the occurrence and distribution of Pythium species on Hainan Island of South china

During the period 2003-2009 a comprehensive study of Pythium species in soil and water samples collected from various habitats on Hainan Island was conducted using conductedusing a combination of baiting and selective agar medium technique. A total of 2348 isolates were identified into 29 species: P. acanthicum, P. acanthophoron, P. aphanidermatum, P. aristosporum, P. arrhenomanes, P. carolinianum, P. catenulatum, P. cucurbitacearum, P. deliense, P. dissotocum, P. graminicola, P. helicoides, P. hydnosporum, P. indigoferae, P. inflatum, P. intermedium, P. irregulare, P. marsipium, P. middletonii, P. monospermum, P. myriotylum, P. oedochilum, P. paroecandrum, P. pulchrum, P. spinosum, P. splendens, P. sylvaticum, P. ultimum and P. vexans. Except for P. acanthicum, P. aphanidermatum, P. catenulatum, P. deliense, P. dissotocum, P. indigoferae, P. marsipium, P. myriotylum and P. splendens, the remaining 20 species are new records for Hainan. Pythium cucurbitacearum is the first record in China. Several species of Pythium which are either terrestrial or occasionally found in fresh water were isolated for the first time from fallen leaves submerged in sea water in or near mangrove habitats: P. vexans, P. aphanidermatum, P. cucurbitacearum, P. helicoides and P. middletonii. It remains to be determined whether they should be treated as halotolerant strains or marine species of Pythium but their repeated isolation pointed out their significance in litter decomposition in the marine habitat. By far, P. vexans is the most widespread and abundant species followed by P. deliense, P. acanthicum, P. aphanidermatum, P. helicoides and P. splendens. Of the 23 sampling sites, the greatest diversity of Pythium species was found in the cities of Wenchang, Haikao, Wuzhishan, Ledong and their vicinity.