Field tests of bacteria and soil-applied fungicides as control agents for take-all in winter wheat

Putative biological and chemical treatments for controlling take-all were used in each of three consecutive years at two locations where winter wheat crops were grown in naturally-infested fields. The chemical treatments more often decreased take-all than the biological treatments, but no treatment consistently and significantly decreased take-all, nor did any cause a significant increase in yield. An isolate of Bacillus cereus var. mycoides and one of B. pumilis, applied as soil drenches in autumn or spring, or in the seed furrows, were usually ineffective. Of the few significant effects on disease, half were associated with increases and half with decreases, and most occurred in April and did not persist to late June. Two strains of Pseudomonas pluorescens applied to the seed were ineffective. The fungicide benomyl, applied as a drench in autumn and spring at 20 kg/ha was ineffective, while nuarimol, applied as a drench in autumn at 2 kg/ha was sometimes effective. Nuarimol incorporated into the seed bed at 2 kg/ha was the most effective treatment. In analyses using a functional relationship model for data from treated and untreated plots 12% of 176 data sets for biological treatments, 38% of 96 data sets for chemical treatments and 81% of 16 data sets for combined treatments showed increasing efficiency of the treatment with increasing disease intensity. These findings also demonstrate an additional advantage of the experimental design, namely that treatments are tested at different disease intensity levels within fields.     

Starvation and Cell Wall Formation in the Myxomycete physarum polycephalum

Microplasmodia of the myxomycete physarum polycephalum weregrown in submersed agitated culture. When transferred from vigorouslygrowing cultures to non-nutrient balanced salt solution, theybegan to subdivide approximately 12 hours later and to formcell walls in a manner similar to that previously describedfor ‘aging’ cultures and for the formation of typicalsclerotia.     

A new species of shrike (Laniidae: Laniarius) from Somalia, verified by DNA sequence data from the only known individual

A new species of bush-shrike is described on the basis of the only known individual. The bird was captured in a disturbed Acacia thicket near the town of Bulo Burti by the Shabeelle River in central Somalia. Believed to represent a species near extinction, the bird was kept alive, studied in captivity and then released. The type material comprises moulted feathers, blood samples and DNA extracted from feather quills. For comparison, DNA from other bush-shrikes was obtained from old museum skins and three live birds. Comparisons of base sequences from the cyt-b gene of mitochondrial DNA support the judgement that the bird represents a full species and is not a colour morph or hybrid of examined taxa. This procedure confirms that, in situations where collecting is not desirable, tissue from live individuals can be used to define taxa, and for comparisons with DNA from museum specimens of other taxa.     

Evolutionary Trends in the Subsocial Sawflies Belonging to the Neodiprion abietis Complex (Hymenoptera: Tenthredinoidea)

Populations of the Neodiprion abietis complex occur on firsand spruces in North America. A distinct western populationon white fir differs greatly in appearance from the four easternstrains, of which two feed on balsam fir and one each on blackand white spruce respectively. Differences in developmentalrates, larval survival on the various food plants, and hostselection by the females supply the isolating mechanisms betweenthe strains in the field. All populations cross-mated freelyin the laboratory, and the resulting hybrids indicate the transmissionof Several morphological and physiological characters. It isspeculated that the ancestral line of the complex fed on pinebefore a jump to spruce and then to balsam was made.     

The relationship between rainfall,water source and growth for an endangered tree

Abstract It is now reasonably well understood that the human impact on the environment since industrialization has led to significant changes in climate. Here we attempt to develop a predictive understanding of the effects that future changes in climate may have on vegetation structure and species diversity. We do this through a determination of the relationship between radial growth and water source for Widdringtonia cedarbergensis Marsh. Our results show that there was no significant relationship between monthly radial growth, as determined using dendrometer bands, and rainfall. There is, however, a significant relationship between the δ¹⁸O composition of the water extracted from the trees and the rain δ¹⁸O values. We speculate that W. cedarbergensis exploits water derived from rain that flows off the rocky substrate of the study area into sumps between the bedding planes of the rocks on which they grow. This runoff occurs rapidly during rain events resulting in δ¹⁸O values for the trees sourcing this water not to be significantly different from that of the rain. Rainfall therefore has to be sufficient to refill these sumps on which the trees are dependent. The dendrometer bands reflect a slow but steady growth of the trees at the study site. While this growth is not dependent on rainfall, it is dependent on reliable access to available water. If climate change predictions for the region are realized and rainfall is reduced then this species will be affected. W. cedarbergensis is endemic to only a very small area within the Cedarberg Mountains in South Africa and is also one of the few trees growing in the fynbos. The extinction of this species in the wild will fundamentally affect both the vegetation structure and species composition of the region.