Soursop (Annona muricata L.): In vitro Propagation by Micrografting Selected Clones, Optimizing the Technique, and Evaluating the Agronomic Performance of Propagated Trees

Annona muricata L. (soursop, or guanábana in Spanish) is a fruit tree native to tropical America. The white pulp of its fruits is used to make juices, yogurts, ice creams, and desserts.

A major problem facing soursop growers is the lack of disease-free planting materials from elite selections. Between 1997 and 1999, we developed a novel methodology for in vitro clonal propagation of elite trees through micrografting. This methodology allows the rapid clonal multiplication of elite varieties and produces disease-free planting materials. Between January 1999 and January 2000, the first trees derived from in vitro propagation were planted for field-testing at CIAT and in farms of experienced soursop growers located in Huila and Valle del Cauca.

In 2001, we:

• Evaluated the agronomic performance of the micropropagated trees in the field;
• Optimized the propagation methodology;
• Adapted the developed in vitro propagation methodology to new promising soursop clones;
• Initiated studies on the use of rootstocks of different soursop selections or related annonaceous species; and
• Initiated studies on managing micropropagated plants in the greenhouse.
  

Contact: Alvaro Mejía

Tree Tomato (Cyphomandra betacea): Developing Cryopreservation Alternatives Useful to National Programs

Using our experience in cryopreservation of cassava, our objective in this project is to design long-term conservation alternatives that are comparable with or better than standard conservation methods, and which can be transferred to national programs in Latin America.

We selected the tree tomato as a case study for cryopreservation, keeping in mind that CIAT is adopting tropical fruits as part of its mandated crops, and that the tree tomato represents a significant alternative income source for many small-scale farmers. This fruit tree grows at high altitudes (1600-3000 m above sea level), where average annual temperatures range between 16 and 22 °C, and annual rainfall is 1300-1600 mm.

Contact: Roosevelt Escobar

Andean Passiflora spp.: Characterizing their Genetic Variability

The Passifloraceae comprise one of the better options for diversifying traditional agriculture in Andean countries. Consequently, as genetic resources, this family of fruits is highly significant, and the characterization and evaluation of both wild and cultivated populations comprise a priority for Andean countries.

Very little is known about the considerable genetic variability of the Passiflora as their exploration, evaluation, and study are only just beginning. The genus Passiflora L., of the order Violales and native to the tropical rainforests of South America, is one of 12 to 18 genera making up the family Passifloraceae. By far the largest genus, the 450 species of Passiflora are found from sea level to the high Andes, generally as low density populations. They are open pollinated, probably by large bees and hummingbirds.

Passiflora species are very difficult to classify accurately. Some are highly variable, whereas others resemble each other closely. Even with those many species and varieties of Passiflora that have already been carefully recorded, obtaining live specimens of them is very difficult. To extend our knowledge, we need to keep comprehensive collections of the genus in Colombia, Ecuador, Venezuela, and Peru, thereby preserving many rare species from extinction and making them available for research.

To explore the evolution of and relationships within the Passiflora species complex, we use genetic characterization, evaluation of variability, and mutational analysis of variation in chloroplast DNA; and we will also use molecular markers, for the first time in Passiflora.

Results from morfological and molecular characterization of Passiflora will provide a base on which to characterize different species and accessions, determine origins, select traits in intra- and interspecific crosses for further improvement, multiply selected genotypes, and conserve the Passiflora as a valuable genetic resource. This work will contribute to recent national efforts to collect, characterize, and evaluate the Passiflora fruit germplasm.

Passiflora fruits, such as banana passion fruit (curuba de Castilla in Spanish) of the subgenus Tacsonia, and passion fruit (maracuyá), sweet calabash (chulupa), and granadillas, all of the subgenus Passiflora; they have high potential in foreign trade as either fresh or processed fruit, particularly for the European and North American winter markets.

To determine the genetic, botanical, and agromorphological variability of the major Passiflora species, a collaborative project was developed on the "Diversity, conservation, and sustainable utilization of genetic resources of native fruits in tropical America". This REDARFIT countries project is financed by Interamerican Development Bank (IDB) and supported technically by Bioversity and CIAT. Most of the project's goals have been implemented in each country, and some Passiflora materials are already characterized on an agromorphological and molecular basis.

The project's work focuses on species of high economic potential such as P. ligularis (granadilla), P. edulis f. edulis, P. edulis f. flavicarpa (passion fruit), P. maliformis (sweet calabash), P. tripartita var. mollissima (banana passion fruit), and P. tarminiana ("Indian" banana passion fruit or curuba india). The knowledge generated on genetic diversity is expected to help improve the orientation of programs for the conservation and sustainable utilization of these resources. New genotypes developed must be robust, environmentally friendly, able to meet demands of the fresh-fruit trade and agroindustry, and able to contribute to the sector's competitiveness and growth. Both the resulting aggregate value and potential trade study will contribute to the better positioning of new products.

Contact: Inés Sánchez