Genetic studies on seedling vigour in sesame

Genetic studies were carried out on seedling and agronomic characters amongst 50 sesame genotypes to estimate the genetic variation, determine the relationships amongst the characters and identify rapidly growing genotypes with vigorous seedling growth. The contribution of genetic variance was highest for the two mature characters, days to first flower (95.6%) and number of nodes to first flower (95.2%), and was medium/high (50–75%) for most of the seedling characters. Strong positive genetic correlations were obtained between various cotyledon and early leaf characteristics measured at 20 days after sowing. Based on these results several genotypes were identified as having rapid seedling growth and these could form an initial gene pool to provide material for screening for tolerance to sesame flea beetle.     

Distribution of Adult Male and Female Baccharis concinna (Asteraceae) in the Rupestrian Fields of Serra Do Cipó, Brazil

Abstract: This study focuses on the sex ratio and spatial distribution of males and females in three populations of the endemic and restricted tropical dioecious shrub, Baccharis concinna (Asteraceae) in the mountainous region of Serra do Cipó, southeastern Brazil. The proportion of female plants in the population at lower elevation (1000 m a.s.l.) was significantly greater than of male plants. At this elevation of P/N and Ca/Al ratios in the soil were also greater indicating better nutritional status of the soils. The concentration of aluminium increased significantly with the elevation ( p < 0.001), perhaps rendering soils less conducive to female plants at higher elevations. Female plants are possibly adversely affected to a greater extent by soil quality than male plants. The spatial distribution of the populations within habitat was tested by the K(t) function, where the neighbourhood of a given individual was defined by a circle with a radius (t) up to 3 m. Despite the strong tendency for aggregation, the distribution of the sexes within habitats was random and the hypothesis was not supported. The independent distribution of the sexes within habitats may be explained by nutrient homogeneity of the soils, as well as by an absence of antagonism between the sexes. Nevertheless, we found a trend for males and females to be aggregated according to their gender.     

Don C. Ohadike: The Man, his Intellectual Legacy and African Historiography

It is difficult to completely understand the life history of an intellectual excluding an understanding of his family upbringing and formative years. Family upbringing and childhood environment, often the less known part of a life history, play crucial roles in shaping the ideas and values individuals espouse in their adult life. Notwithstanding, this paper is not concerned with Don C. Ohadike’s childhood. It rather focuses on the professional career of our able historian – that is the part of his life as revealed by his most outstanding published writings. Ohadike’s published works contain a wellspring of idioms that tell much about his values, quality of mind, and his mission as an African historian. Ohadike was a humanist, an African patriot, and a nationalist crusader. His entire philosophy centered on safeguarding his African identity in an emergent world of cultural imperialism. The funds for this research were provided by a NEH-funded fellowship at the Schomburg Center, New York in the Spring of 2007. I owe a lot of gratitude to Professor John McLeod and Dean Blaine Hudson for granting me the extra incentives to pursue my research in New York. While all errors and misinterpretations are mine, I wish to thank the editors and anonymous reviewers for Journal of Dialectical Anthropology for their perspective comments and suggestions on earlier drafts of this paper.     

Latency of Botrytis cinerea Pers.: Fr. and Biochemical Studies During Growth and Ripening of Two Grape Berry Cultivars, Respectively Susceptible and Resistant to Grey Mould

Latency and development of Botrytis cinerea were assessed under field conditions and after artificial inoculation of two grape varieties, Gamay (susceptible) and Gamaret (resistant). When the percentage of latent Botrytis was the same for both varieties, severity of visible grey mould remained very low in Gamaret berries, while Gamay clusters were destroyed by the disease to a high percentage. Some biochemical parameters were measured in berries, such as constitutive and induced anti‐fungal compounds, polymeric proanthocyanidins and lipid peroxidation products as markers of senescence. Differences were observed in polymeric proanthocyanidins (PPRA) of Gamaret compared with those of Gamay. Concentration and mean degree of polymerization (mDP) of PPRA were always higher in the berries of the resistant variety. The inhibitory effect of Gamaret PPRA on enzyme activity remained until harvest whereas Gamay PPRA lost their inhibitory activity at the beginning of véraison. Based on these results, resistance to B. cinerea seems to be linked to the maintainance of the fungus in its latent form in berries, mainly due to the ability of Gamaret PPRA to inhibit macerating fungal enzyme activities.     

Alpha,beta-dehydrophenylalanine containing cecropin-melittin hybrid peptides: conformation and activity.

Synthesis and conformational studies of a cecropin-melittin hybrid pentadecapeptide CA(1-7)MEL(2-9), and its three alpha, beta-dehydrophenylalanine (DeltaPhe) containing analogs in water-TFE mixtures are described. DeltaPhe is placed at strategic positions in order to preserve the amphipathicity of the molecule. The wild type CAMEL0 and its three analogs, containing one, two and three DeltaPhe residues namely CAMELDeltaPhe1, CAMELDeltaPhe2 and CAMELDeltaPhe3 respectively were synthesized in solid phase and their conformation determined by CD and NMR. CAMELDeltaPhe2 and CAMELDeltaPhe3 peptides exhibit the presence of 3(10)-helix and beta-turns in the former and only turns in the latter. CAMELDeltaPhe1 peptide was found to have a largely extended conformation. Antibacterial and hemolytic activities of the peptides were also evaluated. CAMELDeltaPhe2 peptide is maximally potent against both Staphylococcus aureus ATCC 259230 and Escherichia coli ATCC 11303. CAMELDeltaPhe1 with a single DeltaPhe at the center shows minimal hemolysis.     

