After backcrossing with maize, a 46-chromosome intergeneric hybrid betweenZea maysL. andTripsacum dactyloides(L.) L. (2n=72) gave rise to cytologically and morphologically variable populations. Twenty-chromosome offspring derived from different cytological pathways from the F1to recovered maize were studied. NoTripsacumchromosome insertions to maize were identified by studying pachytene configurations. Ten of 20 lines had significantly reduced chiasmata frequences as compared to F1hybrids between standard maize genetic stocks and the recovered maize lines. Six linkage groups on chromosomes 2, 4, 7 and 9 were analyzed. Significant decreases in crossing over were observed for the 1g1—- g12linkage group of chromosome 2 and for the su1—- g13group of chromosome 4. The linkage groups g12—- V4of chromosome 2 and o2—- g11of chromosome 7 showed increasing crossing over trends for all recovered maize lines. Few significant increases or reductions were observed for the yg2—- g115and g115—- bm4groups of chromosome 9. All morphologically tripsacoid lines had significantly altered crossing over frequencies from check plants while only eight of the 14 nontripsacoid lines were significant.Tripsacumintrogression is believed to be the cause of decreased chiasmata frequencies and linkage relationships.