Leonardo de Jesus Machado Gois de Oliveira

Sanidade de sementes de arroz, biocontrole, caracterização e transmissão de Curvularia lunata em semente-plântula de arroz

Este trabalho objetivou avaliar a qualidade sanitaria de sementes de arroz, quantificar a transmissao de Curvularia lunata associada a semente e a plântula, e avaliar o efeito dos isolados de Bacillus spp., no controle da mancha foliar, do cultivar Bonanca. Para avaliacao da sanidade de sementes, as amostras foram desinfestadas e plaqueadas, sendo avaliadas apos sete dias de incubacao. Na confirmacao da patogenicidade, as plântulas foram inoculadas por meio de pulverizacao e a avaliacao da doenca ocorreu sete dias apos. Na caracterizacao do isolado de C. lunata, foi realizada medicao da largura, comprimento e numero de septos de 100 conidios. Para a taxa de transmissao de C. lunata, foram preparadas 12 bandejas, com 100 sementes cada, de modo a proceder-se as avaliacoes aos 7, 14, 21 dias apos a semeadura (d.a.s.). De cada uma das 100 plântulas, foram separadas as raizes, apos sete dias. A inoculacao dos isolados de Bacillus foi realizada na forma de suspensao, pulverizada sobre a parte aerea das plântulas. Apos uma semana, foi inoculado a C. lunata. A avaliacao foi efetuada aos 15 dias apos inoculacao dos isolados patogenicos, medindo-se o tamanho da lesao. No teste de sanidade foi detectada maior incidencia de C. lunata (70%), o qual se apresentou patogenico a variedade de arroz Bonanca, sendo detectado em todos os orgaos da plântula. Dentre os isolados de Bacillus, os que mais se destacaram no controle foram B41 (B. Cereus) e B35 (Bacillus sp.), confirmando seu potencial biocontrolador.

Supressividade por incorporação de resíduo de leguminosas no controle da fusariose do tomateiro

The use of organic materials that improve physical, chemical and biological soil properties has been studied as inducer of suppressiveness to plant pathogens. This study aimed to evaluate the effect of incorporating legume shoot in the control of Fusarium wilt affecting tomatoes. Fresh residues of the legumes Leucaena, pigeon pea, peanut and jack bean were added to the soil at the concentrations of 0, 20, 40, 60 and 80 g L-1. Seeds from tomato plants of Santa Cruz Kada Gigante variety were sown on trays containing autoclaved soil and earthworm castings. The seedlings were transplanted to pots containing substrate (autoclaved soil + fresh residue) at 15 days after sowing. At 15 days after transplanting, inoculation was done by means of half-moon-shaped injury in the roots, followed by application of 20 mL of a suspension of 1x106 conidia mL-1 plant. The evaluation was carried out at 21 days after inoculation by using a visual grading scale from 1 to 5. Experimental design was completely randomized, with four replicates, and the experimental unit was constituted of two plants per pot. Incorporation of shoot of the legumes Leucaena, pigeon pea, peanut and jack bean was efficient in controlling Fusarium wilt. The highest control percentage was obtained with residues of peanut (40 g L-1), jack bean (60 g L-1) and Leucaena (80 g L-1), resulting in a control percentage of 73.3%. The peanut can be considered most efficient because it requires a lower concentration to reach the same percentage of Fusarium wilt control.

Occurrence of Purpureocillium lilacinum in citrus black fly nymphs

Black fly is a pest of Asian origin that causes direct and indirect damages to citrus, damaging the development and production of plants. For the development of efficient management strategies of the pest, the integration of control methods is necessary, and biological control is the most appropriate. Among the agents that can be used, entomopathogenic fungi are considered one of the most important and wide-ranging use. This work investigated the occurrence of Purpureocillium lilacinum (Thom.) Luangsa-ard et al. (= Paecilomyces lilacinus), attacking nymphs of citrus black fly, Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae). The fungus was isolated from infected Black fly nymphs, present on Citrus spp leaves in the municipality of Morros, Maranhão. After isolation, purification and morphological and molecular characterization, pathogenicity test was performed with A. woglumi nymphs. Morphological and molecular correspondence was verified between inoculum and the reisolated, proving the pathogenicity of P. lilacinum.