Validation of molecular markers linked to apospory in tetraploid races of bahiagrass, Paspalum notatum Flugge

Tetraploid (2n = 4x = 40) races of Paspalum notatum Flugg, are important natural forage grasses for the tropical and subtropical areas of the Americas. Almost all natural accessions reproduce by obligate aposporous apomixis. Previous work on the species allowed the identification of several molecular markers completely linked to apospory, one component of apomictic reproduction. Moreover, after a fingerprinting characterization of a germplasm collection, 11 amplified fragment length polymorphism (AFLP) markers exclusive to apomictic accessions were detected. The objectives of this work were (1) to validate the presence of molecular markers linked to apospory in tetraploid races of different geographic origins, (2) to determine if markers specific to apomictic accessions were associated with the mode of reproduction, and (3) to develop single-locus markers of apospory that can be used for marker-assisted selection. Thirteen natural apomictic accessions were analyzed. Moreover, the parental plants Q4188 (non-aposporous) and Q4117 (aposporous) and 44 F1 progenies (36 non-aposporous, 8 aposporous) derived from them were used as a validation population. Nine markers [two random amplification of polymorphic DNA (RAPD) and seven AFLP] 100% linked to apospory in Q4117 were tested. Amplification reactions with the corresponding primers showed that all markers were present in the 13 aposporous (apomictic) accessions, but were absent in the non-aposporous controls. On the other hand, linkage analysis of the 11 AFLP markers specific to the apomictic accessions showed that all of them were linked in coupling to apospory (r = 0.00, LOD 13.245). Based on one AFLP (E36M37c), two sequence characterized amplification region (SCAR) markers (SPNA1 and SPNA2) co-segregating with the trait and present in the 13 apomictic accessions were developed. The presence of markers associated with apospory was conserved among tetraploid accessions of different geographic origins. Moreover, the single-locus markers SPNA1 and SPNA2 could be used for routine marker-assisted selection in hybrid populations segregating for apospory and to facilitate the isolation of apospory-related genes.