天然杂交是品种混杂退化的重要原因。因此，生产种子必须严防混杂，以防止天然杂交，加速品种的混杂退化。但另外由于品种间种植的插花、混杂，不可避免地会使水稻品种间的天然杂交，Ｆ１产生优势，其中表现为优良的优势株，同原品种具有显著差异，故极易发现。后代用系谱法进? Natural hybridization is an important reason for the variety degeneration. Therefore, the production of seeds must be to prevent hybrids to prevent natural hybridization, accelerate the hybrid varieties of degradation. In addition, because of the intercropping of flowers and hybrids among cultivars, it is inevitable that natural hybridization between rice cultivars will give rise to the superiority of F1. Among them, the superior dominant strains show remarkable differences from the original cultivars and are therefore easily found. Descendants using genealogy method?