Variation in dormancy duration of the U.K. wheat cultivar Hornet due to environmental conditions during grain development

Dormancy of wheat grains, the property conferring sprouting resistance, is affected by environmental conditions experienced during grain development. We investigated the hypothesis that short dormancy duration in U.K. wheat grain (thus a high risk of post-maturity sprouting) is related to weather conditions, i.e. high temperatures during grain development. Four wheat varieties were grown at four sites ranging from the far south to the far north of the country in the years 1995–1997,ensuring different temperature and rainfall conditions during grain development. This paper focuses on one variety, Hornet, which has a high sprouting resistance rating. Other varieties gave similar results. Serial laboratory germination tests (seven days, 20°C) at 100°C-dayintervals were used to measure dormancy duration, which was assessed from logistic curves fitted to the data. During the experiment the mean temperatures during grain development differed by over4°C, due to the site × year effect. Significant effects (p>0.05) of site and year (i.e. weather) on dormancy were found, when definitions of dormancy duration of D_A (number of days from anthesis to 50% germination in seven days at 20°C) or D_P (number of days from physiological maturity at 45% grain moisture to 50% germination) were used. Dormancy was markedly shorter in the hot, dry year 1995 compared to the cooler, wetter years 1996 and 1997. A relationship, as postulated by Belderok, between accumulated temperature during the dough stage of grain filling and dormancy duration was not found. However, a relationship of dormancy duration to the mean temperature during grain development was found, with short dormancy periods occurring after high mean temperatures were experienced. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of tissue culture explant source on sugarcane yield components

Clonal propagation of sugarcane(interspecific hybrids of Saccharum)is conducive to spread of systemicdiseases, such as ratoon stunting disease,caused by Leifsonia xyli subsp. xyli. This important disease iscontrolled by obtaining and plantinghealthy seed-cane. In Louisiana, commercialseed-cane initially produced through tissueculture is available to sugarcane farmersand is being widely planted. Long-termacceptability of this seed-cane productionmethod depends on the production of healthyplants that do not differ significantly inphenotypic and yield characteristics fromthe clones originally selected and releasedas commercial cultivars. To determinewhether tissue culture affects yield or itscomponents, three cultivars, CP 70-321, LCP85-384, and HoCP 85-845, were compared inthree successive crops initially plantedwith stalks from three sources: plantsderived from callus culture of the leafroll above the apical meristem, directregeneration from the apical meristem, andconventional bud propagation. Stalks ofplants derived from both explant sourceswere typical of seed-cane farmers wouldpurchase for planting that had beenpreviously rogued for phenotypic variantsand increased by bud propagation.Differences in yield components amongtissue culture explant sources and budpropagated cane only occurred in CP 70-321.Stalk diameter and stalk weight were lowerand stalk population was higher for plantsderived from leaf roll callus compared tobud propagated cane. Yield components weresimilar for plants derived from an apicalmeristem and bud propagation. Individualplant phenotypic variants resulting fromsomaclonal variation were not observed inany of the cultivars derived from eitherexplant source. In summary, genotype andexplant source affected persistent, uniformphenotypic variation resulting from tissueculture that changed some yield components. However, apical meristem culture wassuitable for production of seed-cane, assugarcane derived by meristem culture ofthree cultivars did not differsignificantly from the original germplasmfor any measured yield trait.     

Pesticide extraction efficiency of two solid phase disk types after shipping

An interlaboratory study was conducted to compare pesticide recovery from Empore C(18) and Speedisks C(18)XF solid phase extraction disks after shipping. Four pesticides were used for the comparison of the two disk extraction materials: atrazine, diazinon, metolachlor, and tebuconazole. These pesticides were chosen to provide a range of physiochemical properties. Water samples were extracted onto the disk types and shipped to a cooperating laboratory for elution and analysis. The mean recoveries from Empore disks were atrazine, 95%; diazinon, 91%; metolachlor, 92%; and tebuconazole, 83%. The recoveries from Speedisks C(18)XF were atrazine, 89%; diazinon, 87%; metolachlor, 86%; and tebuconazole, 79%. Means for each of the pesticides using the different disk types were not statistically different (alpha = 0.05), but results were more variable when using Speedisks C(18)XF as compared to Empore disks. Reasons for the increased variability are discussed, but overall results indicate that Speedisks C(18)XF could be used as an alternative to Empore disks. Speedisks C(18)XF are enclosed in a plastic housing, so they can be used more easily in remote sampling sites without the possibility of glassware breakage, no prefiltration of samples is needed, and there are realignment problems that can be associated with the Empore disks.     

