When coleader Jay Farrar quit the rootsy alternative-rock band Uncle Tupelo last year, the group renamed itself Wilco and cut A.M. (Reprise). As it turns out, Wilco’s Jeff Tweedy is a better singer than Farrar; his voice has an affecting rasp, and his songwriting persona has the shaggy, winning air of a 30ish hippie struggling to grow up. Though the second-generation country-rockers have a ’90s bleakness far removed from the sunny romanticism of the Byrds and Poco, Tweedy & Co. are following the same urge as those earlier acts: the need to sink roots into something more nourishing than mere rock & roll flash without losing their edge. Wilco is more subversive than the Mavericks, and a lot more listenable than Webb Wilder. The only thing they lack is one truly memorable song that rises above high-level competence and knocks you dead.