Avaliação de indutores de haploidia e identificação de linhagens duplo-haploides em milho
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Data
2018-06-29
Autores
Revolti, Lucas Tadeu Mazza [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Programas de genética e melhoramento de milho possuem o foco de lançar híbridos com alta produtividade, sendo uma das principais dificuldades a obtenção de linhagens. Melhoristas de milho buscam novas alternativas para tornar esse processo mais rápido e com menor custo, sendo a tecnologia do duplo-haploide viável para esta finalidade. A pesquisa teve como objetivo avaliar a eficiência de indução de indutores de haploidia e a identificação de linhagens duplo-haploides em milho. Utilizou-se cinco híbridos simples de milho e três grupos de indutores de haploidia, os quais foram semeados e cruzados nas safras 2013/2014, 2014/2015 e 2015/2016. Das sementes provenientes dos cruzamentos selecionou-se os possíveis haploides pelo marcador morfológico visual R-navajo, pela avaliação de comprimento de raiz, vigor e coloração de plântulas. Realizou-se a duplicação cromossômica dos possíveis haploides e após a aclimatação em casa de vegetação, as plantas sobreviventes foram transplantadas para campo. As análises de citometria de fluxo foram realizadas com os genótipos sobreviventes em campo para confirmação das ploidias e descarte dos falsos haploides. Como resultados, há diferenças entre os três grupos de indutores de haplodia. Na safra 2015/2016 a taxa de indução de possíveis haploides foi de 1 a 20%, 1 a 35% e 1 a 42% para os grupos 1, 2 e 3, respectivamente. Houve diminuição do número de plantas no decorrer das avaliações, sendo que, do total de 332 plantas transplantadas em campo, foi possível realizar a análise de citometria de fluxo em 228 plantas. Constatou-se plantas diploides e diploides/tetraploides pela realização da citometria de fluxo. Os indutores do grupo 3 apresentaram maiores taxas de indução de haploides putativos sendo mais promissores para a adoção em programas de melhoramento de milho visando obter linhagens duplo-haploides. A técnica de citometria de fluxo permitiu o descarte de falsos haploides e é uma técnica de fácil execução e rapidez.
Maize breeding programs are focused on releasing novel high productive hybrids and one of the main difficulties in maize breeding programs is obtaining inbred lines. Plant breeders have been looking for new alternatives to make this process faster and with a lower cost and doubled-haploid technology is an alternative. The objective of the research was to evaluate the efficiency of induction of tropical haploid inducers and the identification of doubled-haploid inbred lines in maize. Five maize hybrids and three haploid inducing groups were used, which were sown and crossed in the 2013/2014, 2014/2015 and 2015/2016 seasons. Possible haploids seeds were selected by the visual morphological marker R-Navajo, by the evaluation of root length, vigor and seedling staining. Chromosome doubling of the possible haploids was performed and after acclimatization in the greenhouse, the surviving plants were transplanted to the field. The flow cytometric analyzes were performed with the surviving genotypes in the field to confirm the ploidy and discard the false-haploids. As results, there are differences between the induction rates of the three haploid inducers groups. In the 2015/2016 crop season the induction rate was 1 to 20%, 1 to 35% and 1 to 42% for groups 1, 2, and 3, respectively. The number of plants decreased during the evaluations, and of the total of 332 plants transplanted in the field it was possible to perform flow cytometric analysis in 228 plants. Diploid and diploid/tetraploid plants were observed by flow cytometry. The inducers from group 3 present higher rates of putative haploid induction, being more promising for its adoption in breeding programs to obtain doubled haploid inbred lines. The technique of flow cytometry allowed the discarding of false-haploids and it is a technique of easy and fast execution.
Maize breeding programs are focused on releasing novel high productive hybrids and one of the main difficulties in maize breeding programs is obtaining inbred lines. Plant breeders have been looking for new alternatives to make this process faster and with a lower cost and doubled-haploid technology is an alternative. The objective of the research was to evaluate the efficiency of induction of tropical haploid inducers and the identification of doubled-haploid inbred lines in maize. Five maize hybrids and three haploid inducing groups were used, which were sown and crossed in the 2013/2014, 2014/2015 and 2015/2016 seasons. Possible haploids seeds were selected by the visual morphological marker R-Navajo, by the evaluation of root length, vigor and seedling staining. Chromosome doubling of the possible haploids was performed and after acclimatization in the greenhouse, the surviving plants were transplanted to the field. The flow cytometric analyzes were performed with the surviving genotypes in the field to confirm the ploidy and discard the false-haploids. As results, there are differences between the induction rates of the three haploid inducers groups. In the 2015/2016 crop season the induction rate was 1 to 20%, 1 to 35% and 1 to 42% for groups 1, 2, and 3, respectively. The number of plants decreased during the evaluations, and of the total of 332 plants transplanted in the field it was possible to perform flow cytometric analysis in 228 plants. Diploid and diploid/tetraploid plants were observed by flow cytometry. The inducers from group 3 present higher rates of putative haploid induction, being more promising for its adoption in breeding programs to obtain doubled haploid inbred lines. The technique of flow cytometry allowed the discarding of false-haploids and it is a technique of easy and fast execution.
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Palavras-chave
Citometria de fluxo, Genética, Genótipos endogâmicos, Melhoramento de plantas, R-navajo, Zea mays, Flow cytometry, Endogamic genotypes