ABSTRACT The local cacao varieties prevalent in the Atlantic Forest region in Bahia, Brazil, have been multiplied by farmers with seedlings produced by the most productive plants. However, these plants have not been evaluated for resistance to Ceratocystis wilt. Thus, in the present study, the resistance levels of different genotypes of local cacao varieties were assessed, aimed at their use in breeding for resistance to this disease. Leaf disks from 119 cacao genotypes, locally named as varieties ‘Common’ (49 genotypes), ‘Maranhão’ (34), and ‘Pará’ (36), were inoculated with Ceratocystis cacaofunesta. Based on the mean number of perithecia formed on those disks, different cacao genetic groups were defined according to the Scott-Knott test. For the three varieties, most genotypes were classified together with the resistance control variety (‘Jaca’), while less than one third of the genotypes were classified together with the susceptible control (CCN51). Therefore, there is variability for resistance to Ceratocystis wilt among the local cacao varieties, and resistant genotypes will be useful in breeding aimed at resistance to this disease.

RESUMO As variedades locais de cacau predominantes na Região de Mata Atlântica na Bahia, Brasil, vêm sendo multiplicadas pelos agricultores a partir de mudas produzidas com sementes das plantas mais produtivas. No entanto, essas plantas não têm sido avaliadas quanto à resistência à Murcha de Ceratocystis. Desta forma, nesta pesquisa, os níveis de resistência de diferentes genótipos de variedades locais de cacaueiro foram avaliados, visando à sua utilização no melhoramento para resistência a essa doença. Discos foliares de 119 acessos de cacaueiro, localmente denominados de variedade Comum (49 acessos), Maranhão (34) e Pará (36), foram inoculadas com Ceratocystis cacaofunesta. Com base no número médio de peritécios formados nesses discos, foram definidos diferentes grupos genéticos de cacau dentre os genótipos testados por meio do teste de Scott-Knott. As três variedades apresentaram a maioria dos genótipos classificados juntamente com a variedade controle de resistência (‘Jaca’), sendo que menos de um terço dos genótipos foram classificados junto com o controle suscetível (CCN51). Conclui-se que há variabilidade para resistência à Murcha de Ceratocystis nas variedades locais de cacau, sendo os genótipos resistentes úteis ao melhoramento visando resistência a essa doença.

ABSTRACT Plants of local cacao variety from Southern Bahia were evaluated in order to verify if there are different levels of resistance to witches’ broom disease in the study population and if the evaluation of adult plants in the field is a good predictor of these resistance levels. The seedlings were maintained under greenhouse conditions and inoculated with the fungus Moniliophthora perniciosa. Evaluations of symptoms occurred 60 days after inoculation. In the field, the same genotypes were evaluated by counting the number of dry brooms per plant, per year, and assessing trunk diameter size. The data were subjected to analysis of variance and averages grouped by the Scott–Knott test, differentiated by Tukey’s test and compared by Student’s T test. The Scavina-6 and CCN51 clones as well as the Catongo variety were used as resistance, moderate resistance and susceptibility patterns, respectively. Twenty-eight percent of the genotypes were among the most resistant and the genotypes 4119 and 4033 were considered the most susceptible to the disease in both field and greenhouse evaluations. Field evaluation was promising as a predictor of resistance level. The selected materials presented good characteristics for witches’ broom resistance, with different levels deserving special attention in the context of reducing the vulnerability of Brazilian cacao cultivation to the effects of the disease, especially in the cacao region of Bahia.

Resumo: O objetivo deste trabalho foi determinar uma metodologia para simulação de estresse hídrico in vitro, para seleção de genótipos de bananeira (Musa sp.) tolerantes à seca. As cultivares BRS Tropical e Prata Anã foram cultivadas in vitro em meio MS líquido, contendo sacarose e benzilaminopurina (BAP), e suplementado com diferentes concentrações de polietileno glicol ou de sorbitol. Avaliou-se o índice de estabilidade de rendimento de matéria seca. O cultivo por 30 dias em meio contendo 15 g L-1 de PEG ou 36,4 g L-1 de sorbitol é apropriado para simular a condição de estresse hídrico in vitro.

Abstract: The objective of this work was to determine a method to simulate water stress in vitro to select drought-tolerant banana (Musa sp.) genotypes. The BRS Tropical and Prata Anã cultivars were grown in vitro in an MS liquid medium containing sucrose and benzylaminopurine (BAP), supplemented with different concentrations of polyethylene glycol (PEG) or sorbitol. The yield stability index of dry matter was evaluated. Cultivation for 30 days in a medium containing 15 g L-1 PEG or 36.4 g L-1 sorbitol is appropriate to simulate water stress in vitro.