Histopathology of Colletotrichum gloeosporioides on guava fruits (Psidium guajava L.)

Abstract

-Anthracnose, caused by Colletotrichum gloeosporioides, produces brown lesions on guava fruits, causing severe losses on postharvest. In this study, the infection and colonization of guava fruits by C. gloeosporioides has been examined using scanning and transmission electron microscopy. Fruits at the physiologically mature stage were inoculated with a 10 5 conidia/mL spore suspension. Afterward, fruits were incubated at 25 °C in a wet chamber for periods of 6, 12, 24, 48, 96 and 120 h to allow examination of the infection and colonization process. Conidia germination and appressoria formation occurred six hours after inoculation (h.a.i). Penetration occurred directly via penetration pegs from appressoria, which penetrated the host cuticle 48 h.a.i. Notably, the appressoria did not produce an appressorial cone surrounding the penetration pore. Infection vesicles were found in epidermal cells 96 h.a.i. The same fungal structures were found in epidermal and parenchymal cells of the host 120 h.a.i. Colonization strategy of C. gloeosporioides on guava fruit was intracellular hemibiotrophic. Index terms: colonization, penetration, pre-penetration, ultrastructure. HISTOPATOLOGIA DE Colletotrichum gloeosporioides EM FRUTOS DE GOIABEIRA (Psidium guajava L.).RESUMO -A antracnose, causada por Colletotrichum gloeosporioides, é caracterizada por lesões marrons nos frutos de goiabeira, causando severas perdas em pós-colheita. Os processos de infecção e colonização de C. gloeosporioides foram estudados usando microscópio eletrônico de varredura e transmissão. Frutos em plena maturação fisiológica foram inoculados com suspensão de 10 5 conídios/mL. Posteriormente, os frutos foram incubados em câmara úmida a 25 °C, por períodos de molhamento de 6; 12; 24; 48; 96 e 120 h para o estudo do processo de infecção e colonização. Germinação de conídios e formação de apressórios ocorreram seis horas após a inoculação (h.a.i). A penetração ocorreu diretamente, por meio da formação do peg de penetração emitido da base do apressório, o qual penetrou na cutícula 48 h.a.i. O apressório não produziu o cone apressorial ao redor do poro de penetração. Foram observadas vesículas de infecção nas células epidérmicas 96 h.a.i. As mesmas estruturas fúngicas foram encontradas nas células epidérmicas e parenquimáticas do hospedeiro, após 120 h da inoculação. A estratégia de colonização de C. gloeosporioides foi do tipo hemibiotrófica intracelular. Termos para indexação: Colonização, penetração, pré-penetração, ultraestrutura. JEGER, 1992;JEFFRIES et al., 1990;PRUSKY;FREEMAN;DICKMAN, 2000). Although anthracnose symptoms may appear in the field, depending on the host and environmental conditions, Colletotrichum also cause quiescent infections in fruit, placing them amongst the most important postharvest pathogen. Thereby the pathogen infects the fruit still in the field, but symptoms appear only during ripening (JEFFRIES et al. 1990).Anthracnose is one of the main guava diseases in all guava-growing countries, causing considerable postharvest...

Effect of temperature, wetness duration and cultivar on the development of anthracnose in guava fruits

“…The colonization process of C. gloeosporioides in guavas is intracellular hemibiotrophic (3,19), and the penetration can occur through wounds, natural openings or directly via appressorium (12). The ripening process of red pulp guava seems not to depend on the storage temperature.…”

“…The infection can occur in the young fruit, in which the fungus remains quiescent after the formation of appressorium and penetration peg (19). However, symptoms are usually observed later on the ripening fruit.…”

Identificação de espécies de Colletotrichum associados à antracnose em plantas de atemóia e colonização do fungo nos frutos

“…Por exemplo, estudos realizados com C. gloeosporioides em frutos de goiabeira, mostraram que a germinação de conídios deste fungo e formação de apressórios ocorreu seis horas após a inoculação (h.a.i) (14), sendo este tempo superior ao que foi observado no presente trabalho. …”

Prepenetration and Penetration of Colletotrichum gloeosporioides into Guava Fruit (Psidium guajava L.): Effects of Temperature, Wetness Period and Fruit Age

“…Successful penetration of C. gloeosporioides on guava fruit is followed by the formation of spherical vesicles inside the cells 96 h after inoculation (Moraes et al. ). Penetration may be correlated with the thickness of the cuticle because the cuticle thickness declined as the fruit aged, as observed with the electron microscope.…”

“…In guava, the infection process of Colletotrichum includes a conidial attachment on the fruit surface, conidial germination, appressorium formation, appressorium melanization and penetration (Moraes et al. ). Guidarelli et al.…”