Diploid and tetraploid populations of Turnera ulmifolia are distylous and exhibit a strong self-incompatibility system. Distyly is governed by a single locus with two alleles. Several self-compatible variants were, however, obtained and the nature and genetic control of self-compatibility was assessed using controlled crosses. The study documented the occurrence of self-compatible variants in four contrasting situations. These included the following. (i) Self-compatibility in a diploid short-styled variant. The gene(s) governing self-compatibility interact with the distyly locus and are expressed only in short-styled plants. When tetraploids carrying the genes were synthesized, self-incompatibility reappeared. (ii) Self-compatibility occurred in a cross between geographically separate diploid populations. Self-compatibility appeared sporadically in the F1. Crosses revealed that self-compatibility is likely under polygenic control. (iii) Low levels of self-compatibility occurred in a tetraploid population. Crosses revealed that self-compatibility was under polygenic control. A small response to selection for increased self-compatibility was observed, (iv) Hexaploids were synthesized from crosses between distylous diploids and tetraploids. All hexaploids obtained were long- or short-styled indicating that hexaploidy per se does not cause homostyly. A single long-styled plant showed aberrant pollen behaviour, resulting in a moderate degree of self-compatibility. All of the variants studied exhibited either aberrant pollen or stylar incompatibility responses. In no instance was the genetic control of self-compatibility solely the result of segregation at the distyly locus.Key words: Turnera, dimorphic incompatibility, polyploidy, self-compatibility, distyly.
One of 18 Chorthippus vagans males from a natural population was heterozygous for an interchange between the L1 and M4 chromosomes when examined cytologically. Chiasma distribution within multiple chromosome configurations and the relation between chiasma formation in the interstitial segments and centromere orientation were investigated. Our results confirm previous observations that adjacent-2 is the most common orientation in absence of chiasmata on the interstitial segments.Key words: Chorthippus, interchange, interstitial segments, chiasma distribution, orientation.
The genotype at the Q locus on chromosome 5A of Triticum durum Desf. (2n = 28, AABB), a species with keeled glumes and tough rachis, was studied by either crossing the species with, or substituting its 5A into, a hexaploid common wheat, T. aestivum (L.)Thell. ssp. vulgare (Vill.) MK. cv. Chinese Spring (2n = 42, AABBDD, QQ genotype). Contrary to the opinion of previous researchers that keeled-glumed wheats always have the spelta gene, q, the durum strains studied had a hypermorphic allele, the vulgare gene, Q. No speltoid plants appeared in the progeny of the crosses, and disomic substitution lines (2n = 2) had squareheaded (= vulgare type) spikes. Also, three doses of the long arm of 5A of durum produced compactoidy. Apparently, Q does not produce round glumes in the genetic backgrounds of most tetraploids except T. carthlicum Nevski. The phenotype conditioned by Q, which is evidently present in all free-threshing tetraploid wheats, is somewhat different at the tetraploid level from that in hexaploids. The presence of Q tends to magnify the differences in the degree of expression of certain minor characters.Key words: Triticum, phylogeny, vulgare gene, pleiotropic gene, dosage effect, interaction.
The presence of inversions is important in the evolution and cultivar differentiation of wheats, Even though we can't have conclusive cytological proof of the presence of inversions in wheat, we can use the indirect way of screening paracentric inversions through chromosome configuration at anaphase I and II. This work presents the comparison of 'Chinese Spring' structure (with respect to the presence of inverted segments) to (i) 52 homozygous wheat lines obtained in the progenies of the cross between a wheat × Agropyron intermedium substitution line and Aegilops speltoides homoeologous pairing promotor and (ii) three wheat cultivars ('Vilmorin 27', 'Ducat', and 'Tormes') that were used in developing the above mentioned lines. The three cultivars present inverted segments relative to 'Chinese Spring' structure. Some of these inverted segments are possibly maintained in some of the lines studied. Four of them show the primitive structure of 'Chinese Spring' even though none of the wheat parents had it. Finally, other lines show new structure that could have been due to the Aegilops speltoides effect, but the method used did not allow us to reach a definite conclusion on this point. It is interesting to emphasize that the use of this homoeologous pairing promotor led to a chromosomal structure that was not so different from that existing in wheats.Key words: pairing (homoeologous), hybridization (interspecific), gene transfer, Triticum, Agropyron, Aegilops.
