II.40 Double trisomics in Betzes barley.
Benard Vering, Agronomy Department, University of Arizona, Tucson, Arizona 85721, U.S.A.
A large number of apparent triploids were found among selections made on the basis of partial sterility in commercial fields of Betzes (C.I. 6398) barley. Progenies of these apparent triploids were planted in the greenhouse and examined cytologically. Approximately 28% of these plants were double trisomics (5II + 2III). Various morphological characteristics of the double trisomics were measured and compared with primary trisomics found in the same progenies. Variations in seed set on the double trisomics were dependent upon which chromosomes were involved in the double trisomic and upon the environmental conditions in the greenhouse. A few double trisomics produced some heads with complete selfed seed set while other double trisomics were self sterile but set nearly 100% seed when pollinated with normal Betzes. Other double trisomics were both self and cross sterile.
The extra chromosomes involved in the double trisomics are being identified by observing the phenotypes of the primary trisomics in their progenies. Each of the seven chromosomes has been involved in at least one double trisomic. Chromosome 3 or 4 has been involved in almost all of the double trisomics classified to date. Also, chromosome 6 has been involved in many of the double trisomics. Double trisomics involving chromosomes 4 and 6 are the most vigorous of all the double trisomics observed so far. They have the leaf type of primary trisomic 4 and the head type of primary trisomic 6. Fragments and isochromosomes have been isolated in the progenies of double trisomics. Some of the plants with fragments appear normal in phenotype.
Double trisomics, the two derived primary trisomics and diploids found in the progenies of double trisomics are being measured, classified and compared for various morphological characteristics.