Inheritance of Stolon Development, Rhizome Development and Setigerous Lemmas in the Digitaria milanjiana Complex, and Its Taxonomic Significance

Abstract

Hybrids were made between nine diploid accessions of Digitaria milanjiana. These included accessions previously included in Digitaria milanjiana subsp. eylesiana, D. swynnertonri, D. sp. aff. mombasana, D. natalensis subsp. stentiana and D. endlichii. All accessions had scabemlous lemmas but they differed in growth habit (tufted, rhizomatous or stoloniferous) and in presence or absence of setae on the sterile lemma. There was a high order of cross compatibility among accessions and chromosome pairing at meiosis was almost complete. The occurrence of 2-4 univalents in hybrids having CPI 59765 or CPI 59727 as one parent suggested some chromosomal divergence within the species. Genetic imbalance occurred in many F1 and F2 progenies. Lemma setigerousness is a recessive character and is possibly controlled by a single gene. Divergence from expected genetic ratios could have been due to linkage of the gene controlling setigerousness to genes associated with genetic imbalance. Rhizome development is controlled by incompletely recessive genes. Stolon development is under polygenic additive gene control, with little evidence for dominance. There was some evidence for different genetic control of stolon development in different stoloniferous accessions. It is concluded that this group of accessions is closely related and in the early stages of genetic divergence. Although the accessions exhibit considerable differences in morphology, this study supports the view that they are biologically a single species and that growth habit and lemma setigerousness are not taxonomically significant characters within the group.