. Olive anthracnose is an important disease in South Africa, which can result in high yield losses and reduced oil quality. This study aimed to identify the Colletotrichum species associated with olive anthracnose in South Africa, determine the in vitro efficacy of four fungicides against the fungi, and evaluate the susceptibility of newly bred olive lines to anthracnose. Olive fruit with typical anthracnose symptoms and twigs showing dieback were collected from olive farms in the Western Cape region. Isolations were made, and causal fungi were identified by amplification and sequencing of the internal transcribed spacers, partial (3-tubulin and actin genes as well from their morphological characteristics. All isolates were identified as Colletotrichum acutatum sensu stricto. Fungicide sensitivity of mycelium growth and conidium germination were assessed for dodine, thiram and the mixtures of boscalid + pyraclostrobin and cyprodinil + fludioxinil. Mycelium growth and conidium germination of C. acutatum were strongly inhibited by boscalid + pyraclostrobin and cyprodinil + fludioxonil. The three most virulent C. acutatum isolates were assessed in a wounded fruit droplet inoculation trial on the olive cultivars Manzanilla (susceptible) and Mission (moderately susceptible). These isolates were also used to assess susceptibility of 18 newly bred olive lines and six reference cultivars. Unwounded fruit samples were dip inoculated with a mixture conidium suspension of the three C. acutatum isolates, and lesion development was recorded. Four potential oil lines and three green table olive lines showed resistance to the fungi. This study reports the first sequence confirmation of C. acutatum s.s. associated with anthracnose of olives in South Africa. Furthermore, the identification of the seven resistant olive lines enabled their selection for further evaluation and development. Fungicide sensitivity, together with newly bred line susceptibility results, will aid in development of integrated disease management for olive anthracnose.
Fungicide sensitivity assessment and susceptibility of newly bred olive lines, to improve anthracnose management in South Africa
COSTA C.;CARLUCCI A.;
2025-01-01
Abstract
. Olive anthracnose is an important disease in South Africa, which can result in high yield losses and reduced oil quality. This study aimed to identify the Colletotrichum species associated with olive anthracnose in South Africa, determine the in vitro efficacy of four fungicides against the fungi, and evaluate the susceptibility of newly bred olive lines to anthracnose. Olive fruit with typical anthracnose symptoms and twigs showing dieback were collected from olive farms in the Western Cape region. Isolations were made, and causal fungi were identified by amplification and sequencing of the internal transcribed spacers, partial (3-tubulin and actin genes as well from their morphological characteristics. All isolates were identified as Colletotrichum acutatum sensu stricto. Fungicide sensitivity of mycelium growth and conidium germination were assessed for dodine, thiram and the mixtures of boscalid + pyraclostrobin and cyprodinil + fludioxinil. Mycelium growth and conidium germination of C. acutatum were strongly inhibited by boscalid + pyraclostrobin and cyprodinil + fludioxonil. The three most virulent C. acutatum isolates were assessed in a wounded fruit droplet inoculation trial on the olive cultivars Manzanilla (susceptible) and Mission (moderately susceptible). These isolates were also used to assess susceptibility of 18 newly bred olive lines and six reference cultivars. Unwounded fruit samples were dip inoculated with a mixture conidium suspension of the three C. acutatum isolates, and lesion development was recorded. Four potential oil lines and three green table olive lines showed resistance to the fungi. This study reports the first sequence confirmation of C. acutatum s.s. associated with anthracnose of olives in South Africa. Furthermore, the identification of the seven resistant olive lines enabled their selection for further evaluation and development. Fungicide sensitivity, together with newly bred line susceptibility results, will aid in development of integrated disease management for olive anthracnose.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
