Heterosis in inter and intrasubspecific crosses over three-environments in rice

Moderate to high heterosis for yield and ten related characters was studied in 45 crosses involving six indica (I) and four tropical japonica (J) varieties of rice under three (E₁-optimum sowing and high fertility, E₂-both optimum sowing and fertility and E₃- late sowing and high fertility) environments. Trends of magnitude of heterosis for grain yield and plant height were I/J > I/I > J/J and for days to 50% flowering I/J > J/J > I/I hybrids. Estimates of standard heterosis (%) for grain yield were –64.5 to 146.1 in E₁, –70.4 to 82.2 in E₂ and –67.2 to 63.8 in E₃. Environment E₁ seemed to be more favorable for higher heterosis expression than others. Higher heterosis in yield also accompanied heterosis in panicle number, dry matter and spikelet and grain number per panicle. Most estimates for days to flower were negative. Heterotic I/J hybrids also recorded maximum heterosis for earliness. Moderate to low standard heterosis for plant height across environments (2.0 to 13.7%) was recorded. Hybrids were identified in specific environments for direct exploitation in hybrid breeding. Hybrids B4116 / Sarjoo 52, B4122 / Pant Dhan 4 and B4122 / Narendera 359 were more stable than others over three environments. This revised version was published online in July 2006 with corrections to the Cover Date.     

methods during the silvopastoral-system establishment in midwestern USA: Cattle performance and tree damage

Silvopastoral systems offer an alternative to the conventional cow-calf segment of the beef industry in the Midwestern region of the United States. Little information exists for transitioning from a conventional pasture-based beef operation to a silvopastoral system utilizing multiple deciduous tree species. Nine pastures approximately 1 ha in size were established with a mixture of cool-season grasses and legumes to investigate tree protection methods and cattle performance. Four tree species (Juglans nigra, Gleditsia triacanthos, Quercus rubra, & Carya illinoensis) were planted within six of these pastures. Three methods of protection were tested, and included a no protection control (Con), foliar application of 0.20% denatonium benzoate (TreeGuard™), or a single strand of electrified poly-wire (EF) in each of the two grazing years. Cattle damage to young trees was prominent during the two years for Con and TreeGuard™. EF offered acceptable protection. Red oak trees suffered the highest degree of damage from livestock. Establishing trees within grazed pastures did not hinder performance of beef cattle. Transitioning from conventional pastures to silvopastures can be accelerated utilizing an electrified fencing system to prevent cattle damage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Central inhibitory activity of the aqueous extract of Crinum giganteum

The aqueous extract of Crinum giganteum given intraperitoneally at doses of 6.25, 12.5 and 25 mg/kg in rats prolonged the duration of pentobarbital sleeping time and in mice reduced spontaneous motor activity, decreased the exploratory activity and attenuated amphetamine-induced stereotype behavior. The intraperitoneal and oral preliminary LD(50) in mice were found to be 627 and 1468 mg/kg, respectively. The data obtained suggest that the aqueous extract of C. giganteum contains some biologically active principles with sedative activity.     

Bioactive constituents of Leptadenia arborea

The aerial part of Leptadenia arborea has been shown to contain pinoresinol (1), syringaresinol (2), leucanthemitol (3) and E-ferulaldehyde (4). These known compounds are being reported for the first time from this plant. Among them, syringaresinol has shown an inhibitory effect against acetylcholinesterase. The IC(50) (the concentration of 50% enzyme inhibition) value of this compound was 200 microg/ml.     

Models for predicting tree and stand development on larch plantations in Hallormsstaður,Iceland

The aim was to model the growth of Siberian larch (Larix sibirica Ledeb.) and Russian larch (Larix sukaczewii Dyl., syn. L. sibirica var. sukaczewii) plantations in Hallormsstaeur, Iceland. The field inventory was carried out in eastern Iceland in June 2006. Models were constructed for predicting dominant height, total tree height and 5-year diameter increment. Several linear and non-linear forms of models were tested in preliminary analyses to find the equations that fitted the modelled characteristics best. Due to the spatially hierarchical correlation structure of the data (stands, plots and trees), the assumption of non-correlated error terms did not hold. Therefore, a random parameter modelling approach was adopted using mixed models when the estimates obtained for the random effects were statistically significant. The variance estimates for the random effects can be further used to calibrate the models. The models generated here performed well with independent test data and were consistent with the forest growth theory. They can be used to evaluate site quality and to estimate the growth and yield of larch stands in eastern Iceland in connection with forest planning.     

Investigation of relationships between cell and pulp properties in Eucalyptus by examination of within-tree property variations

 Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages. The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1% significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types. Received 6 July 1999     

Land tenure and farm management efficiency: The case of smallholder rubber production in customary land areas of Sumatra

This study assesses the impact of land tenure institutions on the efficiency of farm management based on a case study of rubber production in customary land areas of Sumatra, Indonesia. Using the modes of land acquisition as measures of land tenure institutions, we estimated tree planting, revenue, income, and short-run profit functions, and internal rates of return to tree planting on smallholder rubber fields. We find generally insignificant differences in the incidence of tree planting and management efficiency (defined as residual profits) of rubber production between newly emerging private ownership and customary ownership. This is consistent with our hypothesis that tree planting confers stronger individual rights, if land rights are initially weak (as in the case of family land under customary land tenure systems). On the other hand, short-term profits are higher on land that is rented through share tenancy. This result indicates that rubber trees are over-exploited under renting arrangements due partly to the short-run nature of the land tenancy contracts and partly to the difficulty landowners face in supervising tapping activities of tenants in spatially dispersed rubber fields. This revised version was published online in June 2006 with corrections to the Cover Date.     

Associations between grain yield and carbon isotope discrimination in cowpea

Twenty cowpea (Vigna unguiculata L. Walp.) genotypes, comprising Kenyan cultivars and Kenyan and introduced breedings lines, were grown in 15 replicated field trials carried out at three locations in semi-arid eastern Kenya over four seasons. Grain and straw yields and the carbon isotope discrimination (Δ) of this material were determined, and days to flowering and maturity observed.None of the seasons in which the trials were conducted was appreciably drier than the long term average for the sites, and some trials received excessive rain. Averaging the data for the 15 trials, one genotype yielded much less grain (77 g m⁻²) than the 19 others, whose yield ranged from 125 to 177 g m⁻² (average 148 g m⁻²). Trial mean yield trials had a high straw Δ (r = +0.567) and had received more rain between flowering and maturity (r = +0.428) than lower yielding ones. Among genotypes, averaging over trials, the correlation coefficient (r) between grain yield and grain Δ was +0.394, and between grain yield and straw Δ, +0.460. Early genotypes had the highest grain Δ and straw Δ. The correlation among genotypes between date of flowering and grain Δ was −0.632 and with straw Δ, −0.502. When comparisons were made among trials, there was no clear relationship between the strength of the correlations among genotypes between grain yield and straw Δ or grain Δ and the degree of stress experienced by a trial (as indicated by the rainfall it had received). It appeared that this was because the variances of grain Δ and straw Δ were greater in the most droughted trials, whereas the variance of yield was greatest in the least droughted trials.It is concluded that the genetic correlation between grain yield and either grain Δ or straw Δ is unlikely to be strong enough to make either Δ a useful surrogate or adjunct in selecting for high yield in the segregating generations of a breeding programme for semi-arid eastern Kenya, but that Δ may be of value in the selection of parent genotypes.