II. 46. Cross prediction for yield using doubled haploid lines.
E. Simpson and J.W. Snape, Plant Breeding Institute, Trumpington, Cambridge CB 2 2LQ, England. "R"
Methods of using the H. bulbosum technique of haploid production for breeding purposes in addition to their use in straightforward varietal production are being investigated at the Plant Breeding Institute. One of these is the use of small numbers of lines from different crosses for cross prediction as suggested by Kasha and Reinbergs (1975). A pilot field experiment to investigate cross prediction for yield was carried out in 1978. Five crosses were investigated, namely HB855 x Georgie, Hassan x HJ92, Hassan x HJ69, Imber x Bulbeck and Imber x HJ92. For each cross estimates of mean performance, range and genetic variance were obtained. The data for yield is shown in Table 1.
Considering firstly the mean performance of the lines, cross Hassan x HJ69 had the highest cross mean but this was not significantly different from the means of the lines derived from HB855 x Georgie or Imber x Bulbeck. In comparing the cross means with their corresponding mid-parental values only the cross HB855 x Georgie differed significantly, where the cross mean exhibited positive heterosis. There are two possible reasons for this departure. Firstly, unconscious selection may have been carried out in deriving these lines, with potentially low yielding lines failing to survive the di-haploid process or secondly, epistasis of an additive x additive type is an important component of the genetical architecture of yield in this cross. Unfortunately, the present data are insufficient to allow a test of these alternative hypotheses.
The mean and genetic variance of each cross can be combined to give
a probability of genetic advance for each cross since these values provide
estimates which define the distribution of the population of inbred lines
that can be derived from each cross. Thus if each population of lines is
assumed to be normally distributed then
The highest yielding parent used in the experiment was HJ69 and the probabilities of genetic advance for each cross were calculated as the expected proportion of lines in each cross exceeding its yield. Results giving the expected and actual number of lines exceeding this line are given in Table 2. It can be seen that three crosses, namely HB855 x Georgie, Hassan x HJ69 and Imber x Bulbeck are expected to produce lines that are higher yielding than HJ69. Comparison with the actual number shows good agreement with these expectations. Of the three crosses, HB855 x Georgie is clearly the one with most potential and the high proportion of high yielding lines in this cross suggests that it is worthy of more intensive investigation.
Table 2. Expected and actual number of lines outyielding HJ69.
The results of this pilot experiment are encouraging and suggest that small numbers of di-haploid lines can be used for predicting whether a cross has the potential to produce high yielding lines.
References:
Jinks, J.L. and H.S. Pooni. 1976. Predicting the properties of recombinant inbred lines derived by single seed descent. Heredity 36:253-266.
Kasha, J.K. and E. Reinbergs. 1975. Utilization of Haploidy in Barley. Proceedings of III. Barley Genetics Symposium, Garching: 307-315.
