''Phytophthora alni'' is an
oomycete
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...
plant pathogen
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
that causes lethal root and collar rot in
alder
Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...
s. It is widespread across Europe and has recently been found in North America. This species is believed to have originated relatively recently.
Classification
''Phytophythora alni'' was discovered in 1993 in Southern Britain. It has subsequently been reported in many European countries including the Netherlands, Germany, France, Sweden, Belgium, Austria and Hungary
and has recently been found in Alaska. ''P. alni'' consists of three subspecies, the most commonly isolated and most virulent subspecies ''P. alni alni'' (also referred to as the 'standard form') and two less commonly isolated subspecies ''P. alni uniformis'' (also called the Swedish variant) and ''P. alni multiformis'' (which contains the Dutch, German and UK variants).
[ A recent genetic analysis has suggested that ''P. alni alni.'' was generated on many separate occasions by the hybridization of either ''P. alni uniformis'' with ''P. alni multiformis'' or their ancestors.][
]
Reproduction
Members of the genus ''Phytophthora
''Phytophthora'' (from Greek language, Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on cro ...
'' may reproduce by both sexual
Sex is the biological distinction of an organism between male and female.
Sex or SEX may also refer to:
Biology and behaviour
*Animal sexual behaviour
**Copulation (zoology)
**Human sexual activity
**Non-penetrative sex, or sexual outercourse
** ...
and asexual methods. ''P. alni'' is homothallic Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; i.e., having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a si ...
meaning that both structures for sexual reproduction (antheridia
An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. Androecium is also t ...
and oogonia
An oogonium (plural oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes.
In the mammalian fetus
Oogonia are formed in larg ...
) appear in a single culture.[ The antheridia are ]