Induced Resistance in Tomato Against Corynebacterium michiganense pv. michiganense by Prior Inoculation with Pseudomonas syringae Pathovars

Prior inoculation of wounded tomato petioles with a minimum concentration of 5 × 10⁴ cells per wound of various Pseudomonas syringae pathovars completely protected plants against subsequent infection with Corynebacterium michiganense pv. michiganense inoculated on the same site. Only living cells induced effective protection. In protected tissue, cells of Corynebacterium michiganense pv. michiganense remained localized at the inoculation site and their multiplication was restricted. Irrespective of the cell number introduced, initial population decreased slowly and then levelled off below the initial inoculum level. This level remained constant throughout the experimental period (15 days). Similarly, the, cell number of the inducer Pseudomonas syringae pv. phaseolicola levelled off at ca. 10⁶ cells per plant. The protection was not systemic and could be eliminated by removing the upper 5 mm of the inoculated wound tissues containing, the inducer.     

Effects of aldicarb persistence on field populations of Heterodera schachtii

In field trials in 1976 and 1977 various granular formulations of aldicarb (2–8 to 12.8 kg a.i. ha^-1) were applied to sugar-beet fields infested with Heterodera schachtii . The levels of toxic residues of aldicarb and of H. schachtii populations in the soil were monitored at intervals throughout the sugar-beet season.
A severe drought in 1976 seriously affected the field trials and although aldicarb levels were maintained in the soil no aldicarb treatment proved effective in controlling H. schachtii; this was probably due to lack of mobility of the pesticide in the soil. In 1977, the final nematode populations in plots treated with 2.8 or 11.2 kg a.i. ha^-1 added incrementally through the growing season to simulate the effect of a controlled release formulation were not significantly different from those of untreated plots. In contrast treatment at drilling with fast-releasing formulations at all application rates did promote control of H. schachtii populations. No significant increase in yield was found on any trial after treatment with aldicarb.
The value of controlled release formulations of aldicarb for the control of H. schachtii populations over the growing season has not been proven.     

Spermatogenesis in the archaic hydrothermal vent bivalve,Bathypecten vulcani,and comparison of spermatozoon ultrastructure with littoral pectinids

Summary

Bathypecten vulcani is considered a relict species from the Paleozoic, based on shell characteristics such as the presence of calcite prisms. To date, it is the only pectinid species reported from hydrothermal ecosystems. Histological and ultrastructural studies show that spermatogenesis is identical to that of littoral pectinids. The spermatozoon has a 2.7 μm long pyriform head and a 40 μm flagellum. The four mitochondria of the mid-piece are about 1.2 μm in diameter. The nucleus contains dense chromatin fibres and possesses a wide, shallow (0.1 μm) anterior fossa and a narrow, deeper (0.2 μm) posterior nuclear fossa. Comparison of the ultrastructural characteristics of the spermatozoon of B. vulcani with those of littoral pectinids shows that they can be used as a diagnostic feature of this species. In particular, its acrosome characters will be a useful complement to the shell characters in the study of the phylogenetic position of this species in relation to other pectinids.     

Induction of Melanogenesis by Tetradecanoylphorbol‐13 Acetate and Endothelin 3 in Embryonic Avian Peripheral Nerve Cultures

In this study, we have analyzed the melanogenic potential of Schwann cells using in vitro cell cultures of embryonic quail peripheral nerves. It is shown that in Schwann cells, two factors, 12‐O‐tetradecanoylphorbol‐13 acetate (TPA) and endothelin 3, trigger a differentiation pathway toward melanocytes, and that Steel factor has no effect on these cells unless treated simultaneously with TPA. In these cultures, TPA induces the expression of c‐kit, whereas Steel factor enhances the development of melanocytes. In the assay system we employed, neither neuronal nor catecholaminergic phenotypes were obtained, regardless of various combinations of related factors added to the culture medium. These data support our previous observations indicating the existence of bipotent progenitors that are capable of differentiating into Schwann cells or into melanocytes, and the regulatory role of endothelin 3 on those precursors, as revealed by the clonal culture of neural crest cells.     

An assessment of a method based on intrinsic antibiotic resistance for identifying Rhizobium strains

A method based on intrinsic antibiotic resistance (IAR) for identifying large numbers of Rhizobium strains was assessed and found to be unsatisfactory for R. phaseoli and isolates from Cicer arietinum (Rhizobium spp.). Our data showed that the number of different IAR patterns always exceeded the number of strains tested. With 90 nodule isolates from plants inoculated with a mixture of three strains of R. Phaseoli, the technique gave 18 different resistance patterns. When 24 strains of Rhizobium spp., each replicated three times, were examined 68 different resistance patterns were obtained. Single colony isolates from one strain also gave several different IAR patterns. All strains tested with fluorescent“ antibody were readily identified. Attempts to obtain correct strain identification with IAR by simplifying the scoring systems or allowing up to two differences in the resistance patterns were unsuccessful. We were unable to define the source of this variation although incubation time and inoculum concentration were shown to affect the IAR patterns     

Feeding ecology and phylogenetic structure of a complex neotropical termite assemblage,revealed by nitrogen stable isotope ratios

1. In the current ecological classification of termites, four feeding groups (I–IV) are recognised, corresponding to a gradient of decomposition from sound wood to highly mineralised organic matter in the soil. 2. Nitrogen stable isotopes (hereafter δ¹⁵N) were used to place termites from French Guiana rainforests along a wood‐soil decomposition gradient, to test (i) whether feeding group assignation based on morphological characters was accurate and actually represented diet specialisation thresholds, and (ii) to what extent the dietary specialization of species is explained by phylogeny (phylogenetic autocorrelation). 3. δ¹⁵N values vary over a range of 13‰, suggesting that diet diversification contributes to the high species diversity in French Guiana. δ¹⁵N values span a similar interval in all Termitidae subfamilies. Ranges of different subfamilies broadly overlap, although each of them diversified preferentially on one side of the wood‐soil decomposition gradient. Congeneric species share similar feeding habits, whereas distant species tend to feed on distinct substrates. 4. Feeding groups did not completely match stable isotope data: there was no discontinuity between Groups III and IV, and no correlation between anatomical criteria used to distinguish these groups and δ¹⁵N values. Nor was there any consistent difference in δ¹⁵N values between wood feeders of the families Rhinotermitidae (Group I) and Termitidae (Group II). We also suggest that species feeding outside the wood‐soil gradient should be distinguished for their peculiar feeding requirements.