In Vitro Amphidiploid Induction of A Distant Hybrid Populus Simonii × P. Euphratica Cv. ‘Xiaohuyang-2’ and its Effect on Plant Morphology and Anatomy

In plants, highly gametic sterility of distant hybrids usually restricts their utilization in breeding programs. Amphidiploid induction produced by somatic chromosome doubling of distant hybrids can effectively restore their gametic fertility. In this study, nodal-segment and leaf explants of a distant hybrid Populus simonii × P. euphratica cv. ‘Xiaohuyang-2’ were used to induce chromosome doubling with colchicine in vitro. Although chromosome doubling of the nodal-segment explants only produced mixoploids, the treatments of leaf explants on adventitious bud regeneration medium successfully produced 4 amphidiploids, which might be attributed to the direct organogenesis of the adventitious buds on the leaf explants. The highest amphidiploid induction frequency was 16.7%. Both the explant survival rate and polyploidization frequency were significantly affected by colchicine concentration and exposure time. The amphidiploid plants were significantly differed from the diploid and mixoploid plants on morphological and anatomical characteristics. They had larger, thicker, and greener leaves than the diploids and mixoploids. The changes of stomatal features also accompanied with increase of ploidy level. The induced amphidiploid plants of the distant hybrid ‘Xiaohuyang-2’ are expected to play important roles in breeding programs of Populus in future, which can be used as a bridge parent with ability of unreduced gamete formation to cross with fast-growth germplasms to produce triploids pyramiding desirable traits of fast growth, easy cutting propagation, and salt and drought tolerances.

Comparative Transcriptome Analysis between a Novel Allohexaploid Cotton Progeny CMS Line LD6A and Its Maintainer Line LD6B

Cytoplasmic male sterility (CMS) is an important agronomic feature and provides an effective tool for heterosis utilization of crops. This study reports the comparative transcriptomic sketches between a novel allohexaploid cotton progeny CMS line LD6A and its maintainer line LD6B using de novo transcriptome sequencing technology at the pollen abortion stage. A total of 128,901 Unigenes were identified, in which 2007 were upregulated and 11,864 were downregulated. The significantly differentially expressed genes (DEGs) in LD6A show a distant and diverse genetic nature due to their distant hybrid hexaploidy progeny. Further analysis revealed that most of the DEGs participated in the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, histone acetyltransferase activity, sepal development, stigma development, cotyledon development and microsporogenesis. A highly differentially expressed toxic protein, Abrin, was identified in the CMS line LD6A, which can catalyze the inactivation of ribosomes and consequently lead to cell death through the mitochondrial pathway in human cells. Twelve DEGs were selected randomly to validate transcriptome data using quantitative reverse-transcribed PCR (qRT-PCR). This study will contribute to new ideas and foundations related to the molecular mechanism of CMS and the innovation of cotton germplasm resources.