SYNTHETIC HYBRIDS OF AGROPYRON ALBICANS X A. DASYSTACHYUM,SITANION HYSTRIX,AND ELYMUS CANADENSIS

Emasculated crosses of Agropyron albicans Scribn. & Smith with A. dasystachyum (Hook.) Scribn., Sitanion hystrix (Nutt.) J. G. Smith, and Elymus canadensis L. yielded 34, 5, and 9 viable hybrid seeds from 66, 45, and 52 florets, respectively. The hybrids were for the most part morphologically intermediate between their respective parents. The parents behaved cytologically as allotetraploids, 2n = 28; but meiosis in A. albicans was somewhat more irregular than in the other three species. Chromosome pairing was good in all hybrids and indicated that the genomes of the parent species were closely homologous, but only the A. albicans × A. dasystachyum hybrids set seed. Although closely related, A. albicans and A. dasystachyum are not fully conspecific. Agropyron albicans was considered to be a subspecies of A. dasystachyum, as were A. riparium Scribn. & Smith and A. griffithsii Scribn. & Smith ex Piper.     

GENOME RELATIONS AMONG ELYMUS CANADENSIS,ELYMUS TRITICOIDES,ELYMUS DASYSTACHYS,AND AGROPYRON SMITHII

Hand-emasculated Elymus canadensis pollinated by E. triticoides, E. dasystachys, and Agropyron smithii yielded 15, 21, and 1 viable hybrid seeds from 56, 52, and 52 florets, respectively. The 28-chromosome species—E. canadensis, E. triticoides, and E. dasystachys—behaved meiotically as allotetraploids and consistently formed 14 bivalents at metaphase I. Octoploid A. smithii, 2n = 56, averaged 0.41^I, 27.72^II, and 0.03^IV in 87 metaphase-I cells. Agropyron smithii is apparently an allooctoploid or a segmental autoallooctoploid. Meiosis was similar in the E. canadensis X E. triticoides and E. dasystachys hybrids. Chromosome pairing was very low in both hybrids, about two loosely connected open-ended bivalents per cell, and may not represent genuine homologies. The genomes of E. canadensis are distinctly different from those of E. triticoides and E. dasystachys. The E. canadensis X A. smithii hybrid averaged 13.37^I and 14.31^II in 76 metaphase-I cells. More than half of the bivalents were closed at both ends. Inability to distinguish between auto- and allosyndesis resulted in two interpretations of genome relations. Either A. smithii is an alloploid with two of its four genomes similar to those of E. canadensis, or it is a segmental autoalloploid genomically unrelated to E. canadensis. The first interpretation is favored. Agropyron dasystachyum, or one of its close relatives, and E. triticoides are suggested as possible parents of A. smithii.     

SYNTHETIC AGROPYRON-ELYMUS HYBRIDS. I. ELYMUS CANADENSIS × AGROPYRON SUBSECUNDUM

Twenty-four seeds were formed in 34 hand-emasculated E. canadensis florets exposed to A. subsecundum pollen. Fifteen of the 24 seeds germinated, and 12 plants were raised to maturity. Each of the 12 plants proved to be a hybrid. The hybrids were morphologically intermediate between the parents, although they favored A. subsecundum in general appearance. The parent plants were meiotically regular and behaved cytologically as strict allotetraploids, 2n = 28. Fourteen bivalents were formed in 12.6% of the hybrid cells interpreted at metaphase I. All other hybrid cells contained various combinations of univalents, bivalents, and multivalents. Mean chromosome associations of 0.22 univalents, 11.70 bivalents, 0.11 trivalente, 0.23 quadrivalents, 0.01 pentavalents, and 0.55 hexavalents were observed in 135 hybrid cells. All hybrid pollen examined was shriveled and non-staining. Five hybrids produced eight seeds, and seven hybrids were completely sterile. The ready cross-compatibility of E. canadensis and A. subsecundum and the relatively good chromosome pairing in their hybrids suggest a much closer relationship between the parent species than is implied by the prevailing taxonomic treatment. Structural rearrangements appear to be responsible for the relatively few differences between E. canadensis and A. subsecundum genomes and for the sterility of the hybrids. Cytological data from this and other investigations indicate a close relationship between many self-fertilizing Agropyron, Elymus, and Sitanion species. It is postulated that this composite of self-fertilizing Agropyron, Elymus, and Sitanion species originated by hybridization between A. spicatum and an unidentified Hordeum species.     

