Definitions

loimic

Alternaria mali

Alternaria mali is a plant pathogen.

Background

Identity Name: Alternaria mali Roberts Common names: Alternaria blotch of apple

Alternaria mali makes a huge damage to leaves of plants. As an on-line article said: Alternaria blotch has been a serious problem in North Carolina since the late 1980s. By 1993, growers in nine counties in southern and central Virginia reported seeing this problem, some with as much as 50 to 60 percent defoliation on 'Delicious'. Although leaf blotch severity may vary from year to year, there are strong indications that it has spread to new areas in North Carolina and Virginia, and could become a problem in more northern areas of the mid-Atlantic region. Disease severity is aggravated by severe mite infestation. Maintaining good mite management is an important factor in preventing severe disease development. (K.S. Yoder & A.R. Biggs, n.d.)

Pathogen and plant damage

As reported by (K.S. Yoder & A.R. Biggs, n.d.) the Alternaria mali disease cycle is “The fungus can overwinter as mycelium on dead leaves on the orchard floor, in mechanical injuries in twigs, or in dormant buds”. And after that, in the next year “Primary infection takes place about one month after petal fall” (K.S. & A.R., n.d.). The optimum temperature for disease is in a “range of 77 to 86 F (25-30 C)” (K.S. Yoder & A.R. Biggs, n.d.) and in a wet condition. Infection occurs at optimum temperatures “with 5.5 hours of wetting” (K.S. & A.R., n.d.), and two days after infection, a serious outbreak occur in the garden. The disease will efficiently attack susceptible cultivars by a special chemical toxin which produced by fungus (K.S. Yoder & A.R. Biggs, n.d.). Leaves will be infected by the fungus and apples just fine. According to Sawamura (1990), normally the fungus will not attack fruits, except the one which is a very susceptible cultivar, in this condition; fruit-spotting will be on the tree or in storage. Effected plants will show spots on leaves which enlarged in circular. Normally, hypha has a lacking ability adhere on hosts’ surface, but under moist conditions light-grey mycelium might be presented on the surface (CABI &EPPO, n.d.). Sometimes fungus can also causes soft rots on fruit which already has damages on the skin (CABI &EPPO, n.d.).

Plant defense against pathogens

As most plants against diseases, the first line of defense against infection is the physical barrier of the plants epidermis, which consisted of “the epidermis of the primary plants body and the periderm of the secondary plant body” (Neil, & Jane, n.d. p.828). The first defense sometimes is not strong enough, so that Alternaria mali can still get through stomates and hydathodes of leaves (Neil, & Jane, n.d. p.828). Generally most pathogens are resisted by gene for gene recognition (Neil, & Jane, n.d. p.828), so does Alternaria mali. This is because apple trees have an “innate ability to recognize invading pathogens and to mount successful defense” (Neil, & Jane, n.d. p.828). But it seems still not strong enough. Sometimes even plant is affected by a pathogen, and that particular plant has no genetic resistance to this pathogen, the plant is still “able to mount a localized chemical attack in response to molecular signals released from cells damaged by the infection” (Neil, & Jane, n.d. p.828). But apple trees seem to have a weak defense to Alternaria mali, base on the factor that no survivors if leaves has been infected.

Method of control disease

The way to prevent alternaria mali get into plant is: always makes strict quarantine, never import young plant from loimic garden or cion from effected plants; if it is possible, collect fallen leaves and infected twigs and burn them in winter (Bayer cropscience, 2004). The way of controlling alternaria mali normally is the use of resistant cultivars and fungicides. According to Sawamura (1990) apple cultivars which have resistance are: Indo, Red Gold, Raritan, Delicious, Fuji, Golden Delicious, Ralls, Toko, Tsugaru, Mutsu, Jonagold, Jonathan. The chemical control of alternaria mali is using fungicides, examples: iprodione, mancozeb and captan (Lee & Kim, 1986; Osanai et al., 1987).

External links

Index Fungorum
USDA ARS Fungal Database

References

Bayer cropscience. (2004). 苹果斑点落叶病 (translation: apple alternaria blotch). Retrieved November 10, 2007, from http://www.bayercropscience.com.cn/pest/bing23.htm#苹果斑点落叶病 CABI , & EPPO. (n.d.). Alternaria mali. Retrieved November 10, 2007, from http://www.eppo.org/QUARANTINE/fungi/Alternaria_mali/ALTEMA_ds.pdf

Campbell, N.A.,&Reece, J.B. (n.d.).International edition biology: Plant defense (6th ed.).San Francisco: Benjamin Cummings.

Lee, C.V.; Kim, K.H. (1986) Cross tolerance of Alternaria mali to various fungicides. Korean Journal of Mycology 14, 71-78.

Osanai, M.; Suzuki, N.; Fukushima, C.; Tanaka, Y. (1987) Reduced sensitivity to captan of Alternaria mali Roberts. Annual Report of the Society of Plant Protection of North Japan 38, 72-73.

Sawamura, K. (1990) Alternaria blotch. In: Compendium of apple and pear diseases (Ed. byJones, A.L.; Aldwinckle, H.S.), pp. 24-25 American Phytopathological Society, St. Paul, USA.

Yoder, K.S., & Biggs, A.R. (n.d.). Alternaria Blotch, Alternaria mali. Retrieved November 10, 2007, from http://www.caf.wvu.edu/kearneysville/disease_descriptions/omaltblo.html

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