• Saccharum spontaneum L. is one of the most important germplasm resources for modern sugarcane breeding. Exploring the cold tolerance of S. spontaneum  clones with different ploidy levels and screening for cold‐tolerant material can be helpful in parent selection for breeding cold‐tolerant sugarcane.
• Morphological indices, leaf ultrastructure and physiological indices were used to evaluate the cold tolerance of 36 S. spontaneum clones with different ploidy levels (2n = 40, 48, 54, 60, 64, 78, 80, 88, 92 and 96).
• The morphological indices of S. spontaneum clones with different ploidy levels were positively correlated with ploidy. Under low‐temperature stress, the chloroplast and mitochondrial structures of the clones with high ploidy were more severely damaged than were those of clones with low ploidy. A comprehensive evaluation of the physiological indices showed that the 36 S. spontaneum clones could be divided into four categories: strongly cold tolerant, cold tolerant, moderately cold tolerant and cold sensitive. Correlation analysis of the morphological indices and cold tolerance revealed a significant negative correlation between cold tolerance and ploidy. On the basis of the morphological and physiological indices, optimal stepwise regression equations that can be used for the selection of cold‐tolerant S. spontaneum resources were established.
• The S. spontaneum clones with low ploidy are more cold tolerant than those with high ploidy. Clones 12‐37, 13‐10 and 12‐23 are strongly cold‐tolerant germplasm resources, which suggests these germplasm sources have high potential for use in breeding cold‐tolerant sugarcane.

中文翻译：

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根据形态和生理指标评估不同倍性水平的自发性酿酒酵母（Saccharum spontaneum L.）克隆的耐寒性。

• 甜根子草属，是现代甘蔗育种最重要的种质资源之一。探索 具有不同倍性水平的自发链球菌克隆的耐寒性并筛选耐寒材料可以为育种耐寒甘蔗的亲本选择提供帮助。
• 使用形态学指标，叶片超微结构和生理指标来评估不同倍性水平（2n = 40、48、54、60、64、78、80、88、92和96）的36个自发链球菌克隆的耐寒性。
• 不同倍性水平的自发链球菌克隆的形态指标与倍性呈正相关。在低温胁迫下，高倍性克隆的叶绿体和线粒体结构比低倍性克隆的叶绿体和线粒体结构受到更严重的破坏。生理指标的综合评估表明，36个S.stantaneum克隆可分为四类：强耐寒性，耐寒性，中度耐寒性和耐寒性。形态指标与耐寒性的相关分析表明，耐寒性与倍性之间存在显着的负相关。根据形态和生理指标，建立了可用于选择耐寒自发链球菌资源的最佳逐步回归方程。
• 该割手密低倍性克隆更耐寒比那些高倍。克隆12‐37、13‐10和12‐23是高度耐寒的种质资源，这表明这些种质资源在育种耐寒甘蔗中具有很高的潜力。