| I. Research Notes Chromosome numbers of supernumerary spikelet lines of bread wheat (Triticum aestivum L.) G.P. KADKOL and G.M. HALLORAN Brumley Plant and Soil Sciences Centre, University Field Station, Mt. Derrimut School of Agriculture and Forestry, The University of Melbourne DEER PARK, Victoria, Australia, 3023 The term supernumerary spikelets includes the occurrence of both extra spikelets on the rachis as well as extra spikelets on an extended rachilla (branched ear) in a wheat ear (PENNELL & HALLORAN 1984) and the degree of expression of this character is considerably influenced by environment (SWAMlNATHAN et al. 1966, PENNELL & HALLORAN 1984). SINGH and JOSHI (1983) reported that plants with branched ears arising from a wheat-rye cross were trisomics with 43 chromosomes. This condition appeared to be the basis of continued segregation in advanced generations for ear branching in their lines. SINGH and JOSHI (1983) have hypothesized that the super-numerary spikelet character is due to increased dosage of the genes controlling ear morphology brought about by tri- and tetrasomy in their lines. In contrast, KORIC (1973, 1978) and PENNELL and HALLORAN (1983) reported the presence of two and one to two genes, respectively, controlling this character. SWAMINATHAN et al. (1966) reported that the branchedear character in a mutant of cv. N.P. 797 was due to a chromosomal deletion. In view of these conflicting reports on the genetic basis of the supernumerary spikelet character it was decided to study the chromosome numbers of six supernumerary spikelet lines of hexaploid wheat which were used in studies by PENNELL (1983) and PENNELL and HALLORAN (1983, 1984). Materials and Methods Seeds of the six supernumerary spikelet lines of bread wheat (AUS15910, AUS15915, AUS15916, AUS15157, AUS17335, AUS17336, see Table 1 for origin and pedigree) obtained from the Australian Winter Cereals Collection, Tamworth, N.S.W., were germinated on moist filter paper in petri dishes. Root tips were collected from each seedling whose identity was maintained. The seedlings were grown in a glasshouse under normal daylength during the spring of 1985 using 15cm diameter pots cantaining a potting mix. The root tips collected as above were treated with 10-3 M colchicine for four hours after which they were incubated in 1% acetocarmine for 48 hrs at room temperature. The root tips were squashed in 1% acetocarmine. |
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