Estudo genético de populações de soja com fonte de resistência à Heterodera glycines (raça 3) oriundas de topocruzamentos tipo alimento x tipo grão
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Data
2016-01-29
Autores
Teixeira, Lilian Cristina Andrade de Araújo
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Universidade Estadual Paulista (Unesp)
Resumo
A soja [Glycine max (L.) Merrill] é uma leguminosa de ciclo anual que apresenta distintas finalidades, dentre elas, uma crescente vertente relaciona-se ao uso na alimentação humana. Há demanda de cultivares de soja com esta destinação com resistência a patógenos e pragas. Em especial destaca-se o nematoide de cisto da soja (Heterodera glycines) que causa expressiva perda na produtividade. Em virtude do exposto, utilizando topocruzamentos de soja tipo alimento x tipo grão, o objetivo do presente trabalho é: a. Determinar a herança da cor do tegumento, da cor do hilo e da expressão do caráter derramamento de hilo em populações F2:3; b. Determinação do estudo da herança da resistência ao nematoide de cisto da soja (NCS), bem como estimativa do número e modo de ação dos genes envolvidos a fim de contribuir no delineamento de cruzamentos, que envolvem os genitores em estudo, com maior possibilidade de acumular genes que conferem resistência à raça 3 do NCS e; c. Verificar com uma abordagem quantitativa, a adequação das populações a um modelo aditivo-dominante, assim como estimar parâmetros genéticos nos cruzamentos gerados. Utilizaram-se genitores contrastantes, um resistente ao NCS raça 3 (‘BRSMG 810C’) e dois suscetíveis, porém aptos para utilização na alimentação humana (‘BRSMG 790A’ e ‘BRSMG 800A’). Obtiveram-se as gerações F1, RCr, RCs e F2 que foram utilizadas para o estudo da herança da resistência, por meio da segregação do caráter. As avaliações de nematoide foram realizadas utilizando-se como estimador o Índice de Fêmeas (IF) e analisadas pelo teste de Qui-Quadrado (χ2) para testar o ajuste ao modelo proposto para a herança. As sementes F3 provenientes de plantas F2 foram caracterizadas para elucidar a herança para caracteres morfológicos de interesse (cor de tegumento, cor e aspecto de hilo). Para os caracteres morfológicos dos grãos avaliados, os resultados observados se ajustam à proporção esperada considerando a existência de quatro genes (R/I/W/T) controlando a expressão da cor do tegumento e cor do hilo para ambos os cruzamentos. Para o cruzamento ‘BRSMG 810C’ x ‘BRSMG 800A’ genótipos ii impediram a expressão dos genes W e T na pigmentação da semente. Ocorreu variação na expressividade do caráter hilo derramado, com herança monogênica e dominância completa para o fenótipo ausência de derramamento de hilo. Há ligação do locus que confere derramamento do hilo com o genótipo T_ (pubescência marrom). O processo de hibridação foi eficiente na geração de variabilidade. Quanto à avaliação nematológica, as plantas F2 apresentaram dois padrões de segregação aceitos (resistente: suscetível): 1:15 (dois genes recessivos complementares) e 3:61 (um gene dominante e dois recessivos complementares). A herança foi confirmada utilizando-se as plantas do RCr, que segregaram na proporção de 1:7, padrão esperado para herança condicionada por três genes. A hipótese de segregação 1:3 (dois genes) foi rejeitada em RCr. A falta de um dos genes recessivos proporcionou resistência moderada ao NCS raça 3 aceitando-se a hipótese de moderadamente resistente: suscetível na proporção de 3:13 (um gene dominante e um gene recessivo). Assim, nestes cruzamentos, a resistência moderada ao NCS raça 3 é condicionada por dois genes epistáticos (um dominante e um recessivo) e o acúmulo de um terceiro gene recessivo confere resistência completa em relação ao fitonematoide em estudo. Os resultados evidenciam que ambos os cruzamentos apresentam acentuada variabilidade genética em F2. O modelo aditivo-dominante foi suficiente para explicar o caráter, sendo o efeito genético aditivo o mais importante. A resistência ao NCS raça 3 teve grande influência ambiental. De acordo com os resultados obtidos, existe evidência de ganho com seleção em processo seletivo. A herdabilidade no sentido restrito de baixa magnitude indica provável ponderação na pressão de seleção, fato que prioriza a realização de seleção em fase avançada dos programas de melhoramento, como no teste de progênies, para a obtenção de cultivares especiais para a alimentação humana e homozigota para resistência a este fitonematoide.
