Caracterización fenotípica de frutos de "Guayabo del País" (Acca sellowiana (Berg) Burret), en dos poblaciones de hermanos completos

The feijoa or “Guayabo del país” [Acca sellowiana (Berg.) Burret] is a promising native fruit tree, due to the outstanding nutritional properties of its fruits. This fruit tree is extensively cultivated in Colombia, New Zealand and the United States, while in Uruguay it is cultivated only on a small and local scale. Currently, the main objective of the Breeding Program of Guayabo del país in Uruguay (FAGRO-INIA) is to develop and improve superior cultivars, with excellent fruit quality. Supporting this program, in this study fruits of two breeding populations were evaluated with the objective to characterize the phenotypic variation. Additionally, two selection indexes were compared and applied to select individuals with superior fruit characteristics. Two full-sib F1 populations, H5 (139 individuals) and H6 (182 individuals), connected by one common progenitor were characterized. Fourteen morphological variables were evaluated during three years (2015, 2016, 2017) including: fruit diameter, fruit length, diameter-length ratio, fruit weight, pulp weight, skin thickness, total soluble solids, total titratable acidity, 100 seeds weights and flowering date; in addition to the qualitative descriptors: roughness of the skin, pulp oxidation rate y shape of fruit base. For each population, a descriptive analysis was carried out for each variable, the degree of variability between years and populations, as well as the correlation between variables. To meet the breeding objectives, superior individuals were identified through the multiplicative index and the sum of classification index. Both populations presented a high degree of phenotypic variability, consistent between the three years of evaluation. The most high and positive correlations among fruit quality traits were obtained between fruit size (diameter and length) and weight (fruit weight and pulp weight) for both populations. Heritability estimates were moderate to high for all variables analyzed, and similar for both populations except for total soluble solids. A high correlation between the selection index was found (0.79 and 0.80, for H5 and H6 respectively), indicating that the ranking of individuals was well preserved. Thus, 8 and 11 individuals for H5 and H6, respectively, were selected for their remarkable fruit quality. The large phenotypic diversity reported in these breeding populations and the identification of superior genotypes based on multiple fruit traits, represents a valuable contribution for the breeding efforts in A. sellowiana.