Genetic improvement of papayas and promotion of their cultivation
Germplasm (226 accessions) from the genera Carica, Vasconcellea and Jacaratia was collected in Ecuador and Colombia and planted in the field for its morphological characterization. CIAT established the drying and seed imbibition curves and showed that they withstand drying up to 5-11% without loss of viability and storage at temperatures of 22 to -196°C. The most common and economically important species were characterized, C. papaya, V. cundinamarcensis, V. goudotiana, V. stipulata and V. x heilbornii cv. Babaco. Qualitative characteristics were shown to be taxonomically discriminant and quantitative characteristics showed wide variation. Biochemical (isoenzymes) and molecular (microsatellites) characterization techniques were developed. Of 14 enzyme systems tested on 66 accessions, eight showed polymorphism. The microsatellites tested on a sample of 30 Caribbean and 11 Andean genotypes of the genus Vasconcellea, showed polymorphism with 26 initiators in the former and four in the latter and allowed differentiation between the two genera. Six accessions of C. papaya and V. goudotiana were tested for their resistance to nematodes. All showed susceptibility. Susceptibility of V. monoica to ringspot virus was confirmed and it was observed that resistance of V. cauliflora and V. cundinamarcensis exists only in certain plants of these species. Resistance to the canker bacteria was found in four of six genotypes tested.
The technological solution
The technological solution, for the tropical fruit production sector, has been the constitution of a germplasm collection of different papaya genera and species. This collection is cultivated in field and the numerous accessions have been characterized morphologically, biologically and molecularly through laboratory procedures that can be replicated by different research institutions. This is a dynamic solution because the collections can be continuously enriched with new accessions and also with hybrid material produced according to the needs of the production systems and markets.
An important result is the establishment of national collections of germplasm from different genus and species of papayas, which exceed 50 accessions, properly conserved in field collections. Another result is the morphological characterization of the germplasm, complemented with the biochemical and molecular characterization of a wide sample of accessions, through the use of isoenzymes and microsatellite markers. For this last purpose, an enriched genotheque of di-nucleotide sequences was built. As a corollary of the above preliminary results, the establishment of a regional nuclear collection and the selection of elite papaya genotypes for further intraspecific breeding and interspecific crosses have been achieved. An inventory of ringspot virus and canker bacteria strains has been achieved, complemented with data on the diversity of both pathogens.
The direct beneficiaries of the project are genebanks and biodiversity conservation institutions. So are the researchers of the national institutions, trained in morphological, biochemical and molecular characterization techniques of germplasm and in long-term seed conservation procedures. The indirect beneficiaries will be the farmers who will receive planting material that is more productive and more resistant to pests and diseases.
Sustainable Development Goals
- Universidad Central de Venezuela (UCV) - Venezuela
- International Center for Tropical Agriculture (CIAT) - Colombia
- CIRAD - Francia
- Corporación Colombiana de Investigación Agropecuaria (CORPOICA) - Colombia
- DENAREF - Ecuador
- Instituto Nacional de Investigaciones Agrícolas (INIA) - Venezuela
- IPGRI - Colombia
- MAG - Costa Rica
- Universidad de Costa Rica (UCR) - Costa Rica
- UdeC - Colombia
- Universidad Nacional de Colombia (UNAL) - Colombia
- UTA - Ecuador