| Aegilops searsii1),
a new species from Israel and Jordan2) Moshe FELDMAN3) and Mordechai KISLEV Plant Genetics, Weizmann Institute of Science, Rehovot and Department of Life Sciences. Bar-Iran University, Ramat-Gan, Israel A new species of Aegilops named Ae. searsii FELDMAN et. KISLEV, from Judean Mountains and Samaria in Israel and Gilead, Ammon and Moav in Jordan, was recently described. The formal publication of this species as Ae. searsii and as Triticum searsii is at present in press (FELDMAN and KISLEV, in press). It belongs to section Sitopsis ZHUK. (Platystachys EIG). Ae. searsii is most closely related to Ae. longissima SCHWEINF. et MUSCH. Both have a 1-rowed ear which generally disarticulates only very close to its base, and its awns are restricted to the uppermost spikelet. Other common features such as very few fertile florets per spikelet and 2-toothed apex of glume of the lateral spikelets, characterized subsection Emarginata EIG, to which they belong together with Ae. sharonensis EIG and Ae. bicornis (FORSK.) JAUB. et Sp. Ae. searsii differs from its related species by various principal characters such as the proportionate length of glume and lemma and adaptation to a certain type of soil. A peculair character of Ae. searsii is the single, terminal, arched or diagonally oriented awn of the dispersal unit, and the + or - free kernel. Cytogenetic studies show that the F1 hybrid between Ae. searsii and Ae. longissima exhibits meiotic irregularities and is highly sterile (FELDMAN et al., submitted). Ae. searsii, like all other members of section Sitopsis, is a diploid with 2n=14. All the chromosomes are large, with median or submedian centromeres. Like all other species of this section, Ae. searsii contains two pairs of satellited chromosomes. However, while the related species of subsection Emarinata contains one pair of large and one pair of small satellites, the karyotype of Ae. searsii is characterized by one chromosome pair with large satellites and one pair with median-sized satellites. The karyotype of Ae. searsii differs from those of other Emarginata species also by the arm ratio of several chromosomes. Ae. searsii, which is endemic to the hills of both sides of the Jordan, has an unusual habitat as compared to that of other members of subsection Emarginata. While the other species grow on light and sandy soils in relatively dry climate, the habitat of Ae. searsii has typically terra rossa soil and sub-Mediterranean climate. Section Sitopsis contains the Aegilops species which are morphologically most similar to wild and cultivated wheats (ZHUKOVSKY 1928, EIG 1929). Species of both subsections were regarded as the putative donors of genome B of polyploid wheats, e.g., Ae. speltodies by SARKAR and STEBBINS (1956) and Riley et al. (1958), and Ae. bicornis by SEARS (1956). However, of all the Sitopsis species, Ae. searsii is the only one which is distributed sympatrically and forms mixed populations with the wild tetraploid wheat, Triticum dicoccodies KOERN, in Israel and Jordan. In southern Syria material described as Ae. longissima but may well be Ae. searsii, is distributed together with T. dicoccodies. This ecogeographical resemblance as well as several morphological and karyotypical similarities suggest that Ae. searsii (and/or Ae. longissima) is the likliest donor of genome B of polyploid wheats. Seeds of Ae. searsii can be obtained from the authors. Literature Cited EIG, A. 1929. Monographisch-kritische Ubersicht der Gattung Aegilops. Beih. Repert., Sepc. nov. Regni veg. 55: 1-228. FELDMAN, M. and M. KISLEV Aegilops searsii, a new species of section Sitopsis (Platystachys). Isr. J. Bot. (in press). FELDMAN, M., I. STRAUSS and A. VARDI Chromosome pairing and fertility of F1 hybrids between Aegilops searsii and Ae. longissima. (submitted to the Can. J. Genet. Cytol.). RILEY, R., J. UNRAU and V. CHAPMAN 1958. Evidence on the origin of the B genome of wheat. J. Hered. 49: 91-98. SARKAR, P. and G.L. STEBBINS 1956. Morphological evidence concerning the origin of the B genome in wheat. Amer. J. Bot. 43: 297-304. SEARS, E.R. 1956. The B genome of Triticum. Wheat Inf. Serv. 4: 8-10. ZHUKOVSKY, P.M. 1928. A critical-systematical survey of the species of the genus Aegilops L. Trudy prikl. Bot. Genet. Selek. (Russian with English summary) 18 (1): 417-609. (Received May 18, 1977) |
| 1) Named in honor of E.R. Sears from the University of Missouri, U.S.A.
2) Supported in part by a grant from the Stiftung Volkswagenwerk, Az. 112073. 3) The Marshall and Edith Korshak Professor of Plant Cytogenetics. |