DataSheet_4_Striking variation in chromosome structure within Musa acuminata subspecies, diploid cultivars, and F1 diploid hybrids.pdf

The majority of cultivated bananas originated from inter- and intra(sub)specific crosses between two wild diploid species, Musa acuminata and Musa balbisiana. Hybridization and polyploidization events during the evolution of bananas led to the formation of clonally propagated cultivars characterized by a high level of genome heterozygosity and reduced fertility. The combination of low fertility in edible clones and differences in the chromosome structure among M. acuminata subspecies greatly hampers the breeding of improved banana cultivars. Using comparative oligo-painting, we investigated large chromosomal rearrangements in a set of wild M. acuminata subspecies and cultivars that originated from natural and human-made crosses. Additionally, we analyzed the chromosome structure of F1 progeny that resulted from crosses between Mchare bananas and the wild M. acuminata ‘Calcutta 4’ genotype. Analysis of chromosome structure within M. acuminata revealed the presence of a large number of chromosomal rearrangements showing a correlation with banana speciation. Chromosome painting of F1 hybrids was complemented by Illumina resequencing to identify the contribution of parental subgenomes to the diploid hybrid clones. The balanced presence of both parental genomes was revealed in all F1 hybrids, with the exception of one clone, which contained only Mchare-specific SNPs and thus most probably originated from an unreduced diploid gamete of Mchare.

绝大多数栽培香蕉均起源于两个野生二倍体物种——小果野芭蕉（Musa acuminata）与野蕉（Musa balbisiana）的种间及种内（亚种间）杂交。香蕉演化过程中的杂交与多倍化事件，催生了以基因组杂合度高、育性降低为特征的无性繁殖栽培品种。可食用无性系育性低下，加之小果野芭蕉亚种间染色体结构存在差异，这两大因素极大阻碍了优良香蕉栽培品种的选育工作。本研究采用比较寡核苷酸染色体涂染（comparative oligo-painting）技术，对一系列野生小果野芭蕉亚种，以及源自自然杂交与人工杂交的栽培品种中的大型染色体重排现象进行了分析。此外，本研究还对姆查雷香蕉（Mchare bananas）与野生小果野芭蕉‘Calcutta 4’基因型杂交获得的F1后代的染色体结构展开了分析。对小果野芭蕉内部染色体结构的分析显示，存在大量染色体重排现象，且这类重排与香蕉物种形成过程存在显著相关性。本研究通过Illumina重测序对F1杂种的染色体涂染分析进行补充，以明确亲本亚基因组对二倍体杂交无性系的基因组贡献。所有F1杂种均呈现双亲基因组均衡共存的特征，仅一个无性系例外：该无性系仅携带姆查雷香蕉特异性单核苷酸多态性（SNPs），因此极有可能源自姆查雷香蕉产生的未减数二倍体配子。