SYNTHETIC HYBRIDS OF HORDEUM BOGDANII WITH ELYMUS CANADENSIS AND SITANION HYSTRIX

Seven viable hybrid seeds were obtained from 48 hand-emasculated Elymus canadensis L., 2n = 28, florets pollinated by Hordeum bogdanii Wilensky, 2n = 14. The hybrids were large, vigorous, and completely sterile plants that bore a closer morphological resemblance to E. canadensis than to H. bogdanii. Chromosome associations in the 21-chromosome hybrids averaged 9.98^I, 5.40^II, and 0.08^III in 264 metaphase-I cells. Chromosome pairing was attributed to allosyndetic pairing between E. canadensis and H. bogdanii chromosomes. The H. bogdanii genome appears to be partially homologous with one of the two E. canadensis genomes. One Sitanion hystrix (Nutt.) J. G. Smith X H. bogdanii hybrid was obtained from a cross involving 37 emasculated S. hystrix florets. This triploid, 2n = 21, hybrid was morphologically intermediate between the parents and totally sterile. Averages of 9.09^I, 5.72^II, and 0.16^III were observed in 106 cells at metaphase I. A modified form of the H. bogdanii genome appears to occur in S. hystrix as well as in E. canadensis. Many allotetraploid Agropyron, Elymus, and Sitanion species apparently contain a genome derived from Hordeum.     

THE ORIGIN OF AGROPYRON SMITHII

The hypothesis that North American octoploid Agropyron smithii Rydb., 2n = 56, originated by hybridization between tetraploid Agropyron and Elymus species, followed by chromosome doubling, was tested by observing chromosome pairing in hybrids of A. smithii with an induced amphiploid, 2n = 56, derived from E. canadensis L., 2n = 28, X E. dasystachys Trin., 2n = 28, F₁'s. Chromosome pairing in A. smithii averaged 0.52^I, 27.70^II, 0.01^III, and 0.01^IV in 184 metaphase-I cells; and the amphiploid averaged 1.13^I and 27.44^II in 195 cells. Chromosome pairing in A. smithii X amphiploid hybrids averaged 8.20^I, 23.38^II, 0.34^III, and 0.05^IV in 101 metaphase-I cells. It was concluded that A. smithii was genomically similar to the E. canadensis-E. dasystachys amphiploid. The basic genome formula of the amphiploid is SSHHJJXX, with the SSHH genomes coming from E. canadensis and the JJXX genomes coming from E. dasystachys. Consideration of the morphological, ecological, and reproductive characteristics of all North American species that contain the basic SSHH and JJXX genomes led to the conclusion that A. dasystachyum (Hook.) Scribn., SSHH, and E. triticoides Buckl., JJXX, are the probable progenitors of A. smithii.     

SYNTHETIC AGROPYRON-ELYMUS HYBRIDS: III. ELYMUS CANADENSIS X AGROPYRON CANINUM,A. TRACHYCAULUM,AND A. STRIATUM

Hybrids were produced with relative ease from controlled crosses of Elymus canadensis L. with European Agropyron caninum (L.) Beauv., North American A. trachycaulum (Link) Malte ex H. F. Lewis, and Asian A. striatum Nees ex Steud. All hybrids appeared to be completely sterile and were, for the most part, morphologically intermediate between their parents. The E. canadensis × A. caninum hybrids were exceptionally vigorous and leafy and may have some potential as forage grasses if fertility can be achieved. All parent plants were tetraploid, 2n = 28, and they behaved cytologically as alloploids. Chromosome pairing in the hybrids indicated that both E. canadensis genomes were closely homologous with those of A. trachycaulum and somewhat less homologous with those of A. caninum. Interchanged and inverted chromosome segments apparently constitute the major differences between E. canadensis, A. trachycaulum, and A. caninum genomes; however, cryptic structural differences must also exist. Partial homologies were detected between one A. striatum and E. canadensis genome, but their other genomes were distinctly different. The genome relations between the parent species were expressed in terms of the following genome formulas: E. canadensis, S₁S₁X₁X₁; A. trachycaulum, S₂S₂X₂X₂; A. caninum, S₃S₃X₃X₃ : and A. striatum S₄S₄YY or X₄X₄YY, where “S” refers to a genome derived from A. spicatum and “X” and “Y” are genomes of unknown origin.     

