Hereditas 86: 225-236 (197n Chromosomal polymorphism in isolated populations of Elymus (Agropyron) in the Aegean 111. Elymus diae WAHEEB K. HENEEN Institute of Genetics, University of Lund, Sweden HENEEN,W. K. 1977. Chromosomal polymorphism in isolated populations of Elymus (Agropyron) in the Aegean. 111. Elymus diae. - Hereditas 86: 225-236. Lund, Sweden. ISSN 0018-0661. Received April 27, 1977 Elymus diae is an octoploid (2n = 56) littoral species that grows in small isolated populations on the Aegean islands. A striking chromosomal polymorphism was found in twenty plants raised from seeds collected from four natural populations. All four populations had unique satellite and marker chro- mosome constitutions. Further chromosomal polymorphism was observed among plants originating from one of these populations. There were similarities in the appearance of the satellite chromosomes in E. diae, E. rechingeri and E. striatulus which denotes a close relationship between the three species. This is ascertained by a karyotype analysis of a polyhaploid individual of E. diae. The genome formula J4J4J141J~4,J5J5J6J6or J4J4J,41J141J~l,Jl,,J6J6was suggested for the species. Analysis of the satellite and marker chromosomes in 33 plants raised from seeds obtained in the greenhouse, following open pollination, inferred a predominance of self-fertilization or intrapopulation crosses. Aneuploids were found among plants raised from seeds collected in nature or obtained in the greenhouse. During meiosis, paired chromosomes usually appeared as bivalents and rarely as multivalents. Univalents occurred frequently which might be related to the prevailing chromosomal polymorphism. In the polyhaploid, most of the pollen mother cells had 4-7 bivalents which evidenced the presence of two closely related genomes. During the first pollen mitosis, chromosome numbers of 28 and 27 were observed in octoploid plants, whereas in the polyhaploid there were variable chromosome numbers. W. K. Heneen, Institute of Genetics, University of Lund, S-223 62 Lund, Sweden Efymus diue is a littoral species found by RUNEMARK Materials and methods in the Aegean area. The species belongs to the series Junceae established (within Elytrigia) by NEVSKI The somatic metaphase chromosomes of Elymus diue (1936). On morphological and cytological grounds it were studied in a total of 54 plants. Twenty of these is closely related to Elymus furctus (=Agropyron plants were raised from seeds collected by RUNEMARK junceum), E. striatulus and E. rechingeri (HENEEN from the Aegean islands. This material was from four 1962, 1977a; HENEENand RUNEMARK1962, 1972). small populations found on three different islands. The Aegean species E. striatulus, E. rechingeri and Collections from these populations were given dif- E. diae all grow in small isolated populations and the ferent numbers (R-oo00) by RUNEMARK.The localities latter two species show morphological diversity be- of these populations are as follows (Fig. 1): tween populations and uniformity of morphological R-3617: Crete, Dia, Glaronisi. characters within populations. R-3620 and R-3621: Dodecanisos, Karpathos, north- E. diae is octoploid and exhibits chromosomal poly- east of Kastello point. It cannot be excluded that morphism expressed mainly in the variable appear- these two small populations are part of a large popula- ance of the satellite chromosomes. Similar poly- tion. morphisms have been described for two other Aegean R-3673: Crete, Spinalonga, north-east point. species: the tetraploid E. rechingeri (HENEENand The other 34 individuals studied were raised from RUNEMARK1962; HENEEN1977a) and the diploid seeds obtained under greenhouse conditions from the E. striatulus (HENEENand RUNEMARK1972). above-mentioned 20 plants. Out of these 34 offspring The present study deals mainly with the cytology of plants, 33 resulted after open pollination and consti- E. diae. A taxonomic and morphological description tuted a sample of the first progeny obtained under of the species will be dealt with elsewhere (RUNEMARK, cultivation. One individual was offspring after isola- in preparation). tion. 226 W. K. HENEEN Hereditus 86 (1977) u3620 .## 3621 0 M 100 km Fig. 1, A map of the Aegean area showing the localities of the four populations from which seeds of Elymusdiue were collected. The method described by OSTERCRENand HENEEN (1962) was used for making Feulgen-squashes from 2. Chromosome morphology root-tips. For meiosis, spikes were fixed in Carnoy A. Chromosomal polymorphism within and between (alcohol, chloroform, acetic acid; 6:3 : 1) and pollen mother cells were stained according to the Feulgen populations method. Lacto phenol-acid fuchsin was used as a stain The chromosomes of E. diae are in a length range of for pollen. 