Fernando da Silva Rocha

Incidência e viabilidade de sementes crioulas de milho naturalmente infestadas com fungos em pré e pós-armazenamento

Objetivou-se com este trabalho avaliar a qualidade sanitaria e fisiologica de quatorze variedades de sementes de milho crioulas em pre e pos-armazenamento em embalagens de polietileno tereftalato (PET). Houve efeito das variedades e das epocas de avaliacoes sobre a incidencia de fungos e germinacao. Dentre a micobiota observada, Fusarium moniliforme (88%), Penicillium spp. (6,9%) e Aspergillus spp. (2,1%) tiveram a maior porcentagem de incidencia. Apos o armazenamento, houve decrescimo de F. moniliforme (69%) e aumento de Penicillium spp. (35%) e Aspergillus spp. (22%). A incidencia desses fungos nao comprometeu a qualidade fisiologica das sementes, que apresentaram elevadas porcentagens de vigor e germinacao.

Correlations among methods to estimate lipid reserves of second-stage juveniles and its relationships with infectivity and reproduction of Meloidogyne incognita

We studied the correlations between the processes used to estimate the body lipid of second-stage juveniles (J2) of Meloidogyne exigua and M. incognita, and the infectivity and reproduction of the M. incognita J2. The lipids were quantified by image analysis of the area stained red with Oil Red O dye and by the dark area of the non-stained J2. The content of neutral lipids of stained J2 of M. exigua and M. incognita correlated positively to the lipid index, body mass lipid and the dark area of J2. The period of incubation of J2 decreased the neutral lipids content and correlated significantly with the reductions of infectivity and reproduction. The period of 6 days incubation of M. incognita resulted in losses of more than 50% of the neutral lipid content, representing the threshold period for infectivity on tomato, whereas, for reproduction, the threshold was 3 days incubation.

Etiology of root rot and wilt disease of chickpea in Brazil

Fusarium wilt caused by Fusarium oxysporum f. sp. ciceris (Padwick) Matuo & K. Sato has become the main limiting factor for chickpea (Cicer arietinum L.) production around the world. Although the cultivation of this legume is recent in Brazil, there are reports on Fusarium spp. occurrence causing crop losses. Fourteen isolates obtained from roots of chickpea plants showing wilt and yellowing symptoms in Brazil were evaluated through phylogenetic analysis of the EF-1α region, morphological markers and pathogenicity tests. Three isolates were clustered within a distinct lineage from those already described for the FSSC. The remaining 11 isolates were clustered within the FOSC, in a different clade from F. oxysporum f. sp. ciceris. All isolates were pathogenic but showed differences in aggressiveness. Isolates of the different complexes elicited the same symptoms: yellowing, wilt and root rot of chickpea plants. Morphological markers allowed differentiating isolates from distinct complexes but not differentiating between lineages.

Caracterização de Fusarium solani f. sp. piperis, produção de fitotoxina e incidência da fusariose no norte de Minas Gerais

Root rot caused by Fusarium solani f. sp. piperis is one of the major diseases affecting black pepper in the north of Minas Gerais State, Brazil. The aims of this study were to quantify the disease incidence in the main black pepper growing areas of Northern Minas Gerais State, to identify the causal agent of root rot, to test the pathogenicity of isolates and to evaluate the effect of Fusariumsolani f. sp. piperis filtrates on both detached leaves from black pepper and Trichoderma asperellum. The incidence of root rot was randomly evaluated in 1,000 or 500 plants at zigzag. The reaction of black pepper cv. Cingapura was evaluated against two fungal filtrates (FPC1 and FPB2), and the isolate FPB2 was used to evaluate the reaction of cultivars Cingapura and Guajarina. Another experiment was performed to study the influence of FPB2 filtrate dilutions on the leaves of cultivar Cingapura. To evaluate the effect of toxins of the filtrates on the Mycelial Growth Index (MGI) of T. asperellum, a trial was carried out with different concentrations and two filtrates. The disease incidence in the sampled areas was 31.5 to 100% for the municipalities of Bocaiuva and Montes Claros, respectively. Based on the sexual compatibility test, the isolates were identified as F. solani f. sp. piperis. Nine isolates were pathogenic when inoculated in seedlings of black pepper at four-month development. FPB2 filtrate produced the greatest severity (average of 93.6% necrotic leaf area), compared to FPC1 isolate (5.8%). The cultivar Cingapura was more sensitive to the action of the filtrate. The FPB2 filtrate dilution reduced the percentage of diseased leaf area. Furthermore, the increase in the concentrations of FPC1 filtrate contributed to increase the MGI of T. asperellum, whereas FPB2 filtrate showed opposite effect, reducing the MGI of this antagonistic fungus.

Health quality and germination of Butia capitata seeds treated with bactericide and fungicide

A propagacao do coquinho-azedo (Butia capitata) e limitada devido a dormencia e a alta incidencia de fungos em suas sementes. O objetivo deste trabalho foi avaliar o efeito do tratamento de sementes de coquinho-azedo com diferentes concentracoes de bactericida e/ou fungicida na incidencia de fungos e na germinacao das sementes. Para isto, sementes de coquinho-azedo foram imersas em quatro doses do bactericida kasugamicina (0, 1.5, 3.0 e 4.5 mL/L) e/ou em quatro concentracoes do fungicida carbendazim + thiram (0, 2.92, 5.84 e 8.75 mL/Kg), totalizando 16 tratamentos. Apos o tratamento, retirou-se o operculo das sementes, as quais foram colocadas em bandejas contendo areia autoclavada, revestidas com filme plastico transparente, e mantidas em viveiro. No teste de germinacao, os tratamentos foram distribuidos em delineamento de blocos casualizados em esquema fatorial 4 x 4 (doses do bactericida e doses do fungicida), com 4 repeticoes de 50 sementes por parcela. Para o teste de sanidade foi empregado o metodo do “Blotter test” em delineamento inteiramente casualizado utilizando 20 repeticoes com 10 sementes. A qualidade sanitaria e a germinacao foram avaliadas 15 e 40 dias apos o tratamento das sementes, respectivamente. Nao houve interacao entre o bactericida e o fungicida sobre a germinacao e o controle dos fungos associados as sementes. Porem, houve efeito das concentracoes de fungicida sobre os parâmetros avaliados. Observou-se correlacao negativa entre as concentracoes do fungicida carbendazim + thiram e a incidencia fungica e correlacao positiva entre as concentracoes do fungicida e a germinacao das sementes. Portanto, o tratamento fungicida reduz a incidencia fungica e propicia melhor germinacao das sementes do coquinho-azedo.