Yield and foliar injury responses of mature plum trees to salinity

Summary The salt tolerance of mature Santa Rosa plum trees was assessed on 20-year-old trees grown in the San Joaquin Valley of California. The experimental design consisted of six levels of irrigation water salinity (electrical conductivities of 0.3 to 8 dS/m) replicated five times with each replication consisting of ten trees. Salinity treatments imposed in March 1984 did not influence tree yields harvested in June 1984. In 1985, the second year of treatments, yield from the highest salt treatment (electrical conductivity of irrigation water, EC _i , of 8 dS/m) was reduced by half; the number of fruit harvested was reduced 40%, and fruit size was reduced significantly. Foliar damage was so severe by the end of 1985 that nonsaline water was applied to the two highest salt treatments (EC _i = 6 and 8 dS/m) in an attempt to restore tree vigor. In 1986 salt effects had become progressively worse on the continuing saline treatments. A linear piece-wise salt tolerance curve is presented for soil salinity values, expressed as the electrical conductivity of saturated extracts (EC _e ) integrated to a soil depth of 1.2 m over a 2-year period. The salt tolerance threshold for relative yield (Y _r ) based on 3 years of data was 2.6 dS/m and yield reduction at salinity levels beyond the threshold was 31% per dS/m (Y _ir=100 – 31 [EC _e – 2.6]j). Significant foliar damage occurred when leaf chloride concentrations surpassed 200 mmol/kg of leaf dry weight (0.7%). Sodium concentrations in the leaves remained below 10 mmol/kg (0.02%) until foliar damage became severe. This suggests that chloride was the dominant ion causing foliar damage.     

Did the breakout of laurentia turn gondwanaland inside-out?

Comparative geology suggests that the continents adjacent to northern, western, southern, and eastern Laurentia in the Late Proterozoic were Siberia, Australia-Antarctica, southern Africa, and Amazonia-Baltica, respectively. Late Proterozoic fragmentation of the supercontinent centered on Laurentia would then have been followed by rapid fan-like collapse of the (present) southern continents and eventual consolidation of East and West Gondwanaland. In this scenario, a pole of rotation near the Weddell Sea would explain the observed dominance of wrench tectonics in (present) east-west trending Pan-African mobile belts and subduction-accretion tectonics in north-south trending belts. In the process of fragmentation, rifts originating in the interior of the Late Proterozoic supercontinent became the external margins of Paleozoic Gondwanaland; exterior margins of the Late Proterozoic supercontinent became landlocked within the interior of Gondwanaland.     

A deviant strain of potato virus Y infecting potatoes in South Africa

Summary From 1980 to 1982 a mosaic disease of potatoes was prevalent in a major seed potato production area in South Africa. The virus causing the disease was serologically identified as a strain of potato virus Y (PVY). Its host range and symptoms were similar to those of PVY^o and it was designated PVY-81. PVY-81 failed to induce necrotic lesions on leaves ofSolanum demissum×S. tuberosum ‘A6’, but it did so on the potato cultivars BP-1, Buffelspoort and Koos Smit. PVY-81 was non-persistently transmitted byMyzus persicae. Monitoring of aphid migrations showed that aphid species that do not naturally colonize potatoes could have caused the primary spread of the virus into potato fields.

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Zusammenfassung Von 1980 bis 1982 war im Hauptgebiet der Saatkartoffelproduktion in Südafrika eine Mosaikkrankheit an Kartoffeln verbreitet. Das Virus, das die Krankheit verursacht, wurde an Hand seiner Partikelmorphologie und der serologischen Verh?ltnisse als ein Stamm des Kartoffelvirus Y (PVY) identifiziert. Er wurde als PVY-81 bezeichnet. Der Wirtskreis des PVY-81 war auf Solanaceen und Chenopodiaceen beschr?nkt. Die durch diesen Stamm induzierten Symptome an Wirtspflanzen ?hnelten denjenigen, die durch PVY^O verursacht wurden mit Ausnahme der nicht induzierbaren Lokall?sionen auf den abgetrennten Bl?ttern vonSolanum demissum×Solanum tuberosum ‘A6’. Die nekrotische Reaktion auf den inokulierten Bl?ttern der Sorte Koos Smit wurde mit einbezogen, um den ‘A6’-Test zu ersetzen (Abb. 1). Die Reaktion einiger Kartoffelsorten (Tab. 1) auf die Infektion mit diesem Stamm unterschied sich von derjenigen auf PVY^O und PVY^N. Drei Sorten, King George, Pentland Dell und 890/20 waren offensichtlich resistent gegenüber der Blattlausübertragung (Tab. 2). Das Virus wurde vonMyzus persicae nicht-persistent übertragen. Die Befunde, die sich aus der Erfassung der Blattlauspopulation ergaben, wiesen darauf hin, dass die nicht auf Kartoffeln kolonisierenden Blattl?use wieAcyrthosiphon pisum, Rhopalosiphoninus staphyleae undRhopalosiphum padi vermutlich hauptverantwortlich für die Ausbreitung des PVY-81 waren. Eine sehr geringe Anzahl vonM. persicae undMacrosiphum euphorbiae wurden w?hrend der gesamten Wachstumszeit in den Fallen gefangen (Tab. 3). Das Pflanzen von gesundem Saatgut und das rechtzeitige Entfernen von Volunteer-Kartoffeln aus der vorhergegangenen Saison hat zur Kontrolle der Krankheit geführt.

