Inbreeding and Yield Prediction in Synthetic Cultivars of Maize: II. Alternative Methods

Abstract

The first generation (Syn‐l) of synthetic cultivar is obtained by making the possible crosses among the components or parental inbred lines (Syn‐0). The second generation (Syn‐2) is the result of randomly mating Syn‐l. When the number of inbred lines is large, it is difficult to make the total number of possible crosses. Thus, in order to facilitate the hand pollination work, a smaller number of crosses among the inbred lines is desired. The yield of a synthetic cultivar depends on its inbreeding coefficient. Therefore, for an alternative method of obtaining Syn‐I to be valid, the inbreeding coefficient of its Syn‐2 has to be equal to the inbreeding coefficient of the synthetic obtained by the conventional method, in which all possible crosses are made. In this paper the inbreeding coefficient of Syn‐2 is calculated for five alternative methods of crossing to obtain Syn‐l. Results show that the inbreeding coefficient of Syn‐2 is the same for the five methods as long as each component line has the same chance of contributing to Syn‐l. In practice, choosing the method will depend on the purpose of the synthetic, the number of lines, the availability of skilled hand labor to make pollinations, and whether there is an even number of lines. It is shown that with any of the methods yield of Syn‐2 is always the same.