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It can infect and destroy the leaves, stems, fruits, and tubers of potato and tomato plants, and has been known to infect other plants of the Solanaceae family as well.

Late blight has been referred to as a ‘community disease’ due to its ability to spread rapidly from field to field under the right weather conditions. Asexual spores travel easily on the wind when the weather is cool and moist, and can rapidly infect neighboring fields. Phytophthora infestans can adapt very rapidly to selection pressures created by agrochemicals, which makes it a difficult pathogen to manage ( Rocha-castro et al 2014; Fry et al 2015).

Disease cycle of Phytophthora infestans the cause of potato late blight (Redrawn from Agrios by James Hutton Institute and reproduced by kind permission of Dr D.E.L. Cooke).”

Phytophthora infestans is an oomycete or water mold, a microorganism that causes the serious potato and to;ato disease known as late blight or potato blight. ( early blight is caused by Alternaria solani, is also often called “potato blight”.)

P. infestans is diploid, with about 11-13 chromosoms, and in 2009 scientists completed the sequencing of its genome. The genome was found to be considerably larger (240Mbp) than that of most other Phytophthora species whose genomes have been sequenced. This big genome code for around 18000 genes, 74% are repetative DNA.

It contains diverse variety of transponsons and gene family encoding for “effector proteins”. These “effectors” motif are involved in translocation of pathognen protein into host, and they are split in two groups, the one produce in the symplast (inside plant cells) and in the apoplast (between plant cells). These effector proteins produced in the symplast may contain a signal peptide (SP) followed by the canonical RXLR protein (Arginine X Leucine Arginine) domain. (Birch et al, 2006, Hein et al, 2009, Lamour et al 2012a).

Some RXLR are avirulence protein, meaning they can be recognized by the plant and lead to an hypersensitivity response which restricted the growth of the pathogen.

Most of resistant variety in potato are recognizing this kind of protein from the pathogen. The effector recognition inductible defense response is often by nucleotide biding, leucine-rich rpeat (NLR) disease resistance proteins, and the resulting incompatibility is known as effector triggered immunity (ETI) (Jones & Dangl, 2006; Dodds&Rathjen 2010, John et al 2016)

Effectors which are not recognized by the plant are describe as virulent.