The meiotic behaviour and pollen fertility of Lambert sweet cherry (Prunus avium L.) and irradiation propagates of Lambert were investigated. Chromosome clumping, due to associations between the centromere region of non-homologous chromosomes, characterized early meiotic stages in Lambert. While the associations, which were evident as chromatic centers, complicated interpretation of pachynema, the pachytene morphology of the eight chromosomes was described. Except for small chromatic areas delimiting the centromere, all chromosomes were basically achromatic. Three chromosomes had an additional one or two chromatic regions, which in all cases were in the short arm. One chromosome, designated number 3, had a major heterozygous interstitial deletion in the short arm. Marked repulsion between the homologous chromosomes during diplonema resulted in a diffuse stage. The single pair of univalents, occasionally observed throughout meiosis and considered to be of desynaptic origin, were first detected in diplonema. Subsequent meiotic stages were usually normal, and the incidence of abnormal meiosis and tetrad stages containing micronuclei were estimated to be 9-62 per cent and 3.24 per cent respectively. Meiosis was characterized by synchronous division within the anther locules. Cytoplasmic connections were evident between neighbouring meiocytes during meiosis I, and cytomictic phenomena were observed occasionally. Abortion of 50 per cent of the developing microspores occurred prior to the first mitotic division of the spore nucleus, and was attributed to the heterozygous deletion in chromosome 3. Pollen abortion at anthesis was estimated to be about 42 per cent. Annual or regional effects on the incidence of abnormal meiosis or pollen abortion were not evident. Forcing of blossom buds at 15°C did not appear to affect meiotic behaviour. Twelve irradiation propagates of Lambert were investigated. Of these, seven had pollen fertility similar to the parental Lambert clone, and their meiotic behaviour also was comparable. The remaining five propagates had reduced pollen fertility. One propagate was found to have a greatly increased incidence of the single pair of univalents, as compared to parental Lambert; two propagates contained a reciprocal translocation; and two contained a paracentric inversion. The extent of pollen abortion was predictable from the meiotic behaviour in only one of the latter five propagates. Pollen studies revealed significant annual variation among the 12 irradiation propagates, some varying more than others. With one exception, forcing of blossom buds at 15°C did not appear to affect meiotic behaviour. / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 11, p. 2010-2011. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 32-35).

Variation in pollen viability and the meiotic behaviour of sweet cherry Prunus avium L. cv. Lambert were studied. Pollen viability was estimated using aceto-carmine. Three types of pollen grain were observed; large, triangular; small, aborted; and intermediate. Only the first type were considered to have been viable at time of blossom harvest. No significant differences were detected between trees, between branches, or within branches, except for a North and South branch of one tree. Highly significant differences were detected among blossoms in a bud. The relative frequency of abnormal pollen was 42.26 per cent. Premeiotic budwood was stored at -5°C. Subsequent forcing at 10°, 15°, 20°, and 25°C to bring the buds to meiosis, and staining in alcoholic hydrochloric acid-carmine, revealed meiotic abnormalities at all temperatures except 15°C. Early meiotic division stages of additional material forced at this temperature were synchronous, but asynchrony developed after first metaphase. The first meiotic division was characterized by the frequent presence of a single pair of univalents, which appeared to arise from desynapsis of a bivalent in diplotene. Meiotic abnormalities associated with the univalents were observed at later division stages. The metaphase-anaphase division was typified by sequential disjunction of the bivalents, characteristic for sweet cherry meiosis. The relative frequency of abnormal first meiotic divisions was 45.49 per cent. / Land and Food Systems, Faculty of / Graduate