The role of wounds in the infection of oranges by Penicillium digitatum Sacc

Abstract

S U M M A R YInocula of spores of Penicillium digitatum in water applied to apparently uninjured skin of oranges do not cause lesions to develop. Addition of citric acid, orange juice, or various extracts of rind had little effect on susceptibility to infection.When spores in water are applied to wounds made between oil vesicles, lesions develop only from wounds that penetrate deeply into the albedo. The flavedo of most oranges seems to be resistant to infection even when damaged, but in a few consignments it showed much less resistance. Increasing the number of conidia in the inoculum caused more lesions to develop but some fruits developed lesions from inocula containing very few spores. T h e method and timing of spore application to wounds had a considerable effect on the incidence of lesions; emanations from infected fruit had no effect.Lesions developed more rapidly and readily when suspensions of spores in water were applied to wounds in the skin that damaged oil vesicles; wounds as shallow as 0.25 mm allowed lesions to develop.

Potencial do flavedo (epicarpo) de Citrus aurantifolia cv. Tahiti no controle do bolor verde e da antracnose em citros

“…Em injúrias causadas nos frutos, durante as fases de colheita e pós-colheita, o esporo germina rapidamente, e inicia a infecção através dos ferimentos (12). O interior do fruto só é colonizado, após o consumo dos compostos presentes no flavedo (14).…”

Evaluation of alternatives to synthetic fungicides to control citrus postharvest diseases.

“…Disease incidence is probably the most important parameter to account for the susceptibility of any fruit to a postharvest disease. Conidia of P. digitatum or P. italicum situated in peel wounds of mature fruit that rupture oil glands or penetrate into the albedo typically bring irreversible infection within 48 h at 20-25°C (Green, 1932;Kavanagh and Wood, 1967). Immature fruit, by contrast, have in the peel considerable amounts of preformed antifungal compounds such as citral or different flavonoids that interfere with fungal development and inhibit decay (Del Río and Ortuño, 2004).…”

Cambios de expresión génica asociados a la respuesta de los frutos cítricos frente a la infección por hongos del género Penicillium.

“…Es específico de frutos cítricos, no descrito en otros sistemas vegetales. Es un patógeno de herida, por lo que necesita de pequeñas lesiones en la piel para penetrar en el tejido vegetal (Kavanagh y Wood, 1967). La contaminación de este hongo tiene lugar durante la recolección, confección, transporte y manipulación, aunque el inóculo mayoritario procede del campo (Tuset, 1987).…”

“…Estos requieren la presencia de heridas o daños que faciliten su penetración. Este es el caso de los hongos P. digitatum y P. italicum, en los que la presencia de heridas junto a una humedad ambiental alta, pueden provocar el desarrollo de la infección durante el almacenamiento (Kavanagh y Wood, 1967). La inoculación del hongo sobre una herida suele acabar con el desarrollo de la infección.…”

“…La inoculación con esporas de P. digitatum en heridas de menos de 2 mm. de profundidad generalmente tiene más dificultades de progresar y desarrollar la infección, lo que indica que el flavedo es un tejido más resistente a la infección (Kavanagh y Wood, 1967). Esta mayor resistencia del flavedo ha sido asociada con una mayor concentración de compuestos antifúngicos pre-existentes (Rodov et al, 1995).…”