Cytogenetic studies in the Wakegi, Allium fistulosum var. caespitosum


Karyological observation has disclosed that a local form of the Wakegi, A. fistulosunz var. caespitoszm, grown on the suburbs of Fukuoka City, is clearly heterozygous in its karyotype and is conspicuously irregular in the meiosis of its pollen mother-cells. Karyotype analysis of this Wakegi form have revealed that the following formula will be assigned to the plant :- K(2n) = 13V + J_1 + J_2 + J_3T. At meiotic metaphase-I in pollen mother-cells of this form, (8--2)Ⅱ+ (0--12)Ⅰ configuration was ascertained. In a small proportion of cells several pentavalent, tetravalent, and trivalent chromosomes were found. Thus the meiosis proceeded quite irregularly, and there usually appeared, in addition to some lagging univalents, the fragments and chromatid bridges, so that the formation of micronuclei was quite prevalent at the interkinesis and at the tetrad stage. Young pollen-grains of the Wakegi soon degenerated without any further division of their nuclei. Artificial pollinations with the pollengrains of A. fistulosusn have been tried without obtaining any viable seeds. The appearance of chromosome fragments was first observed at diplotene, and in the succeeding stages, there frequency appearance increased towards anaphase-I. Most of the fragments, showing continuous variation in their sizes and increasing in their number up to 3 per cell at metaphase-I, are considered to have been derived through the breakage-fusion mechanism operating between two related chromatids and only a few others, if any, may be ascribable to the crossing-over within the inverted sections. Observations in the Wakegi, carried out upon the morphological, ecological, and the karyological features, have made it quite conceivable that this plant form will be a certain product derived through the hybridization among A. fistulosum, A. cepa, and some other closely related species in the genus Allium

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Kyushu University Institutional Repository

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