Lolium temulentum and L. persicum are non-crop species found in wheat and barley fields. L. temulentum has non-shattering seeds like the associated grain crops, whereas L. persicum seeds shatter after maturity. We analyzed the inheritance mode of shattering tendency by comparing the F2 of L. temulentum and L. persicum hybrids. The selfed progeny of L. temulentum and L. persicum exhibited typical non-shattering (1.6% shattering) and shattering phenotypes (70.8%), respectively. F1 hybrids of L. temulentum×L. persicum and its reciprocals were of the shattering phenotype (71.4% and 63.8%, respectively), indicating that shattering is dominant to non-shattering. When the phenotype ratio was assumed to be 15 shattering: 1 non-shattering, the χ2 value for F2 segregation was not significant at the 5% level, and the reciprocal effect was not detected. This indicates that the non-shattering tendency is controlled by two recessive genes. The two-gene inheritance model of shattering tendency suggests that harvest is the selector for seed shattering in cultivated fields, thus the alternative tendency for non-shattering seeds of L. temulentum or shattering of L. persicum would be better adapted to cultivated fields.