In vivo HAPLOID INDUCTION AND EFFICIENCY OF TWO CHROMOSOME DUPLICATION PROTOCOLS IN TROPICAL MAIZE

Abstract

Artificial chromosome duplication is one of the most important process in the attainment of doubled haploids in maize. This study aimed to evaluate the induction ability of the inducer line KEMS in a tropical climate and test the efficiency of the R1-Navajo marker by flow cytometry to evaluate two chromosome duplication protocols and analyze the development of the doubled haploids in the field. To accomplish this goal, four genotypes (F1 and F2 generations) were crossed with the haploid inducer line KEMS. The seeds obtained were selected using the R1-Navajo marker and subject to two chromosome duplication protocols. Duplication was confirmed using flow cytometry. The percentages of self-fertilized plants after duplication as well as the quantities of doubled haploid seeds obtained after the self-fertilization processes were analyzed. It was observed that the germplasm influences haploid induction but not the duplication rates of the tested protocols. Protocol 2 was more efficient for the duplication of haploids, in the percentage of self-fertilized plants after duplication, and in the attainment of doubled haploid lines. Moreover, the haploid inducer line KEMS can produce haploids in a tropical climate. Other markers, in addition to the R1-Navajo system, should be used in the selection of haploid seeds.Index terms: R-Navajo; colchicine; induction of maternal haploids; Zea mays. RESUMOA duplicação cromossômica artificial está dentre as etapas mais importantes na obtenção de duplo-haploides em milho. Este estudo objetivou avaliar a capacidade de indução da linhagem indutora KEMS em clima tropical e testar a eficiência do marcador R1-navajo por meio de citometria de fluxo; avaliar dois protocolos de duplicação cromossômica e, analisar o desenvolvimento dos haploides duplicados no campo. Para isso, quatro genótipos (gerações F1 e F2) foram cruzados com a linhagem KEMS. As sementes obtidas foram selecionadas pelo marcador R1-navajo e submetidas a dois protocolos de duplicação cromossômica. A duplicação foi confirmada por meio de citometria de fluxo. As porcentagens de plantas autofecundadas após duplicação foram analisadas, bem como as quantidades de sementes duplo-haploides obtidas após as autofecundações. Foi observado que o germoplasma influencia a indução de haploides, mas não na taxa de duplicação dos protocolos testados. O protocolo 2 foi mais eficiente na duplicação de haploides, na porcentagem de plantas autofecundadas após duplicação, e na obtenção de linhagens duplo-haploides. Além disso, a linhagem indutora KEMS pode induzir haploides em clima tropical. Outros marcadores além do sistema do R1-navajo devem ser utilizados na seleção de sementes haploides.Termos para indexação: R-navajo; colchicina; indução de haploides maternos; Zea mays.

Corn genotypes and crop seasons on the rate of putative haploids with the expression of gene R1-navajo

“…Several authors have highlighted differences in the behavior of inducers due to varying environments (locations or crop seasons), the interaction between source genotypes and inducers for the haploid induction rate, and putative haploids (Röber et al, 2005;Prigge et al, 2012b;Battistelli et al, 2013;Couto et al, 2015;Ishii et al, 2016). The effects of the environment and of putative haploids on induction rates is almost a consensus among the works on doubled haploids (Prigge et al, 2012b).…”

“…The selection of haploids for chromosome duplication is an essential stage for the production of doubled haploid lines in corn (Zea mays L.) (Couto et al, 2015;Ribeiro et al, 2018). According to the potential of the inducer, the rate of true haploids produced by the source genotype, also known as the haploid induction rate (Battistelli et al, 2013), can range from 2 to 15% in relation to the total of seeds (Chaikam et al, 2019).…”

“…Putative haploids sorted via R1-nj are related to the true induction rate, synonymous with the haploid induction rate (Prigge et al, 2012b;Battistelli et al, 2013;Couto et al, 2015). The production rate of true or putative haploids depends not only on the effects of the inducer, source genotype, and crops, but also on the effects of factors linked to the environment of the induction site, endosperm texture, inbreeding generation, and genetic basis of the source material (Aman & Sarkar, 1978;Röber et al, 2005;Kebede et al, 2011;Prigge et al, 2012b;Battistelli et al, 2013;Couto et al, 2015). However, these factors are usually evaluated in isolation or only combined in two or three ways, and, many times, the interaction between them cannot be assessed.…”

Anatomical tool in the identification of ploids in maize seedlings and potential use in initial stage of double haploides obtainment process

“…The seeds used in this work were obtained from an experiment previously developed by [23] through the cross between four simple hybrids (DKB393, GNS 3225, GNS 3264, GNS 3032) with the haploid inducer KEMS, used as male parental. Seeds from these crosses were separated by staining of the embryo and endosperm and selected as possible haploids according with the marker R-navajo [24].…”

Breeding strategies for tropical maize targeting in vivo haploid inducers

“…This trait is related to an adequate fertilization management and various other environmental factors. Moreover, specifically the use of binomial models has been intensified in other related studies (Wegenast et al 2010, Batistelli et al 2013, Couto et al 2015. Couto et al (2020) used the multinomial model to evaluate haploid induction rate, diploid seed rate and inhibition seed rate.…”