Abstract
To characterize the gradient of resistance to black pod disease experimentally, the leaf disk assay was applied to 217 cocoa genotypes. The parameters time interval, number of leaves evaluated per genotype and distribution of experimental treatments were evaluated. Significant differences between genotypes were found, resulting in the grouping in five homogenous groups (p < 0.01). In the assessments with the leaf disk test, five and seven days after inoculation, the F value was highest after seven days, clearly separating the resistant from susceptible genotypes. There was no difference between the clones behavior and the use of more than one box to group the genotypes (p = 0.56) and the use of different leaves of the same genotype (p = 0.08). The resistance gradient observed indicates variability enough for mapping and cocoa breeding in the population.
Highlights
Cacao (Theobroma cacao L.) is a perennial plant whose primary diversity center lies in the Amazon basin (Dias 2001, Bartley 2005)
The leaves of the clones Sca6, ICS1, TSH516 (F1 of Sca6 x ICS1) and SIC19 (Forastero susceptibility standard to black pod) and 213 F2 genotypes (Sca6 X ICS1) used for the tests were obtained, respectively, from cacao trees growing in the Active Germplasm Bank and in the greenhouse of the Centro de Pesquisas do Cacau/ Comissão Executiva do Plano da Lavoura Cacaueira (CEPEC/ CEPLAC), in Itabuna, Bahia, Brazil
The F values were discrepant regarding the infection level (IL) (F = 92.6 and 251.9, after five and seven days, respectively); the period of seven days with the highest value of F was used for the experiments
Summary
Cacao (Theobroma cacao L.) is a perennial plant whose primary diversity center lies in the Amazon basin (Dias 2001, Bartley 2005). Of the seven species of Phytophthora that cause black pod in cacao, P. palmivora is the most widely distributed in the world; in Brazil, its occurrence has increased considerably in recent years due to increased rainfall (Luz and Silva 2001). Among the measures adopted to control this disease are appropriate cultural practices including fungicide application. This practice, widespread, has the disadvantage of increasing the production costs (Tan and Tan 1990), polluting the environment (Akinnifesi et al 2006) and being little effective in the field control of black pod if not applied properly (Nyassé et al 2006). A promising alternative of black pod control, similar to other cacao diseases (Faleiro et al 2004), is the use of resistant genotypes enriched with genes of morphological and agronomic traits of interest (Nyassé et al 2003, Pokou et al 2008)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
