The apple scar skin disease was first re- ported 60 years ago in China ( Manchuria) with the name “Manshu-sabika-byo” (19). Twenty years later, two apple. Cause These diseases are caused by Apple scar skin viroid. Many infected cultivars of apple or pear do not express symptoms of disease. Apple scar skin viroid(ASSVd), a pathogenic RNA viroid, infects apple and pear trees. To determine if ASSVd can also infect apricot, we performed reverse.

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Knowledge Bank home Change location. Go to distribution map The symptoms of ASSVd in apple are usually found at the calyx end of the fruit, and include scar skin reddish brown patches with brownish scar-like tissuecracking, or dapple spotting symptoms. Infected fruits often remain small and hard, do not ripen properly, and develop an unpleasant off-flavour.

Almost all fruit on an infected tree of a susceptible cultivar will show symptoms and are unmarketable. Dapple symptoms, which develop nearer to harvest, usually appear on the appple cultivars e.

In the susceptible cv. Ralls Janet, water-soaked blotches appear first, followed by scar tissue, and then cracking.

Apple scar skin viroid

Although symptoms of ASSVd are usually confined to the fruit, under certain conditions, some apple cultivars s,in develop leaf roll or leaf epinasty symptoms Ito and Yoshida, ; Koganezawa et al. Most commercial pear cultivars show no symptoms when infected with ASSVd.

However, in Hebei, China, the Chinese pear P. Some Japanese pear cultivars develop fruit dimpling symptoms when infected with the viroid Osaki et al. The causal agent is controlled through the use of healthy propagation materials indexing programmes and, if necessary, the removal of diseased trees. Heat therapy of ASSVd-infected apple materials can be effective as long as plants are first subject to a dormant stage before heat therapy and shoot-tip grafting Howell et al.


In pear, in vitro therapy followed by apical meristem culture can be used to eliminate the viroid Postman and Hadidi, In sensitive cultivars, infection with the viroid sdar significant reductions in fruit size and quality.