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Pythium stipitatum is a slow-growing oomycete and has been isolated from soil samples and plant materials from France, Tunisia, Turkey and India. Its morphological characteristics are reminiscent of those of Pythium ramificatum, discovered in Algeria by the corresponding author. Unfortunately, the Algerian isolate was not deposited in any culture collection and ultimately got lost. Those were the days when molecular description of fungi was not a fashion; hence, no molecular characteristics of the Algerian isolates were deposited to the GenBank. Moreover, its coralloid antheridial branches made it an easy prey to be considered as synonymous to Pythium minus. Because there are no living strains of P. ramificatum, and no sequence at the GenBank, it is being treated as 'nomen invalidum' here. However, we have now isolated the same type of oomycete from four different countries and we have sufficient evidence, both molecular and morphological, to describe it as a new species, quite different from P. minus. In this article, we are giving the morphological and molecular evidence to separate it as a distinct species, P. stipitatum, belonging to the 'Clade E' of the genus Pythium. Taxonomic description of this oomycete, its comparison with related species, and the sequence of the internal transcribed spacer region of its rRNA gene, are discussed here. |
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