II.23 Desynaptic genes in Betzes barley.
R. T. Ramage* and Juan Hernandez-Soriano. Agronomy Department, University of Arizona, Tucson, Arizona 85721, U.S.A. (*Research Geneticist, Plant Science Division, ARS, USDA).
Ten desynaptic lines were found in a collection of partially sterile plants selected from commercial fields of Betzes (C.I. 6398) barley. The desynapsis is controlled by a single recessive gene in all of the ten lines. These desynaptic lines may represent undescribed (new) genes or reoccurrences of the two described genes (lc by Burnham and ds by Enns and Larter).
Incomplete allele tests among eight of the Betzes desynaptics indicate that at least five different loci are involved. None of the Betzes desynaptics have been tested against lc or ds. Crosses are being made to complete the allele tests among the Betzes desynaptics and to test them against lc and ds.
A high frequency of aneuploids is found in the progenies of the desynaptic lines. Of 70 plants examined cytologically for use as parents in allele tests, 10 were aneuploids and of 190 plants from intercrosses among the desynaptics grown for allele tests, 39 were aneuploids. All seven of the primary trisomics in Betzes are identifiable morphologically. We plan to use the trisomics found in the progenies of the desynaptic lines to determine which chromosome carries each desynaptic gene.
To obtain trisomic F1 plants, two methods will be employed: (1) Trisomic plants will be isolated from selfed progenies of each desynaptic line. The trisomics will be pollinated with normal Ds pollen. The F1's will be grown and trisomic F1 plants will be selected. (2) Diploid desynaptic plants will be pollinated with normal Ds pollen. The F1's will be grown and trisomic F1 plants will be selected. The second method may be more practical as desynaptic plants set only about 20 to 25 percent selfed seed and set about 40 to 60 percent crossed seed when pollinated with normal pollen.
F1 trisomics obtained by both methods will be classified morphologically as to which chromosome is extra. They will be either Ds ds, if the locus is not carried on the trisome, or Ds ds ds if the locus is carried on the trisome. If the locus is not carried on the trisome, a diploid F2 ratio for desynapsis is expected. If the locus is carried on the trisome, a trisomic F2 ratio for desynapsis is expected. By this method, it will be possible to assign the various desynaptic genes to the chromosomes upon which they are carried.