Auxotrophic complementation was achieved by protoplast fusion between two auxotrophic cell lines of Datura innoxia P. Mill. that required either pantothenate or adenine for their growth. Protoplast fusion was induced by polyethylene glycol enriched with calcium chloride at pH 6.8. Initial culture of fusion products in nonselective conditions increased the total number of somatic hybrids finally recovered under selective conditions. In addition to the prototrophy, the somatic hybrids regained the ability to turn green and some the ability to regenerate shoots on a cytokinin-supplemented medium. Both the parental cell lines grew as pale white callus without showing any sign of organogenesis, irrespective of the type and concentration of the cytokinin used. Approximately all the parental chromosomes (176 ± 8) were retained by the hybrid cell lines.Key words: protoplast, complementation, Datura.
Meiotic chromosomes of a cockroach field strain that is highly resistant to several insecticides were compared with those of a susceptible field strain. The resistant strain was characterized by extensive autosome–autosome associations. They resulted in fragmentation, deletions, and insertion or attachment of segments in novel positions. The distribution pattern of chiasma frequency was also aberrant. One individual was heterozygous for an interchange between chromosomes 6 and 12. Properties of the susceptible strain were generally similar to those described earlier from a laboratory susceptible strain, except that a terminal knob on chromosome 4 was frequently present.Key words: Blattella, cockroach, chromosome, resistance.
Elymus alatavicus (Drob.) A. Love and E. batalinii (Krasn.) A. Love were studied to determine (i) meiotic behaviour, (ii) the mode of reproduction, (iii) the relationship between the two species, (iv) genomic constitutions, and (v) the most logical taxonomic classification of both species. A series of F1 hybrids between E. alatavicus, E. batalinii, and six "analyzer" species were developed. Chromosome pairing was studied at metaphase I to identify genomic similarities or differences. The results showed that E. alatavicus and E. batalinii are caespitose, self-fertile allohexaploids (2n = 42) with the same genomic formula SSYYXX. The F1 hybrids between E. alatavicus and E. batalinii had complete pairing (21 bivalents) at metaphase I in 7% of the cells and almost complete pairing in the remaining cells. High chromosome pairing and partial fertility (4 seeds/plant) in the F1 hybrids shows that the two species are closely related. Hybrids were obtained between E. alatavicus or E. batalinii and the following "analyzer" species with known genomic formulas: Pseudoroegneria spicata (Pursh) A. Love, 2n = 14, SS; P. cognata (Hack.) A. Love, 2n = 14, SS; E. lanceolatus (Scribn. &Smith) Gould, 2n = 28, SSHH; E. trachycaulus1 (Link) Gould ex Shinners, 2n = 28, SSHH; E. mutabilis (Drob.) Tzvelev, 2n = 28, SSHH; and E. drobovii (Nevski) Tzvelev, 2n = 42, SSHHYY. Chromosome pairing in this series of hybrids demonstrated that E. alatavicus and E. batalinii contain an S and probably a Y genome plus an unknown genome, X, that may have been derived from Psathryostachys huashanica Keng or from Agropyron. Elymus alatavicus and E. batalinii are correctly classified in the genus Elymus.Key words: cytotaxonomy, Agropyron, meiosis, chromosome.
Mature triploid seed from reciprocal (2n = 4x × 2n = 2x) crosses in Triticum monococcum was minute and shrivelled because of endosperm collapse and therefore failed to germinate. This necessitated the excision of embryos from successful pollinations and their growth in vitro to ensure subsequent germination so as to obtain viable and vigorous autotriploids. A comparison of these triploids with their diploid and tetraploid progenitors revealed that cell size, kernel weight, and pistil size increased with an increase in ploidy level. However, unlike other species, optimum expression was observed in these triploids for plant height, tillering, size of spikes, number of spikelets/spike, and leaf size. Earliness, althoughenhanced in tetraploids relative to diploids, was delayed in the triploids. Mean numbers of univalents, bivalents, and trivalents per microsporocyte were 2.65, 2.60, and 4.38, respectively. Only chains (93.5%), which formed V-shaped metaphase I (MI) configurations, frying pan (5.0%), and Y-shaped (1.5%) trivalent associations occurred. On the average, two reciprocal exchanges occurred per bivalent and trivalent. Trivalents corriented randomly at MI. At anaphase I, all sets of three homologues segreated randomly to the two poles, lagging univalents always divided equationally, and only meiocytes with such chromosomes formed micronuclei. The reasons for similarities and differences in meiotic behaviour of T. monococcum triploids with those of other species are discussed. Confirmation of the conclusions drawn with respect to the cytology of the triploids was obtained from similar cytological observations with primary single trisomics. These triploids produced euploids, primary single trisomics as well as some double and triple trisomics all of which differed phenotypically from diploids. Triticum monococcum, like most diploid species, is highly intolerant of aneuploidy. Possible reasons for the differences in levels of tolerance of aneuploidy in species like T. monococcum and those like Petunia hybrida, which are highly tolerant of aneuploidy, are discussed. Pollen fertility was high and seed fertility was very low. Reasons for the latter as well as the high fertility in species that are highly tolerant of aneuploidy and allotriploids are discussed.Key words: Triticum monococcum, autotriploid, trisomic, cytology, breeding behavior, fertility, morphology.
