ASYNAPSIS IN PEPPER FOLLOWING X IRRADIATION OF THE POLLEN

Journal Article · Fri Mar 01 04:00:00 EST 1963 · Cytologia (Tokyo)

DOI:https://doi.org/10.1508/cytologia.28.102· OSTI ID:4123460

Morgan, Jr, D T

Failure of normal first division association of homologous chromosomes was observed in two pepper plants during cnological studies on the causes of sterility in the first generation following x irradiation of the pollen. Other than asynapsis, no chromosomal abnormality was evident in either plant. Irradiation of the pollen induced genotypic alterations affecting ths capacity of like chromosomes to remain associated through metaphase I in X/sub 1/ microsporocytes. A description is given of meiosis in the two sterile plandts, which differed primarily in the degree of asynapsis. Two autodiploid lines of pepper were used as female parents and crossed with x-rayed pollen of the variety Floral Gem. Autodiploid G188A, developed from a haploid of the variety Goliath, was crossed with pollen exposed to 500 r. An asymptic plant, designated V8, occurred among 11 male sterile individuals in the X/sub 1/. The other asymptic XX24 plant was detected among 105 male sterile plants from crosses of autodiploid P1A, derived from a haploid of Perfection Pimento, with pollen of Floral Gem irradiated at 2000 r. The pollen was irradiated at a rate of 170 r/min with a unit operated at 100 kvp, and at a target distance of 30 cm with 0.25 mm of aluminum filtration. The microspores produced by both plants were highly irregular. Micronuclsi were evident in many of the spores, and the occurrence of small, supernumerary spores was frequent. Pairs of large spores were found infrequently in both plants. No mitotic irregularities were observed in longitudinal and cross sections of root-tips. In XX24, metaphase I was characterized by varying numbers of scattered univalents, ordinarily remotely located from the clumped bivalents on the metaphass plate; andd two homologous chromosomes, comprising a bivalent at diakinesis and metaphase l, were associated terminally in the partially asynaptic cells. The average number of univalents per cell for the 30 asymptic microsporocyts of XX24 was 12.5. With the exception of a single cell having four bivalents and the remainder of the complement disassociated, the metaphase I configurations of V9 were characteristically clumped, so that a precise analysis of the numbers of bivalents and univalents was not possible. However, 1 to 16 univalents, ordinarily widely separated from the clumped chromosomes on the metaphase plates, were detected in 74% of the metaphase I configurations examined; an average of 5.7 univalents occurred in the cells showing asynapsis. Lagging chromosomes and unequal distribution of dyads were evident at anaphase I and telophase I in both plants. Because of the tangled nature of ths pachnene and earlier prophase I stages, comparison of the frequency of failure of pairing during early prophase I with the frequency of univalents at metaphase I could not be made, and it was not possible to determine whether the univalents detected at diakinesis and metaphase I were the result of initial failure of synapsis or desynapsis following pairing of homologous chromosomes. (BBB)

• Research Organization: Univ. of Maryland, College Park
• Sponsoring Organization: USDOE
• NSA Number: NSA-18-005040
• OSTI ID: 4123460
• Journal Information: Cytologia (Tokyo), Journal Name: Cytologia (Tokyo) Vol. Vol: 28
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALUMINUM
BIOLOGY AND MEDICINE
CHROMOSOMES
CYTOLOGY
DISTRIBUTION
ENERGY
FILTERS
FOOD
GENETICS
MICROSPORES
MITOSIS
PLANTS
POLLEN
QUANTITY RATIO
RADIATION DOSES
RADIATION EFFECTS
REPRODUCTION
ROOTS
SEX
X RADIATION