Relations of Cercospora beticola with Host Plants and Fungal Antagonists
Cerco pora leaf pot (CLS) cau ed by Cercospora beticola Sacc., is sti ll considered to be the mo t important foliar di ease of ugar beel. The di ea e ha been reported wherever ugar beet i grO\\ n (Bieiholder and Weltzien 1972). Since the di ease wa fir t identified. management of CLS of ugar beet has been an ongoing mi ion of plant pathologists. Toda}. everal trategie are available and applied either s ingly or in combination to manage the di ea e. The e management trategie , which were ummarized by Windels et al. (1998), include cultural practice uch a deep tillage, rotation with non-host crops and identification and elimination of econdary weed host . Other include breeding and use of re i.tant cultivars and application of fungicide. The u e of re i tant sugar beet cultivars has long been an integral pan of CLS management; however, problems associated with selection of re i tant cuhivars again t CLS are wel l documented and were recently reviewed by Weiland and Koch (2004). According to the author , resistance to CLS in sugar beet has been de cribed as quantitatively in herited and rate limiting with respect to disease development (Smith and Gaskill 1970, Ro i et a l. 1999). Although resistant cultivars have proven effective in both North America and Europe, they nonetheless exhibit low heritability (Smith and Ruppel 1974), and cultivar bred for Cercospora resistance can still exhibit leaf pots if climatic condition favorable for the disease occur.
Root infection of sugar beet by Cercospora beticola in a climate chamber and in the field
Sugar beet root infection by Cercospora beticola, the causal agent of Cercospora leaf spot (CLS), was studied in a climate chamber and in the field. In the climate chamber, root incubation of susceptible seedlings with a conidial suspension resulted in disease incidences that were significantly different for two sugar beet cultivars (Auris: 0.8 ± 0.14 and A00170: 0.5 ± 0.18; P < 0.05) with regard to the control treatment 35 days after root incubation in a standard potting soil-fine river sand mixture. In a field trial with susceptible cv. Savannah with soil-incorporated CLS-infested leaf material, disease developed four weeks earlier in the infested plots than in the control plots. The probability that disease develops in the field was significantly higher for the infested than for the control plots (P < 0.05). Symptomless plants from infested field plots transferred to the glasshouse to induce leaf spot symptoms showed a significantly higher probability to induce symptom development (0.4 ± 0.08), than plants from control plots (0.02 ± 0.02) (P <0.05) 14 days after transfer. This probability was significantly higher than for plants that remained in three of the infested field plots (0.2 ± 0.04; 0.2 ± 0.05 and 0.2 ± 0.04 respectively), except for one infested field plot (0.4 ± 0.05) on July 5. We conclude that C. beticola is able to infect sugar beet seedlings through their roots and that latent CLS infections in sugar beet lead to symptom development at high temperatures (> 20 °C) and high relative humidity (> 95) in our climate chamber or after canopy closure in the field. Quantification of root infection and long term survival in soil is necessary to assess its contribution to the epidemiology and life cycle of Cercospora beticola. Cultural methods such as a wider crop rotation, management of crop debris and ploughing systems may provide control strategies alternative to or reducing fungicide input.
Heukels' Flora van Nederland
Inhoudsopgave Soorten en soortvorming Een andere indeling van plantenfamilies Over de samenstelling van de wilde flora Verspreiding van wilde planten in Nederland Hoofdsleutel Klasse 1: Lycopsida (Wolfsklauwen en biesvarens) Klasse 2: Pteropsida (Varensachtigen) Klasse 3: Spermatopsida (Zaadplanten) Een flora is een boek met sleutels en beschrijvingen waarmee je planten op naam kunt brengen. De Heukels' Flora bestaat al 122 jaar en geldt als 'officieel', wat wil zeggen dat bij twijfel over naamgeving of indeling van onze Nederlandse wilde planten van de Heukels' wordt uitgegaan. Een grotere ommezwaai dan met deze 23e druk is er in al die jaren niet geweest: de indeling van de plantenfamilies gaat nu uit van modern DNA-onderzoek, en dus niet meer van uiterlijke kenmerken. Daarmee is het de eerste ter wereld. Binnen families speelt het uiterlijk nog wel, want het DNA-onderzoek is daarvoor nog niet toereikend. Wat hetzelfde gebleven is, is dat de functionaliteit voorop staat: het op naam kunnen brengen van elke wilde plant in Nederland. Daarom staan er geen uitgebreide beschrijvingen in of kleurenillustraties, maar wel veel, heel veel afkortingen. Met verwijzingen naar de Oecologische Flora (Eddy Weeda) kan de gebruiker op zoek naar meer informatie. Alle voorgaande drukken zijn met de komst van de 23e sterk verouderd. Dit is het standaardwerk over de flora van Nederland. U vindt in een band de meest complete, wetenschappelijk betrouwbare flora. Met 2.000 soorten - een toename van 8% sinds 1996 - en een schat aan gedetailleerde illustraties. De enige flora die op ruime schaal op veldexcursies wordt getest.