Characterization of Guava Accessions by SSR Markers, Extension of the Molecular Linkage Map, and Mapping of QTLS for Vegetative and Reproductive Characters

Abstract

The guava accessions assembled in the Cuban germplasm collection at Alquízar (Havana Province) were previously characterized by phenotypic descriptors as well as by AFLP DNA markers (Rodríguez et al., 2004; Valdés-Infante et al., 2003). Here, SSR DNA markers were applied in the establishment of phylogenetic relationships. Furthermore, three guava mapping populations were produced by controlled crosses with the dwarf cultivar 'Enana Roja cubana' as the female parent. Based on segregating AFLP markers, an integrated molecular linkage map of guava was constructed for the first mapping population MP1 under investigation. The previously published linkage map (Valdés-Infante et al., 2003) was extended by arranging a total of 220 markers into 11 linkage groups possibly representing the 11 chromosomes (2n = 22) of the guava genome with 11 to 30 markers per linkage group and a total genome length of 1379 cM. QTL analysis for vegetative characters identified a total of fifteen loci contributing to leaf length, leaf width, petiole length, height, and growth rates for diameter and height. The QTL analysis for fruit characters resulted in the identification of loci such as fruit weight, acidity, total soluble solids, vitamin C content, and pulp thickness.

Breeding Guava (Psidium guajava L.)

“…Although AFLP detected lower diversity than SSR in the guava collection from Cuba, the second could not identify between two highly related genotypes 'N6' and 'Ibarra', using the same primer number (Rodríguez et al 2007). This corroborates the necessity of an integrated study to prevent wrong deductions related to misclassification, duplicates detection and variability estimation.…”

“…Furthermore, it is a potentially useful molecular resource for genetics investigations in the genus Psidium . The primer combinations mPgCIR05, mPgCIR07, mPgCIR09, mPgCIR10, mPgCIR11, mPgCIR15, mPgCIR16 and mPgCIR19 revealed clear polymorphism in guava accessions from Cuban germplasm (Rodríguez et al 2007). …”

“…Rueda et al (2003) found a relatively high level of genetic diversity in Corpoica Palmira germplasm (Colombia); while Prakash et al (2002) detected from low to moderate variability in India germplasm, both using the same molecular marker (RAPD). On the other hand, Valdés-Infante et al (2003) detected a low level of diversity using AFLP, although micro-satellites revealed a moderate heterozygosis level in the same Cuban guava germplasm (Rodríguez et al 2007). This difference might result from the inheritance of each molecular marker and the genomic region explored.…”

“…Using RAPD markers in guava germplasm collections, some authors have identified genotypes coming from diverse foreign regions (Prakash et al 2002;Rueda et al 2003). Nevertheless, overall interpretation of the genetic relationships among guava accessions with AFLP and SSR (Rodríguez et al 2007) in Cuba indicates the absence of separate clusters representing local and foreign germplasm. This reflects the selection of guava lines from open pollination rather than from controlled crosses.…”

“…Despite the fact that a comparative study related with the use of molecular markers for guava fingerprinting is still to be developed, the utility of AFLP, ISTR and SSR for genotype identification have been corroborated (Hernández et al 2003;Rodríguez et al 2003;Valdés-Infante et al 2003;Rodríguez et al 2007). Besides, RAPD analysis has proven good results (Prakash et al 2002;Rueda et al 2003), although their reproducibility across different laboratories remain under discussion (Donini et al 2000).…”