Development of the Safe Tractor Assessment Rating System

We describe the development of the Safe Tractor Assessment and Rating System (STARS), a design-based tractor safety rating system that can be applied to new or used tractors to provide an objective assessment of their inherent safety features. A predictive rating system model, based on technical inspection, was used. Key principles underlying the system included the potential for design features to reduce the risk of an injury event occurring, and to reduce the risk of injury if such an event did occur. The rating system was based on current standards, research literature, injury and fatality data, and farmer input via focus groups. Development was an iterative process involving field, pilot, and inter-rater reliability tests. The final system was divided into six domains: rollover protection, runover protection, user protection, information and controls, pedestrian protection, and options. Within each domain, optimum design features were described for the common or serious potential injury risks, and a score was assigned for each feature. Scores were translated into a star rating, from zero stars for virtually no inherent safety features to five stars for the highest inherent safety, for each of the six domains. STARS distinguished well between older tractor models known to have few inherent safety features and newer tractor models known to have higher levels of inherent safety. STARS can provide tractor manufacturers, dealers, and users with information critical for managing tractor-associated injury risk. In Australia, it is initially being implemented within the curriculum of the technical education and training sector.     

Waterfowl-habitat associations during winter in an urban North Atlantic estuary

Coastal habitats near urban centres in North Atlantic estuaries often support substantial numbers of wintering waterfowl, but little is known of the effects of landscape setting and urbanisation on habitat use. We conducted surveys of waterfowl at 32 wintering sites in Narragansett Bay, Rhode Island, to identify characteristics that may influence habitat use. Sites were chosen along a gradient of urbanisation and reflected the dominant habitat types used by waterfowl in the Bay. Mean waterfowl abundance was 206.7 ± 209.5 birds per site, and sites in the inner part of the estuary had higher overall waterfowl abundances (r² = 0.40, p = 0.021). Species richness ranged from 3.2 to 13.0 and decreased with increasing hunting activity (r² = 0.36, p = 0.040). Hunting activity and habitat characteristics (e.g., latitude, shoreline configuration, prey density) explained 13-27% of the variation in waterfowl abundance and species richness among sites, but landscape characteristics (e.g., surrounding residential development, vegetated land, or wetland surrounding the sites and the extent of wetland edge) explained an additional 1-26%. The landscape characteristics extent of adjacent residential development and vegetated upland were the most common variables entering into the models; most species were more abundant at sites with more adjacent vegetated upland and less adjacent residential development. Our results suggest that landscape setting may be influencing the distribution of wintering waterfowl, and should be considered when developing strategies for the conservation for these species in urban North Atlantic estuaries.     

Mutagenic activity of soils amended with two refinery wastes

The mutagenic potential of the acid, base, and neutral fractions of petroleum sludge amended soil was determined using the Salmonella/microsome assay and Aspergillus methionine assay. Organic compounds were extracted from two different soils amended with either storm-water runoff impoundment or combined API-separator/slop-oil emulsion solids waste. Application of either waste to soil reduced the mutagenic activity of organic compounds extracted from equal weights of soil. However, biodegradation increased both the total and the direct-acting mutagenicity of all fractions residual in the waste-amended soil. The maximum level of mutagenic activity per milligram residual C was detected in the sample collected 360 days after waste application for the acid and base fractions from the storm-water runoff impoundment amended soils and the acid, base, and neutral fractions of the combined API separator/slop-oil emulsion waste amended soils. A comparison of the results based on equivalent weights of soil indicates that the mutagenic potential of both wastes was reduced by soil incorporation. The results from the Salmonella assay indicate that while the bulk of the solvent extractable organics in both wastes was rendered non-mutagenic, the mutagenic potential of the organic compounds in the acid fraction from the storm-water runoff impoundment sludge amended soil was increased. The results from the Aspergillus assay of both wastes indicate that the mutagenic potential of all three fractions was eventually reduced to a level that would be considered non-mutagenic. Thus, while degradation may have increased the mutagenic potential of specific organic compounds that were residual in the soil, the overall effect of degradation was to reduce the weighted activity of the waste amended soil.     

Alkalinity destruction by sediment organic matter dissolution during neutralization of acidified lakes

In this study we report on the effect of sediment, from an acidified lake, on the neutralization of the acidified water column. The results of this experimental study show that organic acids (presumably humic or fulvic acids) can dissolve from the sediment and destroy alkalinity as measured by a Gran plot analysis. Alkalinity destruction by organic acid dissolution was shown to be a function of pH. Some Na ion exchange for sediment H⁺ was also observed. This ion exchange was shown to be a function of pH and Na concentration.     

Biological effects of El Niño on the Galápagos penguin

Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans.