Alternaria mali
Species of fungus
From Wikipedia, the free encyclopedia
Alternaria mali, also called alternaria blotch of apple, is a pathogenic fungus affecting plants. It is prevalent in the southern United States and elsewhere, and damages the leaves of infected apple trees.
| Alternaria mali | |
|---|---|
| |
| Alternaria mali infection | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Dothideomycetes |
| Order: | Pleosporales |
| Family: | Pleosporaceae |
| Genus: | Alternaria |
| Species: | A. mali |
| Binomial name | |
| Alternaria mali Roberts (1914) | |
Pathogenesis
Aleternaria mali can overwinter as mycelium on dead leaves on the ground, in mechanical injuries in twigs, or in dormant buds.[1] Primary infection occurs about one month after petal fall the following year.[2] The disease is favoured by temperatures between 77 and 86 °F (25 and 30 °C), and by wet conditions.[1] Infection occurs at optimum temperatures with 5.5 hours of wetting,[2] and an outbreak can become serious within two days of infection. The fungus attacks susceptible cultivars using a chemical toxin.[1] Affected plants exhibit circular spots on the leaves that enlarge as the disease advances. Normally, hyphae cannot adhere to the surface of the host, but under moist conditions light-grey mycelium might be present on the surface.[3] Normally the fungus will not attack fruits except in highly susceptible cultivars;[2] fruit-spotting may occur on the tree or in storage, particularly on fruits with already damaged skin.[3]
Plant defense
Plants' first lines of defense against A. mali infection are the physical barrier provided by the epidermis on the primary body and the periderm on the secondary body.[4] A. mali can still penetrate the stomates and hydathodes of leaves.[4]
As with most pathogens, Alternaria mali resistance involves a gene-for-gene relationship.[4] Apple trees can recognize invading pathogens and mount a defense.[4] Often, the plant may be able to resist the pathogen, even though it has no genetic resistance to same. Apple trees seem to have a weak defense to A. mali, base on the fact that no survivors if leaves has been infected.[clarification needed]
Control
Alternaria mali prevention consists of strict quarantine, never importing plants or scions from affected plants and collecting fallen or infected leaves and burning them in winter.[5] Apple cultivars can be ranked in order of increasing resistance as follows: Indo, Red Gold, Raritan, Delicious, Fuji, Golden Delicious, Ralls, Toko, Tsugaru, Mutsu, Jonagold, Jonathan.[2] Chemical control uses fungicides such as iprodione, mancozeb and captan.[6][7] Disease severity is aggravated by severe mite infestation; thus good mite management is an important factor in preventing severe disease development.[1]