ABSTRACT Elephant grass is an allogamous perennial forage crop with asexual propagation, allowing plant breeders to explore heterosis and develop hybrids. However, selecting parents for diallel crossing schemes is a major hurdle in the development of hybrids. In addition, this perennial crop has several harvests, which increases the dataset size and the complexity of the statistical analyses. Here, we propose a diallel analysis based on linear mixed models with repeatability information to identify parents and hybrids, and the optimum number of harvests. We performed a complete diallel crossing of 11 parents with data from five harvests for morphological traits and two harvests for nutritive value traits. The diallel model with repeatability information aids in the estimation of the genetic effect of diallel analysis to infer the ideal number of harvests and genotype × harvest interaction. We observed that the specific combining ability (SCA) is more critical for morphoagronomic traits, while the general combining ability (GCA) has greater importance for traits related to nutritive value. Furthermore, we detected that five harvests were sufficient for the morphoagronomic traits with a coefficient of determination (R2) of 0.8; however, ten harvests were required for an R2 of 0.9. The model is a promising single-analysis alternative for plant breeders to analyze a diallel with repeated measures and to estimate important parameters without incurring in additional financial costs. propagation hybrids However addition analyses Here 1 interaction SCA (SCA GCA (GCA Furthermore R (R2 0.8 08 0 8 however 09 9 0.9 singleanalysis single costs (R 0.

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.

ABSTRACTArtificial 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.