Can a kind of hot and sour tomato cultivated by scientific method be patented?

No, you can't apply for a patent for new plant varieties. Please refer to Article 25 of the Patent Law of People's Republic of China (PRC). No patent right shall be granted for the following items:

(1) scientific discoveries;

(2) rules and methods of intellectual activities;

(3) Methods of diagnosis and treatment of diseases;

(4) Species of animals and plants;

(5) substances obtained by nuclear transformation.