QUANTITATIVE GENETICS OF RICE - II - A COMPARISON OF THE EFFICIENCY OF 4 BREEDING METHODS

A comparison of the efficiency of four breeding methods, the pedigree, modified pedigree and bulk methods, and single seed descent, with a p air of crosses whose potential was assessed in a previous paper, showe d that, on average, the Fg products of the three methods in which sele ction had been practiced outscored those produced by single seed desce nt for most characters for which improvement was sought. However, thou gh the best lines produced by these methods achieved the desired targe ts for every character considered singly, none were significantly bett er than the best single seed descent line for any character in either cross. These results indicate that while it has been possible to pract ice effective negative selection during the course of inbreeding, by c ulling plants of poor performance, attempts to carry out positive sele ction of plants of superior performance were less successful. An audit of the costs incurred in producing the most promising F-6 lines that were extracted by these methods from each cross revealed that the sing le seed descent lines were the cheapest and those of the pedigree and modified pedigree methods the most expensive. These results indicate, therefore, that single seed descent is at least as effective as the ot her methods, is less costly and, where three generations can be raised per annum, is more rapid. Comparison of the observed proportions of s uperior single seed descent F-6 lines, with those predicted from infor mation obtained from the F-3 generation of these crosses showed that f or the majority of characters, the former were close to the latter. Si ngle seed descent, therefore, has the further advantage that it is pos sible to predict the potential of a cross on information obtained from the early generations of the pedigree. (C) 1998 Elsevier Science B.V.