Response of A-genome cotton germplasm to the seedling disease pathogens,Rhizoctonia solani and Pythium ultimum

Summary Approximately two hundred A-genome cotton (Gossypium arboreum L. and G. herbaceum L.) accessions were evaluated for resistance to the seedling disease pathogens Rhizoctonia solani Kühn [Thanatephorus cucumeris (A. B. Frank) Donk], and Pythium ultimum Trow. Susceptibility rating was based on a scale of 1 to 6 where 1 = no symptoms and 6 = dead. Variation was found among A-genome accessions in response to R. solani and P. ultimum, but none were highly resistant to these pathogens. As a group, the A-genome cottons were more susceptible to the pathogens than the G. hirsutum control.Abbreviations STV-A G. hirsutum Stoneville 506 with agar only - STV-NP G. hirsutum Stoneville 506 with non-pathogenic isolate - STV-P G. hirsutum Stoneville 506 with pathogenic isolate - A₁ G. herbaceum - A₂ G. arboreum - GRIN Genetic Resources Information Network     

Evaluation of Gossypium arboreum L. Germplasm for resistance to thrips

Summary As part of a project to assess the U.S. Asiatic Cotton Germplasm Collection as a source of genes for pest resistance, forty-three accessions of Gossypium arboreum L. were evaluated for resistance to thrips. Thrips, Thysanoptera spp., are a minor, but widespread pest on cotton, G. hirsutum L. and G. barbadense L. Accessions were planted in free-choice field tests in 1988, 1989, and 1990 at the Cotton Branch Experiment Station, Marianna, Arkansas. Damage ratings, based on a scale of 0 (no damage) to 7 (severe damage), were made approximately one month after planting. Relative score was computed by dividing the rating of each accession by the rating of the reference, G. hirsutum Stoneville 506. The relative score averaged over all G. arboreum accessions by year varied with the year, but was less than 100 (relative score for Stoneville 506) in each case. When data were combined for all three years, twenty-five accessions were significantly better than Stoneville 506. Introgression of the better accessions into G. hirsutum is now in progress.Abbreviations NPGS National Plant Germplasm System - STV 506 G. hirsutum Stoneville 506     

Isoyield Analysis of Barley Cultivar Trials in the Canadian Prairies

Classification of test sites used for cultivar trials into groups with similar within‐group site performance and response (isoyield groups) is an important step towards identification of appropriate cultivars that are best suited for different productivity levels in farm fields. The objective of this study was to determine isoyield environments in the Canadian prairies based on the analysis of cultivar trials consolidated from individual provinces for barley (Hordeum vulgare L.). Yield data for the analysis were taken from 324 replicated trials at 84 sites across the prairies during 1995–2003. The combined use of regression and cluster analyses of the data normalized for averaging the multi‐year unbalanced data led to a stratification of the 84 sites into 13 isoyield groups. A comparison was made of the distributions of the variability among and within groups according to three modes of grouping: isoyield groups, soil zones and agroecoregions. There was more variability among isoyield groups and correspondingly less within the groups than that among and within soil zones or agroecoreions. Similar contrasting pattern existed for the variance components involving genotype–environment interaction (GEI), although the GEI variability was generally small under all three modes of grouping. Relationships of site sensitivity (regression coefficient) and stability (coefficient of determination) with site productivity were shown to be a useful aid for selecting a subset of test sites in an effort to improve efficiency and quality of future cultivar testing. Thus, isoyield analysis should be a valuable tool for subsetting heterogeneous environments and for reducing GEI impact in cultivar testing and recommendation.     

Laser altimeter observations from MESSENGER's first Mercury flyby

A 3200-kilometers-long profile of Mercury by the Mercury Laser Altimeter on the MESSENGER spacecraft spans approximately 20% of the near-equatorial region of the planet. Topography along the profile is characterized by a 5.2-kilometer dynamic range and 930-meter root-mean-square roughness. At long wavelengths, topography slopes eastward by 0.02 degrees , implying a variation of equatorial shape that is at least partially compensated. Sampled craters on Mercury are shallower than their counterparts on the Moon, at least in part the result of Mercury's higher gravity. Crater floors vary in roughness and slope, implying complex modification over a range of length scales.     

Experimental inoculation of raccoons (Procyon lotor) with Spiroplasma mirum and transmissible mink encephalopathy (TME)

The primary objective of this study was to determine whether or not Spiroplasma mirum would be capable of producing lesions of transmissible spongiform encephalopathy (TSE) when inoculated in raccoons (Procyon lotor) and, if that was possible, to compare the clinicopathological findings with those of transmissible mink encephalopathy (TME) in the same experimental model. For this purpose, 5 groups (n = 5) of raccoon kits were inoculated intracerebrally with either S. mirum and/or TME. Two other groups (n = 5) of raccoon kits served as sham-inoculated controls. All animals inoculated with TME, either alone or in combination, showed clinical signs of neurologic disorder and were euthanized within 6 mo post-inoculation (MPI). None of the carcasses revealed gross lesions. Spongiform encephalopathy was observed by light microscopy and the presence of abnormal disease-causing prion protein (PrP(d)) was detected by immunohistochemistry (IHC) and Western blot (WB) techniques in only the raccoons administered TME. Raccoons inoculated with Spiroplasma, but not administered TME agent, were euthanized at 30 MPI. They did not show clinical neurologic signs, their brains did not have lesions of spongiform encephalopathy, and their tissues were negative for S. mirum by polymerase chain reaction (PCR) and for PrP(d) by IHC and WB techniques. The results of this study indicate that Spiroplasma mirum does not induce TSE-like disease in raccoons.     

Cell-to-cell transfer of interferon-induced antiproliferative activity

Interferon-treated cells rapidly and efficiently transferred the antiproliferative activity of interferon to untreated cells. This phenomenon was not due to the carry-over of interferon by the interferon-treated cells. Thus, to evoke an antiproliferative state, interferon did not directly contact each cell in a population. The results suggest a novel mechanism by which interferon may indirectly regulate cell growth, and suggests that cells other than those of the immune system may play a role in controlling tumor growth in tissue where cell-to-cell contact occurs.     

Turgor pressure: direct manometric measurement in single cells of Nitella

A small capillary, fused at one end, serves as a micromanometer when the open end is inserted into a large Nitella cell. The cell's ability to compress the gas reveals its turgor pressure directly-save for a small correction due to capillarity. The method gives a lower limit to turgor pressure for the same cell in the normal state. The common method, incipient plasmolysis, gives an upper limit. On Nitella axillaris cells the two methods limit the turgor pressure at 5.1 to 5.7 atmospheres. The manometric method is also applicable to growing cells, where osmotic equilibrium is not present.     

Floral evolution: attractiveness to pollinators increases male fitness

Because availability of resources often limits seed or fruit set, increased visits by pollinators may not always lead to increases in maternal reproduction. This observation has led evolutionary biologists to hypothesize that a plant's ability to attract pollinators may have its primary impact on male fitness achieved through the fertlization of ovules. This interpretation of angiosperm reproductive ecology is supported by field experiments. Pollinating insects strongly discriminated between two Mendelian petal-color morphs in Raphanus raphanistrum, a widespread, self-incompatible crucifer. In experimental populations composed of petal-color homozygotes. color discrimination by naturally occurring pollinators had no statistically significant effect on relative maternal function (fruit and seed production) in the two morphs. In contrast, yellow-flowered individuals were far more successful as fathers (pollen donors) than were the less visited whites. These results suggest that the evolution of floral signals such as petal color may be driven primarily by selection on male function.