João José Dias Parisi

Teste de envelhecimento acelerado para avaliação da qualidade de sementes de alface e almeirão

O uso de testes de vigor para avaliacao da qualidade dos lotes de sementes e uma ferramenta imprescindivel para producao e comercializacao. No entanto, para sementes de alface e almeirao as pesquisas relacionadas a avaliacao de sua qualidade ainda sao escassas. Para sementes de alface, apenas o teste de germinacao e considerado padronizado, enquanto os demais devem ser aprimorados visando fornecer informacoes mais precisas. Com intuito de adequar a metodologia do teste de envelhecimento acelerado para avaliar a qualidade de lotes de sementes de alface e almeirao, foram utilizados quatro lotes de sementes de alface das cultivares Maravilha e Verdinha e quatro lotes de sementes de almeirao das cultivares Catalonha e Pao-de-Acucar. Na conducao do teste de envelhecimento acelerado as sementes foram submetidas ao envelhecimento tradicional, e ao envelhecimento com solucao saturada e diluida de NaCl; usaram-se tres periodos distintos: 48, 72 e 96 horas. Para caracterizar a qualidade dos lotes foi determinado o grau de umidade das sementes, e realizados os testes de germinacao, primeira contagem de germinacao e emergencia de plântulas em casa de vegetacao. Concluiu-se que o teste de envelhecimento acelerado aos 41 °C possibilita a separacao dos lotes em diferentes niveis de vigor, podendo ser utilizado em sementes de alface e almeirao, considerando-se o periodo de envelhecimento de 48 horas pelo metodo tradicional ou o de 72 horas pelo metodo com solucao saturada de NaCl. Quanto ao metodo modificado pelo uso da solucao diluida de NaCl, o periodo de 48 horas e adequado para as sementes de alface e o de 72 horas, para as de almeirao.

Deterioração de sementes de espécies brasileiras de Eugenia em função da incidência e do controle de fungos

A conservacao de sementes intolerantes a dessecacao como as do genero Eugenia e realizada com alto grau de umidade, favorecendo o ataque de microrganismos. Essa interacao da semente com fungos de armazenamento pode acelerar consideravelmente a velocidade de deterioracao das mesmas. O tratamento com fungicidas pode contaminar o meio ambiente com residuos toxicos, tornando necessario o desenvolvimento de metodos alternativos como os tratamentos termicos e osmoticos. No presente trabalho, objetivou-se analisar a influencia da reducao do teor de agua e a eficiencia de tratamentos termicos (imersao das sementes em agua, de 35 °C a 75 °C, por 30 a 150 min), osmoticos (imersao continua em solucao osmotica a -1,5 MPa a -4,0 MPa) e quimicos (fungicidas carboxin+tiram, captan e carbendazin+tiram) na reducao do potencial de inoculo inicial de fungos. Os tratamentos quimicos foram os mais eficientes para o controle de Penicillium sp., Cladosporium sp., Fusarium sp., Pestalotiopsis sp. e Alternaria sp., detectados com mais frequencia em sementes de Eugenia brasiliensis (grumixameira), E. pyrifomis (uvaieira) e E. uniflora (pitangueira). Tratamentos termicos e osmoticos demonstram grande potencial de controle, mas necessitam ajustes metodologicos, incluindo-se a associacao de ambos e a reaplicacao dos tratamentos durante o armazenamento.

Survival of seed-borne fungi associated to the physiological quality of triticale (X. triticosecale Wittmack) stored seeds.

Triticale seeds of the IAC-2 cultivar presented germination of 85% after harvest and natural incidence of the following pathogenic fungi: 34.5% Pyricularia grisae, 12% Bipolaris sorokiniana, 15% Fusarium graminearum and 35% Alternaria alternata. The seeds were stored at 10 oC and under natural ambient conditions for twelve months. The seed physiological quality was evaluated at bimonthly intervals by the germination, accelerated aging, tetrazolium and field emergence tests and fungi survival was evaluated by the blotter test. The seeds stored at 10 oC maintained the same level of germination, viability and vigor for twelve months even though the fungi incidences also remained almost unchanged too. The germination and viability of seeds stored under natural ambient conditions decreased and the level of dead seeds increased due to a higher speed of deterioration and an increased level of storage fungi, mainly Penicillium spp.. The pathogenic fungi levels decreased, reaching very low values at the end of the storage period. However, the pathogen survival was still harmful at the time of the planting season (April).

Método do rolo de papel toalha modificado para a detecção de Sclerotinia sclerotiorum em sementes de feijão

White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) is one of the most damaging diseases of beans. Dissemination of the pathogen by infected seeds is important because it can infest new planting areas and the disease may establish in the beginning of the crop cycle. The present work describes an adaptation of the seed health test using the germination paper towel method, originally developed for the detection of Colletotrichum lindemuthianum, for assessing the presence of S. sclerotiorum in bean seeds. The test consisted of placing bean seeds in germination paper towels, which were rolled and placed in a germination chamber and kept at 100% relative humidity and 20 oC for seven days. After this period, the infected seedlings and the dead seeds surrounded by a white cottony growth were collected and placed in a gerbox over two wet filter papers. The sclerotia characteristic of the pathogen appeared around the seeds after tree to four days of incubation. This method is relatively rapid, inexpensive, and has the additional advantage of detecting simultaneously other important plant pathogens in bean seeds, such as Colletotrichum lindemuthianum, Macrophomina phaseolina and Rhizoctonia solani.

Damage caused by fungi and insects to stored peanut seeds before processing

The aim of this study was to gather data on the incidence of fungi associated with peanut seeds stored in their pods, before being processed by the State of Sao Paulo seed-producing companies, and the relation of the fungi to the seed damage caused by insects and to the quality of the stored seeds. Samples were taken from seed lots of cultivars IAC 886 and IAC 503 stored by these companies at the beginning and end of a six-month storage period. The peanut seeds were shelled and half of each sample was treated with fludioxonil + metalaxyl. Untreated and treated seeds were analyzed for moisture content, germination, vigor and health. The following insects were found to damage the peanut seeds: Cyrtomenus mirabilis (Perty) (Hemiptera: Cydnidae) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). Both species reduced seed quality. When present, fungi of the genera Aspergillus, Fusarium, Penicillium and Rhizopus infected seeds and seedlings during the germination process and were considered the main limiting factor for obtaining normal seedlings. Nevertheless, despite their presence, peanut seeds maintained their germination capacity and vigor after six months of storage in their pods.