Hybrids were obtained at the rate of 0.8% of pollinated florets in crossing of Thinopyrum intermedium spp. trichophorum onto Secale cereale cv. Puma. The morphology of the hybrid was similar to the paternal parent. The mean chromosome pairing in the hybrid was 18.80 I + 3.71 II + 0.56 III. A bivalent frequency of 0.04 was attributed to intergenomic pairing, the remainder being autosyndetic.Key words: hybrids (intergeneric), Secale, Thinopyrum, chromosome pairing, autosyndetic pairing.
The meiotic behaviour of three hexaploid triticale × Triticum aestivum L. hybrids having different doses of ph1 mutant alleles was investigated using C-band staining of pollen mother cells at first metaphase. D-genome chromosomes that were clearly distinguished by their small size and unbanded response to Giemsa staining were increasingly promoted to pair with the homoeologous chromosomes of the A and B genomes in the absence of Ph1 genes. However, the wheat–rye associations were not enhanced when one or two ph1 alleles were present. The distribution of meiotic configurations was significantly different for each chromosome in the ph1/ph1 hybrid. Thus, 1B did not form multivalents in this hybrid, and the remaining identified chromosomes differed significantly in the level of involvement in tri-, quadri-, or quinque-valents. The hybrids should be of value for hexaploid and wheat breeding programs.Key words: Triticale, Triticum aestivum, C-banding, ph1 mutants.
Disomic substitution stocks in which chromosome 7D of Triticum aestivum cv. Canthatch was replaced by the corresponding homologous chromosome of each of four varieties of Triticum tauschii were crossed with 'Canthatch' to investigate the degree of differentiation for this chromosome between these two species. These disomic substitutions were also crossed with a 'Canthatch' plant double monotelosomic for chromosome 7D. Three double telotrisomics were produced, one of which had the complete 7D chromosome derived from 'Canthatch', one had 7D derived from the T. tauschii var. typica, and one had 7D from T. tauschii var. strangulata. Analysis of chromosome pairing demonstrated that chromosome 7D from var. typica formed fewer bound arms with 'Canthatch' 7D than did the corresponding chromosome from the other three tauschii varieties. The reduction in pairing between chromosomes 7D of var. typica and 'Canthatch' is greater than that previously reported from intraspecific D-genome chromosome pairing studies within T. aestivum. It is suggested that intraspecific divergence for at least chromosome 7D occurred between var. typica and these other three tauschii varieties before the synthesis of common hexaploid wheat.Key words: Triticum, aneuploidy, chromosome pairing, chromosome substitution.
Newly resynthesized AC amphihaploids, which were characterized by high meiotic pairing and multivalent formulation, after doubling of their chromosome number showed preferential pairing and bivalent formation in the resynthesized amphidiploid Brassica napus (AACC). However, univalents as well as multivalents were also formed indicating that their chromosome behaviour was not fully diploidized. Stabilization of chromosome pairing in newly resynthesized amphidiploids can be achieved through genetic control or structural modification of the homoeologous chromosomes. A comparison of the meiotic behaviour of spontaneous haploids of natural rapeseed with that of the newly synthesized AC amphihaploids provides some evidence that both processes may be involved in the regulation of chromosome pairing in Brassica.Key words: Brassica, amphihaploid, amphidiploid, meiosis, univalents, multivalents.
Frequencies of pollen mother cells with different numbers of bivalents significantly deviated from that expected with a binomial distribution in Capsicum annuum desynaptic mutants controlled by a recessive gene. This pattern varied in F 2 segregants.Key words: Capsicum, chili pepper, desynaptics, bivalent distribution.
Technical innovations in barley breeding have resulted in the ability to reduce generation times. Single seed descent and doubled haploidy have become practical propositions in barley improvement. These Fx samples are also powerful tools for genetical analyses and have been used in this paper together with conventional generations to investigate the linkage of genes controlling quantitative characters. Such investigations are of relevance to barley breeders since the detection of significant levels of repulsion linkages would indicate that the single seed descent (SSD) technique would be preferable to doubled-haploid (DH) methods. The present study indicated that estimates of D (the additive genetic variance) from DH and SSD sampled did not differ significantly. Thus linkage disequilibrium is not an important component of the genetic architecture of the five crosses investigated. Hence F1-derived doubled haploids or SSD will be equally effective in producing desirable recombinant inbred lines.Key words: Hordeum, doubled haploids, linkage disequilibrium.
