II.49. Genetic stability of doubled haploid lines in barley.
E. J. Walsh, (present address: University College Dublin, Ireland), K. J. Kasha and E. Reinbergs, Crop Science Department, University of Guelph, Guelph, Ont., Canada.
The haploidy technique (Kasha and Kao, 1970; Kasha and Reinbergs, 1972) has been proposed as a method whereby barley breeders can produce homozygous lines in just one step. Thus, in contrast to conventional breeding methods, the breeder might proceed to the yield evaluation phase immediately. This evaluation of doubled haploids is of interest only in predicting the relative performance of those lines in subsequent generations. How well this can be predicted will depend on the evaluation technique used and on the genetic stability of the lines. Changes in the genetic constitution of doubled haploids as a result of genetic stability would render such evaluations and predictions useless. It might be hypothesized that colchicine, or other treatment applied during the culturing or chromosome doubling phases of the production process, are mutagenic in themselves, or that doubled haploids are genetically unstable per se.
A test was planted at the Elora Research Station in 1972 to evaluate genetic stability of doubled haploids. It included 25 lines from a single doubled haploid from an F1, (Brant x OAC 21), 10 lines from a single doubled haploid from a pure line variety Brant, and 25 conventional lines from a pure line variety Fergus. Each line originated from a single seed on the doubled haploid plant and had been advanced three generations by bulked single row increases in the field. The 60 entries, replicated 10 times were planted on May 11, 1972, in hill plots. Twenty-five seeds were planted, in a clump, at the center of each 12" x 12" plot. The only data recorded were grain yields since previous observations, on the same material, had indicated genetic stability for observable characters such as plant height and days to heading.
The results of the test, although of limited inferential value because of the relatively small number of lines included and these being tested at only one location in one year, do indicate that the degree of heterogeneity among lines originating from a single doubled haploid is certainly not excessive. It was only between conventional lines emanating from a pure line variety that significant differences in grain yield were found. The differences in yield between lines derived from a doubled haploid from either an F1, or a pure line variety, were not significant (Table 1). In fact in neither of the two populations originating from a doubled haploid could a genetic variance component be calculated because in both cases the error mean square was slightly greater than the "among lines" mean square. This can be interpreted as a complete lack of genetic variability in the two populations (Table 2). That this result is not due to excessive experimental errors is seen from the relative magnitudes of the error mean squares and the coefficients of variation (Table 1).
Table 1. Summary of analysis of variance for grain yield.
Our limited results on yield evaluations indicate that treatments applied during the production process were not mutagenic in themselves. They are consistent with our observations on numerous other plots and characteristics in the field. Consequently, the breeder can be reasonably confident in selecting among doubled haploids on the basis of preliminary yield tests.
Since the lines included in this test were bulk populations arising from a subdivision of the progenies of doubled haploids in the first generation, our experiment did not detect heterogeneity that might arise in subsequent generations as a result of predisposition to mutation. Further studies in which progenies are subdivided at intervals would be needed to investigate this aspect of genetic stability.
References:
Kasha, K. J. and K. N. Kao. 1970. High frequency haploid production in barley (Hordeum vulgare L.) Nature 225 (5235):874-876.
Kasha, K. J. and E. Reinbergs. 1972. The haploid technique in barley breeding. Tech. Quarterly 9:128-130.