Morphological differentiation and resource polymorphism in three sympatric whitefish Coregonus lavaretus(L.) forms in a subarctic lake

Three field‐identified whitefish Coregonus lavaretus forms in Lake Muddusjärvi, Finland, were compared in morphology, diet and prey size. First, these forms were studied with univariate and multivariate analysis to assess morphological divergence at a higher resolution level than in the field. Second, stomach contents were analysed to estimate diet‐overlap among forms. Finally, the relationship between prey size and morphology was examined. The whitefish were assigned to the initial field‐classification with 99·2% and 98·8% accuracy for morphologic and meristic traits, respectively. The small sparsely‐rakered form (SSR) had the shortest rakers and largest gillraker space, followed by the large sparsely‐rakered form (LSR) with intermediate gillraker length and gillraker space, while densely‐rakered whitefish (DR) had the longest rakers and smallest gillraker space. The two sparsely‐rakered whitefish forms (LSR and SSR), consumed mainly benthic macroinvertebrates, while densely‐rakered whitefish (DR), utilized pelagic food items. Average diet‐overlaps between whitefish forms were low in June‐September (Schoener's α = 0·02 − 0·23). Gillraker number and length were negatively correlated to prey length in the diet ( r  = −0·73, and r  = −0·60), while gillraker space was positively correlated with prey length ( r  = 0·81). The fact that these whitefish forms were morphologically and ecologically segregated, and that gillraker traits probably have a functional value in food selection, further suggests that natural selection has been important in structuring life‐history trajectories into divergent niche use.     

Transformation of the forage legume Trifolium repens L. using binary Agrobacterium vectors

A system was established for introducing cloned genes into white clover (Trifolium repens L.). A high regeneration white clover genotype was transformed with binary Agrobacterium vectors containing a chimaeric gene which confers kanamycin resistance. Transformed kanamycin resistant callus was obtained by culturing Agrobacterium inoculated stolon internode segments on selective medium. The kanamycin resistance phenotype was stable in cells and in regenerated shoots. Transformation was confirmed by the expression of an unselected gene, nopaline synthase in selected cells and transgenic shoots and by the detection of neomycin phosphotransferase II enzymatic activity in kanamycin resistant cells. Integration of vector DNA sequences into plant DNA was demonstrated by Southern blot hybridisation.     

The effect of diffusion and convection on the rate of transfer of solutes across an interface

The transfer of substances across the interface between water and a membrane or between water and a solvent occurs in series with transport up to and away from the interface. These processes have been difficult to resolve. Recently D. M. Miller (Biochim Biophys Acta 856: 27–35, 1986) has used a moving drop technique to measure the rates of transfer of short-chain alcohols and tritiated water between water andn-octanol. This technique produces equivalent unstirred layers which are less than about 10 m thick. Based on the trends in the observed rates of phase transfer, he proposes that the transfer is limited by the actual interfacial step. If so, water-oil interfacial transfer would be sufficiently slow to limit the rate of permeation of lipid membranes by these substances. It is shown here that the observed rates of phase transfer can be explained quantitatively if they are limited by convection or by diffusion across the combination of 5–10 m unstirred layers both inside and outside the moving drops. For water, comparison of the observed rates with the rate of evaporation from a clean surface, suggests that the interfacial step at the water-octanol interface is not rate-limiting.     

Delayed inducible resistance against a leaf-chewing insect in four deciduous tree species

Summary Both mechanical damage to mountain birch foliage and rearing of moth larvae on the trees reduced the growth of Epirrita autumnata larvae reared on these trees in the following year. The effects of physical damage and some other cues from insects were additive. On bird cherry the performance of Epirrita larvae was equal on untreated trees and on trees artificially defoliated in the previous year, but larval growth was reduced on previously insect-damaged branches. With mountain ash just physical damage per se reduced the performance of Epirrita larvae. On Salix phylicifolia there were no significant differences in the growth or survival of Epirrita on untreated control bushes and on bushes with partial larval damage during the previous year. Among untreated control trees the growth and survivorship of Epirrita were higher on fast-growing willow and bird cherry than on the slow-growing mountain birch. Mountain birch and mountain ash, the two deciduous tree species adapted to nutrient-poor soils, showed delayed inducible resistance triggered by defoliation (artificial or insect-made). This supports the hypothesis that delayed inducible resistance may be a passive response due to nutrient-stress caused by defoliation. On the other hand, the additional increase in the resistance of mountain birch triggered by specific cues from insects suggests that this response may be an evolved defense against leaf-eating insects.     

The effect of simulated acid rain on performance of the aphid Euceraphis betulae (Koch) on silver birch

Summary The effect of artificial acid rain on the reproduction and survival of the aphid Euceraphis betulae on silver birch was studied in Turku, southern Finland. Eight bioassays were done during 1984–1986. In four of the bioassays the aphids produced 40% to over 100% more progeny on birches watered with dilute sulphuric acid (pH 3.5) than on control trees. In four other cases the performance of aphids did not differ between the treatments. An index of aphid reproduction pooled over the whole study was significantly higher on acid-treated than on control birches. The reproduction of aphids on acid-treated birches was enhanced when precipitation was below long term average, suggesting an interaction between the stress caused by acid treatment and dry periods.