Multivalent Association Research Articles

The identification of faba bean (Vicia faba L.) trisomics by translocation tester set

Five subtelocentric primary trisomics of Vicia faba L. were isolated from crosses between asynaptic mutants and normal plants or translocation tester stocks. The extra chromosome of each trisomic was identified cytologically by critical multivalent association at metaphase I of meiosis.

Cytogenetic studies of aneuploids in rapeseed. II. Morphology, fertility, and cytology of self-pollinated progenies of monosomic plants of Brassica napus L.

Cytogenic studies were conducted on self-pollinated progenies from two monosomic lines of Brassica napus to ascertain the mode of transmission of the monosomic chromosome. An approximately 1:1 ratio of disomic to monosomic plants was obtained. Only one nullisomic plant was found among a total of 71 plants analyzed. The 1:1 ratio and the anaphase I disjunction (19–18) suggest that the gametes (n) were twice as competitive or functional as their counterpart (n − 1). Since quadrivalents were observed in the disomic plants and only trivalents in the monosomics, the monosomic chromosomes were believed to be the ones that were involved in the formation of multivalents. The percentage of multivalent association in monosomic plants was almost double that in disomic plants. In the disomic plants, an average of 11.96% of pollen mother cells had one to two quadri-valents. The average frequency of trivalents in the monosomics was 23.63%. It was suggested that pairing of these homologs was genetically controlled with a dosage effect. The absence of one chromosome increased the frequency of multivalents. Key words: monosomic, Brassica, rapeseed, aneuploid.

Chromosome orientation and sterility in gamma-ray induced interchanges in chili pepper (Capsicum annuum L.).

After gamma irradiation (30 Kr) of seeds of Capsicum annuum cultivar cerasiformis (2n=24) two plants were recorded each carrying two interchanges. The nucleolus organiser chromosome appeared not to be involved. The interchange heterozygotes were weak and meiosis was irregular. At least one multivalent as-sociation per PMC was recorded. At metaphase I the predominant orientation was adjacent. The probable reasons for anaphase I and other meiotic irregularities and the incidence of high pollen sterility are discussed.

Preferential pairing in Dactylis glomerata?

Key words: Dactylis, preferential pairing, multivalents.

Meiotic studies of some South African cultivars of <i>Lantana camara</i> (Verbenaceae)

Lantana camara L. is a polyploid species with a basic chromosome number of 11 (x = l l ) . Chromosome association in 39 cultivars indicated the occurrence of univalents to heptavalents with bivalents predominating. Multivalent association analysis revealed the presence in South Africa of at least four different groups of L. camara at the diploid level. The potential for sexual reproduction must exist, at least at the diploid level, to account for differences in chromosomal behaviour that can only be attributed to hybridization. The possibility exists that the basic chromosome number may be lower than 11, or else postspeciation genomic evolution must have occurred. No cytogenetical correlation exists between the South African and Indian cultivars. The number of chiasmata per genome increases with an increase in the polyploid level. Most multivalents are of the chain type. Univalents during diakinesis are the result of asynapsis. Triploid and pentaploid plants display a markedly abnormal meiosis. L. camara is a segmental allopolyploid species.

Intergeneric hybridization between Agropyron tsukushiense and Hordeum bulbosum (4X).

In order to obtain polyhaploids in genus Agropyron by the bulbosum method, nine species were pollinated by Hordeum bulbosum (4x). Among progenies obtained by embryo culture, six plants did not show elimination of any chromosomes derived from H. bulbosum and were intergeneric hybrids between A. repens or three ecotypes of A. tsukushiense and H. bulbosum. Out of six hybrids obtained, two plants of A. tsukushiense EE-4 or ST-1× H. bulbosum (4x) (2n=34 or 2n=35) were examined morphologically and cytologically. These hybrids were shorter, but had numerous tillers. They were completely sterile. The spike morphology resembled female parent rather than intermediate between parents. Several characteristics of pollen parent were also observed in these hybrids. The average chromosome pairing per cell at MI of PMCS in A. tsukushiense EE-4 and ST-1×H. bulbosum hybrids was 2.8II+28.4I and 4.6II+25.8I, respectively. The loosely associated bivalent formation, a rare occurrence of cells with more than seven bivalents, and absence of multivalent association in these hybrids suggest a lack of segmental homology among chromosome complements of three genomes of A. tsukushiense and two of H. bulbosum.The production of these intergeneric hybrids suggests that genome balance hypothesis proposed in interspecific hybrids of Hordeum can not beapplicable to intergeneric hybrids between Agropyron and H. bulbosum.

Cholinergic sites in skeletal muscle: interaction with concanavalin A.

Abstract– The interaction of normal and denervated skeletal muscle cholinergic sites with the lectin concanavalin A and concanavalin A‐Sepharose are detailed. Concanavalin A blocks the binding of 125I‐α‐bungarotoxin to both the high and low affinity sets of cholinergic sites described previously. The characteristics of the block of 125I‐α‐bungarotoxin binding to the high affinity set (acetylcholine receptor) is not competitive. The data suggest that the concanavalin binds multivalently to the macro‐molecular complex containing the ACh receptor site and sterically prevents the α‐bungarotoxin binding. The interaction of both sets of cholinergic sites with concanavalin A‐Sepharose was also studied. The macromolecule(s) containing both the high and low affinity sets of sites bind to the concanavalin A‐Sepharose. The data indicate a multivalent association with the affinity resin. Following the affinity procedure, a partial purification in both sets of sites is effected. The equilibrium binding of 125I‐diiodo‐α‐bungarotoxin to the preparations from the affinity procedure (both normal and denervated muscle) was examined. The KD of the α‐bungarotoxin binding to the high affinity sets of sites (acetylcholine receptor) in both normal and denervated preparations changes from ∼10−9mol/l to ∼ 10−10 mol/l following purification. No change in the KD of the α‐bungarotoxin binding to the low affinity set of sites was observed following purification. The 125l‐α‐bungarotoxin binding to the partially purified acetylcholine receptor was blocked by unlabelled α‐bungarotoxin, concanavalin A, d‐tubocurarine and carbamylcholine.

Colchicine induced polyploidy in chickpeas (Cicer arietinum L.)

The most successful induction of tetraploidy was obtained with 2 hour treatment by 0.25% aqueous colchicine solution of 18-hour watersoaked desi chickpeas material. However, kabuli types needed only 1 hour treatment under similar conditions. Gigantism accompanied induction of polyploidy in desi as well as kabuli types but yield and fertility were greatly reduced. The meiotic abnormalities accompanying polyploidy were multivalent association of chromosomes followed by unequal disjunction, chromosome bridges, laggards etc. The percentage of stainable pollen, however, was at par between diploids and tetraploids. Gene control of percentage seed setting was observed in both levels of ploidy. A striking feature of the studies was the high seed setting percentage in 4n F 1 material resulting from diverse crosses, viz., desi×kabuli. A probable reduction in multivalent association coupled with yield increases in segregants from the later generation of tetraploids indicates the possibility of selection for higher yield and fertility from polyploids, particularly from some hybrid material.