Filogenómica de Feijoa sellowiana (O. Berg) O. Berg (“guayabo del país”) tipo Uruguay y Brasil basado en pan-plastoma

In Uruguay, the native feijoa (Feijoa sellowiana, Myrtaceae), also known as the “guayabo del país,” is the native woody species with the greatest potential for commercial fruit production and derived products. The “Uruguay type” and “Brazil type” variants are recognized. The development of cultivars at the regional and international levels is recent and stems from the “Uruguay type,” “Brazil type,” or their hybrids. However, there is little information to help clarify the recent and historical phylogenetic relationships among wild accessions, domesticated forms, and cultivars.

The reduction in the costs of massive sequencing technologies makes it possible to implement intraspecific genetic studies based on complete chloroplast genomes, rather than traditional universal markers. There are no precedents for implementing these studies in feijoa. In this study, a new version of the feijoa plastome annotation was developed and validated. Additionally, a feijoa pan-plastome was generated for the first time, including 33 accessions (wild, selections, and cultivars) from Uruguay, Argentina, Brazil, and New Zealand.

The feijoa pan-plastome ranged from 159,330 bp to 159,401 bp in length and encoded 117 unique genes. In total, 51 indels, 135 SNPs, and 13 haplotypes were detected. Three hypervariable intergenic regions (rps16-trnQ(UUG); psbZ-trnG(GCC); ndhF-rpl32) were used to develop new markers for the species. No significant evidence of adaptive selection was identified among the protein coding genes.

The phylogenetic analysis divided the accessions into two main clades, which largely separated the “Brazil type” variants (clade 1) from the “Uruguay type” variants (clade 2). Clade 1 included 10 Brazilian accessions (three cultivars) and one New Zealand cultivar. Furthermore, this clade corresponded to haplogroup 1, including six of the 13 haplotypes identified in this study. For its part, clade 2 comprised two subclades and one orphaned Brazilian accession. Subclade 2.1 included two Brazilian accessions (one cultivar) and three Argentinian ones, for which some data suggest that they produce fruits of intermediate size between the “Uruguay type” and the “Brazil type”; this clade corresponded to haplogroup 2 (four haplotypes). Subclade 2.2 preferentially grouped the “Uruguay type” accessions, including the Uruguayan accessions (four cultivars), six New Zealand cultivars, and one Brazilian cultivar. This subclade corresponded to haplogroup 3, which consisted of only two haplotypes, with representatives of cultivars and accessions from Uruguay in both lineages. This study reports the first evidence of clear evolutionary differentiation between the “Uruguay type” and the “Brazil type” based on pan-plastome data; it also identified two chloroplast lineages for Uruguayan guavas and two others for Argentine guavas, and found that 10 cultivars derived from three breeding programs (Uruguay, Brazil, and New Zealand) share a common maternal lineage originating in Uruguay.

Overall, this study provides new evidence on the genetic variability of the species and contributes to our understanding of its evolutionary history, as well as the recent processes of domestication and genetic improvement. These topics warrant further investigation in future studies.