Soybean [Glycine max (L.) Merrill] is an annual leguminous that has distinct purposes, among them, a growing amount is related to the human feed. There is a demand of cultivars aiming this destination, which are resistant to pathogens and plagues. A special plague is highlighted, the soybean nematode of cyst (Heterodera glycines) (NCS). It causes expressive loss of productivity. Facing this, using soybean topcrosses feed-like x grain-like this work aims: a. determine the tegument color, hilum color, and hilum spread character heritance in F2 populations; b. determine the NCS resistance heritage, as well the involved genes number and action mode estimative in order to contribute in the crosses design, which involve the parents studied, with a higher possibility of accumulation of genes which provide resistance to the NCS race 3; and c. Verify in a quantitative approach the adequacy population in an additive-dominant model, as well estimate the genetic parameter into the crossings. We used contrasting parents, being resistant to the race 3 (‘BRSMG 810C’) and two susceptible, however suitable to the human feed (‘BRSMG 790A’ and ‘BRSMG 800A’). Thus, the generations F1, RCr, RCs, and F2 were created. They were used to study heritage resistance through the character segregation. The nematode evaluations were done using as estimator the Female Index (IF) and they were analyzed by the chi-square test (χ2) to test the adjustment to the suggested model to the heritage. The F3 seeds from the F2 plants were characterized to elucidate the heritage to interest morphologic traits (seed coat color, hilum color and hilum aspect). For the morphological character of grain, the results observed of descendent were adjusted to the expected proportion, considering that there were four genes (R/I/W/T) controlling the expression coat and hilum color to both crossings. At crossing ‘BRSMG 810C’ x ‘BRSMG 800A’, the allele ii genetic owners hindered the expression of genes W and T at seed pigmentation. There was variation in the expression of spread hilum character, presenting monogenic heritance and full dominance to the characteristic. There are locus binding that gives outpouring of spread hilum with T_ locus (brown pubescence). The hybridization process was efficient to obtain genetic variability. Regarding to the nematologic evaluation, F2 plants presented two segregation patterns accepted: (resistant:susceptible) 1:15 (two complementary recessive genes) and 3:61 (one dominant gene and two complementary recessive genes). The heritability was confirmed using the BCr plants, which segregated at 1:7 proportion. Such proportion is expected in heritance conditioned to three genes. The 1:3 segregation hypothesis (two genes) was rejected in BCr. The lack of one of recessive gene provided moderate resistance to NCS race 3, accepting the hypothesis of moderately resistant: susceptible at 3:13 proportion (one dominant and one recessive). Thus, in these crossings, the moderate resistance to NCS race 3 is conditioned by two epistatic genes (one dominant and one recessive) and the accumulation of a third recessive gene provides full resistance to the phytonematodes evaluated in this article. The results highlight that both crossings have high genetic variability in the F2. The additive-dominant model was enough to explain the character, where the most important genetic effect was the additive. The NCS race 3 resistance had a great environmental influence. According to the obtained results, there is an evidence of gain with selection in the selective process. The heritability in the narrow sense of low magnitude indicates a probable weighting in the selection pressure. This fact prioritizes the selection conduction in a more advanced phase of breeding program, like in the progenies test, to obtain special cultivars to feed humans, and in the homozygote to resist to this phytonematode.
Soybean [Glycine max (L.) Merrill] is an annual leguminous that has distinct purposes, among them, a growing amount is related to the human feed. There is a demand of cultivars aiming this destination, which are resistant to pathogens and plagues. A special plague is highlighted, the soybean nematode of cyst (Heterodera glycines) (NCS). It causes expressive loss of productivity. Facing this, using soybean topcrosses feed-like x grain-like this work aims: a. determine the tegument color, hilum color, and hilum spread character heritance in F2 populations; b. determine the NCS resistance heritage, as well the involved genes number and action mode estimative in order to contribute in the crosses design, which involve the parents studied, with a higher possibility of accumulation of genes which provide resistance to the NCS race 3; and c. Verify in a quantitative approach the adequacy population in an additive-dominant model, as well estimate the genetic parameter into the crossings. We used contrasting parents, being resistant to the race 3 (‘BRSMG 810C’) and two susceptible, however suitable to the human feed (‘BRSMG 790A’ and ‘BRSMG 800A’). Thus, the generations F1, RCr, RCs, and F2 were created. They were used to study heritage resistance through the character segregation. The nematode evaluations were done using as estimator the Female Index (IF) and they were analyzed by the chi-square test (χ2) to test the adjustment to the suggested model to the heritage. The F3 seeds from the F2 plants were characterized to elucidate the heritage to interest morphologic traits (seed coat color, hilum color and hilum aspect). For the morphological character of grain, the results observed of descendent were adjusted to the expected proportion, considering that there were four genes (R/I/W/T) controlling the expression coat and hilum color to both crossings. At crossing ‘BRSMG 810C’ x ‘BRSMG 800A’, the allele ii genetic owners hindered the expression of genes W and T at seed pigmentation. There was variation in the expression of spread hilum character, presenting monogenic heritance and full dominance to the characteristic. There are locus binding that gives outpouring of spread hilum with T_ locus (brown pubescence). The hybridization process was efficient to obtain genetic variability. Regarding to the nematologic evaluation, F2 plants presented two segregation patterns accepted: (resistant:susceptible) 1:15 (two complementary recessive genes) and 3:61 (one dominant gene and two complementary recessive genes). The heritability was confirmed using the BCr plants, which segregated at 1:7 proportion. Such proportion is expected in heritance conditioned to three genes. The 1:3 segregation hypothesis (two genes) was rejected in BCr. The lack of one of recessive gene provided moderate resistance to NCS race 3, accepting the hypothesis of moderately resistant: susceptible at 3:13 proportion (one dominant and one recessive). Thus, in these crossings, the moderate resistance to NCS race 3 is conditioned by two epistatic genes (one dominant and one recessive) and the accumulation of a third recessive gene provides full resistance to the phytonematodes evaluated in this article. The results highlight that both crossings have high genetic variability in the F2. The additive-dominant model was enough to explain the character, where the most important genetic effect was the additive. The NCS race 3 resistance had a great environmental influence. According to the obtained results, there is an evidence of gain with selection in the selective process. The heritability in the narrow sense of low magnitude indicates a probable weighting in the selection pressure. This fact prioritizes the selection conduction in a more advanced phase of breeding program, like in the progenies test, to obtain special cultivars to feed humans, and in the homozygote to resist to this phytonematode.
Descrição
Palavras-chave
Estudo da herança, Nematoide de cisto da soja, Parâmetros genéticos, Pigmentação, Soja alimento, Heritance study, Soybean cyst nematode, Genetic parameters, Pigmentation, Soybean human consumption