BGN 2: Maintenance and efficient use of lethal seedling mutations in barley BARLEY GENETICS NEWSLETTER, VOL. 2, III. GENETIC AND CYTOLOGICAL TECHNIQUES
Tsuchiya, pp. 120-121

III.4. Maintenance and efficient use of lethal seedling mutations in barley*.

T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80521, U.S.A.

*This research was partly supported by NSF Research Grant GB30493 and Colorado State University Experiment Station Project (Hatch 8).

It has been a problem to maintain genetic stocks for lethal seedling mutations and to use them in genetic and linkage studies, unless the heterozygotes can be identified.

Ogawara and Hayashi (1964) reported the method of breaking dormancy or germinating prematured seeds before entering dormant stage.

The methods described by Ogawara and Hayashi (1964) have been applied to the maintenance and efficient use of lethal seedling mutations in genetic studies in barley with considerable success. This method is also used to speed up experiments by germinating F1 and F2 seeds in premature stages. This article describes the method used with some results obtained. More than 3000 seeds from 131 plants of 26 lethal chlorophyll mutant stocks, 418 crossed seeds (F1 combinations) and 2781 seeds of F2 generations from 57 cross combinations were used in these experiments. The materials were grown in the greenhouse in the winter of 1971-1972. The young seeds 26 to 40 days after pollination (as early as soft dough to as late as hard dough stages) were harvested, immediately dehusked, cut in half, placed on wet germination paper in germination boxes which were placed in a cold room (temperature 2° to 4° C) for 3 to 7 days. The seeds are taken from the cold room and placed in a room at ordinary temperature (20-23° C). Germination resulted in 3 to 4 days. In Table 1 is a summary of results.

Table 1. Germination percentage of immature seeds treated as mentioned in the text.

The results showed that the germination percentage was very high and was comparable to that for seeds stored for 2-3 months after harvesting at complete maturity.

This method is extremely useful for allelism testing of seedling mutations that are either lethal or viable such as white streak, yellow streak, glossy and chlorina.

This method of germinating immature seeds was also used in selecting heterozygous plants for intercrossing of lethal seedling mutants. Flowering date of the first spike was marked on a tag attached to the plant. About 26 to 35 days after pollination seeds were germinated by the above described procedure and tested for normal homo or mutant hetero condition. Normal homo plants were discarded and only the mutant hetero plants were used for crossing. In this way it has become possible to conduct trisomic analysis and allelism testing with lethal seedling mutants much easier than ever before.

For the maintenance of these stock, it has become possible also to handle the materials just like viable homozygotes: After finding the normal homo- and mutant hetero-plants all normal homozygotes are discarded, all heterozygotes are saved to grow to maturity. These heterozygotes are harvested and threshed in bulk similar to viable stocks.

This technique can be used not only for lethal chlorophyll mutations but also for other lethal seedling mutations such as minmin for minute.

References:

Ogawara, K. and J. Hayashi. 1964. Dormancy studies in Hordeum spontaneum seeds. Ber. Ohara Inst. Landw. Biol. 12:159-188.

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