Chitosan and fungicides on postharvest control of Guignardia citricarpa and on quality of 'Pêra Rio' oranges

Abstract

Citrus fruits are affected by the black spot disease caused by the fungus Guignardia citricarpa. Chitosan can be used as covering for fruits and may delay the ripening process and inhibit the growth of some fungi. Thus, the control of citrus black spot using chitosan and the fungicides thiabendazole and imazalil was assessed in addition to the physicochemical quality of 'Pêra Rio' oranges. The oranges were immersed into chitosan, thiabendazole or imazalil, and in chitosan mixed with both fungicides. The fruits were then stored at 25 °C, 80% RH, for 7 days and, after this storage period, subjected to physicochemical analyses. Chitosan in association with the fungicides reduced black spot in 'Pêra Rio' oranges and delayed the change in the orange skin colour from green to yellow during the postharvest storage. Total soluble solids, titratable acidity, pH, ascorbic acid content and ratio were not influenced by the treatments. Thus, chitosan applied with the fungicides thiabendazole and imazalil showed potential to control the development of black spot lesions on 'Pêra Rio' oranges during the postharvest period.

The Effects of Postharvest Hot Water and Fungicide Treatments on Guignardia citricarpa Growth and the Development of Citrus Black Spot Symptoms on ‘Valencia’ Orange Fruit

“…3A and B). This is in agreement with the reports of Lucon et al (2010) and Rappussi et al (2011). Korf et al (2001) also reported that the commercial postharvest chemicals guazatine, imazalil sulphate, and 2,4-D sodium salt could reduce viability of P. citricarpa on CBS-infected fruit, but did not eliminate the pathogen completely.…”

Phyllosticta citricarpa and sister species of global importance to Citrus

“…() demonstrated that the combination of standard packhouse fungicide treatments aimed at green mould or sour rot control (including pre‐packhouse drench, packhouse dip and brush application of a wax coating) followed by cold storage (common shipping protocol for exported fresh fruit) consistently showed moderate to high levels of control of CBS in lemons and oranges. Several other studies also reported control of latent P. citricarpa infections through application of various chemical or biological postharvest treatments (Lucon et al ., ; Rappussi et al ., , ; Seberry et al ., ; Yan et al ., ). On the contrary, Agostini et al .…”

“…In addition, the movement of leaf litter from infected orchards through vehicle/ machine movement is also important (Dewdney et al, 2018;Silva-Junior et al, 2016a). Citrus fruit is not considered to be a realistic pathway for spread of P. citricarpa to new areas (USDA APHIS, 2010) for the following reasons: (i) the airborne ascospores cannot be produced on fruit, (ii) pycnidia are only produced in certain fruit lesion types (Brentu et al, 2012;FAO, 2014;Kotzé, 2000;Marques et al, 2012;OEPP/EPPO, 2009;Wager, 1952) and conidia are short-lived with low germination ability (Kiely, 1948b), (iii) conidium dispersal from fruit lesions is by means of short-distance (<1 m) wash-down dispersal (Kiely, 1948b;McOnie, 1965;Spósito et al, 2008Spósito et al, , 2011Whiteside, 1967), (iv) standard packhouse treatments and cold storage effectively control P. citricarpa infections (Korf et al, 2001;Lucon et al, 2010;Rappussi et al, 2009Rappussi et al, , 2011Schreuder et al, 2018;Seberry et al, 1967;Yan et al, 2016), and CBS lesions on fruit or discarded peel segments have a very low reproductive potential (Korf et al, 2001;Schreuder et al, 2018;Schutte et al, 2014), and (v) fallen leaves are not susceptible to infection (Truter et al, 2007). Inter-state movement of commercial packhouse-treated fruit from CBS present to CBS-absent areas is therefore permitted in the USA, in line with their Pest Risk Analysis conclusion that fruit is not a realistic pathway (USDA APHIS, 2011).…”

Antifungal Edible Coatings for Fresh Citrus Fruit: A Review

“…Polysaccharides contain highly polar polymers with hydroxyl groups and present a good barrier to oxygen at low RH, but low moisture barrier due to hydrophilic properties [30]. Polysaccharide materials typically used to formulate edible or biodegradable coatings include cellulose, starch, pectin, chitosan, alginate, carrageenan, pullulan, and various gums [25,30,31,[33][34][35][36][37][38][39][40][41][42][43][44].  The ability of different proteins to form edible coatings is highly dependent on their molecular characteristics: molecular weight, conformation, electrical properties, flexibility, and thermal stability [45].…”

“…Such complementary antifungal treatments can be of different nature (physical treatments [93], chemical fungicides [34], food additives [91], biocontrol antagonists [94,95], etc.) and may be applied to citrus fruit before or after the application of chitosan-based coatings.…”