EFFECTS OF CULTURAL TREATMENTS ON WHEAT AND ON THE INCIDENCE OF EYESPOT, LODGING, TAKE-ALL AND WEEDS. Field Experiments 1945–8

An experiment was made on the fourth, fifth and sixth successive crops of winter wheat to determine the effects of various treatments on the troubles which result from close cereal cropping. Eyespot and lodging were prevalent in the first year (1946); weeds in the second; eyespot, lodging, take-all and weeds in the third.
Spraying with H₂SO₄ reduced the incidence of eyespot, lodging and weeds, and increased yield of grain on plots which received sulphate of ammonia (by 2.7, 2.2 and 10.0 cwt./acre in successive years).
Sulphate of ammonia increased the incidence at harvest of eyespot and lodging, reduced take-all and consistently increased yield of straw. Eyespot and lodging reduced the effect of the fertilizer on yield of grain, take-all increased it.
Increase in seed rate increased the incidence of severe eyespot and of take-all; it increased lodging except when plants were dwarfed by take-all.
Weight of straw and percentage straws with severe eyespot lesions independently affected lodging, together accounting for 51% of the variance in percentage area lodged at harvest and 64 % of that lodged 33 days earlier.
Mean yields of grain on untreated plots sown with 3.3 1/2 bushels seed/acre fell from 26.0 to 22.5 to 11.7 cwt./acre in successive years, whereas yields of 28.4, 29.9 and 29.1 cwt./acre were obtained on sprayed plots sown with 1 1/2.2 bushels seed/acre which received 4 cwt./acre sulphate of ammonia, showing that high yields were maintained when eyespot, lodging, take-all and weeds were controlled.
By 1948 yields of grain on unsprayed plots had fallen to the level of those on similarly manured plots on the continuous wheat experiment on Broadbalk field. Spraying increased grain by amounts similar to those resulting from one year's fallow on Broadbalk; but fallow had its greatest effects on plots with low nitrogen, spraying on those with high nitrogen.     

Morphological variation and genome constitution in some perennial Triticeae

JARVIE, J. K. & BARKWORTH, M. E., 1992. Morphological variation and genome constitution in some perennial Triticeae. A numerical analysis of species of five genomically defined genera of the Triticeae was undertaken, based on 42 morphological characters and 142 operational taxonomic units (OTUs). The primary goal was to determine the degree of congruence between morphological variation and genomic constitution. The second goal was to determine which existing supraspecific classification, if any, best reflected the morphological variation encountered. The five genera investigated were Thinopyrum (J genome), Lophopyrum (E genome), Pseudoroegneria (S genome), Trichopyrum (EES genome) and Elytrigia (SJE/SSX genome). Both principal co-ordinate and cluster analysis of the data placed the OTUs in supraspecific groups that reflected their genomic constitution. Monogenomic taxa were clearly separated. Allotetraploids between the E and S genomes were situated between E and S monogenomic taxa. Allotetraploids between the J and E genomes were situated closest to J genome taxa. The EES taxa of Trichopyrum were placed closest to Lophopyrum. OTUs of Elytrigia overlapped those of Pseudoroegneria , but not those of Lophopyrum or Thinopyrum.     

Identification and characterization of simple sequence repeat markers from Brassica napus expressed sequences

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 24 expressed sequence tags (EST)‐SSR markers from Brassica napus and their cross‐amplification across Brassica species. The markers show reliable amplification, genome specificity and considerable polymorphism, demonstrating the utility of EST‐SSRs for genetic analysis of wild Brassica populations and commercial Brassica germplasm.     

Mutual mate choice by mountain pine beetles: size‐dependence but not size‐assortative mating

1. Mutual mate choice may be rare, occurring when both sexes invest heavily in reproduction, mating opportunities are abundant, and individuals differ in quality. 2. Mountain pine beetles, Dendroctonus ponderosae (Curculionidae: Scolytinae) appear to meet the conditions for mutual mate choice. We introduced males to females in breeding sites and observed the occurrence and speed of a male entering a female's gallery. We tested for consequences of mutual mate choice, namely condition‐dependent choosiness and assortative mating. 3. Males were more likely to enter a female's gallery when the gallery was in a smaller tree with less resin production and when the gallery was larger. Female body size and condition did not influence the probability of entry. Larger males were less likely to enter a gallery than were smaller males, probably because of size‐dependent choosiness rather than physical limitations. 4. Small males took longer to enter galleries of large females than of small females, whereas large males entered as quickly into galleries of large females as small females. This suggests size‐dependent choosiness by females. 5. No assortative mating by body size was detected, probably because males appeared to choose on the basis of female‐associated resources rather than on female traits.     