Cytomorphology of solanum nigrum L. (2n = 6x = 72) and S. americanum Mill. (2n = 2x = 24) was studied. Crosses were made between these two species, but crosses were successful only when the higher ploidy form was used as the maternal parent. The F 1 hybrid was a tetraploid (2n = 4x = 48) and showed highly irregular meiosis. It did not set fruit either on selfing or on open pollination. A fertile octoploid branch spontaneously grew from the sterile hybrid. The octoploid had regular meiosis and produced several fruits with viable seeds. Pollen stainability was 82%. From cytological studies of the tetraploid and its amphiploid, it is concluded that hybridization and polyploidy have played a significant role in the origin and evolution of higher chromosomal forms of Solanum section Solanum (Maurella).Key words: Solanum, polyploid, sterility.
The extent of variation in the mitochondrial DNAs (mtDNAs), chloroplast DNAs (ctDNAs), and double-stranded RNAs (dsRNAs) of sunflower lines carrying fertile and male-sterility conferring cytoplasms was examined. To minimize nuclear gene effects, efforts were concentrated on two chromosomally isogenic lines, CM400 (fertile) and cmsCM400 (male sterile), which differ only in their cytogenes. A circular 1.45 kilobases (kb) plasmid DNA was found in the mitochondria of the four fertile lines examined, but was absent in the male-sterile line. Restriction enzyme analysis of mtDNAs of the fertile and male-sterile cytoplasms with BamHI, EcoRI, and HindIII revealed no fragment mobility differences between them other than those which could be ascribed to the 1.45-kb circle. Similar restriction analysis of ctDNA showed no differences between fertile and male-sterile cytoplasms. Both CM400 and cmsCM400 contain dsRNA molecules. The number and sizes of these dsRNAs varied from preparation to preparation in both lines. Species of 3.3 and 1.5 kb, which were the only dsRNAs common to all preparations from CM400, were also the only species common to all preparations from cmsCM400. Thus, no consistent differences between the fertile and male-sterile cytoplasms were seen in these molecules. The specific association of the 1.45-kb plasmid with fertile cytoplasm together with the absence of variation in ctDNA and dsRNA, suggests the involvement of mtDNA in sunflower cytoplasmic male sterility.Key words: DNA (mitochondrial), sterility (male), sterility (cytoplasmic), Helianthus, sunflower, DNA chloroplast.
A reciprocal translocation was found with a high frequency (average 44.44%) in four natural populations of Allium paniculatum L. (Liliaceae) from the South of Spain. The chromosomes involved are 1 and 7. The translocation is reciprocal and unequal. Chiasma frequency in the chromosomes not involved in the interchange is not affected, but chiasma frequency is decreased in the translocated chromosomes in the heterozygotes. As a satellite chromosome is involved in the interchange, the nucleolus is associated with the quadrivalent and the pattern of nucleolus formation is changed in heterozygotes, which have a lower mean number of nucleoli [Formula: see text] than homozygous standard individuals [Formula: see text]. The spontaneous mutation rate for interchanges during the early stages of microsporogenesis is high (μ = 1.08 × 10−2). No interchange homozygotes were found in any of the four populations analyzed. Furthermore, a comparative analysis of heterozygous (HT) and homozygous standard (HM) individuals in two populations demonstrated that homozygous standard plants show, on the whole, higher fitness than the heterozygotes. This can be attributed to a greater egg cell fertility and seed set. The possible causes of maintenance are discussed: the interchange in A. paniculatum is probably not maintained by overdominance for generative reproductive characters, nor by a mutation–selection equilibrium. One possibility, that heterozygotes have superior vegetative reproduction, still remains open for future investigation.Key words: Allium paniculatum, interchange polymorphism, fitness.
Cultural instability is a common phenomenon in the genus Fusarium. As with other species, Gibberella baccata (Fusarium lateritium) contains cultures that are less morphologically stable than others. When grown on certain media, such as potato dextrose agar, these cultures produce areas of aberrant growth (mutant patches) after 6 weeks. Single conidial cultures from these patches produce colonies different from the original culture and from each other in growth rate, colony color, aerial mycelium production, and pionnote production. Random ascospore analyses of crosses of the original morphological type to the mutant types showed there had been a one gene change in each case. Mutant patch forming and nonforming isolates of Gibberella baccata were crossed in all possible combinations, and the progeny were rated for ability to produce mutant patches. Broad sense heritability estimates for inheritance of mutant patch formation were high (60.0 to 95.9%), strongly indicating a genetic basis with a limited number of genes involved. The mutator activity of these genes appeared to be conditional and mutant patch development was dependent on the presence of some unknown factor in certain media rich in carbohydrates and other compounds.Key words: Gibberella baccata, Fusarium lateritium, colony morphology, spontaneous mutability, cultural instability.
