No abstract

Acca sellowiana, known as feijoa or pineapple guava, is a diploid, (2n = 2x = 22) outcrossing fruit tree species native to Uruguay and Brazil. The species stands out for its highly aromatic fruits, with nutraceutical and therapeutic value. Despite its promising agronomical value, genetic studies on this species are limited. Linkage genetic maps are valuable tools for genetic and genomic studies, and constitute essential tools in breeding programs to support the development of molecular breeding strategies. A high-density composite genetic linkage map of A. sellowiana was constructed using two genetically connected populations: H5 (TCO × BR, N = 160) and H6 (TCO × DP, N = 184). Genotyping by sequencing (GBS) approach was successfully applied for developing single nucleotide polymorphism (SNP) markers. A total of 4,921 SNP markers were identified using the reference genome of the closely related species Eucalyptus grandis, whereas other 4,656 SNPs were discovered using a de novo pipeline. The individual H5 and H6 maps comprised 1,236 and 1,302 markers distributed over the expected 11 linkage groups, respectively. These two maps spanned a map length of 1,593 and 1,572 cM, with an average inter-marker distance of 1.29 and 1.21 cM, respectively. A large proportion of markers were common to both maps and showed a high degree of collinearity. The composite map consisted of 1,897 SNPs markers with a total map length of 1,314 cM and an average inter-marker distance of 0.69. A novel approach for the construction of composite maps where the meiosis information of individuals of two connected populations is captured in a single estimator is described. A high-density, accurate composite map based on a consensus ordering of markers provides a valuable contribution for future genetic research and breeding efforts in A. sellowiana. A novel mapping approach based on an estimation of multipopulation recombination fraction described here may be applied in the construction of dense composite genetic maps for any other outcrossing diploid species.

El objetivo de este estudio fue caracterizar cinco colores de cáscara de fruta de guayabo del país establecidas en una escala visual utilizada en la selección y mejoramiento genético de esta especie en Uruguay con los parámetros colorimétricos en el espacio tridimensional CIELAB y cuantificar el contenido de clorofila total, clorofila a, clorofila b y carotenoides totales. La escala visual analizada comprende los colores de cáscara Amarillo (A), Amarillo Verde (AV), Verde Amarillo (VA), Verde (V) y Verde Verde (VV). La luminosidad y la saturación del color de la cáscara de los frutos bajaron al aumentar el color verde de la escala visual (L* 57,2 a 36,4; C* ab 41,4 a 15,9). El tono varió de 90,4 a 121,3 ºh ab coincidiendo con lo percibido en la escala visual en las categorías de color de cáscara desde A a VV. La diferencia de color (∆E ab) entre las categorías de la escala visual es distinguida fácilmente por un observador no experto. El índice de color discriminó estadísticamente los cinco colores de cáscara siendo los valores 0 (A),-4 (AV),-5 (VA),-12 (V) y-17 (VV). El contenido de clorofila total (0,160 a 0,119 mg g-1) y de clorofila a (0,085 a 0,362 mg g-1 peso fresco) se correlacionó positivamente con la escala creciente de verde de la cáscara (r = 0,56 y 0,80; p ≤ 10-5). En cambio, los carotenoides totales (0,043 a 0,119 mg g-1 peso fresco) no se correspondieron claramente en función de la escala visual (r =-0,03; p 0,225) probablemente enmascarados por la clorofila y también con contenido de clorofila más alto en los frutos VV.

The Feijoa “Guayabo del país” (Acca sellowiana) is a native Myrtaceae whose fruits have a great commercial potential for their nutritive properties. The objectives of this study were to determine the extent to which fruit production depends on biotic pollination and to identify potential pollinators in Uruguay. Two farms and three park, located in Salto and Canelones were used for the study. The percentage of fruit set in the branches excluding pollinators did not exceed 5.1%, whereas in the branches with free access of pollinators it varied between 10.4% (Salto) and 90.9% (park trees, Canelones). A total of 28 insect species and 3 Passeriforme species were identified on the flower varying with the region. Apis mellifera were present on all plantations with high frequency. Remarkably, 7 species of native bees and 3 species of native passerines were found only in the southern trees of the country. Some pollinators can be managed to improve production, of commercial quality, like honeybees or bumblebees.