-Cacao was introduced in Bahia in

Molecular markers (RAPD, AFLP and microsatellites) were used to generate a linkage map and to identify QTLs associated to witches' broom (Crinipellis perniciosa) resistance in cacao (Theobroma cacao), using 82 individuals of an F 2 population derived from the clones ICS-1 (susceptible) and Scavina-6 (resistant). Fifteen evaluations of the number of brooms have been carried out in six years (1997)(1998)(1999)(2000)(2001)(2002). In order to increase the precision and accuracy in the measures of resistance, each F 2 plant was cloned in three replications in a randomized block design with singletree plots and evaluated over 2 years. Three hundred and forty-two markers were obtained, being 33 microsatellites, 77 AFLPs and 232 RAPDs. The distribution of the number of brooms in the F 2 population was skewed to resistance, suggesting the involvement of major genes controlling resistance and the repeatability estimated for resistance was 44%. A strong putative QTL was detected as being related to witches' broom resistance. Associated to this QTL, the microsatellite mTcCIR35 explained 35.5% of the phenotypic variation in resistance. This marker is being used for marker-assisted selection in Scavina-6 progenies, including those selected in private plantations, as an auxiliary tool to the phenotypic selection.

No abstract

The witches' broom disease caused by the fungus Crinipellis perniciosa is the main phytossanitary constraint for cacao production in Brazil. The integrated management of the disease involves resistance as one of the components. The breeding program conducted by the Brazilian Institution, CEPLAC is directed toward the pyramidation of resistance genes from different sources to achieve a more durable resistance. This study aimed to identify sources of resistance in progenies of cacao accessions collected in the basins of ten Amazonian rivers and compared to progenies from the Peruvian clones 'Scavina 6' and 'Sacavina 12'. Progenies from 40 Amazonian accessions and 'Scavina' were evaluated in the field for six years for witches' broom resistance through multivariate and repeated measurement analyses evaluating the effect of progeny, area, block, year, and their interactions. There were differences in the mean number of vegetative brooms on some Amazonian progenies and 'Scavina' descendants. There was an increase in the number of vegetative brooms in the last year for 'Scavina' progenies, but that was not observed for the Amazonian progenies 64, 66, 156, 194, 195, 269 and 274. There were different gene/alleles for resistance in the Amazonian progenies in comparison to the traditional 'Scavina' accessions. These new sources of resistance will be important for pyramiding resistance genes and consequently increasing the stability and durability of the resistance to witches' broom.

Resumo -O objetivo deste trabalho foi avaliar a diversidade genética de acessos de cacau, selecionados previamente como produtivos e resistentes à vassoura-de-bruxa na Bahia, e estudar suas inter-relações com genótipos no banco de germoplasma. Amostras de DNA de folhas dos 120 acessos, coletados em 17 fazendas de sete municípios do Sul da Bahia, foram amplificadas pela técnica de RAPD ("random amplified polymorphic DNA"). Os coeficientes de dissimilaridade genética, calculados pelo método de Jaccard a partir das bandas RAPD, permitiram evidenciar, pela análise de agrupamento, que a maioria das seleções das fazendas (89,2%) agrupou-se com acessos do banco de germoplasma considerados representativos da diversidade de cacau (híbridos, trinitários, Scavinas, amazônicos e cacau-comum). As demais seleções distribuíram-se em outros sete grupos distintos. Há elevada diversidade genética entre as seleções das fazendas, e algumas delas devem ter-se originado de genitores não incluídos nesta análise. Esses materiais apresentam potencial para seleção de clones com maior diversidade para novos cruzamentos ou uso pelos agricultores.Termos para indexação: Theobroma cacao, marcador molecular, melhoramento genético, vassoura-de-bruxa. Genetic diversity among farm and germplasm bank accessions of cacao in Bahia, BrazilAbstract -The objective of this work was to assess genetic diversity of farm cacao accessions, previously selected as productive and resistant to witch broom in Bahia, Brazil, and to study their interrelationship with reference genotypes on germplasm bank. DNA samples from 120 cacao accessions, collected on 17 farms in seven counties in Southern Bahia, were amplified by RAPD technique (random amplified polymorphic DNA). The coefficients of genetic dissimilarity, calculated from the RAPD bands by Jaccard method, allowed to show by cluster analysis that most farm selections (89.2%) grouped with accessions from germplasm bank considered representatives of the cacao genetic diversity (hybrids, Trinitarian, Scavina, Amazon and common cacao). The other selections were distributed in seven distinct groups. There is high genetic diversity among farm selections, and some of them may have originated from other progenitors not included in this analysis. These materials present potential for clone selection with higher diversity for new crossings or direct use by agriculturists.

-The objective of this work was to identify genotypes with high general combining ability for resistance to witches'-broom (Moniliophthora perniciosa) in populations formed from a first cycle of recurrent selection. Highly productive and resistant clones from different origins were interbred using the North Carolina II design. The clones SCA 6, CSUL 7, RB 39, CEPEC 89, OC 67, BE 4, EEG 29 and ICS 98 were used as paternal parents, while the maternal ones were NA 33, CCN 10, IMC 67, P 4B, CCN 51, CEPEC 86, SGU 54 and ICS 9. Twenty days after germination, 56 seedlings of each cross (four replicates of 14 seedlings) received the inoculation of a 1-mL suspension with 7.5x10 4 basidiospores mL -1 . Symptoms were evaluated 60 days after inoculation. Significant differences were observed among paternal and among maternal parents, for resistance to witches'-broom assessed according to the proportion of progeny seedlings with the disease symptoms. Differences were also observed between groups of mothers or fathers previously defined as resistant, and groups previously defined as susceptible. It is possible to obtain a combination of genes that can increase the level of resistance to witches'-broom directly from the first cycle of recurrent selection.

Witches' broom is a severe disease of Theobroma cacao L. (cacao), caused by the basidiomycete Moniliophthora perniciosa.

Pathogenic variability of Moniliophthora perniciosa in three agroecological zones of the cacao region of Bahia, Brazil