Rhizobium leguminosarum bv. trifolii WSM1325

Rhizobium leguminosarum is a widely studied alpha-proteobacterial N2-fixing legume symbiont of legumes. It has three biovars - viciae, trifolii, phaseoli - that differ in their host specificity. The host-specificity genes are carried on large plasmids that also carry the genes for nitrogen fixation. All strains of R. leguminosarum have several large plasmids, but the number and sizes of plasmids varies among strains. This large number of plasmids distinguishes R. leguminosarum from the other rhizobia for which complete genome sequences have been determined.Strain WSM1325 was isolated in 1993 from a nodule recovered from the roots of an annual clover plant growing near Livadi beach on the Greek Cyclades island of Serifos. It is compatible with many perennial clovers of Mediterranean origin used in farming, such as T. pratense, and is therefore one of the most important clover inoculants. However, WSM1325 sometimes nodulates and never fixes nitrogen with American and African perennial clovers, such as those nodulated by WSM2304. It is important to understand this incompatibility (adapted from 10.4056/sigs.852027). (HAMAP: RHILS)