Project Number: 6631-21000-017-20
Project Type: Specific Cooperative Agreement

Start Date: Sep 29, 2006
End Date: Sep 28, 2011

Objective:
a) Development of screening methodologies: To optimize the artificial methods for screening resistance to Moniliophthora perniciosa and roreri, and Ceratocystis fimbriata. Study diversity and pathogenicity of M. perniciosa and roreri populations. b) Germplasm evaluation and variety development: The development of new improved cultivars of cacao using Marker Assisted Selection (MAS) that are resistant to the aforementioned diseases and highly productive has been underway for the last four years based on the previous cooperative agreement. This activity will be maintained and expanded to include new families and new mapping populations to identify stable Quantitative Trait Loci (QTL) for disease and productivity. The development of new cultivars can be divided into two activities based on the germplasm used to initiate the cultivar selection; Nacional (A types) and non-Nacional (B types) type clones. Nacional type clones (A types) and Intercrosses between Nacional types will be produced, screened for disease resistance and productivity and evaluated for release as new cultivars. Non-Nacional type clones (B types) Characterize and utilize non-Nacional clones in a MAS program to select for disease resistance and productivity. This includes using productive clones, such as CCN-51, as parents in crosses with primitive disease resistant clones from the Ecuadorian Amazon regions. Seedings from selected hybridizations are screened from disease resistance, evaluated with molecular markers, and selected for advanced yield trials in accordance with the accelerated MAS program developed at the ARS Miami lab. Germplasm Release Policy The research under this agreement involves two different kinds of genetic resources: A: The Nacional types (including hybrid or pure Nacional genotypes) and B: the non-Nacional types. It is understood that the results of this research will be managed under two different policies: Clones or any varieties issued from this agreement from the study of genetic materials of the A type will be managed under the strict discretion of INIAP, as these materials possess particular national value. Those derived from type B will reside within the public domain. INIAP agrees to facilitate the sharing of scientific results from the utilization of type A individuals while permitting the dissemination of scientific results as well as clones or varieties derived from the utilization of type B individuals to the international community.

Approach:
Scientists participating in the USDA cacao-breeding initiative in Latin America will be able to share scientific expertise on the current methods in order to optimize screening protocols for the three pathogens listed in the objectives. Attempts will be made also to develop new improved screening methods as part of this project. The pathogenic variability among isolates of M. perniciosa is not well known. To understand the genetic diversity in the pathogen, collections will be made from diverse geographical regions. Using a standard set of cacao clones, the differential pathogenicity of the isolates will be studied. Genetic diversity among the isolates will be estimated using molecular markers. Isolates will be collected from diverse geographical regions in Ecuador, and isolates from Brazil, Bolivia and Trinidad will be also studied in collaboration with scientists from these countries. Attempts will be made to produce basidiocarps in vitro. This technique allows basidiocarp production from single basidospores and is critical for the study of pathogenic variability. A set of reference clones will be chosen with differential susceptibility. These reference clones will be used in all studies. Each witches' broom isolate will be evaluated using the set of reference clones. SSR markers will be developed for witches' broom and the geographical diversity of the isolates will be evaluated. Any association between pathogenicity and a specific molecular marker will be noted A similar approach to which will be developed for M. perniciosa will be used in the study of M. roreri (in coordination with ongoing projects in CATIE and Reading University). Markers associated with the resistance genes are being used in MAS programs to select for new varieties with resistance to witches' broom, frosty pod and black pod. Saturated linkage maps have been produced and QTL identified for genes controlling resistance to witches' broom, frosty pod. Assays are being developed to use these markers for selection in current breeding populations. These assays will be used to pre-select genotypes for field testing allowing greater efficiency in the identification of superior individuals. Early screening for WB has been implemented through evaluating progenies for symptoms to WB in an highly infected area. Plants showing fewer symptoms will be selected and grafted to be established in an accelerated hybrid trial. New crosses from the best parents identified in the highly WB infected area will be used in a second generation of crosses to recombine different traits of agronomic interests. A series of new activities are described below that aim to enhance the selection processes (described under the cooperator agree section).