<i>Synchytrium gangeticum</i> , sp. nov., associated with wart disease on <i>Andrographis paniculata</i> , with polygenic phylogeny of family Synchytriaceae

A novel <i>Synchytrium</i> species, <i>Synchytrium gangeticum</i>, sp. nov. (Chytridiomycota: Synchytriaceae), is described as the causal agent of wart disease in <i>Andrographis paniculata</i> (a medicinally important herb) in northern India. <i>Synchytrium gangeticum</i> exhibits host specificity toward <i>A. paniculata</i>, inducing the formation of small, raised, red/brown galls on leaves and stems, with rapid spread observed during early rainy seasons. The microscopic analysis revealed distinct spore morphology and gall development, characteristic of a long-cycled <i>Synchytrium</i> species. It is distinguished by unique resting spore dimensions (90-170 µm) and sporangium size (40-70 µm) and produces uniflagellate zoospores measuring 1-3 µm. Phylogenetic analyses, based on rDNA gene cluster (internal transcribed spacer [ITS], 18S, and 28S), positioned <i>S. gangeticum</i> closest to <i>Synchytrium collapsum</i>, but with significant morphological, and genetic divergence. This study presents the first comprehensive description of a <i>Synchytrium</i> species pathogenic to <i>A. paniculata</i>, providing insights into its host specificity, life cycle, and phylogenetic relationship within the genus.