Phytophthora oleae,a new root pathogen of wild olives

Wild olive (Olea europaea subsp. europaea var. sylvestris) is an important component of Mediterranean forests and a key genetic source for olive improvement programmes. Since 2009, a severe decline caused by Phytophthora cryptogea and P. megasperma has been detected in a protected wild olive forest of high ecological value (Dehesa de Abajo, Seville, Spain). In this natural forest, sampling of roots and soil was carried out on 25 wild olives with symptoms in 2014 and 2015. Apart from the already known P. cryptogea A1 and P. megasperma, a third Phytophthora species was consistently isolated from wild olive rootlets with symptoms. These isolates conformed morphologically with the newly described species P. oleae and were confirmed by analysis of their ITS regions and cox1 sequences. Temperature–growth relationships showed a maximum growth at 19.9 °C on carrot agar medium, making it the lowest temperature Phytophthora species infecting wild olive roots. Pathogenicity was confirmed on 1-year-old healthy wild olive seedlings and was similar to the previously known pathogenic phytophthoras. As temperature requirements are quite different, the three Phytophthora species may be active against wild olive roots in different seasons. However, the prevalence of P. oleae infecting wild olives in recent years could be due to its introduction as a new invasive pathogen. The probable invasive nature of P. oleae, together with increasing rain episodes concentrated in short periods frequent in southern Spain, would allow the outbreak of infections in wild olive forests, and also put cultivated olive orchards at risk.     

Effect of gibberellic acid on sprouting,growth of internodes,tuber shape and yield in different varieties of potatoes

Summary Sprouting was hastened by one week by treatment for 5 min, with gibberellic acid (GA) at a concentration of 25 p.p.m. in newly dug potatoes ofUp-to-Date andVoran. A similar effect was noted inRoyal Kidney treated at a concentration of 50 p.p.m. Although some sprouting occurred within 7 days in treated tubers, 100% sprouting had not occurred until 21–36 days after treatment. There was increased extention of internodes following treatment with GA at concentrations of 25, 50 and 100 p.p.m. Treatment at 100 p.p.m. resulted in the greatest extention of internodes. At the higher concentrations the maximum extension occurred between internodes 4–6 inRoyal Kidney andVoran, and 4–7 inUp-to-Date. Treatment with GA had a depressing effect on leaf indices inRoyal Kidney andUp-to-Date whereas inVoran it had the reverse effect. In all varieties, yield in pot experiments was increased by treatment with GA at 100 p.p.m. for 90 min. All treated seed invariably produced deformed tubers the numbers of which increased with the concentration of GA.

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Zusammenfassung Das Auskeimen von frisch geernteten Kartoffeln der SortenUp-to-Date undVoran (Abb. 1 b und c) wurde durch Behandlung mit Gibberellins?ure (GA) (Eintauchzeit 5 Minuten, Konzentration 25 ppm) um eine Woche beschleunigt. Eine ?hnliche Wirkung konnte bei der SorteRoyal Kidney festgestellt werden, die mit GA in einer Konzentration von 50 ppm (Abb. 1 a) behandelt wurde. Obwohl einige der behandelten Knollen nach 7 Tagen austrieben, wurde 100%ige Keimung erst 21–36 Tage nach der Behandlung erreicht. Die Behandlung mit GA in Konzentrationen von 25, 50 und 100 ppm bewirkte eine Verl?ngerung der Internodien. Die Konzentration von 100 ppm verursachte die gr?sste Ausdehnung der Internodien. Bei der h?chsten Konzentration lag die gr?sste Verl?ngerung zwischen den Internodien Nr. 4-6 beiRoyal Kidney undVoran, zwischen 4–7 bei der SorteUp-to-Date (Tabelle). Behandlung mit GA hatte bei den SortenRoyal Kidney undUp-to-Date eine Verkleinerung des Blattindexes zur Folge, w?hrend beiVoran eine umgekehrte Wirkung hervorgerufen wurde (Abb. 2). Topfversuche ergaben nach Behandlung mit GA in einer Konzentration von 100 ppm und einer Eintauchzeit von 90 Minuten bei allen Sorten h?here Ertr?ge (Abb. 3). Alle Behandlungen führten zu Knollendeformationen, deren Anzahl sich mit der st?rker werdenden Konzentration von GA erh?hte (Abb. 4).

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Résumé Un traitement pendant 5 minutes à l'acide gibberellique (G.A.) à une concentration de 25 p.p.m. a avancé d'une semaine la germination de tubercules nouvellement récoltés des variétésUp-to-Date etVoran (Fig. 1, b et c). On a obtenu un semblable effet avecRoyal Kidney traitée à une concentration de 50 p.p.m. (Fig. 1 a). Quoique quelque germination apparaissait endéans 7 jours chez les tubercules traités, la germination à 100% ne se manifestait que 21 à 36 jours après le traitement. Un allongement des entre-noeuds suivait le traitement avec G.A. aux concentrations de 25, 50 et 100 p.p.m. Le traitement à 100 p.p.m. causait le plus grand allongement des entrenoeuds. Aux concentrations les plus élevées, l'accroissement maximum se manifestait entre les entre-noeuds 4 et 6 chezRoyal Kidney etVoran, et 4 et 7 chezUp-to-Date (Tableau). Le traitement au G.A. a un effet dépressif sur les indices foliaires chezRoyal Kidney etUp-to-Date, tandis que chezVoran l'effet est inverse (Fig. 2). Chez toutes les variétés, la production dans les expériences en pots est accrue par le traitement avec G.A. à 100 p.p.m. pendant 90 minutes (Fig. 3). Tous les plants traités produisent invariablement des tubercules déformés dont le nombre augmentait avec les concentrations de GA (Fig. 4).

     

THE EFFECT OF IRRIGATION AND STOCKING RATE ON THE OUTPUT FROM A SWARD

The dairy-cow results are presented from an experiment in which the response to grass irrigation was measured at two stocking rates. The method and herbage results have already been described (1).
Over two years, with an average application rate of 5·5 in of water per year, the main effect of irrigation was to increase the number of grazing days obtained by 35%. Neither yield per cow nor milk quality was significantly affected by the treatments.
The data emphasize the importance of high stocking rates for the full exploitation of irrigation. The practical implications of the results are discussed; they suggest that in the right circumstances of herd potential and grassland management, irrigation for milk production can be highly profitable.     

Experiments on Curative Low and Ultra-low Volume Spraying Against Dacus oleae Gmel.

Applications of 1, 2, 4, 6 and 12 lit. of spray per tree, each volume containing 6 g. of dimethoate a.i., did not show significant differences between the treatments, but olive fly pupae and third instar larvae were found to be more resistant than first and second instar larvae. Also, no differences became apparent between treatments with Dimecron 50, Carbicron 50 and Nuvacron 50 at rates of 7, 10 and 14 c.c. per tree respectively; these experiments will be continued.