The origin and meiotic behaviour of hexaploid northern wheatgrass (Agropyron dasystachyum)

The occurrence of hexaploid (2n = 6x = 42) forms in some otherwise natural tetraploid populations of Agropyron dasystachyum (2n = 4x = 28) was cytologically detected and studied. The hexaploid plants are morphologically similar to the tetraploids except for a small reduction in the anther size. The general survey of chromosome numbers of natural Northern Wheatgrass (A. dasystachyum 2n = 4x = 28) populations derived from eight different regions of Alberta indicated that the occurrence of hexaploid variants was not restricted to a single locality. A comparative study of chromosome pairing in the natural and the synthetic hexaploids revealed that the naturally occurring 42-chromosomed plants of A. dasystachyum originated as a result of fertilization between unreduced (SSHH) and the natural (SH) gametes, both coming from the tetraploid form of A. dasystachyum. Based on chromosome pairing, the genomes of the natural hexaploid A. dasystachyum have been designated as SSSHHH. The natural hexaploids appear to intercross among themselves and also with tetraploids producing euploid and aneuploid hybrids. The possible evolutionary significance of these findings is briefly discussed.     

THE ORIGIN OF AGROPYRON ALBICANS

Previous suggestions of introgression between Agropyron spicatum (Pursh) Scribn. & Smith, 2n = 14 & 28, and Agropyron dasystachyum (Hook.) Scribn., 2n = 28, were confirmed. Fertile, meiotically regular, 28-chromosome plants morphologically identical to Agropyron albicans Scribn. & Smith, 2n = 28, occurred in first- and second-generation open-pollination progenies of diploid A. spicatum × A. dasystachyum hybrids, presumably by backcrossing to A. dasystachyum. These A. albicans-like derivatives were fully cross-compatible with naturally occurring A. albicans. First and second generation open-pollination progeny of tetraploid A. spicatum × A. dasystachyum F₁'s contained approximately 5% A. albicans-like plants; but none was tetraploid, cytologically stable, and fertile. Although introgression occurs freely between tetraploid A. spicatum and A. dasystachyum, derivation of fertile true-breeding A. albicans from their early-generation progeny seems unlikely. Agropyron griffithsii Scribn. & Smith ex. Piper, the glabrous counterpart of A. albicans, probably originated from hybrids between diploid A. spicatum and Agropyron riparium Scribn. & Smith, the glabrous form of A. dasystachyum. Genome formulas of diploid A. spicatum, A. dasystachyum (riparium), and A. albicans (griffithsii) may be written as S₁S₁, S₂S₂XX, and S_1-2 S_1-2XX, respectively. The relationship between A. albicans and A. dasystachyum is so close that A. albicans should be regarded as no more than a subspecies of A. dasystachyum.     

Production and cytogenetic analysis of intergeneric hybrids betweenElymus anthosachnoides andPsathyrostachys huashanica (Poaceae: Triticeae)

Intergeneric hybridization betweenElymus anthosachnoides (2n = 28,SSYY) andPsathyrostachys huashanica (2n = 14,NN) was performed. Three hybrid plants, obtained via embryo rescue, were intermediate between the parents in morphology and developed vigorously, but were completely sterile. The mean chromosome configuration was 19.48 I + 0.76 II per cell in the hybrids at meiotic metaphase I. This result indicates thatE. anthosachnoides andP. huashanica are distantly related and that there is little or no homoeology betweenN (P. huashanica) andS orY (E. anthosachnoides) genomes.     

