What is cross protection in the context of plant pathogens?

Cross protection refers to a phenomenon in plant pathology where a plant that has been infected with a mild strain of a virus or pathogen develops resistance against a more virulent strain of the same or different pathogen. This process is believed to involve the plant's immune response, where prior exposure to a less harmful pathogen leads to an enhanced defense mechanism. The presence of the mild strain effectively primes the plant's defenses, allowing it to better respond to subsequent infections from more severe pathogens.

This concept is particularly relevant in managing viral diseases, where inoculating plants with a mild strain can provide substantial protection against more severe strains without causing significant damage to the plant itself. This biological mechanism showcases the complexity of plant-pathogen interactions and the potential for using strategic infections to bolster plant health and yield.

Other options do not accurately capture the essence of cross protection. For instance, emphasizing enhancement of growth or prevention of all infections overlooks the specificity and nuanced nature of cross protection, while induction of resistance via chemical treatments pertains to a different mechanism unrelated to cross protection's infectious basis.