 weeks after planting). However, as few as one barnyardgrass or redroot pigweed per meter of row reduced marketable tuber yield 19 to 33% when seeded in the row at the time of potato planting. Redroot pigweed reduced tuber yield more than barnyardgrass did in 1 yr of research. The correlation coefficients were similar for both weed density and weed biomass regressed on tuber yield. Aboveground potato biomass was not consistent in predicting total tuber yield. Furthermore, variability in aboveground potato biomass was not due to increasing weed weight or density. Neither specific gravity nor tuber quality was altered by the presence of any density of either weed species.

Experiments were conducted to evaluate the effect of tillage, rye residue levels, and control strategies on weed suppression and potato yield. Reduced tillage (RT) yields in 1989 were lower than in conventional tillage (CT) due to high hairy galinsoga populations. However, in 1990, potato yields were greater in RT when early emerging weeds were suppressed. Increasing residue levels up to 2300 kg ha-1 had no effect on weeds or yields in either year. In a separate study, preemergence herbicides (linuron plus metolachlor, 1.7 kg ai ha-1 each) applied 10 d after planting (DAP) in reduced tillage controlled weeds for 6 wk, but efficacy decreased after hilling. Metribuzin applied postemergence (0.19 kg ai ha-1) 7 d after hilling controlled late germinating weeds. Potato yields were greatest when the preemergence herbicides were applied.

Evolutionary and closer structural relationships are demonstrated by phylogenetic analysis, peptide prediction and molecular modelling between Solanum tuberosum apyrase, Schistosoma mansoni SmATPase 2 and Leishmania braziliensis NDPase. Specific protein domains are suggested to be potentially involved in the immune response, and also seem to be conserved during host and parasite co-evolution. Significant IgG antibody reactivity was observed in sera from patients with American cutaneous leishmaniasis (ACL) and schistosomiasis using potato apyrase as antigen in ELISA. S. mansoni adult worm or egg, L. braziliensis promastigote (Lb) and Trypanosoma cruzi epimastigote (EPI) have ATP diphosphohydrolases, and antigenic preparations of them were evaluated. In ACL patients, IgG seropositivity was about 43% and 90% for Lb and potato apyrase, respectively, while IgM was lower (<19%) for both. In schistosomiasis patients IgM (>40%) or IgG (100%) seropositivity for both soluble egg (SEA) and adult worm (SWAP) antigens was higher than that found for potato apyrase (IgM=10%; IgG=39%). In Chagas disease, IgG seropositivity for EPI and potato apyrase was 97% and 17%, respectively, while the IgM was low (3%) for both antigens. The study of the conserved domains from both parasite proteins and potato apyrase could lead to the development of new drug targets or molecular markers.

Based on international findings, Irish co-existence guidelines for the cultivation of GM potato stipulate that an isolation distance of 20 m is required to minimize the spread of transgenic pollen in accordance with required labeling thresholds. As potato tolerant to Phytophthora infestans is the most applicable GM crop from an Irish context, we tested the efficacy of this isolation distance under Irish environmental conditions using the conventional variety Désirée as a pollen donor and the male-sterile variety British Queen as a pollen receptor. Gene flow was determined by scoring for berry presence on receptor plants and confirmed using a microsatellite marker system designed to assess paternity in F1 seedlings. 99.1% of seedlings recovered were identified as having Désirée paternity. Whereas 19.9% (140/708) of total berries formed on receptor plants occurred at a distance of 21 m from the pollen source, only 4 of these berries bore viable true potato seed (TPS), from which 23 TPS germinated. TPS-bearing berry formation was negatively correlated with distance from the pollen source, and although overall distribution of berries and seeds was non-random across the plot, no significant correlation was evident with respect to wind direction. Microsatellite markers were also used to confirm that the foraging beetle Meligethes aeneus is a vector for the transmission of potato pollen, but a more detailed statistical analysis of this dataset was limited by inclement weather during the trial. To conclude, we recommend that a two-tiered system be established in regard to establishing isolation distances for the experimental trial and commercial cultivation of GM potato in Ireland, and that responsible crop management be adopted to minimize the establishment of TPS-derived volunteers, which we have noted will emerge through a rotation as a result of pollen-mediated gene flow.

As seed dormancy is released within a seed population, both the rate and percentage of germination increase progressively with increasing dose of a dormancy-breaking treatment or condition. Population-based models can account for this behaviour on the basis of shifting response thresholds as dormancy is alleviated. In particular, hydrothermal time analysis of germination sensitivity to water potential (Ψ) and temperature (T) can describe these features of seed behaviour. We used the hydrothermal time model to analyse the effects of dormancy-breaking treatments on germination of dormant true (botanical) potato (Solanum tuberosum L.) seeds (TPS). After-ripening (37°C and 4% seed moisture content) of TPS for 7 or 30 days partially or fully alleviated primary dormancy. The median base water potential required to prevent germination [Ψb(50)] decreased from –0.25 MPa in control seeds to –0.87 MPa and –1.83 MPa after 7 and 30 days of after-ripening, respectively. In contrast, the base temperature for germination (Tb) was relatively unaffected (0–3.3°C). Fluridone (50 μM), an inhibitor of abscisic acid (ABA) biosynthesis, also promoted germination of dormant TPS and lowered Ψb(50), indicating a role for de novo synthesis of ABA during dormancy maintenance. Moist chilling (3 days at 4°C) or gibberellin (100 μM) alleviated secondary dormancy and lowered Ψb(50) values from –0.08 MPa to –0.36 and –0.87 MPa, respectively. The hydrothermal time model allows quantification of dormancy levels and explains why changes in germination speed and percentage are closely correlated during dormancy alleviation.

In plant mitochondria, editing of messenger RNA by C-to-U conversions is essential for correct gene expression as it usually improves the protein-sequence conservation between different species or sometimes affects the reading frames (for a review, see Maier et al., 1996). Editing sites have been identified in mitochondrial (mt) RNA of all major groups of land plants, including Bryophytes, Pteridophytes, Prespermaphytes, and Spermaphytes (Hiesel et al., 1994a,b; Malek et al., 1996). Editing mainly affects messenger RNA, but editing sites have also been identified in three transfer RNAs. In dicot mitochondria a C-to-U editing event corrects a C:A mismatch into a U:A base pair in the acceptor stem of tRNAPhe(GAA) (Maréchal-Drouard et al., 1993; Binder et al., 1994). In the gymnosperm Larix leptoeuropaea, three C-to-U conversions restore a U:A base pair in the acceptor stem, D stem, and anticodon stem of tRNAHis(GUG), respectively (Maréchal-Drouard et al., 1996b). The third example described is the Oenothera berteriana mt tRNACys(GCA), where a C28:U42 mismatch is converted into a U28:U42 noncanonical base pair (Binder et al., 1994). In the case of both tRNAPhe and tRNAHis, editing of precursors is a prerequisite for 5′ and 3′ processing to generate a mature tRNA (Marchfelder et al., 1996; Maréchal-Drouard et al., 1996a, 1996b; Kunzmann et al., 1998). The role of editing in the case of tRNACys has not been studied so far, although it has been shown that it occurs at the precursor level (Binder et al., 1994). In this letter, we report an evolutionary and functional study of mt tRNACys(GCA) editing in plant mitochondria.