Intergeneric chromosome-specific painting reveals differential chromosomal transmission from Tripidium arundinaceum in sugarcane progeny

Sugarcane has recently attracted increasing attention for its potential as a source of sugar and bioethanol,so increasing its yield is essential to ensure the sugar security and bioenergy production.Intergeneric hybridization is a highly efficient method to produce new genetic variants of crop plants,particularly those species with high ploidy such as sugarcane(Saccharum spp.).Tripidium arundinaceum exhibits many desirable agronomic traits,and has been widely studied to produce hybrids with improved stress tolerance and other characteristics in sugarcane breeding.However,the genetic relationship between T.arundinaceum and Saccharum species,and the individual T.arundinaceum chromosomal compositions in sugarcane hybrids are still elusive.Here we used whole-genome single-nucleotide polymorphisms(SNPs)to ascertain the phylogenetic relationships between these species and found that T.arundinaceum is more closely related to Saccharum than Sorghum,in contrast to the previous narrow genetic analyses using chloroplast DNA.Additionally,oligonucleotide(oligo)-based chromosome-specific painting derived from Saccharum officinarum was able to distinctly identify the chromosomes of T.arundinaceum.We developed the oligo-genomic in situ hybridization(GISH)system for the first time,to unveil the novel chromosome translocations and the transmission of individual T.arundinaceum chromosomes in sugarcane progeny.Notably,we discovered that the chromosomal transmission of T.arundinaceum exhibited several different inheritance modes,including n,2n,and over 2n in the BC1 progenies.Such inheritance patterns may have resulted from first division restitution(FDR)or FDR+nondisjunction of a chromosome with the sister chromatids in the second meiosis division/second division restitution(FDR+NSC/SDR)model during meiosis.These results will be of substantial benefit for the further selection of T.arundinaceum chromosomes for sugarcane genetic improvement.

甘蔗与斑茅杂交染色体组构成特征研究

斑茅是甘蔗重要的野生种质资源,渗入斑茅血缘来提高甘蔗抗性是目前甘蔗育种的重要途径之一。对甘蔗与斑茅杂交后代进行染色体分型有利于高效利用斑茅的各种优异性状。本研究利用斑茅特异引物鉴定斑茅与甘蔗杂交高世代材料的真实性,通过荧光原位杂交对甘蔗与斑茅染色体进行分型,以探究斑茅和甘蔗染色体在子代中的遗传与分离,并分析其染色体组结构特征。结果表明,杂交群体中有30份为斑茅的真实后代,包含斑茅染色体从1~10条不等,说明其后代群体基本服从n+n的遗传方式,占整个真实后代群体的60%。斑茅与甘蔗发生染色体水平的重组约16.67%,并且斑茅与不同血缘甘蔗重组的概率趋近一致。割手密种特异探针共定位结果表明,斑茅血缘的渗入降低了近现代栽培甘蔗种中热带种血缘与重组血缘的占比,并同时提高了割手密血缘的比例。本研究分析的甘蔗与斑茅杂交后代中不同血缘染色体组的遗传及结构特点,为提高斑茅种质资源在甘蔗育种中的开发利用提供了细胞遗传学基础。

甘蔗属及其近缘属代表性种质的转录组比较分析

甘蔗近缘种斑茅(Tripidium arundinaceum)、甘蔗属内野生种割手密(Saccharum spontaneum)和大茎野生种(Saccharum robustum)具有茎部强壮、耐旱、耐涝、耐霜和抗病性等对现代甘蔗品种改良具有重要价值的性状。本研究通过比较甘蔗属及其近缘属四个代表性种质,包括一个甘蔗属近缘种质(斑茅)、两个甘蔗属野生种(割手密、大茎野生种)和一个甘蔗属驯化种(热带种)的转录组,以探讨它们在转录层面的差异。研究发现,甘蔗近缘种斑茅与甘蔗属野生种割手密(BM vs Y83)、甘蔗属内的两个野生种割手密与大茎野生种(Y83 vs N57)以及甘蔗属内的野生种割手密和驯化种热带种(N57 vs NJ)之间的差异表达基因主要涉及光合作用、次级代谢和信号转导等,这可能导致甘蔗属及其近缘属物种间在光合能力、抗生物和非生物胁迫能力以及营养利用方面存在差异。割手密在氮代谢表现出较斑茅和大茎野生种更强的潜力,表明其在氮素利用上可能更具优势。此外,割手密的特异表达基因涉及光感受器、昼夜节律时钟和开花途径,这可能与其开花特性相关。本研究还鉴定了甘蔗属及其近缘属、甘蔗属内野生种和驯化种之间的4325个直系同源基因,这些基因的正选择分析结果表明割手密可能在自然选择下逐渐改变基因表达模式以适应环境,而热带种从大茎野生种驯化后的分化和适应可能与植物激素信号转导的改变相关。