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FORMATION OF 2N MEGAGAMETOPHYTES IN DIPLOID TUBER‐BEARING SOLANUMS
Author(s) -
Stelly David M.,
Peloquin Stanley J.
Publication year - 1986
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1986.tb10876.x
Subject(s) - biology , ploidy , meiosis , megaspore , meiocyte , gametogenesis , clone (java method) , botany , genetics , gene , embryogenesis
Development of megaspores and megagametophytes was analyzed for several diploid potato clones ( Solanum spp.) that exhibit either high (HI) or low (LO) seed set when crossed as female with the tetraploid cultivated potato S. tuberosum Group Tuberosa. The objectives were to determine the relationship between ploidy and diam of nuclei and nucleoli, and to determine the mechanism(s) and frequencies of 2 n megagametophyte formation. Sizes of nuclei and nucleoli were found to depend on ploidy. For HI clones, the distributions of sizes indicated that doubling occurred during meiosis, and that 30 to 50% of the megaspores and megagametophytes were 2 n rather than haploid. Omission of the second meiotic division led to formation of second division restitution (SDR) 2 n megagametophytes. Only one HI clone had abnormal meiosis I, in addition to omission of meiosis II in some meiocytes; this clone seemed to produce not only 1 n and 2 n , but also 4 n megagametophytes. The results indicated that high crossability of the HI clones as female with tetraploids largely was due to formation of SDR 2 n megagametophytes, a finding strongly supporting the hypothesis that sexual polyploidization is the driving force behind polyploidization of Solanums. The results contribute to increasing evidence that meiotic mutants and abnormalities play an important role in angiosperm evolution.