Experimental designs for complete diallel cross(CDC) system IV with equal number of replications of each cross has been studied extensively in the literature. In this book, we have proposed incomplete block designs for CDC system IV with unequal number of replications for crosses through two-associate classes of partially balanced incomplete block (PBIB (2))designs where none of two treatments which are ith associates occur together exactly in the same blocks (i =1,2) is zero. In addition to the block effects and general combining abilities effects, the model also includes the parameter of...