Diallel analysis of tolerance to aluminium in alfalfa

Summary Acid soils having high levels of aluminium (Al) can drastically reduce yields in alfalfa and the most economically viable solution to the problem appears to be the development of Al-tolerant cultivars. To assist with the choice of a breeding method, a six-parent alfalfa diallel (crosses and reciprocals included but not parents) was evaluated in Al-toxic nutrient solution in terms of height (HT) and dry weight (DW). General combining ability was significant for both traits and constituted the majority of the genetic variation. Specific combining ability was significant only for HT and reciprocal effects were significant only for DW. Tolerance appeared to be at least partially dominant to sensitivity. Results indicate that a mass selection scheme, such as recurrent phenotypic selection, may be effective in increasing levels of tolerance in at least some alfalfa populations and that minor grains may also be achieved through exploiting non-additive genetic variation.     

Starch Pasting and Textural Attributes of Elbow Macaroni as Impacted by Dough Moisture,Dough Mixing Time,and Macaroni Cooking Time

The effects of dough moisture, mixing time, and cooking time on uncooked and cooked elbow macaroni by means of starch pasting and macaroni textural characteristics were investigated. In conventional elbow macaroni production, cooking time was found to have significant contributions to cooked macaroni starch pasting properties, indicating that degree of starch cook dependent on cooking time was the main influence on cooked macaroni starch pasting phenomena. Dough moisture also showed some significant (P < 0.05) relationships with cooked macaroni starch pasting properties; however, mixing time did not show significant effect. Cooked macaroni starch pasting properties showed significantly (P < 0.05) high correlations with cooked macaroni firmness and stickiness. Cooking time was the only major variable contributing to variations in cooked elbow macaroni starch and consequently in pasting and texture characteristics. Cooking time was highly related to firmness and stickiness of cooked elbow macaroni (P < 0.0001, R² = 0.8148; P < 0.0001, R² = 0.6215, respectively). In addition, dough moisture had a slight significant (P < 0.05) effect on cooked elbow macaroni firmness and stickiness. Cooked elbow macaroni firmness and stickiness were found to be highly correlated (P = 0.0001, R² = 0.8459). Increases in firmness increased cooked elbow macaroni stickiness. As a result, when elbow macaroni was cooked for shorter times, firmer and stickier macaroni was obtained.     

Terrestrial habitat requirements of nesting freshwater turtles

Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of > 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m for Malaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6–98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (<200 m zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys, Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings.     

Production of Perchlorate by Laboratory Simulated Lightning Process

Perchlorate (ClO₄⁻), a thyroid hormone disruptor, is both naturally occurring and a man-made contaminant increasingly found in a variety of terrestrial environments. The environmental presence of ClO₄⁻ is considered to be the result of atmospheric formation and deposition processes. The ultimate processes, particularly heterogeneous-based reactions, leading to natural ClO₄⁻ formation are not well understood. Oxidation of chlorine species by an energetic source such as lightning is considered to be one of the potential heterogeneous sources of natural ClO₄⁻. Currently, there is very little information available on lightning-induced ClO₄⁻. We designed a laboratory electrical discharge reactor capable of evaluating ClO₄⁻ formation by the oxidation of “dry” sodium chloride (NaCl) aerosols (relative humidity (RH) <70%) in electrical discharge plasma at voltages and energies up to 24 kV and 21 kJ, respectively. Similar to other non-electrochemical ClO₄⁻ production processes, the amount of ClO₄⁻ produced (0.5–4.8 μg) was 3 orders of magnitude lower than the input Cl⁻ (7.1–60.1 mg). The amount of ClO₄⁻ generated increased with peak voltage (V) and theoretical maximum discharge energy with ΔClO₄⁻/ΔV = 0.28 × 10⁻³ μg V⁻¹ (R ² = 0.94) and ΔClO₄⁻/ΔE = 0.44 × 10⁻³ μg J⁻¹ (R ² = 0.83). The total ClO₄⁻ generated decreased with an increase in relative humidity from 2.8 ± 0.1 μg (RH ∼46%) to 0.9 ± 0.1 μg (RH ∼62%) indicating that the presence of moisture inhibits the formation of ClO₄⁻. Additional modifications to the reactor support the hypothesis of ClO₄⁻ formation due to the action of plasma on Cl⁻ aerosols as opposed to direct oxidation on the surface of the electrodes. Finally, the contribution of lightning-induced ClO₄⁻ in North America is calculated to have a wide range from 0.006 × 10⁵ to 5 × 10⁵ kg/year and is within the range of the measured ClO₄⁻ depositional flux in precipitation samples obtained across the USA (0.09 × 10⁵–1.2 × 10⁵ kg/y).     

