Increasing the sucrose content of sugarcane, a major sugar crop, is a key breeding objective. However, the complex genetic background of sugarcane affects development of sugarcane hybrids. In this study, we sequenced 292 sugarcane germplasm accessions and identified 2,542,965 single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels). We performed a genome-wide association study (GWAS) for two important sugarcane traits: sucrose content and stem diameter. Both traits followed a normal distribution and showed typical characteristics of quantitative traits. Population structure analysis revealed four subpopulations with an average genetic distance of 0.236. GWAS of the sucrose content detected 27 SNPs. After annotating genes at or near significant loci, 17 candidate genes were screened. For stem diameter, GWAS revealed 19 SNPs, from which 9 candidate genes were identified. These results improve our understanding of genetic mechanisms affecting sucrose content in sugarcane, and identify important genetic resources to accelerate breeding of new sugarcane varieties with high sucrose content.
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This study aims to investigate whether application of trehalose could mitigate the adverse effects of drought stress by enhancing the defense response in sugarcane (Saccharum spp. hybrid), and to provide a theoretical basis for stable high yield of sugarcane under drought conditions.
The present investigation was conducted to assess ameliorative effects of adding trehalose on the growth, malondialdehyde (MDA) content, and antioxidant responses of two sugarcane cultivars ROC22 and YZ05-51 under the treatment of 30% PEG6000 and 12% PEG6000. In the preliminary experiment, four treatment concentrations of trehalose were set at 0, 10, 100 and 200 mg·L-1. The dry weight, fresh weight and adventitious roots of tissue-cultured sugarcane seedlings were measured at 9 d after treatment to clarify the optimal concentration of trehalose in promoting sugarcane growth under drought stress. Then, the MDA content and the activity of antioxidant enzyme peroxidase (POD) and superoxide dismutase (SOD) were determined under control, drought stress and drought stress combined with optimal trehalose treatment. Finally, the expression level of drought-resistance genes ScTPS1, ScSnRK2.3, ScSnRK2.4 and ScDREB2b-1 was quantified by qRT-PCR at 0, 12, 24 and 48 h in YZ05-51 after exposed to 30% PEG6000 and 30% PEG6000 adding with optimal trehalose concentration, respectively.
Application of trehalose could alleviate the drought-induced decrease of fresh weight and dry weight of two sugarcane cultivars, and the growth recovery of plantlet was better in 100 mg·L-1 trehalose group than that in 10 and 200 mg·L-1 trehalose groups. Under 30% PEG6000 stress, the MDA content was notably increased, and a considerable improvement was recorded in the activity of the antioxidant enzymes POD and SOD. Adding trehalose significantly reduced the content of drought-induced MDA, and enhanced the activity of POD and SOD, respectively. However, external trehalose had little effect on the MDA content and antioxidant enzyme activity of tissue-cultured sugarcane seedlings under 12% PEG6000 stress. Compared with drought controls, the expression of drought-resistance genes ScTPS1, ScSnRK2.3, ScSnRK2.4 and ScDREB2b-1 was up-regulated in the trehalose-treated plantlet.
Application of trehalose can alleviate the negative impact of drought on the growth of sugarcane seedlings, and promote adventitious root growth. External addition of trehalose may reduce the oxidative toxicity caused by drought stress by increasing the activity of antioxidant enzymes POD and SOD. Meanwhile, application of trehalose induces the expression of drought-resistance genes ScTPS1, ScSnRK2.3, ScSnRK2.4, and ScDREB2b-1, indicating that applying trehalose can improve the drought resistance of sugarcane. The results will provide a reference for developing drought resistance strategies in sugarcane breeding and productive practice.
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