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Sena K.,State University of Santa Cruz | Alemanno L.,CIRAD - Agricultural Research for Development | Gramacho K.P.,Cacao Research Center
Plant Pathology

The development of the basidiomycete Moniliophthora perniciosa in resistant and susceptible Theobroma cacao genotypes was analysed. The infection process leading to broom formation in shoot apexes was characterized by studying the kinetics of basidiospore germination, mode of penetration and colonization of the pathogen. Both resistant and susceptible cacao genotypes were inoculated with M. perniciosa and kept in the greenhouse for 90 days, explants were collected, treated for histological studies and meristematic tissues were observed by electron and light microscopy. Variation in the kinetics of germination between the cacao genotypes was detected 4 h after inoculation. The fungal penetration occurred through the star-shaped trichome base, natural openings on the cuticular surface and stomata. Host responses between genotypes were found to be different. Compared with non-infected plants, the swelling of all the stem tissues was evident at 60 days after inoculation. In the susceptible genotype, typical symptoms developed and fungal colonization was more intense than in resistant genotypes, which showed little or no fungal colonization. The investigations reported herein provide an important step in understanding the pattern of pre- and post-penetration events of M. perniciosa in cacao genotypes with different levels of resistance to this disease. © 2014 British Society for Plant Pathology. Source

Santos R.M.F.,Cacao Research Center | Santos R.M.F.,State University of Santa Cruz | Silva S.D.V.M.,Cacao Research Center | Sena K.,Cacao Research Center | And 3 more authors.
Tropical Plant Biology

Theobroma cacao L., the chocolate tree, is an important tropical tree-crop that provides sustainable economic and environmental benefits to some of the poorest and most ecologically sensitive areas of the world. Ceratocystis wilt (CW), caused by the fungus Ceratocystis cacaofunesta, is a highly dangerous disease capable of killing the cacao plant. Histopathological studies of the host-pathogen interaction are an effective resource to study pathogenesis which will ultimately lead to a better elucidation of the mechanisms of host resistance. We analyzed the development of C. cacaofunesta reproductive structures, the pattern of fungal colonization and the anatomical responses of cacao resistant (TSH 1188) and susceptible (CCN 51) genotypes to CW. Results showed that conidia germination started within 4 h after inoculation (hai) in agar, by 12 hai conidia germination was 80 %. The resistant genotype showed little or no fungal colonization compared to the susceptible genotype. Host reactions were characterized by greater quantities of gels, gums and tyloses in the susceptible genotypes compared to the resistant. The susceptible genotype had a large number of cells surrounding the xylem vessels that were infused with dark brown phenolic compounds. The host defense reaction observed near the xylem in the resistant genotype, suggest that a mechanism involved with resistance to C. cacaofunesta. © 2013 Springer Science+Business Media New York. Source

Cruz Neto R.O.C.,UESC | de Souza Junior J.O.,Jr. | Sodre G.A.,Cacao Research Center
Revista Brasileira de Fruticultura

Levels of Zn in tropical soils profoundly influences growth and nutrition of tree crops. Research was undertaken to assess the effect of soil Zn on growth and nutrition of clonal cacao tree seedlings of PH 16. Three acidic Oxisol soils differing in texture were used with nine doses of Zn (0, 1, 2, 4, 8, 16, 32, 48, and 64 mg dm-3). Rooted clonal seedlings were grown in plastic pot with 11 dm-3 of the soils at varying Zn levels for 240 days. At harvest growth (dry matter mass of leaves, stems, shoots, roots, and total) and nutrient concentrations were determined. The clonal cacao seedlings showed differences for production of dry matter mass and foliar nutrient concentrations for P, K, Ca, Mg, Mn, Fe, Zn, and Cu. There was Zn toxicity in all soils. © 2015, Sociedade Brasileira de Fruticultura. All rights reserved. Source

Melo B.L.B.,Cacao Research Center | Melo B.L.B.,University Estadual Of Santa Cruz Ppggbm | de Souza J.T.,Federal University of Reconcavo da Bahia | Santos R.M.F.,Cacao Research Center | And 7 more authors.
Forest Pathology

Moniliophithora roreri, causal agent of cacao frosty pod rot, is considered one of the most devastating pathogens of this crop. In this study, we report the development of and validation of 28 microsatellite loci from an enriched library. From these, ten loci were demonstrated to be polymorphic in an Ecuadorian population composed of 27 isolates. The mean number of alleles per locus was 3.2, and the observed mean and expected heterozygosity were 0.03 and 0.43, respectively. The polymorphic microsatellites described herein may be used to study the genetic diversity as well as to comprehend other aspects of M. roreri population biology. © 2014 Blackwell Verlag GmbH. Source

Santos R.M.F.,Cacao Research Center | Santos R.M.F.,State University of Santa Cruz | Lopes U.V.,Cacao Research Center | Silva S.D.V.M.,Cacao Research Center | And 5 more authors.
Molecular Breeding

Ceratocystis wilt (CW) in cacao (Theobroma cacao L.), caused by Ceratocystis cacaofunesta, is a drastic disease that results in plant death. The pathogen was recently identified in the major cacao-producing region of Brazil-Bahia. The identification of genetic markers tightly linked to disease resistance loci is a valuable tool for the development of resistant cultivars using marker-assisted selection (MAS). Branches of 143 six-year-old individuals of an F2 Sca 6 × ICS 1 population were wounded by making a 3-mm deep cut with a sterile scalpel, and inoculated with a 20-μl drop of a spore suspension of 3 × 104 CFU/ml. The inoculation method used allowed the population to be quantitatively phenotyped. The length of the xylem discoloration followed a continuous distribution. These results imply that the resistance was quantitatively inherited. Quantitative trait loci (QTL) analysis revealed two genomic regions (in linkage groups 3 and 9) associated with CW resistance. The QTL explained individually from 6.9 to 8.6 % of the phenotypic variation. The QTL identified are crucial for identifying genes for resistance and can be applied in the genetic breeding of cacao using MAS. © 2012 Springer Science+Business Media B.V. Source

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