| Sugarcane is one of the important sugar crops and a leading energy crop worldwide. Genetic improvement and breeding for easily-defoliating sugarcane varieties are urgently needed to accelerate the process of mechanical harvesting, reduce the production cost and increase the amount of sugar in the case of increasing labor costs increased in China. In this research, eight major agronomic traits closely related to defoliation characteristic were investigated during mature early stage. Several models to predict defoliation characteristic measurements and identified several relevant agronomic traits that support systematic quantification of defoliation characteristic of sugarcane were executed. Illumina HiSeq2000 sequencer and bioinformatics tools were implemented to construct sugarcane sheath transcriptome and gene expression profiles. The main results were as follows:1、To evaluate the defoliation characters of sugarcane, eight agronomic traits associated with defoliation were measured, including the total internode number (TIN), self-defoliating number (SDN), self-defoliating rate (SDR), stalk diameter (SD), angle (ASR) and length (LSR) of sheath ruptured from stalk, the defoliation force (DF) and mean defoliation force (MDF). Principal component analysis with the variance maximum rotated component matrix was carried out to identify and evaluate the important appraisal indicators of defoliation traits that were rank transformed prior to analysis by IBM SPSS 22.0. The results revealed that the length and angle of the sheath ruptured from stalk, defoliation force and self-defoliation were the most contribution traits for quantitative assessment of sugarcane defoliation. To simplify the investigation of the defoliation traits, the differences of DF, LSR and ASR we compared from the top 6th leaf to the basal 16th leaf. The results shown that LSR, ASR or DF on each leaf from 10th to 13th could stand for the difference of sugarcane defoliation.2、Defoliation character of 38 sugarcane varieties from the National Regional Test Program for Sugarcane in China were evaluated on the basis of the above six screened defoliation traits (SDN, SDR, LSR, ASR, DF and MDF) and three screened defoliation traits from the leaf 10th leaf (SDR, ASR and DF). The results revealed that SDR, ASR and DF at the 10th leaf would be suitable and feasible to quantify for the sugarcane defoliation.3、By analyzing the transcriptome,95061 unigenes with average length of 740.08bp and 1301bp of N50 were obtained from two sugarcane lines that defoliation character was significantly different, but their parents were the same.43.36%(41221) of unigenes were annotated against NR database,22.5%(21390) of unigenes were annotated against Swissprot database,11.5%(10931) of unigenes were annotated against KEGG PATHWAY and 5.67%(5388) of unigenes were common annotated against NR, Swissprot, String, KEGG and Pfam. But 56.47%(53679) of unigenes were unknown function. The transcriptome database obtained in sugarcane sheath was the foundation of sugarcane genetic research, which will be beneficial to expression profiles studies and functional gene mining.4、Gene expression profiles of sugarcane sheath were obtained. A total of 7313 differentially expressed genes were found for D-1 and D-7,4125 for E-1 and E-3,3661 for D-3 and E-3 3661 and 2709 for D-3 and D-7. There were 812 commonly differentially expressed genes among four groups. A total of 3379 differentially expressed genes were found for D-1 and D-3 and 1955 for D-1 and E-1. Based on KEGG analysis, the deferentially expressed genes were annotated to more than 200 KEGG pathway, and 226 common metabolic pathway, respectively. They participated into pathways like metabolic pathways, biosynthesis of secondary metabolites, microbial metabolism in diverse environments, ribosome, plant-pathogen interaction and plant hormone signal transduction. |
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