Intergeneric hybridization between<Emphasis Type="Italic"> Erucastrum cardaminoides</Emphasis> and two diploid crop<Emphasis Type="Italic"> Brassica</Emphasis> species

Two intergeneric hybrids involving wild species Erucastrum cardaminoides (2n=18, E^cd E^cd) and two crop brassica species, Brassica rapa (2n=20, AA) and B. nigra (2n=16, BB), were synthesized through in vitro sequential ovary culture. Morphological, molecular and cytological studies were conducted to establish their hybridity. Both hybrids, though morphologically distinct, were intermediate phenotypically between their respective parents. Cytological analysis of the E. cardaminoides × B. rapa hybrid (2n=19), revealed the occurrence of 17 I+1 II at diakinesis/metaphase in the majority (28%) of the pollen mother cells (PMCs), whereas in E. cardaminoides × B. nigra hybrid (2n=17), 13 I+2 II was the predominant (32%) meiotic configuration. A maximum of 5 II was recorded in both hybrids, indicating homoeologous pairing in the respective combined genomes. Chromosome doubling by colchicine application gave rise to two new amphiploids (AA E^cdE^cd and BB E^cdE^cd) having normal chromosome pairing and pollen fertility. The occasional occurrence of one quadrivalent in the amphiploids confirmed partial homoeology between the E^c and A/B genomes. The E. cardaminoides ×B. nigra hybrid and amphiploid appeared to be tolerant to alternaria blight under field conditions.Communicated by H.F. Linskens     

Cytogenetics of a Hordeum vulgare x Elymus patagonicus hybrid (n=4x=28)

Summary Hordeum vulgare L. (2n=2x=14) was hybridized with Elymus patagonicus Speg. (2n=6x=42). The hybrid had 28 chromosomes, genomically represented as HSH₁H₂, and was perennial with a codominant phenotype. The chromosomes were meiotically associated as 19.6 univalents + 0.004 ring bivalents + 2.6 rod bivalents + 0.8 trivalents + 0.14 quadrivalents in 1,129 meiocytes, with a chiasma frequency of 4.77 per cell. The bivalent pairing presumably is an autosyndetic but modified expression of the H₁H₂ genomes of E. patagonicus, since ring bivalents were rare. This does not preclude the association of the H. vulgare H genome chromosomes with either H₁ and/or H₂ genomes of E. patagonicus to form bivalent or multivalent associations. A further evaluation of the genome homologies of H. vulgare, H. bogdanii, E. canadensis and E. patagonicus is proposed.     

Meiotic configuration and chromosome number in some Iranian species of Elymus L. and Agropyron Gaertner (Poaceae: Triticeae)

Chromosome numbers and analyses of meiotic metaphase I are reported for the following taxa: Agropyron cristatum subsp. incanum (2n= 42), A. cristatum subsp. pecttnatum (2n=28 – 33), Elymus elongatus subsp. ponticus (2n= 69, 70), E. hispidus var. hispidus (2n= 41 43), var. podperae (2n= 42) and var. villosus (2n= 41, 42), E. libanoticus (2n= 14), E. pertenuis (2n= 28, 28+1B), E. repens (2n= 42), E. transhyrcanus (2n= 40–42), E. hispidus var. villosus x E. cf. repens (2n= 42). Chromosome numbers only are reported for the following taxa: E. gentri (2n= 41, 42), E. nodosus subsp. dorudicus (2n= 28), and E. elongatiformis (2n= 56, 57). The haploid genomic constitution SP is reported for Elymus pertenuis. Variable chromosome numbers (2n= 28–32) were observed in the meiotic metaphase I within single anthers of Agropyron cristatum subsp. pectinatum, and the supernumerary chromosomes in this taxon are assumed to have originated from crosses with hexaploids. Partial elimination of these supernumerary chromosomes probably occurs during archesporial mitotic divisions or at an early stage in the meiotic cycle. A hybrid, morphologically intermediate between E. hispidus and E. repens, was obtained from a seed of E. hispidus collected in the field. The meiotic metaphase I configuration in this E. hispidus hybrid suggests that the pollen parent may itself be a hybrid or hybrid derivative of E. repens x E. hispidus.     

