The sporangia and sporangiophores appear white on the lower surface of the foliage. 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. Life cycle, signs and symptoms Infected potato Life cycle on potato 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 the word 'to infest' is derived. 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.

Disease resistant potatoes