Changes in the content of steroidal glycoalkaloids in potato tubers grown in the field and in the greenhouse under different conditions of light, temperature and daylength

Differences in the content of steroid glycoalkaloids (SGA) were noted in the peels of potato tubers cultivars Alpha, Cara, Désirée and LT-7. Cultivar LT-7 had always the highest SGA content, Désirée was intermediate and Alpha and Cara had the lowest SGA content, regardless of growing conditions, tuber ageing and tuber treatments. Tubers grown during the summer developed the highest SGA content as compared to those grown in the spring and winter seasons, respectively. Tubers grown during winter showed an increase in SGA toward the end of the storage period. Similar results were obtained with tubers of LT-7 grown in a greenhouse under cool temperatures in combination with short days (which imitate the winter conditions in Israel). A decrease in SGA content was observed in tuber slices treated with a fungal cell-wall preparation fromPhytophthora citrophthora. This decrease was much stronger in the pith than in the peel, indicating a possible role for SGA in the defence mechanism because peels are the first part of the tuber to be invaded by pathogens. The above results were observed in tubers of all cultivars regardless of the growing season or tuber ageing.     

Australian Uromyces viciae-fabae: Host and nonhost interaction among cultivated grain legumes

Uromyces viciae-fabae, rust of faba bean, parasitizes other legume crops such as lentils (Lens culinaris) and field peas (Pisum sativum) in some environments. In this study we examined the host range of two Australian isolates of U. viciae-fabae collected and purified from a faba bean crop and classified as U. viciae-fabae ex V. faba. Field pea (P. sativum), chickpea (Cicer arientinum), lupin (Lupinus spp.), lentil (L. culinaris), and mung bean (Vigna radiata) genotypes were tested with these isolates, as well as resistant and susceptible genotypes of the faba bean host. Race specificity for these two pathogen isolates was observed on Vicia faba, with two faba bean genotypes showing partial resistance. Both U. viciae-fabae isolates also colonized field pea seedlings and successfully produced uredinia under glasshouse conditions, despite this fungus not being known as a pathogen of Australian field pea crops. No sporulation of either isolate of U. viciae-fabae ex V. faba was observed on any of the remaining legume species tested. However, obvious differences in fungal growth were observed, ranging from small infection sites with very rare haustorium formation in mung bean to more extensive growth and the development of potential uredinial structures in chickpea. These observations are discussed in relation to the phylogenetic relationship of these host and nonhost species.     

Reduced Germination and Seedling Vigor of Weeds with Root Extracts of Maize and Soybean,and the Mechanism Defined as Allelopathic

Journal of Crop Science and Biotechnology - Due to the negative consequences of synthetic herbicides use and their reducing effectiveness due to development of resistant weeds, promotion of...     

Aerobic microbial respiration in 86-million-year-old deep-sea red clay

Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O(2) liter(-1) year(-1) near the sediment-water interface to 0.001 micromoles of O(2) liter(-1) year(-1) at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10(-3) femtomoles of O(2) cell(-1) day(-1) 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux.     

Effect of ammonia-N on growth and feeding of juvenile Macrobrachium rosenbergii (De-Man)

Survival rate, growth and feed intake were determined for late juveniles (4.31 ± 0.18 g) of river prawn Macrobrachium rosenbergii in freshwater with total ammonia‐N (NH₃‐N+NH₄‐N) concentrations of 0.015 (control), 0.5, 1.0 and 1.5 mg L⁻¹ for 60 days at pH 7.53 ± 0.04 and temperature 24.0 ± 2.5°C. Survival rate was significantly (P<0.05) lower (54 ± 4.2–70 ± 5.4%) for total ammonia concentrations from 0.5 to 1.5 mg L⁻¹ [0.0139–0.0419 mg L⁻¹ of unionized ammonia (NH₃)]. Growth (0.026–0.030 g day⁻¹ range) of the prawns did not differ for the different NH₃ levels but were significantly (P<0.05) lower compared with control (0.056 g day⁻¹). Feed intake rates also diminished significantly (P<0.05) from 77.60 ± 2.45% at control (0.015 mg L⁻¹ NH₃‐N) to 48.69 ± 2.13% at 1.5 mg L⁻¹ NH₃‐N (0.0419 mg L⁻¹ of unionized NH₃).     

