Tales Poletto

Germination and development of pecan cultivar seedlings by seed stratification

The objective of this work was to evaluate the effect of seed stratification on germination rate, germination speed, and initial development of seedlings of six pecan ( Carya illinoinensis ) cultivars under subtropical climatic conditions in southern Brazil. For stratification, the seeds were placed in boxes with moist sand, in a cold chamber at 4°C, for 90 days. In the fourteenth week after sowing, the emergence speed index, total emergence, plant height, stem diameter, and number of leaves were evaluated. Seed stratification significantly improves the germination potential and morphological traits of the evaluated cultivars.

Culture Medium, Light Regime and Temperature Affect the Development of Sirosporium diffusum

Sirosporium diffusum is the causal agent of the brown leaf spot disease on pecan trees that seriously damages the foliage of adult plants and seedlings. This fungal species is difficult to grow satisfactorily in a culture medium. Therefore, the aim of this study was to evaluate the effects of different physical conditions on the development of S. diffusum . In the first assay, eight culture media and five light regimes were combined, while in the second, the three treatments that promoted highest sporulation were combined with three temperatures. The trials were conducted in a two-factorial arrangement in a fully randomized design with six replicates. V8, V8CaCO 3, and CA media under a 24-h photoperiod produced the highest respective sporulations: 29 × 10 4 , 35 × 10 4 , and 41 × 10 4 conidia ml -1 . The best temperature for sporulation was 20±1 °C for all culture media, especially V8CaCO 3 and CA. The best artificial conditions for obtaining good mycelial growth and sporulation consisted of a photoperiod of 24 h, temperature of 20±1 °C and V8CaCO 3 or CA culture medium.

MÉTODOS DE SUPERAÇÃO DE DORMÊNCIA DA SEMENTE DE NOGUEIRA-PECÃ Carya illinoinensis (Wangenh.) K. Koch1

A cultura da nogueira-peca tem grande importância para a economia de varios municipios do Sul do Brasil. Entretanto, problemas como baixa porcentagem de germinacao das sementes e irregularidade na emergencia das plântulas trazem dificuldades no processo de propagacao, decorrentes da influencia do fenomeno da dormencia. O objetivo deste trabalho foi avaliar diferentes tecnicas de superacao da dormencia de sementes de nogueira-peca e o posterior desenvolvimento das plântulas. Para tanto, foram testados quatro diferentes metodos de superacao de dormencia, em que, nos tratamentos testemunhas, as sementes permaneceram em ambiente protegido sem qualquer tratamento; no metodo com escarificacao, as sementes foram lixadas na parte apical no momento da semeadura e na estratificacao, acomodadas em caixas com areia umida e mantidas na temperatura de 4 oC. Tambem foi testada a combinacao escarificacao e estratificacao, simultaneamente. Os tratamentos foram compostos por 10 repeticoes de tres sementes cada. Apos cada periodo (30, 60 e 90 dias), as sementes foram semeadas em bandeja contendo substrato Mecplant® e mantidas a 25 oC ± 2 oC, sob fotoperiodo de 12 h. Avaliaram-se a altura da parte aerea, o diâmetro do colo, o numero de folhas, a emergencia total, o indice de velocidade de emergencia, a biomassa seca, a area foliar e o comprimento da raiz pivotante. O melhor desenvolvimento de plântulas de nogueira-peca, bem como sua emergencia, foi observado no tratamento com estratificacao por 90 dias e, quando combinadas escarificacao mais estratificacao, por 90 dias.

Aspectos epidemiológicos da podridão-de-raízes da erva-mate (Ilex paraguariensis)

The root-rot of erva-mate, caused for Fusariumspp., Rhizoctoniasp. and Pythium sp., is the main disease of the culture and causes serious damages in nurseries and forest stands. However, few studies exist regarding to the epidemiology of this disease. Thus, the present work studied and described the main epidemic aspects related to erva-mate root-rot in nurseries and forest stands. For that, nurseries and forest stands were chosen for studies in Vale do Taquari, RS state, where flowers, fruits, seeds, plantlets, seedlings and soil were collected for laboratory analyses. It was observed that the pathogens can enter in the patho-system through the flowers, because 80% of them presented contamination of Fusarium sp. and 15% of Rhizoctonia sp. Moreover, the obtaining method and stratification of the seeds, used in the nurseries, contribute to the increase of contamination, reaching 100% of the seeds in the moment of sowing. It was also observed that contaminated seedlings may be symptomless and, after transplanting in the field, contaminate pathogen free areas. Pathogenicity tests with some isolates showed their capacity of causing the disease.

Epidemiological aspects of root-rot of 'erva-mate' (Ilex paraguariensis)

The root-rot of erva-mate, caused for Fusarium spp., Rhizoctonia sp. and Pythium sp., is the main disease of the culture and causes serious damages in nurseries and forest stands. However, few studies exist regarding to the epidemiology of this disease. Thus, the present work studied and described the main epidemic aspects related to erva-mate root-rot in nurseries and forest stands. For that, nurseries and forest stands were chosen for studies in Vale do Taquari, RS state, where flowers, fruits, seeds, plantlets, seedlings and soil were collected for laboratory analyses. It was observed that the pathogens can enter in the patho-system through the flowers, because 80% of them presented contamination of Fusarium sp. and 15% of Rhizoctonia sp. Moreover, the obtaining method and stratification of the seeds, used in the nurseries, contribute to the increase of contamination, reaching 100% of the seeds in the moment of sowing. It was also observed that contaminated seedlings may be symptomless and, after transplanting in the field, contaminate pathogen free areas. Pathogenicity tests with some isolates showed their capacity of causing the disease.

FUNGOS ASSOCIADOS ÀS FLORES E FRUTOS DA NOGUEIRA-PECÃ (Carya illinoinensis)

O presente trabalho teve como objetivo identificar e determinar a incidencia os fungos associados ao sistema reprodutivo, flores e sementes, de nogueira-peca, bem como testar a eficiencia da assepsia em sementes. Este conhecimento e de suma importância para uma boa realizacao das praticas culturais e conservacao dos frutos. Para analise, foram coletadas flores e amendoas em pomares de Santa Maria e de Anta Gorda – (RS), durante os meses de setembro de 2010 a julho de 2011. O material foi analisado atraves de testes de sanidade pelo metodo de papel filtro, comparando a incidencia fungica presente nas flores dos dois locais, e nas amendoas comparando a eficiencia da assepsia. Observou-se alta incidencia de Alternaria sp. nas flores femininas coletadas em Santa Maria e Anta Gorda e em flores masculinas de Anta Gorda. Incidencia elevada de Fusarium sp. e Penicillium sp. foi observada em flores femininas e masculinas de ambas procedencias. Cladosporium sp. esteve presente em flores femininas de Santa Maria e flores masculinas de Anta Gorda. Nas sementes (amendoas) os fungos que ocorreram associados foram: Ceplalosporium sp., Colletotrichum sp., Fusarium sp., Penicillium sp. e Verticillium sp., sendo que nao houve reducao estatisticamente significativa de sua incidencia com a realizacao da assepsia das sementes, exceto para Ceplalosporium sp. Fungos potencialmente patogenicos, tais como Fusarium sp., Pestalotiopsis sp., Alternaria sp., Cladosporium sp. e Colletotrichum sp., foram identificados tanto em flores quanto em frutos de nogueira-peca representando riscos as mudas no caso de sua transmissao via semente.