Estudo genético e seleção de progênies de soja para o grupo de maturidade relativa em populações derivadas de cultivares comerciais
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Data
2018-04-20
Autores
Pedroso Val, Bruno Henrique
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Universidade Estadual Paulista (Unesp)
Resumo
As pesquisas visando a adaptação da cultura da soja e o melhoramento vegetal foram fundamentais para a expansão dessa cultura no Brasil. A descoberta do gene de período juvenil longo e dos genes da série E, relacionados com a época de florescimento e maturação permitiram a expansão da cultura, que inicialmente se adaptou melhor no estado do Rio Grande do Sul para regiões de baixas latitudes, criando novas fronteiras agrícolas. Até o presente momento encontram-se descritos na literatura dez genes da série E, E1 a E10, o gene Dt1 e o gene J que condiciona o período juvenil longo, porém não se sabe ainda quanto e nem como esses genes influenciam o caráter grupo de maturidade relativa (GMR). Tanto para a cultura da soja quanto para as demais culturas o melhoramento não ocorre somente para um único caráter, pois o melhorista trabalha simultaneamente com vários caracteres e o ganho genético deve ser distribuído entre eles. Diante do exposto, os objetivos do presente trabalho consistiram em realizar o estudo genético do número de genes que estão envolvidos no caráter GMR, descobrir qual a ação gênica que controla o caráter e selecionar as melhores progênies com o uso de índices de seleção. Para o estudo genético foram feitos dois cruzamentos biparentais entre cultivares comerciais de soja, onde, para cada cruzamento foram obtidas as gerações F1 e F2. Os genitores e suas respectivas gerações foram conduzidos a campo para a realização da fenotipagem do GMR. Para o estudo de herança do caráter GMR, foi utilizado o teste de escala conjunta por meio dos quadrados mínimos ponderados. A metodologia permite a detecção de genes de menor efeito, ou modificadores da característica em questão, sendo possível a estimação do efeito ambiental. Foram semeadas 129 progênies F3, onde foram avaliados seis caracteres agronômicos: altura de inserção da primeira vagem (AIV), altura da planta na maturidade (APM), número de dias para maturidade(NDM), acamamento (AC), valor agronômico (VA) e produção de grãos (PG). Para as duas populações estudadas, não houve efeito significativo de dominância atuando na expressão do caráter GMR. Na primeira população foi observado que dois genes atuam de maneira aditiva na expressão do caráter e a contribuição média estimada de cada alelo foi em 0,11. Na segunda população foi observado que um gene atua de maneira aditiva na expressão do caráter sendo a contribuição estimada de cada alelo em -0,515. O efeito de progênies foi significativo para o teste F a 5% de probabilidade, apenas para APM e NDM. Em relação aos ganhos genéticos totais obtidos com a aplicação dos índices, os mesmos foram: 16,19 % para soma de “ranks”, 28,68 % para o índice baseado nos ganhos desejados e 20,58 para o índice distância genótipo ideótipo. Entre as progênies selecionadas destacam-se as progênies 16, 46, 81 e 87 por apresentarem caracteres agromorfológicos mais adequados para a região de estudo.
The researches aimed at adapting soybean culture and plant breeding were fundamental for the expansion of culture in Brazil. The discovery of the long-juvenile gene and the E-series genes related to the flowering and maturation time allowed for the expansion of the culture, which was initially better adapted in the state of Rio Grande do Sul to regions of low latitudes, creating new boundaries agricultural activities. Until now, ten genes from the E series, E1 to E10, the Dt1 gene and the J gene that conditions the long juvenile period were described in the literature, but it still unknown how these genes influence the relative maturity group character of (RMG). For soybean and for other crops, breeding does not only occur for a single character, since the breeder works simultaneously with several characters and the genetic gain must be distributed among them. In view of the above, the objectives of the present work were to make the genetic study of the number of genes that are involved in the RMG character, to discover which gene action controls the character and to select the best progenies with the use of selection indexes. For the genetic study two biparental crosses were made between commercial soybean cultivars, for each crossing the F1 and F2 generations were obtained. The parents and their respective generations were sown to the field for RMG phenotyping. For the RMG character inheritance study, was used the joint scale test methodology by means of weighted least squares. This methodology allows the detection of less effect genes or modifiers the characteristic in case, being possible the estimation of environmental effect. A hundred twenty-nine F3 progenies derived from the crosses of commercial varieties were sown and six agronomic traits were evaluated: height of first pod insertion (HPI), plant height at maturity (PHM), number of the days for maturity (NDM), lodging (LD), agronomic value (AV) and grain yield (GY). For the two populations studied, there was no significant effect of dominance acting on RMG character expression. In the first population it was observed that two genes act in an additive way in the expression of the trait and the estimated mean contribution of each allele was 0.11. In the second population it was observed that a gene acts in an additive way in the expression of the character being the estimated contribution of each allele in -0.515. The progeny effect was significant for the 5% probability F test only for PHM and NDM. The effect of progenies was significant for the F test at 5% probability only for PHM and NDM. In relation to the total genetic gains obtained with the indexes application were:16.19 % for the sum of ranking, 28.68 % for index based on desired gains and 20.58 % for the index based on distance genotype ideotype. Between selected progenies highlight 16, 46, 81 and 87 because they present more suitable agromorphological traits for the region of study.
The researches aimed at adapting soybean culture and plant breeding were fundamental for the expansion of culture in Brazil. The discovery of the long-juvenile gene and the E-series genes related to the flowering and maturation time allowed for the expansion of the culture, which was initially better adapted in the state of Rio Grande do Sul to regions of low latitudes, creating new boundaries agricultural activities. Until now, ten genes from the E series, E1 to E10, the Dt1 gene and the J gene that conditions the long juvenile period were described in the literature, but it still unknown how these genes influence the relative maturity group character of (RMG). For soybean and for other crops, breeding does not only occur for a single character, since the breeder works simultaneously with several characters and the genetic gain must be distributed among them. In view of the above, the objectives of the present work were to make the genetic study of the number of genes that are involved in the RMG character, to discover which gene action controls the character and to select the best progenies with the use of selection indexes. For the genetic study two biparental crosses were made between commercial soybean cultivars, for each crossing the F1 and F2 generations were obtained. The parents and their respective generations were sown to the field for RMG phenotyping. For the RMG character inheritance study, was used the joint scale test methodology by means of weighted least squares. This methodology allows the detection of less effect genes or modifiers the characteristic in case, being possible the estimation of environmental effect. A hundred twenty-nine F3 progenies derived from the crosses of commercial varieties were sown and six agronomic traits were evaluated: height of first pod insertion (HPI), plant height at maturity (PHM), number of the days for maturity (NDM), lodging (LD), agronomic value (AV) and grain yield (GY). For the two populations studied, there was no significant effect of dominance acting on RMG character expression. In the first population it was observed that two genes act in an additive way in the expression of the trait and the estimated mean contribution of each allele was 0.11. In the second population it was observed that a gene acts in an additive way in the expression of the character being the estimated contribution of each allele in -0.515. The progeny effect was significant for the 5% probability F test only for PHM and NDM. The effect of progenies was significant for the F test at 5% probability only for PHM and NDM. In relation to the total genetic gains obtained with the indexes application were:16.19 % for the sum of ranking, 28.68 % for index based on desired gains and 20.58 % for the index based on distance genotype ideotype. Between selected progenies highlight 16, 46, 81 and 87 because they present more suitable agromorphological traits for the region of study.
Descrição
Palavras-chave
Ciclo de maturação, Glycine max, Índice de seleção, Melhoramento Genético, Mulamba e Mock, Período juvenil longo