Alternaria mali

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Alternaria mali
Scientific classification
Kingdom: Fungi
Phylum: Ascomycota
Class: Dothideomycetes
Subclass: Pleosporomycetidae
Order: Pleosporales
Family: Pleosporaceae
Genus: Alternaria
Species: A. mali
Binomial name
Alternaria mali
Roberts (1914)

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.

Pathogenesis[edit]

A. 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 (25–30 °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[edit]

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[edit]

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]

References[edit]

  1. ^ a b c d Yoder, K.S., & Biggs, A.R. (n.d.). Alternaria Blotch, Alternaria mali. Retrieved November 10, 2007
  2. ^ a b c d Sawamura, K. (1990) Alternaria blotch. In: Compendium of apple and pear diseases (Ed. by Jones, A.L.; Aldwinckle, H.S.), pp. 24–25 American Phytopathological Society, St. Paul, USA.
  3. ^ a b CABI , & EPPO. (n.d.). Alternaria mali. Retrieved November 10, 2007
  4. ^ a b c d Campbell, N.A.,&Reece, J.B. (n.d.). International edition biology: Plant defense (6th ed.). San Francisco: Benjamin Cummings.
  5. ^ Bayer cropscience. (2004). (translation: apple alternaria blotch). Archived September 12, 2007 at the Wayback Machine (Chinese)
  6. ^ Lee, C.V.; Kim, K.H. (1986) Cross tolerance of Alternaria mali to various fungicides. Korean Journal of Mycology 14, 71–78. (Korean; English abstract available online)
  7. ^ Osanai, M.; Suzuki, N.; Fukushima, C.; Tanaka, Y. (1987) Reduced sensitivity to captain of Alternaria mali Roberts. Annual Report of the Society of Plant Protection of North Japan 38, 72–73.

External links[edit]