Relationship between rind hardness and rind tissue structure in watermelon

This study was carried out to analyze the inheritance of watermelon rind ha rdness and the relationship between rind tissue structure and rind hardness for breeding crack resistant cultivars. For inheritance analysis, a crack- prone cultivar, 'Beni Kodama', was hybridized with a crack resistant cultiv ar, 'Africa 22857' which was introduced from western Africa: their hybrid p rogenies were compared. 1. Hard rind cultivars and lines had thicker chlorenchyma cell layers and s clerenchyma cell layers, consisting of smaller, rounder compact cells in gr eater density than did the soft rind ones. We suppose that the rind tissue structure is correlated with the resistance to cracking following mechanica l shocks. 2. Cell wall thickness is a relatively minor factor in rind hardness. 3. The rind hardness rest of F-1, F-2 and BC1 progenies indicated that 'Afr ica 22857' has partially dominant genes for this characteristic. 4. Most characteristics associated with rind tissue structure are heritable because those in the F-2 generation and back cross progenies are similar t o that of 'Africa 22857'.