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Résumé De 1980 à 1982, une mosa?que de la pomme de terre s'est répandue dans une grande région de production de plants de pommes de terre en Afrique du Sud. Le virus responsable de la maladie fut identifié comme souche du virus Y de la pomme de terre (PVY) sur la base de la morphologie de sa particule et des caractéristiques sérologiques. Il fut identifié comme PVY-81. La gamme h?te de PVY-81 était limitée aux Solanaceae et aux Chenopodiaceae. Les sympt?mes sur plantes-h?tes induites par cette souche sont similaires à ceux causés par PVY^O sauf qu'elle n'entr?ne pas de lésions locales sur feuilles détachées deSolanum demissum ×S. tuberosum ‘A6’. La réaction nécrotique sur feuilles inoculées de la variété Koos Smit fut incorporée en complément du test A6 (figure 1). La réaction de certaines variétés (tableau 1) à l'infection par cette souche diffère de celle provoquée par PVY^O et PVY^N. Trois variétés King George, Pentland Dell et 890/20 furent apparamment résistante à la transmission du virus (tableau 2). Le virus fut transmis de fa?on non persistante parMyzus persicae. Les résultats obtenus par comptage des populations aphidiennes montrent que les espèces qui ne colonnisent pas les pommes de terre telles queAcyrthosiphon pisum, Rhopalosiphoninus staphyleae etRhopalosiphum padi sont parmi les plus responsables de la dissémination de PVY-81. Un faible nombre deM. persicae etMacrosiphum euphorbiae a été capturé pendant la période de croissance (tableau 3). La plantation de plants sains et l'enlèvement au bon moment des repousses de la période précédente ont conduit à maitriser la maladie.

     

Coordinated reactivation of distributed memory traces in primate neocortex

Conversion of new memories into a lasting form may involve the gradual refinement and linking together of neural representations stored widely throughout neocortex. This consolidation process may require coordinated reactivation of distributed components of memory traces while the cortex is "offline," i.e., not engaged in processing external stimuli. Simultaneous neural ensemble recordings from four sites in the macaque neocortex revealed such coordinated reactivation. In motor, somatosensory, and parietal cortex (but not prefrontal cortex), the behaviorally induced correlation structure and temporal patterning of neural ensembles within and between regions were preserved, confirming a major tenet of the trace-reactivation theory of memory consolidation.     

Esterase 1 and Hordein C allelic and genotypic frequencies in CC XXXI,a male sterile barley population

Summary Seeds from the 5th, 6th, 12th and 18th generation of enforced outcrossing in CCXXXXI-B, a barley (Hordeum vulgare L.) population containing genetic male sterility, were assayed for genotypic distribution of Est 1 and Hor C alleles. The result suggest that natural selection was effective in altering allelic frequencies at both loci and that genotypic frequencies were often different from what would be expected if allelic frequencies solely determined genotypic frequencies. Departures of actual from expected genotypic frequencies occurred in that shifts in allelic frequencies were detected.Joint contribution of the USDA-ARS and published with the approval of the Director of the Montana Agric. Exp. Sta. Journal Series No. 2281.     

Airway physiology and clinical function testing.

The advent of pulmonary function testing in small animals has opened the door to new interpretations of old diseases. This article reviews the salient features of airway pathophysiology in dogs and cats that relate to the interpretation of newly developed airway function tests.     

Mycoplasma felis pleuritis in two show-jumper horses.

Mycoplasma felis was identified as the cause of acute pleuritis in 2 show-jumping horses. The pleural exudate was proteinaceous, contained large numbers of neutrophils, and had a markedly increased lactate concentration. M. felis was isolated in pure culture from pleural fluid. Rising serum antibody titers to M. felis as well as a precipitous decline in titers to equine influenza virus were demonstrated in both horses. Pleural effusion in both horses and a pneumothorax detected in one of the horses resolved following a single drainage of pleural fluid and intravenous fluid, antibiotic, and analgesic therapy.