Estratégias para exploração do germoplasma e aptidão para cultivo de Toona ciliata no Brasil

Abstract

Toona ciliata M. Roem is one of the most important species for timber production and has been increasingly planted worldwide in tropical and subtropical regions. Despite its high timber value and its ecological importance, the species lacks basic information such as genetic variability, genome-widestudies, structure of forest tree breeding programs and edaphoclimaticsuitability. For a sustainable exploration of a species, genomic tools can be used to access genomic variability, useful information both for population management in breeding programs and for the conservation of natural populations. In addition, knowledge of the edaphoclimatic conditions required by it is fundamental for allocating plantations in environments with high yield potential and assisting breeding programs to develop populations for wide edaphoclimatic conditions. Thus, the present study aims to: (i) infer about the structure of quantitative character variability in native subpopulations of T.ciliata introduced from Australia; (ii) Fit the climate zoning for T. ciliata in Brazil, aiming to provide subsidies for the allocation of new planted forests (ii) identify and characterize microsatellite regions in the genome of T. ciliata. For genetic evaluations, 74 progenies of T. ciliata, from 13 subpopulations sampled in Australia, were phenotyped for total height (m) and diameter (cm) and data were fitted in mixed linear models for subsequent estimation of genetic parameters. For climate zoning, data from the natural occurrence of T. ciliata in Australia were used to train a logistic model using 20bioclimatic as predictor variables. The prediction of T. ciliata in Brazilian territory was doneusing historical climatic normals (1970-2000) and predicted for three future periods: 2021-2040; 2041-2060 and 2061-2080 using the predictive model of climate change. The MISA (MIcroSAtellite Identification Tool) pipelinewas used to identify microsatellite loci (SSR) in the T. ciliata genome and subsequently classify them according to type, motif size and number of repeats. The results of the genetic evaluations for quantitative traits showed medium to high structuring of the quantitative variance of T. ciliata between subpopulations, with Q_stvalues ranging from 0.14 and 0.23 for height and diameter, respectively. The individual narrow-sense heritability (h_a^2) estimated for the two traits were moderate (0.31 and 0.25, respectively). The highest selection gains were obtained for diameter while the highest values of effective population size (N_e) were obtained for height. As for climate zoning, 65.1% of the Brazilian territory was classified as areas of high and good suitability for T. ciliataplanting, with a concentration of areas of high suitability in the north and south of Brazil, with precipitation (mm) being the edaphoclimatic condition with the greatest influence on fitness prediction. 39,085 SSR loci were identified in the genome of T. ciliata, where 32.3% were classified as mononucleotides, 56.8% were dinunucleotides, 7.9% were classified as tri-, tetra-, penta- and hexanucleotides, as well as 3% of total loci were classified as complex SSRs. Dinucleotides with 10 and 11 repeats were the most abundant loci and the most frequent type of motif was the AT/AT mononucleotide, representing 42.8% of the total number of motifs.