SYNTHESIS OF HOMOZYGOUS INTERCHANGE STOCKS IN BARLEY (H.VULGAREL.) INVOLVING TWELVE CHROMOSOMES IN A SINGLE COMPLEX

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Abstract
In an attempt to synthesize an interchange stock in barley that involves all 14 chromosomes in a single complex, T3-5-7-4-6a, a stock homozygous for interchanges involving 10 chromosomes was exposed to 10,000 r units of X-rays to induce further interchanges. In all, 10 new interchange stocks were produced, in which 11 interchanges were involved. Five of the 10 stocks were homozygous for interchanges involving 12 chromosomes in a single complex. In 4 of these, chromosome 2 was added to the interchange complex. Diallel crosses between these 4 indicated that none of the interchange patterns were identical. The induced interchanges were analyzed to determine if differential radiosensitivity of chromosomes exists. Interchanges occur at randombetween the different chromosomes of barley. The interchange heterozygotes with aG12 + la and 814 MI configuration were almost completely sterile, indicating that the "Oeno-thera" method for gametic selection would not be practical. Possible reasons for unduly high s terility were discussed. The present procedure of selecting interchanges en the basis of partial sterility probably tends to discriminate against the development of more fertile interchange stocks.