Creating a hybrid apple plant suitable for hot climates, such as the "Hot Climate HR-99" hybrid, through grafting involves a specific set of steps tailored to the characteristics of the desired variety. Here's a generalized guide:

1. Research and Selection: Gather information on the "Hot Climate HR-99" hybrid apple variety, including its characteristics, heat tolerance, and preferred growing conditions. Select appropriate scion wood from a healthy HR-99 apple tree.

2. Rootstock Selection: Choose a rootstock suitable for hot climates and compatible with the HR-99 scion. Rootstocks like MM.111 or M.9 are often used for their adaptability to various environmental conditions.

3. Grafting Technique: Employ a grafting technique such as whip-and-tongue or side-veneer grafting to join the HR-99 scion onto the selected rootstock. Ensure proper alignment and a tight graft union to facilitate successful integration.

4. Optimal Growing Conditions: Provide the grafted plant with optimal growing conditions for hot climates. This includes well-draining soil, sufficient water, and sunlight. Consider mulching around the base of the plant to retain soil moisture and regulate temperature.

5. Protection from Heat Stress: Shield the grafted plant from excessive heat stress, especially during peak summer months. This can be achieved by providing shade, using reflective materials to deflect sunlight, or employing shade cloth.

6. Regular Maintenance: Monitor the grafted plant regularly for signs of stress, disease, or pest infestation. Prune as necessary to maintain shape and promote airflow. Apply organic fertilizers as needed to ensure healthy growth.

7. Training and Support: Train the grafted plant's growth to encourage a strong framework and optimal fruit production. Provide support if necessary, particularly during the early stages of growth.

8. Patience and Observation: Be patient, as it may take some time for the grafted plant to establish and begin producing fruit. Observe the plant's growth and adjust care practices as needed based on its response to the environment.

9. Documentation: Keep records of the grafting process, including dates, techniques used, and any observations made during the plant's growth. This information can be valuable for future reference and refinement of techniques.

By following these steps and providing attentive care, you can increase the likelihood of success in grafting a "Hot Climate HR-99" hybrid apple plant suitable for hot climates.