A Comparation of Watermelon Flesh Texture across Different Ploidy Levels Using Histology and Cell Wall Measurements

Abstract

Watermelon fruits of different ploidy exhibit significant variations in texture. In order to investigate the primary factors influencing texture differences, this study was conducted to investigate the differences in fruit texture development using homozygous autogamous diploid (2X)lines and their autotriploid (3X) and autotetraploid (4X) lines 'Yixuan'. The research encompassed fruit development, flesh texture profile analysis (TPA), flesh cell wall polysaccharide content, and flesh cell microstructure analysis, specifically in 2X, 3X, and 4X watermelon fruits.The results showed that as watermelon fruits matured, several characteristics exhibited an ascending trend, including fruit weight, TSS (total soluble solids) content, rind hardness, flesh cell size, and cell wall polysaccharide contents such as crude fiber, cellulose, hemicellulose, lignin, and protopectin. Conversely, the flesh texture parameters and soluble pectin content of the flesh cell wall gradually declined. Notably, significant differences in fruit flesh texture and flesh cell structure were observed among fruits of different ploidy at the 32d. Specifically, 2X fruits displayed considerably lower rind hardness, reduced flesh texture (Hardness, Fracturability, Chewiness, Gumminess), and cell density compared to 3X and 4X fruits. Additionally, 2X fruits exhibited larger cell sizes than 3X and 4X fruits. However, no significant differences were observed in the content of flesh cell wall polysaccharide contents across various ploidy levels.These findings suggested that the variation in texture among watermelon fruits of different ploidy can be attributed to the size and arrangement of flesh cells. Importantly, this research provided a foundation for further exploration of the intrinsic regulatory factors and molecular mechanisms contributing to texture variation in polyploid watermelon fruits.