| Evidence on the origin of the G genome in wheat: Physiological
and quantitative character variation in a Triticum timopheevi-like
mutant By. U. KUSHNIR and G. M. HALLORAN school of Agriculture and Forestry, University of Melbourne, Parkville, Victoria 3052. There has been uncertainty on the question of the origin of the G genome of wheat (LELLY 1976). Certain workers have proposed a separate origin of the G genome of Triticum timopheevi from that of the B genome of wheat (LILLIENFELD & KIHARA 1934; KOSTOFF 1936, 1937). Because of close cytological affinity between T. timopheevi and T. araraticum chromosomes (SVETOZAROVA 1939) it has been proposed that T. timopheevi arose from T. araraticum (SEARS 1948; JAKUBZINER 1958). SHANDS & KIMBER (1973) proposed that Aegilops speltodies contributed the G genome of T. timopheevi and not the B genome of T. turgidum. However, SACHS (1953), WAGENAAR (1961) and TANAKA & ICHIKAWA (1972), using evidence of pairing between T. timopheevi and T. turgidum chromosomes, and ANIOL (1973) using evidence from serological tests and GERLACH et al. (1978) using satellite DNA hybridization, proposed a common monophyletic origin of the B and G genome. This view is in accord with the recent finding of a spontaneous T. timopheevi-like somatic mutat in T. turgidum dicoccoides, the chromosome pairing, karyomorphology and plant morphology of which has recently been described (KUSHNIR & HALLORAN 1983a, 1983b). The aim of the present study was to investigate changes to developmental physiology and certain quantitative characters of the mutant compared with its T. turgidum dicoccoides parent. Materials and Methods The T. turgidum dicoccoides line used in this study was part of a collection of this species made by one of us (U.K.) from wild habitats in Israel. Amongst 350 lines of this collection one plant of the variety spontananeum nigrum milhi (from Upper Galilee) developed four late tillers with T. timopheevi-like morphology, distinctly different from the other tillers on the dicoccoides mother plant. Seed from heads of the apparently mutated sector all gave timopheevi-like progeny, verifying the heritable nature of the somatic mutant. Sowings were made of the T. turgidum dicoccoides mother plant, the timopheevi-like mutant and three different lines of T. timopheevi. The timopheevi representatives were obtained from the Australian Wheat Collection, Tamworth, N.S.W. Two of them, lines 1 and 2 were T. timopheevi var. typicum Zhuk. and line 3 was T. timopheevi var. viticulosum. To quantify the influence of vernalization on rate of development and spikelet number two sets of the above plant material were vernalized, one for 30 days and the other for 60 days. |
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