Articles
The identification of pathogens associated with dead dormant pear buds
Article number
1403_23
Pages
191 – 194
Language
English
Abstract
Dead flower buds are a common phenomenon in pear production in Mediterranean countries and these symptoms have been observed in South Africa.
The symptom expression of the disease includes a reduced number of flowers per bud and buds, which are completely killed.
The proposed causes of the disease are insufficient tree chilling, unmet dormancy requirements, scion and cultivar incompatibility, and biotic stresses such as pathogens and pests.
In this study, the possible biotic agents involved were investigated.
Dead flower buds and non-symptomatic flower buds were collected from three pear orchards.
The buds were surface sterilized in 70% ethanol for 30 s and then transferred to sterilized moisture chambers to incubate at 25°C. After two weeks isolations were done onto PDA+ and after sufficient growth cultures were purified and subjected to molecular identification.
Molecular identification was conducted using ITS sequence analysis.
From primary isolations, Alternaria alternata was confirmed to be present on dead flower buds as well as non-symptomatic flower buds.
From dead flower buds, the fungal pathogen species that had the highest incidence were A. alternata and Epicoccum spp. Eppicoccum spp. were always present in combination with A. alternata. These pathogens were isolated from all three sampled orchards.
In some instances, Botryosphariaceae were also isolated.
These fungal cultures together with environmental stressors can be the causal agents for the dead flower bud phenomenon.
The symptom expression of the disease includes a reduced number of flowers per bud and buds, which are completely killed.
The proposed causes of the disease are insufficient tree chilling, unmet dormancy requirements, scion and cultivar incompatibility, and biotic stresses such as pathogens and pests.
In this study, the possible biotic agents involved were investigated.
Dead flower buds and non-symptomatic flower buds were collected from three pear orchards.
The buds were surface sterilized in 70% ethanol for 30 s and then transferred to sterilized moisture chambers to incubate at 25°C. After two weeks isolations were done onto PDA+ and after sufficient growth cultures were purified and subjected to molecular identification.
Molecular identification was conducted using ITS sequence analysis.
From primary isolations, Alternaria alternata was confirmed to be present on dead flower buds as well as non-symptomatic flower buds.
From dead flower buds, the fungal pathogen species that had the highest incidence were A. alternata and Epicoccum spp. Eppicoccum spp. were always present in combination with A. alternata. These pathogens were isolated from all three sampled orchards.
In some instances, Botryosphariaceae were also isolated.
These fungal cultures together with environmental stressors can be the causal agents for the dead flower bud phenomenon.
Publication
Authors
M.J. Richard, C.L. Lennox, J.C. Meitz-Hopkins
Keywords
Alternaria alternata, Botryosphaeriaceae, dead flower buds, Epicoccum spp
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