Effects of NPK fertilizer combinations on yield and nitrogen balance in sorghum or pigeonpea on a vertisol in the semi-arid tropics

A long-term experiment was carried out on a Vertisol from 1986 to 1992 to examine the combined effects of NPK fertilizers on yield using sorghum (Sorghum bicolor L. Moench cv. CSH 5) and short-duration pigeonpea (Cajanus cajan L. Millsp. cv. ICPL 87). The fertilizer treatments were as follows: 0 (no fertilization), N (150 kg N ha^-1 ), P (65.5 kg P₂O₅ ha^-1), K (124.5 kg K₂O ha^-1), and all possible combinations (NP, NK, PK, and NPK). In this study we continued this experiment during the period 1993 to 1994 and analyzed the crop yield response to fertilizers and the N balance. The amount of N derived from the atmosphere and fertilizer was estimated by the ¹⁵N natural abundance method and ^l5N isotope dilution method, respectively. A combined application of Nand P fertilizers gave the highest grain yield for the two crops under the 8th and 9th continuous croppings, unlike the application of K fertilizer. The values of total N for the two crops were significantly higher in the NP and NPK plots. These crops took up N mainly from soil. There was a significant positive relationship between the uptake of N_dff and N_dfs by each crop. Pigeonpea or sorghum took up more N from the soil in the N fertilizer plots than in the plots without N, suggesting that soil N fertility was enhanced and the amount of N supplied from soil increased in the plots with consecutive application of N fertilizer for 7 y. Even pigeonpea, which fixes atmospheric N inherently, needed N fertilizer to achieve high grain yield, suggesting that N fixation by the nodules was not always sufficient to meet the N requirements of the crop under these conditions. Although fertilizer N exerted a beneficial effect on plant growth and yield in the two crops, the values of fertilizer N recovery (FNR) by the two crops were considerably low. Therefore, it is suggested that the development of N fertilizer management which could maximize FNR of each crop should be promoted.     

Diurnal malate and citrate fluctuations as related to nitrate and potassium concentrations in tomato leaves

Abstract

Two experiments were conducted to determine if malate and citrate change diurnally, if these changes are light dependent, and how these changes relate to K⁺ and NO₃ ^?1 levels. Malate concentration in tomato leaves was shown to increase during the day and decrease at night. The inverse occurred with citrate. The dependency of the changes on light was demonstrated for malate, but not for citrate. A relationship with NO₃ ^? assimilation and K⁺ recirculation may explain the changes in malate concentration.     

Optical density variation in aerial photographs of potato plots infected withPhytophthora infestans

Optical density signatures were developed from infrared photographs of plots infected with late blight caused byPhytophthora infestans (Mont.) d By. Slight differences between optical density signatures of plots with different spray schedules preceded corresponding differences in infection levels that were not visually apparent on the date of photography but were visually apparent later. The technique of density signature development allowed consistent and quantitative differences to be recorded.     

Management of gastrointestinal nematode parasites on sheep farms in New Zealand

AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand.

METHODS: An interview-based cross-sectional study of grazing management and anthelmintic useage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand.

RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased.

CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.