41. Predicting properties of recombinant inbred lines in rice

The proportion of recombinant inbred lines expected to lie outside the parental range for a particular character can be predicted using the genetic estimates of m, [d] and D obtained by using appropriate genetic designs (Jinks and Pooni 1976; Pooni and Jinks 1978). In this experiment, three genetic designs, namely, the Basic generations, Triple Test Cross and F\3\ families were used. Predictions were made for six yield characters of five crosses.

While the Triple Test Cross is the best design available for yielding independent estimates of D and H that are of equal precision, in practice it can be a rather demanding design, especially for rice and other small grain cereals. In principle, it is possible to obtain approximate estimates of m and D from F\3\ families produced by allowing a random sample of F\2\ plants to set seed by self pollination and to use these estimates in predictions as an alternate method to using Triple Test Cross progeny analysis. The analysis of variance of F\2\ families (see Table 1) show very clearly the presence of additive genetical variation for all characters.

The proportion of inbred lines that can be extracted from the F\3\ generation (estimated from m and D obtained from F\3\ family analysis) and from F\2\ generation (estimated by using m obtained by model-fltting and D from Triple Test Cross progeny analysis) are given in Table 1. Taken as a whole, it is clear that there is reasonable agreement between the two sets of predictions. Consequently, the use of F\3\ family analysis can adequately replace large Triple Test Cross analysis for prediction purposes, as previously reported for Nicotiana pustica (Jinks and Pooni 1980).

The recombinant inbred lines from these crosses are at present being produced for testing the predictions at the Faculty of Agriculture, University of Peradeniya, Sri Lanka.

Table 1. Test of significance between F\3\ family variance (a), predictions from F\3\ families (b) and triple test cross families (c) as percentages and proportion greater or less than parent or F\1\ (d).

Jinks, J.L. and H.S. Pooni, 1976. Predicting the properties of recombinant inbred lines derived by single seed descent. Heredity 36: 253-266.

Jinks, J.L. and H.S. Pooni, 1980. Comparing predictions of mean performance and environmental sensitivity of recombinant inbred lines based upon F\3\ and Triple Test Cross families. Heredity 45: 305-312.

Pooni, H.S. and J.L. Jinks, 1978. Predicting the properties of recombinant inbred lines derived by single seed descent for two or more characters simultaneously. Heredity 40: 349-361.