Genetic Analyses of Male Fertility Restoration in Wheat: VI. A Defective-Seed Gene
Cytoplasmic male sterility (CMS) results from interactions between Triticum timopheevii Zhuk. cytoplasm and genes in the T. aestivum L. nucleus. Euploid plants with CMS genes are believed to exhibit no detrimental characteristics other than male sterility. However, seed viability and plant vigor are reduced in ‘Chris’ monosomics of Group 3. Similarly, a monosomic analysis of L222, an R-line, showed that it has a defective seed gene (dfs), but dfs could not be linked to a chromosome with the materials and methods used previously. Our objective was to determine the linkage of dfs to a chromosome. Therefore, we compared the number of disomics, monosomics, seed viability, and fertility in F1, F2, and F3 from crosses of L222 with euplasmic and MS Chris monosomics of Group 3. In general, monosomics with reduced seed set produced fewer disomics and more monosomics than the expected 25 and 75%, respectively. Other results indicated that (i) dfs is located on chromosome 3B of L222; (ii) dfs reversed meiotic drive against 21-chromosome heterosexual gametes or euploid zygotes in euplasmic monosomic 3B and all three CMS monosomics of Group 3; (iii) Rf was epistatic to dfs in L222 and fertile monosomics; (iv) compatibility between 21-chromosome heterosexual gametes or viability of selfed seed with euploid and nullisomic embryos was reduced; and (v) aneuploid gametes and/or zygotes with misdivision products functioned more often than euploid heterosexual gametes or euploid zygotes.
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