ANTHER MORPHOLOGY AND THE ORIGIN OF THE TETRAPLOID WHEATS

Anther morphology of various species of the genus Triticum is consistent with previous evidence that different biotypes of T. boeoticum (AA) and T. urartu (BB) contributed the respective A and B genomes to the emmer (A'A'B'B') and timopheevi (AtAtBtBt) tetraploid complexes. Anther length of T. dicoccoides (2.8 mm) and T. araraticum (3.0 mm) is mid-way between that of T. boeoticum (3.6) and T. urartu (2.2) and the same as that of the sterile hybrid T. boeoticum X T. urartu. With respect to mode of dehiscence, post anthesis reflexion of anther lobes and twisting of the anthers, T. ditoccoides resembles T. boeoticum, whereas T. araraticum resembles T. urartu. With respect to -anther apex, T. dicoccoides resembles neither T. boeoticum nor T. urartu but is identical with their F1 hybrid. Among amphiploids involving four different Aegilops species and T. boeoticum lines, none could similarly account for the length or other diagnostic attributes of the tetraploid anthers. Anther morphology is consistent with the presumed genomic composition of the cultivated tetraploid and hexaploid wheats and seems to distinguisheffectively the different genomic groups of the genus Triticum. THE ORIGIN of the two tetraploid wheat complexes emmer and timopheevi (Table 1) has been deliberated by evolutionists for the last four decades. Both complexes undoubtedly received their A genomes from Triticum boeoticum Boiss. (Sears, 1948). Aegilops speltoides Tausch has been assumed to be the donor of the B genome to the emmer group on evidence from the extrapolation of morphological characters (Sarkar and Stebbins, 1956) and from satellited chromosomes, chromosome pairing and geographic distribution (Riley, Unrau, and Chapman, 1958). However, the protein electrophoretic pattern (Johnson and Hall, 1966; and Johnson, 1972) did not support the hypothesis that Ae. speltoides or any other member of the Sitopsis section of Aegilops contributed the B genome. From chromosome pairing in hybrids, Kimber and Athwal (1972) also judged that Ae. speltoides did not contribute the B genome to the emmer wheat; but Shands and Kimber (1973) concluded that Ae. speltoides did contribute the second genome to T. timopheevi2 Zhuk. Johnson (1975) found that the presumed Transcaucasian endemic T. urartu Tum. was, in fact, sympatric with the wild tetraploid wheats throughout their range. On the basis of protein 1 Received for publication 14 March 1975. Part of a thesis submitted to University of California, Riverside by the senior author in partial fulfillment of the requirement for the Ph.D. degree. The authors are indebted to the National Geographic Society which sponsored a Near East expedition to study the origin and ancestry of the cultivated wheats. The technical assistance of Mr. David Barnhart is greatly appreciated. 2 Correctly spelled T. timophevii according to the International Code of Botanical Nomenclature, 1972. electrophoretic pattern, gene frequency and spikelet morphology he concluded that T. urartu was the donor of the B genome to both of the tetraploid complexes. Lilienfeld and Kihara (1934) reported differences in homology between the second genomes of the emmer and timopheevi complexes. Sachs (1953) and Wagenaar (1961, 1970) concluded that the reduced chromosome pairing between those genomes was due to chromosomal and genetic differentiation while Feldman (1966) attributed it entirely to chromosomal differentiation. Kostoff (1936), Sachs (1953) and Wagenaar (1966) suggested that the second genome of the timopheevi complex had differentiated from that of the emmer complex. In this study anther morphology is found to confirm the hypothesis that T. boeoticum contributed the A, and T. urartu the B genome to both the emmer (AeAeBeBe) and timopheevi (AtAtBtBt) tetraploid complexes as well as their hexaploid derivatives. The possible use of anther morphology in the taxonomy of the genus is discussed. MATERIALS AND METHODS-The materials for this study consisted of representatives of the wild species (Table 1) collected throughout their range of distribution in Turkey, Iraq, Iran, Lebanon, Israel, Greece and Transcaucasia. Cultivated types of the various complexes (Table 1) were also included. Amphiploids between T. boeoticum and Aegilops species, hybrids within the einkorn group, between einkorn and urartu and between einkorn or urartu and the timopheevi complex were also studied. Observations or measurements on the following anther characteristics were made