3 to 8.5 pm and have mainly median or submedian centromeres (Fig. 2). Three pairs have secondary constrictions and are usually easy to identify. The morphology of these chromosomes, however, varied in the different populations studied. The different Results types of satellite chromosomes found are referred to by the letters A, B, D, E and F (Fig. 4). The designa- I. Chromosome number tions given to the satellite chromosomes of E. diae Elymus diae is an octoploid species with 2n = 56 (Fig. are in accordance with, and are a continuation of the 2). Two plants (R-3620) with 55 chromosomes were numbering given to the variant types found in E. among the 20 individuals raised from seeds collected rechingeri and E. striatulus (HENEENand RUNEMARK in nature. Deviating chromosome numbers were also 1962, 1972; HENEEN1977a). Types A, B and D corre- found in five individuals out of the 34 first progeny spond to, or have similarities with satellite chromo- plants analyzed. The deviating plants were four some types found in E. striatulus and E. rechingeri. aneuploids and one polyhaploid. Two of the aneu- Types E and F are new and, as will be pointed out ploids had the chromosome numbers 54 and 55, later on, probably represent variants of types A and B, whereas the other two had 57 chromosomes. The respectively. The letter C was not used to designate plant with 54 chromosomes was among the offspring any type of satellite chromosomes in E. diae since it of a mother plant with 55 chromosomes. The rest of has been adopted for a specific type that occurs in the deviating plants were offspring of euoctoploids. E. rechingeri. The polyhaploid plant had 28 chromosomes (Fig. 3). Other easily identifiable chromosomes in the com- Deviations in chromosome number thus occurred plement are those that seem to be telocentrics or have among plants raised from seeds, either collected in arm-index values markedly deviating from the rest of nature or obtained in the greenhouse. the chromosomes. Such chromosomes have terminal or subterminal centromeres and are here referred to as marker chromosomes (M). Different constitutions of satellite and marker chro- mosomes were found in the 20 individuals which were raised from seeds collected in nature. The frequencies of the different satellite chromosome constitutions are given in Table 1 and representative Herediias 86 (1977) CHROMOSOMAL POLYMORPHISM IN ELYMUS III 227 c Fig. 2. Representative metaphase chromosomes of E. dim;upper cell: population R-3620; lower cell: population R-3617. Satellite and marker chromosomes are indicated by arrows; upper cell: A,A2 A,A, BIB, MIMI; lower cell: AZA, EE(A1oAio) FF(B,B,) M,. See Fig. 4. Scale: 10 pm. 15 228 W. K. HENEEN Hereditas 86 (1977) b Fig. 3a and b. The chromosomes of the polyhaploid individual; a: metaphase spread; b: karyotype. Scale: 10 pm. cells are shown in Fig. 2. Below is a description of the two populations had only one such pair. One of the different kinds of satellite and marker chromosomes two pairs in population R-3673 was difficult to iden- found (Fig. 4). tify. The satellite in this pair was of a relatively smaller Type A.-This is a satellite chromosome with a small size and was often fused to the rest of the short arm. satellite on the short arm. Two pairs were found in This type will be designated A, whereas the most individuals belonging to two populations (R-3673 and usual type is AZ. R-3620), whereas the materials studied from the other Type B. - The secondary constriction in this satellite Fig. 4. Photographs and schematic drawings of the different constitutions of satellite and marker chromosomes found in the four populations of E. diae studied. The appearance ofchromosome type E is shown under different degrees ofcontraction. In highly contracted chromosomes the chromatin segments in the constriction region fuse with the proximal region. Chromosomes D, E and Fare most likely variant A and B types. The long arm of chromosome F would thus correspond to the short arm of chromosome B. Scale: 10 pm. Herediras 86 (1977) CHROMOSOMAL POLYMORPHISM IN ELYMUS III 229 ii A2 A2 Br ii II EE FF A2 A2 (AlO) (B,) I ii A2 A2 35 A2 A2 230 W. K. HENEEN Hereditas 86 (1977) Table 1. Satellite and marker chromosomes in four Some F a variant B (see below), the constitution populations of Elymus diae. Chromosome types D AAEEFF in population R-3617 would be equivalent and E might be variant types of A, also chromosome to AAAABB. This latter constitution was found in type F might be a variant of B two populations (R-3620 and R-3673) and might also be valid for population R-3621. Chromosome type E Population Satellite and marker chromosomes No. of might thus be a variant A, designated as Ale. plants Twe,. F. - This is an easily identifiable satellite chromosome type, being composed of three about R-3673 A2A2 A,A, BIB1 3 equal segments. The presence of a secondary constric- R-3620 A2A2 A2A2 BIB, 6* tion in about the middle of the long arm divides it into R-3621 A2A2 DD(A,A,) BIBl MlM, 5 R-3617 A2A2 E E (AlOAlo) F F (B7B7) 3 two parts each of which is similar to, or slightly R-3617 A,A, E(A,,) FF(B7B7) M, 2 smaller than the short arm.