Genetically controlled chromosome numerical mosaicism in pearl millet

Abstract

In the selfed progeny of a diploid plant ofPennisetum typhoides (Burm) S and H, which was a translocation heterozygote and with chromosome number 2n=13+2 telocentrics, one triploid plant was obtained. In the open pollinated progeny of this triploid, one plant with chromosome numerical mosaicism, chromosome number varying from 2n=28 to 37 of which 23 to 33 normal chromosomes and 3 to 7 telocentrics, was obtained. In PMC meiosis higher associations of 5, 6, 7 or 8 normal chromosomes were observed. This plant was highly sterile. Of the five progeny plants that could be obtained on selfing and open pollination 4 plants showed chromosome numerical mosaicism and one plant had a constant chromosome number of 2n=26+4 telos. As this phenomenon of intraplant chromosome numerical variation can be transmitted from generation to generation it was considered to be genotypically controlled. It was further argued that gene combinations are responsible for the instability and not always associated with higher gene dosage and hence higher polyploidy as suggested by Gildenhuys and Brix in induced amphiploids of Pennisetum. The same factor that was responsible for the chromosome numerical mosaicism seemed to be responsible for the origin of the tetraploid from the triploid.