Ripening of Tomato Fruit and Susceptibility to Botrytis cinerea

Abstract

Botrytis cinerea causes gray mold decay in the ripe fruit of many plant species leading to signifi cant economic losses for the producers, distributers and consumers of fresh and stored produce. This chapter summarizes current knowledge about the biology of a model fl eshy fruit, tomato, during B. cinerea infections. The information presented emphasizes how ripening regulation and events in the host infl uence resistance when fruit are unripe and susceptibility when fruit are ripe. Fruit ripening regulators (e.g., transcription factors, epigenetic modifi ers and hormones) and events unique to ripening that can impact the susceptibility of tomato fruit to B. cinerea are discussed. Understanding the processes in the fruit that underlie the shift from resistance to susceptibility during ripening and resolving how B. cinerea modifi es its strategies of infection in response to the developmental changes of the host may guide efforts to improve the resistance of fruit to B. cinerea and other fungal pathogens.

Grey mould of strawberry, a devastating disease caused by the ubiquitous necrotrophic fungal pathogen Botrytis cinerea

“…However, in the ripe stage, strawberries are highly susceptible and decay rapidly. Fruit susceptibility to fungal disease increases as ripening progresses; hence, B. cinerea appears to promote susceptibility in unripe fruit by activating specific ripening‐related processes (Blanco‐Ulate et al , ). In tomato fruit, master transcriptional regulators of ripening have been shown to have different roles in disease susceptibility.…”

“…Cell wall degradation benefits B. cinerea as it reduces mechanical barriers to infection and spread, increases the possibilities of bruising (e.g. leading to more wounds for pathogen entry) and provides the fungus with access to simple sugars as a carbon source (Blanco‐Ulate et al , ; Blanco‐Ulate et al , ; Brummel and Harpster, ).…”

“…Sucrose levels increase rapidly during de‐greening and red colouring (Jia et al , ). In tomato, it has been shown that the Cnr mutant, which does not accumulate high levels of sugars is still highly susceptible to B. cinerea infection (Blanco‐Ulate et al , ). This observation suggests that even though sugars may serve as a susceptibility factor, high sugar concentrations are not essential for B. cinerea infection.…”

“…However, sugar content could still influence susceptibility to B. cinerea as specific sugars may serve as ripening initiation signals. For instance, sucrose regulates abscisic acid (ABA) levels in strawberries, which are necessary for normal ripening and could influence fruit susceptibility as described below (Blanco‐Ulate et al , ; Jia et al , ; Li et al , ). Like other ripening‐related events, B. cinerea can alter neutral sugar and sugar acid levels in the infected host tissues, mainly by degradation and depolymerization of cell walls.…”

Securing fruit production: Opportunities from the elucidation of the molecular mechanisms of postharvest fungal infections

“…Yet another crucial question is whether the transition from the dormant to the virulent state could favor the fruit ripening process necessary for the infection and subsequent growth of pathogenic fungi. Blanco‐Ulate et al., and Powell (2016) investigated this case during fungi infection of tomatoes. They showed that Botrytis contributed to the ripening and sensitivity of tomatoes.…”