Final Report Summary - GUAVAMAP (Improvement of guava: Linkage mapping and QTL analysis as a basis for marker-assisted selection)
The 'Improvement of guava: linkage mapping and QTL analysis as a basis for marker-assisted selection' (Guavamap) project aimed to improve breeding efficiency of guava.
The project's first objective (guava biodiversity analysis) was pursued by the Latin American partners Brazil, Cuba, Mexico, and Venezuela with Brazil and Mexico belonging to the main producer countries world-wide. Important results were obtained with respect to the application of the collected germplasm and hybrids produced by controlled crosses for production:
(i) The Brazilian guava accessions, in specific the identification of 11 wild growing Psidium species as sources of resistance to the devastating root knot nematode Meloidogyne mayaguensis, now form the basis for controlled crosses and development of new, nematoderesistant varieties for guava production. This nematode is the major pest disease of guava in Brazil and has destroyed more than 60 % of the commercial production in Northeast Brazil. Grafting experiments with nematode-resistant accessions and commercial guava cultivars and experiments on cross-pollination have been initiated, and offer prospects for the development of new, pest resistant varieties.
(ii) The breeding program in Cuba was based on an existing germplasm collection. Within the Guavamap project, a total of 25 with low size have been selected for propagation and variety development. All of them are now being replicated in plots for the evaluation of important agronomic traits in order to select new cultivars for production in Cuba.
In this context it is noteworthy to mention that an undated UPOV descriptor for guava which serves as the basis for agro-morphological description of accessions and cultivars has been developed in the frame of the project.
The second strategic objective of the Guavamap project related to the molecular characterisation of the prospected guava germplasm and complements the agro-morphological analysis of the guava accessions by updated UPOV descriptors. For this purpose and for integration into individual molecular linkage maps and establishment of an integrated, high-density reference linkage map of guava, the massive development of microsatellite (SSR) markers was pursued and a SSR guava linkage map of 378 marker loci integrating 153 SSR markers into 11 linkage groups was constructed.
With respect to the AFLP-based linkage maps, by the end of the project the number of mapped markers increased to 1779 markers (projected: 960-1200 markers) on 3 integrated parental linkage maps derived from the three mapping populations (MPs) with 116 markers (AFLP, SSR, COS) per linkage group available on the three maps.
QTL analyses in all three mapping populations included leaf length, leaf width, fruit length, fruit width, internal and external pulp thickness, seed numbers, average seed weight, vitamin C content, acidity, total soluble solids, maturity index, average fruit weight, plant height, and cumulative yields for the years 2005 to 2008. Certain QTLs from different progenies could be co-located or closely linked targeting the same genes that determine a trait.
Dissemination of project results culminated in the organisation of the 'Second International Symposium on Guava and Other Myrtaceae' in November 2008 in Merida and Aguascalientes, Mexico. All publications from oral and poster presentations have been edited by the Guavamap project and published as a special issue of Acta Horticulturae.
The symposia were followed by practical courses on biotechnology and bioinformatics. From project funds, four fellowships were awarded to young scientists to participate to the Mérida Symposium and the two practical courses.
Partners will also host the 3rd and 4th International Symposium on guava and other myrtaceae in Brazil (2011) and Venezuela (2014), respectively, under the auspices of the ISHS. Thus continuation of the international collaboration on guava which was initiated by the EC-funded Guavamap project is warranted beyond the duration of the project.
The project's first objective (guava biodiversity analysis) was pursued by the Latin American partners Brazil, Cuba, Mexico, and Venezuela with Brazil and Mexico belonging to the main producer countries world-wide. Important results were obtained with respect to the application of the collected germplasm and hybrids produced by controlled crosses for production:
(i) The Brazilian guava accessions, in specific the identification of 11 wild growing Psidium species as sources of resistance to the devastating root knot nematode Meloidogyne mayaguensis, now form the basis for controlled crosses and development of new, nematoderesistant varieties for guava production. This nematode is the major pest disease of guava in Brazil and has destroyed more than 60 % of the commercial production in Northeast Brazil. Grafting experiments with nematode-resistant accessions and commercial guava cultivars and experiments on cross-pollination have been initiated, and offer prospects for the development of new, pest resistant varieties.
(ii) The breeding program in Cuba was based on an existing germplasm collection. Within the Guavamap project, a total of 25 with low size have been selected for propagation and variety development. All of them are now being replicated in plots for the evaluation of important agronomic traits in order to select new cultivars for production in Cuba.
In this context it is noteworthy to mention that an undated UPOV descriptor for guava which serves as the basis for agro-morphological description of accessions and cultivars has been developed in the frame of the project.
The second strategic objective of the Guavamap project related to the molecular characterisation of the prospected guava germplasm and complements the agro-morphological analysis of the guava accessions by updated UPOV descriptors. For this purpose and for integration into individual molecular linkage maps and establishment of an integrated, high-density reference linkage map of guava, the massive development of microsatellite (SSR) markers was pursued and a SSR guava linkage map of 378 marker loci integrating 153 SSR markers into 11 linkage groups was constructed.
With respect to the AFLP-based linkage maps, by the end of the project the number of mapped markers increased to 1779 markers (projected: 960-1200 markers) on 3 integrated parental linkage maps derived from the three mapping populations (MPs) with 116 markers (AFLP, SSR, COS) per linkage group available on the three maps.
QTL analyses in all three mapping populations included leaf length, leaf width, fruit length, fruit width, internal and external pulp thickness, seed numbers, average seed weight, vitamin C content, acidity, total soluble solids, maturity index, average fruit weight, plant height, and cumulative yields for the years 2005 to 2008. Certain QTLs from different progenies could be co-located or closely linked targeting the same genes that determine a trait.
Dissemination of project results culminated in the organisation of the 'Second International Symposium on Guava and Other Myrtaceae' in November 2008 in Merida and Aguascalientes, Mexico. All publications from oral and poster presentations have been edited by the Guavamap project and published as a special issue of Acta Horticulturae.
The symposia were followed by practical courses on biotechnology and bioinformatics. From project funds, four fellowships were awarded to young scientists to participate to the Mérida Symposium and the two practical courses.
Partners will also host the 3rd and 4th International Symposium on guava and other myrtaceae in Brazil (2011) and Venezuela (2014), respectively, under the auspices of the ISHS. Thus continuation of the international collaboration on guava which was initiated by the EC-funded Guavamap project is warranted beyond the duration of the project.