II. 15. Presowing selection of male sterile barley plants for the production of outcrossed seeds.
Duane E. Falk, Joint Doubled Haploid Barley Breeding Programme, C/- DSIR-CRD, Private Bag, Christchurch, New Zealand. "R"
A reliable method of selecting seeds which will produce male sterile plants has been developed (Falk and Kasha, 1980). A stock has been released for use by barley breeders to produce outcrossed seed in a field scale (Falk, et al. 1982). This outcrossed seed can be used in genetic studies or to generate male sterile facilitated recurrent selection populations which will include the presowing selection of male sterile plants in later generations. The elimination of the male sterile gene from breeding populations in the development of pure lines will also be enhanced.
The feasibility of using presowing selection of male sterile plants for the production of outcrossed seed was tested at the University of Guelph, Ontario, Canada during the summer of 1982 and at the Crop Research Division, DSIR, Lincoln, Canterbury, New Zealand during the 1982-83 growing season. The efficiency of presowing selection of male sterile plants and the seed production of six-rowed and two-rowed lines in the two environments were determined.
Plots for outcrossing consisted of a single row of male sterile plants bordered on either side by two rows of the male parent. Row spacing was 30 cm. In Canada, 50 seeds were sown in 2.5 m plots while in New Zealand, 25 seeds were sown in 1 m plots. An attempt was made to preselect male sterile plants by choosing seeds with shrunken endosperm from a number of F2 populations. The male sterile allele (msg 6) was linked in coupling with the orange lemma allele (o) and the shrunken endosperm allele (sex 1), i.e., msg 6 o sex 1/Msg 6 0 Sex 1. Plants in the rows planted with shrunken seeds were harvested individually at maturity; each plant was then classified for male sterility, orange lemma colour and shrunken seed. The data are presented in Table 1.
Table 1. Classification of plants grown from selected shrunken seeds in Canada and New Zealand.
An overall average of 96.21 of the selected seed produced male sterile plants. A total of 2.1% of the plants were derived from misclassified seeds (MS_Sex Sex and MS_Sex sex) and 1.7% were derived from seeds containing a crossover gamete (MS_oo sex sex and MS_O_sex sex). The frequencies of male sterile, misclassified and crossover plants are similar to those reported by Falk et al., 1981. The high frequency of male sterile plants in the selected population is sufficient for the production of female lines for crossing on a field scale. Since fertile plants (misclassified and crossover seeds) can be readily recognized at flowering and maturity, these could be rogued and the all-male sterile rows machine harvested at maturity.
The number of outcrossed seeds produced on each male sterile plant is a consideration as well as the frequency of male sterile plants produced from selected seeds. Table 2 lists the amounts of seed produced on two-rowed and six-rowed male sterile plants. In Canada, the six-rowed plants produced considerably more seed than the two-rowed plants. This can in part be attributed to the greater number of flowers available for pollination as well as the greater pollen production of the six-rowed male parents. The six-rowed plants are also generally more open flowered under Ontario conditions. In New Zealand, both two-rowed and six-rowed plants produced less seed than in Canada. This may be caused by relatively late planting and poor adaptation to the lower temperatures and humidities of the growing season in New Zealand.
Over 1.2 kg of outcrossed seed was produced on male sterile plants by natural cross pollination (approx. 30,000 seeds). Since each male sterile plant was derived from an F2 population, each seed produced would be expected to be genetically different. By manipulating the source of the selected shrunken seeds and the pollen parent used in crosses, populations varying from backcrosses to polycrosses could be generated at the breeder's discretion.
The use of presowing selection of male sterile plants would make mass crossing enterprises such as that undertaken by Suneson and Wiebe (1962) more easily managed, simply by manipulating planting dates of male and female lines. Roguing at flowering would be necessary only to remove misclassified and crossover plants in the female rows. Populations are currently being synthesized at the University of Guelph in Canada and Crop Research Division, DSIR, Lincoln, New Zealand based on the coupled shrunken endosperm, male sterile lines used in this study. Various populations include good agronomic parents as well as cultivars and lines resistant to different disease organisms. After sufficient recombination and selection, the male sterile allele can be eliminated from the population and pure lines developed through conventional selfing techniques or by haploid methods. Roguing undesired plants from the populations prior to flowering should assure that both male and female parents of any seed produced carry desirable genes. Ratios of male and female plants can be manipulated at planting time and differential selection could be applied to them later. Presowing selection of male sterile lines should make the use of male sterile facilitated recurrent selection populations easier and more efficient as a breeding technique.
References:
Falk, D.E. and K.J. Kasha. 1980. A shrunken endosperm, male sterile
stock to facilitate crossing in barley. BGN 10:81-83.
Falk, D.E., K.J. Kasha and E. Reinbergs. 1981. Presowing selection of genetic male sterile plants to facilitate hybridization in barley. In Barley Genetics IV: 778-785. Proc. 4th Int. Barley Genet, Symp., Edinburgh, 1981.
Falk, D.E. and K.J. Kasha. 1982. Registration of a shrunken endosperm male sterile germplasm to facilitate hybridization in barley. Crop Science 22:450.
Suneson, C.A. and G.A. Wiebe. 1962. A "Paul Bunyan" plant breeding enterprise in barley. Crop Science 2:347-348.