CYTOGENETICS OF AGROPYRON FERGANENSE AND ITS HYBRIDS WITH SIX SPECIES OF AGROPYRON,ELYMUS, AND SITANION

Meiosis and mode of reproduction are described in Agropyron ferganense Drob., a perennial forage grass from Central Asia. This species is diploid (2n = 14); it exhibits normal meiosis and reproduces by cross-pollination. Hybrids were produced between A. ferganense and six species with known genome formulas: 1) North American A. spicatum (Pursh) Scribn. & Smith, an SS diploid (2n = 14), 2) Middle Eastern A. libanoticum Hack., an SS diploid (2n = 14), 3) North American A. dasystachyum (Hook.) Scribn., an SSHH tetraploid (2n = 28), 4) Eurasian A. caninum (L.) Beauv., an SSHH tetraploid (2n = 28), 5) North American Sitation hystrix (Nutt.) J. G. Smith, an SSHH tetraploid (2n = 28), and 6) South American Elymus patagonicus Speg., an SSHHHH hexaploid (2n = 42). Almost complete chromosome pairing in the A. ferganense x A. spicatum and A. libanoticum hybrids demonstrated that A. fergenanse is an SS diploid, but it is genetically isolated from the other SS diploids because of high sterility in the F₁ hybrids. S-genome diploids form a network of species that extend from the Middle East through Central Asia to western North America. Frequent occurrence of seven univalents and seven bivalents at metaphase I in the triploid hybrids of A. ferganense x A. dasystachyum, A. caninum and S. hystrix was consistent with the proposed genome formulas of SS for A. ferganense, SSHH for the three tetraploid species, and SSH for the hybrids. Chromosome pairing was highly variable in the A. ferganense x E. patagonicus hybrids; however, some cells had almost complete bivalent pairing, an expected observation in an SSHH hybrid from a cross between an SS diploid (A. ferganense) and an SSHHHH hexaploid (E. patagonicus). Various options were considered concerning the appropriate generic classification of the S-genome diploids, which are now commonly placed in Agropyron. The inclusion of these species in the genus Eiytrigia, as advocated by some Soviet taxonomists, appears to be a reasonable decision.     

SYNTHETIC HYBRIDS OF NEW WORLD AND OLD WORLD AGROPYRONS. IV. TETRAPLOID AGROPYRON SPICATUM F. INERME X TETRAPLOID AGROPYRON DESERTORUM

Emasculated and unemasculated crosses of tetraploid A. spicatum f. inerme X A. desertorum yielded four hybrids. The hybrids were morphologically intermediate between the parent species but resembled A. desertorum more closely than A. spicatum. Both parents behaved cytologically as autoploids. Mean chromosome associations of 0.04 I, 8.60 II, 0.01 III, and 2.67 IV were observed at diakinesis in the 28-chromosome A. spicatum. The A. desertorum parent contained 30 chromosomes, 2 of which were likely supernumeraries, and averaged 0.03 I, 9.85 II, and 2.57 IV at diakinesis. Three hybrids contained 30 chromosomes, and one had 29. The most common chromosome association in the 30-chromosome hybrids was 2 I and 14 II; and the average was 3.00 I, 13.40 II, 0.06 III, and 0.01 IV. A. spicatum and A. desertorum chromosomes were usually distinguishable from each other in the hybrid cell on the basis of size. All pairing in the hybrids was attributed to autosyndesis within parental genomes. A. spicatum, A. desertorum, and their hybrids were represented by genome formulas of SSSS, CCCC, and SSCC, respectively. The hybrids produced 5 to 439 seeds under open pollination. Three controlled crosses between the hybrids yielded 2, 5, and 23 seeds, respectively, on 10 maternal spikes in each cross. The prospects of developing a fertile, cytologically stable allotetraploid species from the hybrids appear favorable.     

