In plant grafting, the success rate is generally highest within the same genus, lower within different genera of the same family, and lowest between different families. Here are some examples to illustrate this:
1. **Grafting within the same genus**:
- **Malus (Apple genus)**: Grafting different species of apple trees, such as the domestic apple (Malus domestica) and the wild apple (Malus sieversii), is usually very successful because they belong to the same genus.
- **Citrus (Citrus genus)**: Grafting an orange (Citrus sinensis) and a lemon (Citrus limon) is also typically successful since they are both part of the Citrus genus.
2. **Grafting within the same family but different genera**:
- **Rosaceae (Rose family)**: Grafting an apple tree (Malus domestica) and a pear tree (Pyrus communis) can be done since they are both in the Rosaceae family. However, the success rate is lower compared to grafting within the same genus because apples and pears belong to different genera (Malus and Pyrus).
- **Cucurbitaceae (Gourd family)**: Grafting a pumpkin (Cucurbita maxima) and a watermelon (Citrullus lanatus) is possible since they are in the same family, but the success rate is lower because they belong to different genera (Cucurbita and Citrullus).
3. **Grafting between different families**:
- **Vitaceae (Grape family) and Rosaceae (Rose family)**: Grafting a grapevine (Vitis vinifera) with an apple tree (Malus domestica) is nearly impossible because they belong to different families (Vitaceae and Rosaceae). Their physiological and anatomical differences are too great.
- **Solanaceae (Nightshade family) and Cucurbitaceae (Gourd family)**: Grafting a tomato (Solanum lycopersicum) with a cucumber (Cucumis sativus) is also virtually impossible because they belong to different families (Solanaceae and Cucurbitaceae).
These examples show that the closer the genetic relationship (e.g., within the same genus), the higher the grafting success rate, whereas the more distant the relationship (e.g., different families), the lower the success rate.