Can i train a model to classify a person which was already trained to detect objects?

I’ve trained and saved a model to detect few diseases in tomato plant, but now i want to extend the capability of the model for other plants also. So can someone give a gist or roadmap to achieve this instead of training the model again for tomato and other plant all together at once.
I wanted to train the model plant by plant depending on the accuracies

Thanks in advance