GENOME ANALYSIS OF AGROPYRON REPENS × AGROPYRON CRISTATUM SYNTHETIC HYBRIDS

Hexaploid A. repens, 2n = 42, and diploid A. cristatum, 2n = 14, were hybridized and gave rise to two 28-chromosome reciprocal hybrids. Approximately 1% of hand-emasculated florets of both parent species produced viable hybrid seed following controlled pollination. Early embryo abortion prevented greater hybrid seed set on A. repens, whereas failure of fertilization appeared to be the major cause of poor hybrid seed set on A. cristatum. Reciprocal differences in hybrid vegetative and spike morphology were striking. The A. repens × A. cristatum hybrid was vigorous, highly rhizomatous, and bore abundant spikes whose morphology was intermediate between that of the parent species. A. cristatum × A. repens hybrids were weak, non-rhizomatous with frequently-malformed spikes. Mean chromosome associations of 0.10 I, 20.10 II, and 0.43 IV were observed in 134 metaphase-I cells of A. repens. Subsequent meiotic stages were regular except for occasional laggards and bridges at anaphase I and II. Metaphase-I chromosome associations averaged 0.07 I and 6.97 II in 124 A. cristatum cells. Chromosome pairing in the hybrids was highly variable and averaged 11.45 I, 7.58 II, 0.44 III, and 0.02 IV per cell in 187 cells interpreted. From 5 to 14 laggards appeared in every hybrid cell at anaphase I. Bridges were observed in approximately 25% of the anaphase-I cells. Similar irregularities were observed at anaphase II. Pollen viability was estimated as 3%, and the hybrids failed to set viable seed. On the basis of chromosome pairing in the species itself and in the hybrids, A. repens was designated as a segmental autoallohexaploid with a genome formula of the type A₁A₁A₂A₂BB. Although A. repens and A. cristatum chromosomes paired occasionally, the genomes of the 2 species were essentially non-homologous. Some of the interpretational difficulties of genome analysis were discussed.     

HYBRIDIZATION AND INTROGRESSION IN THE GRASS GENUS ELYMUS

Brown , W. V., and G. A. Pratt . (U. Texas, Austin.) Hybridization and introgression in the grass genus Elymus. Amer. Jour. Bot. 47 (8) : 669–676. Illus. 1960.—The production of artificial F₁ hybrids that produce some seed between E. virginicus and E. canadensis, E. virginicus and E. interruptus, and E. canadensis and E. interruptus proves that similar plants found in nature are true hybrids. The artificial hybrids constituted the basis of comparison in an analysis of natural local populations in the Austin region. Analysis by scatter diagrams indicates that there is introgression of genes of some species into the genomes of others through the development of hybrid swarms. In the area studied the great variability of virginicus is due to the introgression of canadensis and, possibly, interruptus genes. Such hybridization and subsequent introgression have occurred many times and in many places and are still taking place. It is likely that the named varieties of canadensis and virginicus may be introgressant types that are the results of hybridizations between those species and others that occur sympatrically in Eastern United States.     

MORPHOLOGY AND CYTOLOGY OF SYNTHETIC HYBRIDS OF AGROPYRON TRICHOPHORUM X AGROPYRON CRISTATUM

Dewey, Douglas R. (Utah State U., Logan.) Morphology and (cytology of synthetic hybrids of Agropyron trichophorum X Agropyron cristatum. Amer. Jour. Bot. 50(10): 1028–1034. Illus 1963.—Three hybrids were obtained from controlled crosses of pubescent wheatgrass, A. trichophorum (2n = 42), and hexaploid crested wheatgrass, A. cristatum (211 = 42). The hybrids were intermediate between the parent plants for all vegetative and spike characteristics observed. Under open pollination, 2 of the hybrids set 2 seeds each, and the other hybrid produced 60 seeds. Meiosis in the parent plants was basically regular. Average motaphase-I chromosome associations were 0.09 I, 20.56 II, 0.05 III, and 0.16 IV per cell in the A. trichophorum parent, which was described as a segmental autoallohexaploid. The hexaploid A. cristatum parent averaged 0.18 I, 7.44 II, 0.81 III, 2.86 IV, 0.08 V, and 2.11 VI per cell at diakinesis and was described as an autohexaploid. Chromosome pairing in the hexaploid hybrid averaged 5.08 I, 8.94 II, 4.33 III, 1.11 IV, 0.27 V, and 0.05 VI per cell. On the basis of chromosome pairing in the parent species and their hybrids, it was concluded that 1 of the A. trichophorum genomes was partially homologous with the 3 genomes of hexaploid A. cristatum. Genome formulae for hexaploid A. cristatum, A. trichophorum, and their hybrids were represented as AAAAAA, A₁A₁B₁B₁B₂B₂, and AAAA₁B₁B₂ respectively.     

