Browsing by Author "Stela D.V.M. Silva"

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    Assessment of selected clones of cocoa in southern Bahia to resistance Ceratocystis cacaofunesta
    (2010-12) Stela D.V.M. Silva; Luiz Roberto Martins Pinto; Bruno Ferreira de Oliveira; Jose Luis Pires; Virginia Oliveira Damaceno
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    Evaluation of Phenotypic Stability of Resistance to Phytophthora spp. in Cacao Clones
    (ARTIGOS / ARTICLES, 2007) Luiz Roberto M. Pinto; Stela D.V.M. Silva; Milton M. Yamada
    Resistance of fourteen Theobroma cacao clones to Phytophthora spp. was evaluated using stem inoculations on grafted seedlings. Concepts of phenotypic stability were used to interpret the results and to express horizontality of the resistance. The linear regression coefficient ‘b’, the determination coefficient (R2) and average lesion size were used to determine the level of horizontal resistance, the phenotypic stability and the predictability of all clones. The results indicated that clones P 7 and MA 15 present highest levels of horizontal resistance and stability, but with moderate predictability. Clones CAS 1 and CEPEC 13 were classified as those with high horizontal resistance, stability and predictability, while clones PA 30, UF 650 and SIAL 88 and EET 59 showed intermediate resistance and stability and high predictability. Clones SPA 17, OC 61, PA 150, SIAL 505, ICS 1 and R 41 presented high susceptibility and intermediate or low stability and moderate or high predictability.
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    Novel sources of witches’ broom resistance (causal agent Moniliophthora perniciosa) from natural populations of Theobroma cacao from the Brazilian Amazon
    (2010) Paulo S.B. de Albuquerque; Stela D.V.M. Silva; Edna D.M.N. Luz; Jose L. Pires; Afranio M.C. Vieira; Clarice G.B. Deme trio; Sergio F. Pascholatti; Antonio Figueira
    Witches broom is a severe disease of Theobroma cacao L. (cacao), caused by the basidiomycete Moniliophthora perniciosa. The use of resistant cultivars is the ultimate method of control, but there are limited sources of resistance. Further, resistance from the most widely used source (Scavina 6) has been overcome after a few years of deployment. New sources of resistance have been intensively searched for in the Amazon basin. Here, we evaluated for witches broom resistance, cacao accessions from various natural cacao populations originally collected in the Brazilian Amazon. Resistance of 43 families was evaluated under nursery and/ or field conditions by artificial or natural infection, respectively, based on disease incidence. Screening for resistance by artificial inoculation under nursery conditions appeared to be efficient in identifying these novel resistance sources, confirmed by natural field evaluation over a nine-year period. The increase in natural field infection of Scavina 6 was clearly demonstrated. Among the evaluated families with the least witches broom incidence, there were accessions originally collected from distinct river basins, including the Jamari river (CAB 0371; CAB 0388; CAB 0392; and CAB 0410); Acre (CAB 0169); Javari (CAB 0352); Solimoes (CAB 0270); and from the Purus river basin, the two most outstanding resistant accessions, CAB 0208 and CAB 0214. The large genetic diversity found in cacao populations occurring at river basins from Acre and Amazonas states, Brazil, increased the chance that the selected resistant accessions would be genetically more dissimilar, and represent distinct sources of resistance to M. perniciosa from Scavina 6.