Effect of calcium and magnesium hardness on acute copper toxicity to Indian major carp, Labeo rohita (Hamilton) and catfish, Channa punctatus (Bloch)

Four experiments were conducted to evaluate the effects of calcium and magnesium hardness on the acute toxicity of copper sulphate to Indian major carp, rohu (Labeo rohita, Hamilton) fingerlings and juvenile catfish (Channa punctatus, Bloch) in medium alkalinity experiments. A preliminary bioassay determined the 96 h LC₅₀ of copper sulphate to be 0.56 mg L^?1 for L. rohita fingerlings and 11.78 mg L^?1 for juvenile C. punctatus placed in water with calcium hardness and total alkalinity set at 100 mg L^?1 CaCO₃. In the first experiment, rohu were exposed to 0.56 mg L^?1 copper sulphate in environments where calcium hardness was varied from 50 to 350 mg L^?1 CaCO₃ and total alkalinity was 100 mg L^?1 CaCO₃. As calcium hardness increased, copper‐induced rohu mortalities decreased significantly from 90% at 50 mg L^?1 CaCO₃ to 7% at 350 mg L^?1 CaCO₃. In the second experiment, rohu were exposed to 0.56 mg L^?1 copper sulphate in environments where magnesium hardness was varied from 50 to 350 mg L^?1 CaCO₃ with total alkalinity set at 100 mg L^?1 CaCO₃. Hundred percent mortality was observed in magnesium‐based hardness treatments. In the third experiment, catfish were exposed to 11.78 mg L^?1 copper sulphate in environments where calcium hardness was varied from 50 to 400 mg L^?1 and total alkalinity was 100 mg L^?1 CaCO₃. As calcium hardness increased, copper‐induced catfish mortalities decreased significantly from 90% at 50 mg L^?1 CaCO₃ to 4% at 400 mg L^?1 CaCO₃. In the fourth experiment, catfish were exposed to 11.78 mg L^?1 copper sulphate in environments where magnesium hardness was varied from 50 to 400 mg L^?1 CaCO₃, with total alkalinity set at 100 mg L^?1 CaCO₃. In this case, 100% mortality was also observed in magnesium‐based treatments. Mortality rates in magnesium hardness treatments were consistent with those in the second experiment. These data suggest a calcium‐specific mechanism with respect to acute copper toxicity both in rohu and catfish.     

Diallel analysis over two environments for blossom-end scar size in tomato

Summary To investigate genetic regulation of blossom-end scar size in tomato (Lycopersicon esculentum Mill.), a half diallel cross including 10 parents was grown under warm fall conditions in Bradenton, Florida, and cool winter conditions in Hazeva, Israel. The parents were a random sample representing all available fresh market tomato breeding lines commercially grown under subtropical field conditions. A randomized, complete block design with three replications was used and the blossom-end scar index (BSI), a measure for scar size relative to truit size, was measured on 40 and 25 fruits per plot in Bradenton and Hazeva, respectively. Analysis of variance for BSI indicated highly significant (P=0.001) variation among parents and among F1's in both environments. In Bradenton and Hazeva both, the difference in average BSI between parents and F1's was not significant suggesting insignificant overall dominance effects. Further partitioning of variation within F1's indicated that general combining ability (GCA) effects were highly significant in both environments, whereas specific combining ability (SCA) effects were significant at P=0.001 in Bradenton, but only at P=0.05 in Hazeva. Estimated variance components for GCA and SCA effects indicated that BSI inherited mainly additively in both environments. Analysis combined over environments indicated that variation in sensitivity to environments was 5-fold higher among parents than among F1's. The genotype x environment variance component was not large enough to justify testing over more than one environment for population improvement purposes and early testing of hybrids. Evaluation of inbred lines, however, may have to be done in more than one environment, especially for Suncoast-derived material. Under temperatures in Hazeva, genotype differences were more pronounced and heritabilities higher than under high temperatures in Bradenton. The estimated overall single plot heritability was 0.63. Breeding lines with a pointed blossom-end morphology (e.g. NC 8276 and NC 140 in this study) generally had small blossom-end scars, and intercrossing of these lines or crossing with non-pointed, moderately smooth breeding lines generally resulted in smooth hybrids.     

A random amplified polymorphic DNA (RAPD) molecular marker for the Tm-2 a gene in tomato

Summary A RAPD marker, linked to the Tm-2 ^agene engendering TMV resistance in tomatoes, was identified. The validity of the RAPD marker was corroborated by screening several tomato varieties, and correctly identifying those which carried Tm-2 ^a, as well as by F₂ segregation analysis. All tested resistant varieties descending from a common Lycopersicon peruvianum/esculentum ancestor, LA1791, exhibited this marker.     

The potential of ripening mutants for extending the storage life of the tomato fruit

Summary The effect of the fruit ripening mutants rin, gr, nor and Nr on storage life and pigmentation was investigated in homozygous material, in heterozygous F₁ combinations between the mutants with the colour mutant hp and with the normal cv. Kewalo. Crosses with nor showed a 3-to 5-fold increase in storage life in comparison with the normal cv. or with hp. Maximum pigmentation of the fruits of crosses with nor was pale-red with vineripened fruit and pink with fruit harvested at the breaker stage and ripened on the shelf. The ripening inhibitory effect of rin in the different F₁ combinations was less pronounced than that of nor, and the colour of the fruits was improved. Fruits of the F₁ cross between rin and nor showed greatly improved storage life and developed pink or pale red colour. Most heterozygotes with hp showed improved pigmentation. Problems anticipated in utilizing ripening mutants in breeding for improved keeping quality are discussed.