Influência da distância genética entre genitores na recuperação do parental recorrente na conversão de linhagens de milho
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Data
2021-06-29
Autores
Souza, Elton Otacílio de
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Universidade Estadual Paulista (Unesp)
Resumo
As últimas duas décadas o uso de híbridos transgênicos agregou um valor considerável para o aumento da produção de milho. O método dos retrocruzamentos (RC) é o mais utilizado para a obtenção de linhagens e híbridos transgênicos em milho. Utilizando-se marcadores moleculares para seleção do genoma recorrente nas gerações de retrocruzamento é possível reduzir o tempo para a obtenção de linhagens convertidas. É possível que a utilização de parentais doadores mais similares aos parentais recorrentes possa reduzir ainda mais o tempo de conversão dessas linhagens. Este trabalho teve por objetivo avaliar a recuperação do genoma recorrente e a similaridade das plantas de RC com os parentais recorrentes em função da distância genética entre esses genitores em um programa de conversão de linhagens de milho. Foram avaliadas nove populações de retrocruzamento, com distâncias genéticas entre os parentais doadores e recorrentes variando de 0,238 a 0,499. As populações foram divididas em três grupos, um com distâncias genéticas de 0,238 a 0,286, outro de 0,307 a 0,335 e outro de 0,408 a 0,499. Nas gerações RC1, RC2 e RC3 foram usados marcadores moleculares para identificação das plantas com o maior percentual de recuperação do genoma recorrente e com maior similaridade com o parental recorrente. Na primeira geração de RC as diferenças na similaridade entre as plantas de RC e os parentais recorrentes foram proporcionais as distâncias genéticas iniciais, mas na terceira geração de RC todas as populações obtiveram plantas com similaridade de pelo menos 98% com os parentais recorrentes. Para as populações com menores distâncias genéticas entre os parentais, as linhagens elites já haviam sido recuperadas na segunda geração de RC. Quando o parâmetro usado foi recuperação do genoma recorrente, não foram observadas diferenças entre os grupos em RC3. Esse parâmetro não permitiria observar que nas populações cuja distância genética entre os parentais era menor as linhagens elites poderiam ser finalizadas na segunda geração de RC.
In the last two decades, the use of transgenic hybrids has added considerable value to the increase in maize production. The backcrossing method (BC) is the most used to obtain transgenic hybrid and inbred lines in maize. Using molecular markers for recurrent genome selection in backcross generations, it is possible to reduce the time to obtain converted inbred lines. It is possible that the use of donor parents more like those of parents may further reduce the conversion time of these inbred line. The objective of this work was to evaluate the recovery of the recurrent genome and the similarity of BC plants with recurrent parents as a function of the genetic distance between donors and recurrent parents in a maize inbred line conversion program. And compare the parameters of genetic similarity and recurrent genome recovery for decision management in BC programs assisted by molecular markers. Nine backcrossing populations were evaluated, with genetic distances between donors and recurrent parents ranging from 0.238 to 0.499. As the populations were divided into three groups, a genetic distance of 0.238 to 0.286, another from 0.307 to 0.335 and another from 0.408 to 0.499. In the BC1, BC2 and BC3 generations, molecular markers were used to identify the plants with the highest percentage of recurrent genome recovery and with greater similarity to the parental recurrent. In the first generation of BC as differences in similarity between BC plants and recurrent parent plants, the initial genetic distances were proportional, but in the third generation of BC all populations obtained plants with a similarity of 98% less with the recurrent of the parents. For populations with shorter genetic distances between parents, such as elite inbred line has already been recovered in the second generation of BC. When the parameter used was recurrent genome recovery, no differences were observed between the groups. This parameter does not allow us to observe that in populations whose genetic distances between parents were shorter, because elite lineages could be completed in the second generation of BC.
In the last two decades, the use of transgenic hybrids has added considerable value to the increase in maize production. The backcrossing method (BC) is the most used to obtain transgenic hybrid and inbred lines in maize. Using molecular markers for recurrent genome selection in backcross generations, it is possible to reduce the time to obtain converted inbred lines. It is possible that the use of donor parents more like those of parents may further reduce the conversion time of these inbred line. The objective of this work was to evaluate the recovery of the recurrent genome and the similarity of BC plants with recurrent parents as a function of the genetic distance between donors and recurrent parents in a maize inbred line conversion program. And compare the parameters of genetic similarity and recurrent genome recovery for decision management in BC programs assisted by molecular markers. Nine backcrossing populations were evaluated, with genetic distances between donors and recurrent parents ranging from 0.238 to 0.499. As the populations were divided into three groups, a genetic distance of 0.238 to 0.286, another from 0.307 to 0.335 and another from 0.408 to 0.499. In the BC1, BC2 and BC3 generations, molecular markers were used to identify the plants with the highest percentage of recurrent genome recovery and with greater similarity to the parental recurrent. In the first generation of BC as differences in similarity between BC plants and recurrent parent plants, the initial genetic distances were proportional, but in the third generation of BC all populations obtained plants with a similarity of 98% less with the recurrent of the parents. For populations with shorter genetic distances between parents, such as elite inbred line has already been recovered in the second generation of BC. When the parameter used was recurrent genome recovery, no differences were observed between the groups. This parameter does not allow us to observe that in populations whose genetic distances between parents were shorter, because elite lineages could be completed in the second generation of BC.
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Plantas Melhoramento genético, Diversidade genética, Marcadores genéticos