JP-2JP-2/SIB-1/RF006 - mtDNA haplo IIa, distinguishable by RG57, intermediate level of metalaxyl resistance, Japan, China, Korea, Thailand, 1996–present.FAM-1 - (only presumed to be A1), mtDNA haplo Ia subtype HERB-1, Japan, Philippines, India, China, Malaysia, Nepal, present some time before 1950.Pathogen populations are grouped into clonal lineages of these mating types and includes:Ī1 produces a mating hormone, a diterpene α1. These types each produce a mating hormone of their own. Until the 1980s populations could only be distinguished by virulence assays and mating types, but since then more detailed analysis has shown that mating type and genotype are substantially decoupled. The mating types are broadly divided into A1 and A2. This can have devastating effects by destroying entire crops. In particular, volunteer plants sprouting from infected tubers are thought to be a major source of inoculum (or propagules) at the start of a growing season. The persistence of viable pathogen within tubers, such as those that are left in the ground after the previous year's harvest or left in cull piles is a major problem in disease management.
The exceptions involve oospores, and hyphae present within tubers. Under most conditions, the hyphae and asexual sporangia can survive for only brief periods in plant debris or soil, and are generally killed off during frosts or very warm weather. infestans survives poorly in nature apart from on its plant hosts. Seemingly healthy tubers may rot later when in store. Infected tubers develop grey or dark patches that are reddish brown beneath the skin, and quickly decay to a foul-smelling mush caused by the infestation of secondary soft bacterial rots. White mold will appear under the leaves in humid conditions and the whole plant may quickly collapse. Symptoms include the appearance of dark blotches on leaf tips and plant stems. The early stages of blight are easily missed. Rain can wash spores into the soil where they infect young tubers, and the spores can also travel long distances on the wind. Sporangia develop on the leaves, spreading through the crop when temperatures are above 10 ☌ (50 ☏) and humidity is over 75–80% for 2 days or more. infestans completes its life cycle on potato or tomato foliage in about five days. As for tuber blight, the white mycelium often shows on the tubers' surface. The sporangia and sporangiophores appear white on the lower surface of the foliage. People can observe Phytophthora infestans produce dark green, then brown then black spots on the surface of potato leaves and stems, often near the tips or edges, where water or dew collects. Both sporangia and zoospores are short-lived, in contrast to oospores which can persist in a viable form for many years. infestans on water films found on leaves or soils. The zoospores released from sporangia are biflagellated and chemotactic, allowing further movement of P. Sporangia are spread by wind or water and enable the movement of P. The different types of spores play major roles in the dissemination and survival of P.
Hormonal communication triggers the formation of the sexual spores, called oospores. There is also a sexual cycle, which occurs when isolates of opposite mating type (A1 and A2, see § Mating types below) meet. germ tube emergence from the sporangium), and the re-establishment of hyphal growth. The asexual life cycle of Phytophthora infestans is characterized by alternating phases of hyphal growth, sporulation, sporangia germination (either through zoospore release or direct germination, i.e.
The name Phytophthora infestans was coined in 1876 by the German mycologist Heinrich Anton de Bary (1831–1888). The species name infestans is the present participle of the Latin verb infestare, meaning : "attacking, destroying", from which we get the word "to infest".
#CROP BLIGHT DEFINITION PLUS#
The genus name Phytophthora comes from the Greek φυτό–( phyto), meaning : "plant" – plus the Greek φθορά ( phthora), meaning : "decay, ruin, perish". Lesion growth rates are typically optimal at a slightly warmer temperature range of 20 to 24 ☌ (68 to 75 ☏).
The pathogen is favored by moist, cool environments: sporulation is optimal at 12–18 ☌ (54–64 ☏) in water-saturated or nearly saturated environments, and zoospore production is favored at temperatures below 15 ☌ (59 ☏). The organism can also infect some other members of the Solanaceae. Late blight was a major culprit in the 1840s European, the 1845–1852 Irish, and the 1846 Highland potato famines. Early blight, caused by Alternaria solani, is also often called "potato blight". Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight.
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