In vitro effect of UV-C irradiation on Guignardia citricarpa and on postharvest control of citrus black spot

Abstract

Black spot, caused by Guignardia citricarpa, is one of the main diseases affecting citrus fruits. UV-C irradiation is known to have potential to be used as an alternative method to supplement or replace the use of fungicides, especially because it promotes resistance against pathogens. The aim of this work was to evaluate the in vitro effects of UV-C irradiation on G. citricarpa development and on the control of black spot in postharvest orange. Additionally, changes in skin color of the fruit as a result of UV-C treatment were evaluated. Mycelial growth, conidial germination and appressoria formation were evaluated in vitro after fungal exposure to different irradiation doses. Also, 'Valência' oranges naturally infected were submitted to different irradiation doses to check the possibility of in vivo control. Fruit were stored at 25ºC/80% RH and evaluated 3, 7, 10 and 14 days after treatment and area under the disease progress curve was calculated. UV-C irradiation affected conidial germination of G. citricarpa and apressorium formation. UV-C irradiation was not able to control citrus black spot on fruit at a satisfactory level; however, incidence of quiescent black spot lesions was lower on postharvest 'Valência' orange treated with 7.28 and 15.66 kJ m -2 . Low UV-C doses did not affect the visual aspect of fruit. Thus, UV-C irradiation can contribute for the reduction of postharvest losses caused by citrus black spot and reduce the use or doses of fungicides on disease control. Key words: Citrus sinensis, conidia, mycelium, peel color, physical control. RESUMOEfeito in vitro da irradiação UV-C sobre Guignardia citricarpa e no controle pós-colheita da pinta preta dos citros A pinta preta, causada por Guignardia citricarpa, é uma das principais doenças que afetam frutos cítricos. A irradiação UV-C tem potencial para ser utilizada como método alternativo para suplementar ou substituir o uso de fungicidas, especialmente por promover resistência contra patógenos. O objetivo deste trabalho foi avaliar os efeitos da irradiação UV-C sobre o desenvolvimento in vitro de G. citricarpa e no controle da pinta preta em laranja pós-colheita. Adicionalmente, foram avaliadas as alterações na cor da casca dos frutos. Crescimento micelial, germinação de conídios e formação de apressórios foram avaliados in vitro após a exposição do fungo a diferentes doses de irradiação. Frutos de laranja 'Valência' naturalmente infectados foram submetidos a diferentes doses de irradiação (0,52; 1,04; 3,13; 7,28; 15,66 e 31,20 kJ m -2 ) para verificar a possibilidade de controle in vivo. Os frutos foram armazenados a 25ºC/80% UR e avaliados 3, 7, 10 e 14 dias após o tratamento e a área abaixo da curva de progresso da doença foi calculada. A exposição à UV-C afetou a germinação de conídios de G. citricarpa e a formação de apressórios. A irradiação com UV-C não foi capaz de controlar a pinta preta de maneira satisfatória; no entanto, a incidência de lesões de pinta preta quiescentes foi menor em laranjas 'Valência' tratadas em pós-colhei...

Using UV-C radiation and image analysis for fungus control in tomato plants

“…Until the extent of our knowledge, this result is the first achieved in preharvest condition for controlling powdery mildew on tomato plants after natural infection by the fungus. Reports of UV-C effect in agriculture, are mainly related with postharvest diseases management [8, [47][48][49][50]; and the use of UV-C for controlling diseases in preharvest condition has been poorly achieved, particularly on powdery mildew diseases. Van Hemelrijck et al [25], showed that UV-C, on apples and strawberries with powdery mildew, significantly reduced the disease without negative effects on plant performance in field conditions.…”

Potential of UVC germicidal irradiation in suppressing crown rot disease, retaining postharvest quality and antioxidant capacity of Musa AAA “Berangan” during fruit ripening

“…where UVC at doses of 7.28 and 15.66 kJ m −2 were able to control the incidence of citrus black spot disease that was naturally infected on fruits during storage period (Canale et al, 2011). Nigro, Ippolito, Lattanzio, Venere, and Salerno (2000) reported that UVC at doses of 0.50 and 1.00 kJ m −2 significantly reduced the natural infection of Botrytis storage rot on strawberry fruits.…”

“…UVC is able to enhance the storability of fresh produces by triggering natural disease resistances (Chang‐hong, Lu‐yun, Xian‐ying, Xiao‐xu, & Tie‐jin, ). Several findings revealed the ability of UVC radiation in reducing deterioration of fruits and vegetables when applied after harvest, for instance, in the case of oranges (Canale, Benato, Cia, Haddad, & Pascholati, ; Gunduz, Juneja, & Pazir, ), peppers (Rodoni, Zaro, Hasperue, Concellon, & Vicente, ), “Tatsoi” baby leaves (Tomas‐Callejas, Oton, Artes, & Artes‐Hernandez, ), and button mushrooms (Guan, Fan, & Yan, ).…”

Eficiência de radiação UV-C no controle da antracnose e da podridão peduncular em abacate ‘Hass’

“…A ausência de controle da antracnose e das podridões pedunculares em abacate pode ser atribuída ao fato da radiação UV-C não penetrar no tecido dos frutos e, portanto, não atingir as infecções já estabelecidas (LU et al, 1993) e não ter ocorrido indução de resistência. Em contraste a estes resultados, outros autores relataram eficiência da radiação UV-C no controle de doenças quiescentes em maçã (STEVENS et al, 2005, BARTNICKI et al;), manga (TERAO et al, 2015 e citros (CANALE et al, 2011).…”