Honfi Ana I, Reutemann A Verena, Schneider Juan S, Escobar Lucas M, Martínez Eric J, Daviña Julio R
Programa de Estudios Florísticos y Genética Vegetal, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas, Químicas y Naturales, Universidad Nacional de Misiones (FCEQyN-UNaM), Misiones 3300, Argentina.
Laboratorio de Genética y Mejoramiento de Especies Forrajeras, Instituto de Botánica del Nordeste (CONICET-UNNE), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste (FCA-UNNE), Corrientes 3400, Argentina.
Genes (Basel). 2025 Feb 20;16(3):242. doi: 10.3390/genes16030242.
BACKGROUND/OBJECTIVES: is a key multipurpose species native to American grasslands. This study provides, for the first time, a detailed karyotype analysis of diploid (2 = 2 = 20) and tetraploid (2 = 4 = 40) accessions of , the most common cytotypes within the species.
The constitutive heterochromatin patterns revealed using CMA-DA-DAPI staining and genome size estimations are novel contributions to the understanding of the N genome in .
Chromosomes were small (1.1-2.3 µm), with the diploid karyotype comprising nine metacentric pairs (one bearing microsatellites on the short arms, pair 6) and one submetacentric pair. In tetraploids, the diploid karyotype was duplicated. Heterochromatin analysis revealed two CMA/DAPI bands located on the short arm and satellite of chromosome 6 in diploids, while tetraploids exhibited two to three CMA/DAPI and one to two CMA/DAPI bands. The proportion of GC-rich heterochromatin represented 2.8 and 3.47% of the total chromosome length in diploid and tetraploid cytotypes, respectively. Genome size analysis revealed a reduction in monoploid genome size in tetraploids (1Cx = 0.678 pg) compared to diploids (1Cx = 0.71 pg), consistent with the autopolyploid origin hypothesis.
These findings provide essential cytogenetic insights and suggest only minor structural changes in the N genome following polyploidization, which could guide future studies integrating genomic and cytogenetic maps of .
背景/目的：[物种名称]是原产于美洲草原的一种关键多用途物种。本研究首次对该物种内最常见的细胞型二倍体（2n = 2x = 20）和四倍体（2n = 4x = 40）材料进行了详细的核型分析。
使用CMA-DA-DAPI染色揭示的组成型异染色质模式和基因组大小估计，是对理解该物种N基因组的新贡献。
染色体较小（1.1 - 2.3微米），二倍体核型包括九对中着丝粒染色体（一对短臂上带有微卫星，第6对）和一对亚中着丝粒染色体。在四倍体中，二倍体核型加倍。异染色质分析显示，二倍体中位于第6号染色体短臂和随体上有两条CMA/DAPI带，而四倍体显示两到三条CMA/DAPI带和一到两条CMA/DAPI带。富含GC的异染色质比例在二倍体和四倍体细胞型中分别占总染色体长度的2.8%和3.47%。基因组大小分析显示，与二倍体（1Cx = 0.71 pg）相比，四倍体的单倍体基因组大小减小（1Cx = 0.678 pg），这与同源多倍体起源假说一致。
这些发现提供了重要的细胞遗传学见解，并表明多倍体化后N基因组仅发生了微小的结构变化，这可为未来整合该物种基因组和细胞遗传图谱的研究提供指导。
