ABSTRACT
The lesion nematode Pratylenchus jaehni occurs at low frequency in Brazilian coffee orchards but could provoke extensive root damage. Intercropping cover crops is a traditional practice in Brazilian coffee orchards, and the use of non-hosts of P. jaehni as cover crops may be a useful management method. In this work, 10 cover crops were tested concerning reproduction of P. jaehni. Cajanus cajan, Canavalia ensiformis, and Mucuna deeringiana are cover crops commonly used as intercropping in coffee orchards, but they must not be used in orchards infested with P. jaehni, because they are good hosts of this nematode. Brachiaria ruziziensis, Crotalaria juncea, Dolichos lablab, and Pennisetum glaucum were considered poor hosts. Helianthus annuus cv. Catissol and cv. Uruguai and Crotalaria spectabilis proved to be non-hosts to P. jaehni, and therefore, they are the cover crops recommended in coffee orchards infested with this nematode.
ABSTRACT
O objetivo do presente trabalho foi identificar os nematoides associados a plantas de antúrio (Anthurium andraeanum) cultivadas como flor de corte (13 amostras) ou plantas em vaso (41 amostras) nos estados de São Paulo, Paraná e Santa Catarina. Nematoides foram extraídos de 10g de raízes e 250cm3 de solo ou substrato e identificados sob microscópio de luz. A espécie mais frequente foi Radopholus similis, detectada em 54% das amostras de antúrio cultivado como flor de corte. Constituíram novas ocorrências em antúrio no Brasil: Helicotylenchus erythrinae, H. californicus, H. multicinctus, Meloidogyne paranaensis e R. similis. Entretanto, nenhum nematoide parasito de plantas foi encontrado nos antúrios cultivados em vaso, com substrato de fibra de coco. .
The aim of this research was to identify plant parasitic nematodes associated with Anthurium andraeanum plants cultivated as cut flowers (13 samples) or pot flowers (41 samples) in the States of São Paulo, Paraná and Santa Catarina, Brazil. Nematodes were extracted from 10g of roots and 250cm3 of soil by centrifugation method and identified under microscope. The most frequently occurring species was Radopholus similis detected on 54% of anthuriums cultivated as cut flowers. Among the identified species, the following associations constitute new records to Brazil in anthuriums: Helicotylenchus erythrinae, H. californicus, H. multicinctus, Meloidogyne paranaensis and R. similis. However, no plant parasitic nematodes were detected on A. andraeanum cultivated as pot flowers in coconut fiber substrate. .
ABSTRACT
The effect of abamectin, applied as seed treatment, on Meloidogyne incognita penetration, colonization, and reproduction on cotton was evaluated in two greenhouse experiments. Second stage juveniles (J2) penetration was evaluated 3, 9 and 15 days after germination (dag), whereas the nematode colonization was evaluated 27dag, by counting the total number of galls and egg masses per root system. Eggs and J2 were extracted from the roots to assess the nematode reproduction at 50 and 100dag. The seed treatment caused a decrease in J2 penetration in the roots, resulting in lower colonization and reproduction of M. incognita. These findings are discussed considering the environmental aspects of abamectin in the soil and the current practices for the crop management.
O efeito de abamectina em tratamento de sementes na penetração, colonização e reprodução de Meloidogyne incognita, em algodão, foi avaliado em dois experimentos de casa de vegetação. A penetração de juvenis de segundo estádio (J2) foi avaliada aos três, nove e 15 dias após a germinação (dag), enquanto que a colonização 27dag foi avaliada por meio da contagem do número total de galhas e massas de ovos por sistema radicular. Ovos e J2 de M. incognita foram extraídos das raízes para determinar a reprodução do nematoide aos 50 e 100dag. O tratamento de sementes diminuiu a penetração dos J2 nas raízes, resultando em menor colonização e reprodução de M. incognita. Os resultados obtidos são discutidos tendo em vista os aspectos ambientais da presença de abamectina no solo e as práticas agrícolas em uso.
ABSTRACT
* The ability of Burkholderia phymatum STM815 to effectively nodulate Mimosa spp., and to fix nitrogen ex planta, was compared with that of the known Mimosa symbiont Cupriavidus taiwanensis LMG19424. * Both strains were equally effective symbionts of M. pudica, but nodules formed by STM815 had greater nitrogenase activity. STM815 was shown to have a broader host range across the genus Mimosa than LMG19424, nodulating 30 out of 31 species, 21 of these effectively. LMG19424 effectively nodulated only nine species. GFP-marked variants were used to visualise symbiont presence within nodules. * STM815 gave significant acetylene reduction assay (ARA) activity in semisolid JMV medium ex planta, but no ARA activity was detected with LMG19424. 16S rDNA sequences of two isolates originally from Mimosa nodules in Papua New Guinea (NGR114 and NGR195A) identified them as Burkholderia phymatum also, with nodA, nodC and nifH genes of NGR195A identical to those of STM815. * B. phymatum is therefore an effective Mimosa symbiont with a broad host range, and is the first reported beta-rhizobial strain to fix nitrogen in free-living culture.
