MOLECULAR ANALYSIS OF GIGASPORA (GLOMALES, GIGASPORACEAE)

This work presents a cooperative effort to integrate new molecular (is ozyme and SSU analyses) characters into the morphological taxonomy of the genus Gigaspora (Glomales). Previous analyses of published Gigaspo ra SSU sequences indicated the presence of a few polymorphic nucleotid es in the region delimited by primers NS71-SSU 1492'. In our study, th e SSU of 24 isolates of arbuscular mycorrhizal (AM) fungi from the Gig asporaceae were amplified and the NS71-SSU 1492' region was directly s equenced. The corresponding sequences of four more isolates of AM fung i from Gigasporaceae, already published, were also included in our ana lyses. Three Gigaspora groups were identified on the basis of a 6 nucl eotide-long 'molecular signature': Gigaspora rosea group (G. rosea+G. albida), Gigaspora margarita group (G. margarita+G. decipiens) and Gig aspora gigantea, which constituted a group by itself. The isozyme prof iles (malate dehydrogenase, MDH) of 12 of these 28 isolates, and seven other isolates not sequenced, were compared. The results obtained fur ther supported the grouping of isolates provided by the SSU analysis. Both SSU and MDH analysis indicated that two out of the 35 isolates ha d been misidentified, which was confirmed when their morphology was re assessed. The use of the Gigaspora intrageneric molecular signature as a quick, unambiguous and objective method to recognize Gigaspora isol ates under any (field or laboratory) experimental conditions is sugges ted.