Germplasm evaluation and molecular insights into the mechanisms of sugarcane growth crack

Sugarcane growth crack accelerates internal water loss and increases susceptibility to biotic stress, significantly affecting quality. However, the molecular mechanism underlying this phenomenon is poorly understood. This study evaluated eight crack-related traits across 94 sugarcane germplasms. These results of multivariate statistical analysis showed that number of growth crack internodes (NGCI) and growth crack rate (GCR) can be used to evaluate the growth crack of sugarcane. Applying this system to 392 germplasms, two extremes were found: 16–091 (no growth crack) and 16–0946 (severe growth crack). Both varieties exhibited comparable tissue water content, but 16–0946 absorbed more water after soaking, suggesting rapid water uptake within a short time is a key driver of crack growth. In addition, its peel contained significantly higher lignin content, with slightly reduced cellulose and unchanged hemicellulose and pectin. These results indicate that relatively high lignin content in the stem peel is a crucial factor contributing to growth crack. Transcriptomic and metabolomics analysis further supported this hypothesis, with upregulated differentially expressed genes (DEGs) were significantly enriched in lignin biosynthesis pathways, and downregulated DEGs were significantly enriched in regulation of jasmonic acid signaling pathway and regulation of response to water deprivation. The upregulated differentially accumulated metabolites (DAMs) were significantly enriched in the phenylpropanoid biosynthesis pathway, a key metabolic route contributing to lignin biosynthesis. Furthermore, lignin biosynthetic genes (e.g. PAL, COMT, and CCoAOMT) exhibited elevated expression levels in 16–0946. Collectively, these findings enhance understanding of the occurrence mechanism of growth crack and identify potential genetic improvement targets for sugarcane.