Sugarcane (Saccharum spp. hybrids) is an important sugar and bioenergy crop with a high aneuploidy, complex genomes and extreme heterozygosity. A good understanding of genetic diversity and population structure among sugarcane parental lines is a prerequisite for sugarcane improvement through breeding. In order to understand genetic characteristics of parental lines used in sugarcane breeding programs in China, 150 of the most popular accessions were analyzed with 21 fluorescence-labeled simple sequence repeats (SSR) markers and high-performance capillary electrophoresis (HPCE). A total of 226 SSR alleles of high-resolution capacity were identified. Among the series obtained from different origins, the YC-series, which contained eight unique alleles, had the highest genetic diversity. Based on the population structure analysis, the principal coordinate analysis (PCoA) and phylogenetic analysis, the 150 accessions were clustered into two distinct sub-populations (Pop1 and Pop2). Pop1 contained the majority of clones introduced to China (including 28/29 CP-series accessions) while accessions native to China clustered in Pop2. The analysis of molecular variance (AMOVA), fixation index (Fst) value and gene flow (Nm) value all indicated the very low genetic differentiation between the two groups. This study illustrated that fluorescence-labeled SSR markers combined with high-performance capillary electrophoresis (HPCE) could be a very useful tool for genotyping of the polyploidy sugarcane. The results provided valuable information for sugarcane breeders to better manage the parental germplasm, choose the best parents to cross, and produce the best progeny to evaluate and select for new cultivar(s).

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An appropriate planting density could realize the maximum yield potential of crops, but the mechanism of sweet potato storage root formation in response to planting density is still rarely investigated. Four planting densities, namely D15, D20, D25, and D30, were set for 2-year and two-site field experiments to investigate the carbohydrate and lignin metabolism in potential storage roots and its relationship with the storage root number, yield, and commercial characteristics at the harvest period. The results showed that an appropriate planting density (D20 treatment) stimulated cambium cell differentiation, which increased carbohydrate accumulation and inhibited lignin biosynthesis in potential storage roots. At canopy closure, the D20 treatment produced more storage roots, particularly developing ones. It increased the yield by 10.18–19.73% compared with the control D25 treatment and improved the commercial features by decreasing the storage root length/diameter ratio and increasing the storage root weight uniformity. This study provides a theoretical basis for the high-value production of sweet potato.

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