Host Defenses Associated with Fruit Infection by Colletotrichum Species with an Emphasis on Anthracnose of Blueberries

Abstract

Defense mechanisms in fruit against invasion by fungal pathogens fall into several categories, including fruit physiological factors, passive defense responses, and active defense responses. Colletotrichum spp. are common fruit rot pathogens on a variety of crops. The infection strategy of Colletotrichum pp. varies depending upon the host and the tissue type being colonized and range from hemibiotrophy to necrotrophy. Anthracnose fruit rot caused by C. acutatum is the most important postharvest disease of blueberries (Vaccinium corymbosum). In order to better understand host resistance mechanisms in blueberry fruits, the resistant cultivar Elliott was compared with the susceptible cultivar Jersey. Higher levels of hydrogen peroxide and differentially expressed defense-related genes were found in ‘Elliott’ than in ‘Jersey’ fruit after inoculation. Furthermore, higher levels of anthocyanins and flavonols, including two distinctive compounds, were observed in Elliott fruits and two unique flavonols were present in Elliott. Additionally, pH and sugar content were implicated as being involved in host resistance in blueberry fruits. The results from these studies provide a significant contribution to the understanding of the multiple factors that contribute to anthracnose fruit rot resistance in blueberry. Accepted for publication 15 August 2013. Published 25 November 2013.

Repellent, oviposition-deterrent, and insecticidal activity of the fungal pathogen Colletotrichum fioriniae on Drosophila suzukii (Diptera: Drosophilidae) in highbush blueberries

“…to anthracnose 46 . Previous studies have also shown that fruit rot pathogens, Colletotrichum spp., can successfully infect blueberry fruit after only 10 to 12 h postinoculation 26,47 and induce chemical changes in fruit as early as 24 h after incubation 27 . Moreover, in preliminary studies, we showed that field-collected anthracnose-infected fruit had levels of spore concentrations similar to those used in our experiment (1.0 × 10 7 per mL).…”

“…In addition, to remove the conidia from any extracellular enzymatic compounds, a 'filtered' solution was prepared by sterile filtering (Cameo 25 GAS, 0.22 µm; Osmonics Penang, Malaysia) the 'colony' spore suspension described above immediately before use (following methods by Waller et al 19 ). Treated fruit were left to incubate at room temperature for 48 h before use in choice and no-choice assays (see below) to allow the solutions to settle on the fruit surface; this anthracnose incubation period is sufficient to activate defensive genes and induce secondary metabolite production in blueberries 27 . A group of 5 fruit from each treatment was set aside to confirm C. fioriniae infection by checking for symptoms (only fruit treated with the C. fioriniae 'fruit' and 'colony' solutions were symptomatic).…”

“…Under a no-choice scenario, D. suzukii oviposition was reduced in fruits infected by C. fioriniae . Anthracnose infection is known to increase sugar concentrations in fruits, possibly as a defense mechanism 27 because there is a positive correlation between fruit sugar concentration and resistance to Colletotrichum spp. 28 .…”

“…Colletotrichum spp. infection is thought to speed the conversion of acids to sugars as a defense response in blueberries 27 because there is a positive correlation between sugar concentration in fruit and fruit rot resistance 28 . This “overripe” effect of the pathogen on blueberry fruit could stimulate avian and mammalian herbivory 29 – 31 and also have a positive effect on D. suzukii by increasing adult survival, longevity, and oviposition 7 , 32 – 34 .…”

Breeding Climate-Resilient Bananas

“…A particularly cell wall is a notable factor for strawberry resistance or susceptibility (Amil- Ruiz et al 2011). During fruit ripening, some physiological changes occur including cell wall expansion, fruit softening, changes in pH and increase in soluble sugars and the susceptibility of fruits to pests and diseases increase (Miles and Schilder 2013). The plant's ability to synthesize a broad range of secondary metabolites (flavonoids, flavanols, triterpenes, phenolics) is pre-form biochemical barriers and to protect strawberry and raspberry from fungal pathogens and pests (Terry et al 2004;Hukkanen et al 2007;Hanhineva et al 2009;Lee 2010;Slatnar et al 2016).…”