Methane production by microbial mats under low sulphate concentrations

Cyanobacterial mats collected in hypersaline salterns were incubated in a greenhouse under low sulphate concentrations ([]) and examined for their primary productivity and emissions of methane and other major carbon species. Atmospheric greenhouse warming by gases such as carbon dioxide and methane must have been greater during the Archean than today in order to account for a record of moderate to warm palaeoclimates, despite a less luminous early sun. It has been suggested that decreased levels of oxygen and sulphate in Archean oceans could have significantly stimulated microbial methanogenesis relative to present marine rates, with a resultant increase in the relative importance of methane in maintaining the early greenhouse. We maintained modern microbial mats, models of ancient coastal marine communities, in artificial brine mixtures containing both modern [] (c. 70 mm ) and ‘Archean’[] (<0.2 mm ). At low [], primary production in the mats was essentially unaffected, while rates of sulphate reduction decreased by a factor of three, and methane fluxes increased by up to 10‐fold. However, remineralization by methanogenesis still amounted to less than 0.4% of the total carbon released by the mats. The relatively low efficiency of conversion of photosynthate to methane is suggested to reflect the particular geometry and chemical microenvironment of hypersaline cyanobacterial mats. Therefore, such mats were probably relatively weak net sources of methane throughout their 3.5 Ga history, even during periods of low environmental levels oxygen and sulphate.     

Limb bone histology and growth in Placerias hesternus (Therapsida: Anomodontia) from the Upper Triassic of North America

Abstract: Patterns of bone deposition are reported and deduced from mid‐shaft sections of 21 limb bones of the dicynodont Placerias hesternus from the Placerias Quarry (Upper Triassic), Arizona, USA. All sampled elements of P. hesternus have a large medullary cavity completely filled with bony trabeculae surrounded by dense cortical bone. Dense Haversian bone extends from the perimedullary region to at least the mid‐cortex in all sampled bones. Primary bone in the outer cortex of limb elements of P. hesternus is generally zonal fibrolamellar with a peripheral layer of parallel‐fibred bone. These data suggest periodic rapid osteogenesis followed by slower growth. Among dicynodonts, this strategy is most similar to growth previously reported in other Triassic (Lystrosaurus, Wadiasaurus) and some Permian taxa (Oudenodon, Tropidostoma). An external fundamental system (EFS), suggesting complete or near complete cessation of appositional growth, is present in the largest tibia. This is the first report of EFS in dicynodonts and may represent the attainment of maximum size in P. hesternus. Slow‐growing peripheral bone was observed in elements of varying size in our sample and may support a differential growth pattern between P. hesternus individuals from this locality. A complete growth series of P. hesternus, analysis of Placerias specimens from other localities, and further sampling of other Upper Triassic dicynodonts are needed to better understand a more complete picture of the growth and remodelling patterns that we have initially investigated.     

Characterization of polymorphic microsatellite loci for the polychaete tubeworm Hobsonia florida

Eight dinucleotide microsatellite loci were isolated and characterized from Hobsonia florida, a tube‐dwelling ampharetid polychaete. The identified loci were highly polymorphic, with allelic diversity ranging from six to 11 alleles. Levels of expected heterozygosity were 0.52 or greater in all cases, averaging 0.78 across the complete set of loci. Cross‐species amplification was successful in three of the eight loci for one or both of the other species (Melinna cristata and Ampharete acutifrons) tested. Although these novel loci were designed for immediate utility in H. florida population‐level research, these results indicate they may prove useful in studies of other related taxa.     

Protein Kinase C and Melanocyte Transformation

Melanoma cells which have been isolated from metastatic melanoma tissue are able to survive and proliferate in serum supplemented media. In contrast, normal human melanocytes require the presence of growth stimulators if they are to survive in culture. A tumor promotor, 12–0-tetradecanoyl-phorbol-13-acetate (TPA) and substances that increase intracellular levels of cyclic-adenosine-monophosphate (cAMP), such as cholera toxin or isobutylmethyl xanthine, have been widely used for this purpose. The phorbol diester receptor was shown in 1982 to be the phospholipid- and calcium-dependent enzyme protein kinase C (PKC). We therefore directed our studies to the role of PKC regulation in the growth of normal human melanocytes and their transformation. Our studies show that while melanoma cells are inhibited by TPA, the growth of normal melanocytes is stimulated in a dose-dependent manner. The inhibitor, 1-(5-isoquinolinesulfonyl)-2-methyl-piperizine dihydrochloride (H7), which has been found to be the most specific for PKC, had no effect on the growth of normal melanocytes, but inhibited the growth of melanoma cells in a dose-dependent manner. PKC was isolated from the membrane and cytosol of normal melanocytes and melanoma cells. The basal (resting) levels of PKC activity in normal melanocytes was low compared to that measured in melanoma cells, and after short-term (1 hour) treatment with TPA the PKC activity was greatest at the membrane, with the activity decreasing the cytosol. Upon prolonged (48 hours) treatment with TPA, this redistribution of activity continued in normal melanocytes and the total activity increased. In melanoma cells, however, the total PKC activity decreased, particularly in the membrane fraction. A difference in activity and distribution of the enzyme was also seen after short-term (1 hour) treatment with H7. There was very little effect seen on PKC in normal melanocytes; however, the effect on melanoma cells was similar to that seen after 48 hours of exposure to TPA with a decrease in total activity, particularly in the membrane fraction. These results indicate that the regulation of PKC, in particular its activation by TPA, is altered during the transformation of normal human melanocytes