How to recognize and combat alternariosis in fruit

Alternaria sp. is a very large genus of phytopathogenic fungi, comprising numerous species capable of affecting a wide variety of plants, especially weakened, senescent, or damaged plant tissues. Many Alternaria species exhibit primarily necrotrophic behavior, colonizing tissues that have suffered wounds, physiological stress, mechanical damage, or unfavorable environmental conditions. The fungus produces a mycelium made up of branched hyphae that develop on or within the affected tissues and subsequently form conidiophores that produce numerous conidia. These conidia are one of the most important structures for the dispersal of the pathogen and can remain viable for extended periods in plant debris, affected fruit, seeds, soil, crop structures, and other contaminated surfaces. Conidia production increases particularly when infected tissues and favorable environmental conditions are present, and these conidia can be released and transported by wind, water splash, rain, irrigation systems, and agricultural operations. After reaching a susceptible surface, conidia can germinate when sufficient moisture is present, producing germ tubes that penetrate directly into tissues or take advantage of wounds, microlesions, and weakened areas. Once the infection is established, the fungus progressively colonizes cells and tissues, causing their death and forming new lesions in which it can again produce reproductive structures. In this way, successive infection cycles occur during the favorable period. The presence of infected plant debris constitutes an important source of inoculum, since the pathogen can survive between growing seasons in diseased plant material and resume its activity when suitable temperatures and humidity levels are present again. In fruit, infection can occur both during development in the field and during ripening, harvesting, handling, and storage, especially when wounds or damage facilitate fungal penetration.