Karyotype analysis in Stylidium crossocephalum (Angiospermae:Stylidiaceae)

Qualitative studies of karyotypes were carried out on 79 plants of Stylidium crossocephalum from 28 collection sites. The sample included 7 distinct karyotypic classes which could be resolved into 5 clearly distinguishable haploid karyotypes or genomes. Three genomes, J, K and L, were localised in an area covering a southern portion of the species range while the other two genomes, A and B, were found in a region 90km to the north. Two different genome heterozygotes were found, one characterised by a J/K karyotype, the other by an A/B karyotype. —Karyotypic studies of a synthetic hybrid and its two parents showed that the chromosomes of the constituent genomes of the hybrid could be readily and confidently discerned in the karyotypes of the parents. These studies demonstrated that the identification of genomes by the qualitative attributes of their constituent chromosomes constitutes a reliable analytical technique. — Statistical analyses using arm ratio and percentage length measurements of chromosomes from plants allocated to the two groups of genomes confirmed the differences between marker chromosomes and demonstrated additional statistically significant differences among the non marker chromosomes. Some of these statistical differences may be attributable to technical problems inherent in the karyotyping procedures. In two instances, however, they could be convincingly argued as real, demonstrating a further component of chromosome variation in S. crossocephalum.     

超甜玉米种子萌发物质利用性状杂种优势及亲子回归关系分析

为阐明超甜玉米(Zea mays L.var.saccharata Bailey)亲本对F_1种子物质利用性状遗传效应,研究了19份自交系和其测配的10个杂交组合的杂种优势及亲子回归关系。结果表明,超甜玉米自交系及F_1种子的淀粉含量、蛋白质含量、脂肪含量、百粒重、种子物质动用量和种子物质利用率差异较大,10个杂交组合中亲本和F_1种子的淀粉含量、脂肪含量、百粒重均存在显著差异。F_1种子淀粉含量和百粒重均表现出正向超亲优势,即近高亲本遗传;而F_1种子的蛋白质含量、脂肪含量、种子物质动用量和种子物质利用率为近低亲本遗传。聚类分析和杂种优势分析表明,性状差异较大的FH14、Q26、GT22、GT2等亲本测配的杂交组合在种子百粒重或种子物质利用率等性状上具有较强的超亲优势。回归分析表明,母本对F_1种子的淀粉含量、百粒重有负效应,对种子物质动用量和种子物质利用率有正效应;父本对种子淀粉含量有负效应,对种子物质利用率有正效应。     

RAPD-Based Analysis of Introgression of Barley Genetic Material into the Genome of Alloplasmic Wheat Lines (Hordeum geniculatumAll./Triticum aestivum L.)

Genomes of three alloplasmic wheat lines obtained on the basis of barley–wheat hybrid Hordeum geniculatumAll. (2n = 28) ×Triticum aestivumL. (2n = 42)(Pyrotrix 28) were examined using random amplified polymorphic DNA (RAPD) analysis. Line L-29 was obtained after first backcross of the initial hybrid with the wheat variety Pyrotrix 28 and ten subsequent self-pollinating generations. This line was represented by euploid plants with typical to the common wheat chromosome number (2n = 42), as well as by aneuploids, which contained an additional telocentric chromosome in the main karyotype (2n = 42 + t). Lines L-26 and L-27 were obtained by two backcrosses of one BC₁ plant with the wheat variety Novosibirskaya 67 and one subsequent self-polination of one BC₃ plant. Chromosome number in all these plants corresponded to 2n = 40 + 4t. RAPD analysis was carried out using seven primers, which were previously proved to be effective for identification of the barley genome fragments within hybrid genomes of alloplasmic lines. The presence of barley genome fragments in line L-29 was revealed by use of five primers, while in lines L-26 and L-27 these fragments were detected by use of one primer. The significant difference in the number of barley RAPD fragments in the genomes of alloplasmic lines obtained at different backcrossing stages suggests more intense displacement of barley genome during backcrossing compared to self-pollination in BC₁ plants.