During a survey of Streptomyces infecting potato (Solanum tuberosum) in the UK, two strains were isolated which were distinct from S. scabiei, which is already known to occur in the UK. Amplification with speciesspecific PCR primers (Wanner, 2006) identified these strains as S. turgidiscabies (Miyajima et al., 1998) and S. acidiscabies (Lambert & Loria, 1989), and the same PCR assay indicated presence of these species in several fields in England and Scotland. Representative strains were deposited in the UK National Collection of Plant Pathogenic Bacteria as NCPPB4444 and NCPPB4445 respectively. Strain NCPPB4444 was isolated from cv. Desiree tubers, grown in South Yorkshire, England, with large erumpent lesions. A majority of tubers from the same seed stock in the same field exhibited similar symptoms. Strain NCPPB4445 was isolated from cv. Maris Piper, grown in Aberdeenshire, Scotland, on soil of pH 5AE4, where disease incidence was high and dry flaky scab symptoms typically covered almost 100% of the tuber surface. Both strains were isolated on NPPC medium (Schaad et al., 2001), producing small white sporulating colonies.Inoculation of radish seedlings with both strains resulted in severe necrosis within 2 weeks. Potato minitubers (cv. Maris Piper) grown in pots containing sterilized compost were inoculated with 250 mL suspensions of Streptomyces (approx. 10 7 cfu mL )1 ) when leaves first emerged. After 12 weeks, lesions were observed on tubers in each of five replicate pots. Uninoculated controls were free from symptoms. Bacteria recovered from lesions were confirmed by PCR to be the same species as the inocula. To confirm species identity, a portion of the 16S rDNA of each original strain was sequenced. The sequence from strain NCPPB4444 (GenBank Accession No. FJ817424) was 100% identical to that of S. turgidiscabies type strain ATCC700248. The sequence from strain NCPPB4445 (FJ804480) was 100% identical to that of the S. acidiscabies type strain ATCC49003. Although several Streptomyces spp. are known to cause common scab of potato, the species identity is of significance as different diagnosis and control methods may apply. This is the first report in the UK of common scab of potato caused by S. turgidiscabies or S. acidiscabies. Acknowledgements
The growth of plants by the use of Trichoderma occurs through distinct mechanisms, among which it can highlight the synthesis of phytohormones and auxins analogues. The objective of this work was to evaluate Trichoderma spp. commercial strains in the promoting seedlings growth and in the productivity of parsley plants. In laboratory assay, seeds of parsley cv. ‘Graúda Portuguesa’ were treated with 2 mL of Trichoderma suspension (2.5 × 108 ml-1 conidia per 100 g of seeds) submitted to growth test until 28 days after sowing (DAS). For the greenhouse experiment, parsley seedlings were transplanted into 3.0 L pots containing soil, which was previously treated with 5 mL Trichoderma suspension, totaling 1.5 × 108 conidia per pot. In both, a control without Trichoderma application was included, being arranged in a completely randomized design (CRD). The evaluations were: percentage of germination (PG), root length (RL), shoot length (SL), total length (TL = RL + SL), fresh root mass (FRM), fresh shoot mass (FSM), total fresh mass (TFM = FRM + FSM), root dry mass (RDM), shoot dry mass (SDM), total dry mass (BIO = RDM + SDM), root mass ratio (RMR = RDM/BIO), shoot mass ratio (SMR = SDM/BIO), aerial part/root system retio (AP/RS = SDM/RDM) and productivity at 110 DAS. Althougth no diferences was observed among the Trichoderma treatments and the control about yield, Trichoderma spp. strains provided better TFM (18.98 to 22.92 mg), BIO (3.37 to 4.31 mg) and root system superior to the control (14.20 and 2.44 mg, respectively) under greenhouse conditions. T. harzianum ESALQ1306 was the better strain in laboratory assyas, suggsting this isolate for applied in the seeds when it aims the promotion of initial growth.
RESUMO O mofo branco tem sido responsável por danos expressivos à cultura do feijoeiro. Objetivou-se avaliar o efeito de regimes de luz na produção de conídios de Trichoderma harzianum e na efetividade destes em inibir a germinação miceliogênica de escleródios de Sclerotinia sclerotiorum, bem como de isolados de T. harzianum na supressão de lesões causadas por S. sclerotiorum sobre folíolos de feijoeiro. O isolado CEN287 inibiu a germinação miceliogênica de 80 % dos escleródios avaliados. Tal efetividade não se alterou quanto ao regime de luz empregado para a obtenção dos conídios de T. harzianum. Os isolados CEN287, CEN288 e CEN316 proporcionaram os menores valores médios de lesão foliar aos 10 dias após a inoculação, sendo de 4,25 mm2; 2,97 mm2; e 2,98 mm2, respectivamente. Em relação à testemunha, tais valores foram significativamente inferiores (72,90 mm2), o que impediu a rápida deterioração do tecido vegetal.
A queima de alternaria, cujo agente causal é o fungo Alternaria spp., é uma doença ocorrente em áreas de produção de hortaliças da família Apiaceae, devido, principalmente, ao fato de sua veiculação ser por sementes contaminadas. Neste sentido, a qualidade sanitária e fisiológica de sementes é fundamental para o estabelecimento uniforme das culturas em campo, fator que garante o sucesso da produção. O objetivo deste trabalho foi estimar a incidência e caracterizar o fungo Alternaria ocorrente em sementes de salsa cv. ‘Graúda Portuguesa’. A análise de incidência foi realizada pelo método blotter test, empregando-se oito repetições (50 sementes por caixa gerbox). Após 10 dias a 25 ºC e fotoperíodo de 12 h de luz, a avaliação foi realizada examinando-se individualmente todas as sementes em microscópio estereoscópio para a confecção de lâminas semipermanentes, procedendo-se à remoção de micélio e estruturas fúngicas encontradas sobre as sementes infectadas, para caracterização e identificação da espécie do fungo incidente. Os conídios apresentaram dimensões de 21,3 - 37,6 x 6,2 - 13,9 μm (28,8 x 10,9 μm), formato de pera invertida, com coloração marrom clara e bicos de 4,0 - 13,8 μm (7,7 μm), com presença de 1-3 septos longitudinais e 2-4 transversais. Estes marcadores morfológicos levaram à identificação do fungo como A. alternata, com 70% de incidência.
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