Table 2. Watermelon reference genes ranked according to their expression stability as determined by geNorm in different sample sets.
| All samples | Stabilityvalue (M) | Organ andtissue | Stability value (M) | Abiotic stress | Stability value (M) | Biotic stress | Stability value (M) |
| ClYLS8 * | 0.763 | ClTUA * | 0.348 | ClEF1α * | 0.481 | ClCAC * | 0.320 |
| ClPP2A * | 0.763 | ClACT * | 0.348 | ClACT * | 0.481 | ClTUA * | 0.320 |
| ClACT * | 0.970 | ClEF1α * | 0.529 | ClUBCP * | 0.742 | ClEF1α | 0.386 |
| ClEF1α * | 1.000 | ClPP2A * | 0.831 | ClPTB * | 0.809 | ClRPS2 | 0.550 |
| ClTUA * | 1.049 | ClYLS8 * | 0.913 | ClIDH * | 0.859 | ClYLS8 | 0.665 |
| ClCAC * | 1.075 | ClCAC * | 1.014 | ClRPS2 | 0.895 | ClUBCP | 0.826 |
| ClUBCP * | 1.152 | ClUBCP * | 1.146 | ClLUG | 0.934 | ClSAND | 0.918 |
| ClPTB * | 1.239 | ClPTB * | 1.271 | ClTUA | 0.977 | ClPTB | 0.989 |
| ClLUG * | 1.318 | ClSAND * | 1.362 | ClCAC | 1.042 | ClIDH | 1.044 |
| ClSAND | 1.375 | ClGAPDH | 1.430 | ClYLS8 | 1.083 | ClLUG | 1.079 |
| ClIDH | 1.430 | ClLUG | 1.503 | ClPP2A | 1.113 | ClUBC2 | 1.131 |
| ClGAPDH | 1.491 | ClIDH | 1.585 | ClSAND | 1.194 | Cl18SrRNA | 1.175 |
| ClRPS2 | 1.565 | Cl18SrRNA | 1.675 | ClGAPDH | 1.259 | ClPP2A | 1.234 |
| Cl18SrRNA | 1.640 | ClUBC2 | 1.775 | Cl18SrRNA | 1.330 | ClACT | 1.328 |
| ClUBC2 | 1.743 | ClRPS2 | 1.862 | ClUBC2 | 1.536 | ClGAPDH | 1.419 |
*represents the multiple reference genes determined by pairwise variation analysis which are presented in Fig. 3. The recommended threshold of 0.15 is adopted.