SYNTHESIS OF COMPLETE INTERCHANGE STOCKS IN BARLEY (H. VULGARE L.)

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Abstract
Complete interchange stocks in barley (i.e. stocks which on crossing with a normal stock will produce a ring of 14 chromosomes at metaphase 1 in the F1) were synthesized successfully by each of 2 methods. Using irradiation, a homozygous interchange stock T2-3-5-7-6d was exposed to 10,000 r units of X-ray to induce further interchanges. Thirteen interchange stocks were produced of which one (designated as T1-2-3-5 -7-4-6a) was identified to be homozygous for a [THETA]14 chromosomes and 3 were identified as being homozygous for a [THETA]8 + [THETA]4 + 1 II[center dot] The 2nd method involved crossing complex interchange stocks that differed in their interchange patterns. From the cross of T(3-5-7) (l-2)a x T3-5-7-4-6a a stock homozygous for a [THETA]10 + [THETA]4 chromosomes was obtained. This was designated as T(3-4-7-4-6-) (l-2)a. From crosses between Tl-3-5-7-4-6a and each of T2-3-5-7-4-6a and T2-3-5-7-4-6c, two complete interchange stocks were produced. These were designated as Tl-3-5-7-4-6-2a and T1-3-5-7-4-6-2b. The 2 methods of obtaining the complete interchange stock were compared and were essentially equal on a predictable basis. The interchange heterozygotes with a [THETA]14 were sterile indicating that the "Oenothera" method for gametic selection would not be practical. The possibility of inducing diploidi-zation in autotetraploid barley by doubling the complete interchange heterozy-gote([THETA]14) was discussed.