| Cytological and electrophoretic analysis of several
speltoid and compactoid mutants of Triticum aestivum PAPOGLOU Chr. and H. COUCOLI Department of Botany, University of Thessaloniki, Greece Speltoid and compactoid macromutants of common wheat, mostly radiation induced mutants, phenotypically similar in spike morphology with T. aestivun subsp. spelta and T. aestivum subsp. compactum respectively, have been the object of serious work as regards their cytogenetic origin (MAC KEY 1954, SEARS 1956, MURAMATSU 1963, SINGH 1968). The information so far available, accepts that the vulgare gene Q, located on the distal end of 5AL, a gene with speltoid suppressing effect, is chiefly responsible for the mutation rate in irradiated material. This gene is considered to function as hypermoprhic allele of the spelta gene q, modified by duplicates in homoeologous loci, and manifesting dose effect due to deficiency-duplication mechanism (KUCKCUK 1959, MURAMATSU 1963). Another gene, the awn inhibitor B1, been designated to locate also on chromosome arm 5AL, at a distance of 35 crossover units from Q locus, has also been known to affect spike morphology (SEARS 1944, 1975). The causal events which lead to speltoidy or compactoidy have been mostly defined as structural aberrations; however point mutations, though less frequently, can result in giving the same off-types (MAC KEY 1954). Present work aims at further elucidating the nature of Q-influenced or Q-associated mutations, by analysing several macromutans both by cytological and electrophoretic procedure. An alteration of enzymes, presumably caused by mutation, would result in differential electrophoretic mobilities of the molecules and provide additional means for designating the particular mutants. Seeds of two hexaploid wheat cultivars, G-58383 (fully bearded) and G-38290 (beardless), both produced in the Institute of Cereals of Thessaloniki, were irradiated by gamma-rays or thermal neutrons (SKORDA 1971). The progenies were screened on single plant basis, for speltoid and compactoid mutants. After M3 several mutant types, phenotypically stable and cytologically euploid, have been maintained. Seven speltoid and seven compactoid mutants, selected at the fifth generation, and in addition the two parental varieties, have been the subject of the present work (Fig. 1). The experimental design was chosen, because it offers a basis for comparative study of mutants which derived from the same parent, while it makes it possible to evaluate similar mutants of different varietal origin. Precisely, G-38290 has proved more susceptible in giving speltoids, whereas G-58333 has the tendency to produce compactoid mutants. All compactoids used in this study are derivatives of the same martyr G-58383 (m1). Each of them was distinct both in spike density (26-36) and stem height and characterised by phenotypic uniformity. The majority of speltoids (S1, S2, S5, S7, S8) have been also produced from m1. Among them, mutant S5 is unique in lacking awns, in contrast to the bearded parental type. Speltoids S3 and S4 Originated from G-38290 (m2). The first one is awnless like the parental variety. The second, a spontaneous mutant of G-38290, is distinct in bearing awns. |
| --> Next |