| Microsporogenesis of two wheat cultivars with Aegilops
caudata, Aegilops ventricosa and Triticum timopheevi cytoplasms
N. JOUVE and Araceli FOMINAYA Departamento de Genetica, Escuela Tecnica Superior de Ingenieros Agronomos, Madrid, Spain KIHARA (1951) and FUKASAWA (1953) obtained the first alloplasmic wheats with the cytoplasms of alien species of the genera Triticum and Aegilops, and made preliminary observations on the male-sterility effects that are produced in some nucleo-cytoplasmic combinations. A great deal of information on cytological, morphological, physiological and biochemical effects of foreign cytoplasms has been subsequently accumulated. MAAN (1975) assumed the existence of 16 distinct cytoplasms among 18 species of the genera Triticum, Aegilops and Secale, on the basis of reduced male fertility and reduced plant vigor effects of alloplasmic forms of T. turgidum and T. aestivum. The present paper reports a comparative study on meiotic behavior, development of anthers and male fertility of two Spanish common wheat cultivars : "Aragon 03" and "Toroma" and its alloplasmic forms with the cytoplasms of Aegilops caudata, Ae. ventricosa and T. timopheevi obtained by substitution backcrosses. Meiotic behavior data are presented in Tables 1 and 2. The cytoplasms of Ae. caudata and T. timopheevi seem to induce more meiotic irregularities than the vantricosa cytoplasm. The forms of common wheat with this cytoplasm show higher number of PMC with 21 bivalents, and higher average number of chiasmata and of ring bivalents per PMC than with the other two cytoplasms. However, the average number of bivalents per PMC in all alloplasmic forms shows the same difference of one unit with respect to their analogues possessing their own cytoplasm. The statistical test comparing the distribution of univalents between alloplasmic and normal forms with the same nuclear genotype (intercytoplasmic comparation) shows significant differences at the 0.1% level in all cases (p1). The same test comparing forms with different nuclear genotype and the same cytoplasm (internuclear comparation) shows not significant differences at the 5% level (p2). The number of meiotic irregularities at anaphase I and tetrads shows a greater influence of the caudata and timopheevi cytoplasms, independently of the nuclear genotype. Other observations have been made on anthers development and male fertility with the following results : - pseudopistilloid anthers, in all plants possessing caudata cytoplasm, and occasionally in several flowers of the alloplasmic form of the variety "Toroma" with timopheevi cytoplasm, - abortion of several anthers, in all forms possessing caudata and timopheevi cytoplasm. This has not been observed in forms with ventricosa cytoplasm, - reduced number of PMC per anther, in all alloplasmic forms, the reduction being more intense in forms possessing caudata cytoplasm, - asynchrony in the cellular cycle of the PMCs of the same anther, only observed in alloplasmic forms with caudata and, timoheevi cytoplasms, - male-sterility, in forms possessing caudata and timopheevi cytoplasms, and male-fertility in the alloplasmic forms with ventricosa cytoplasm, The results presented here show a differential nucleo-cytoplasmic interactions that affect the meiotic behavior, development of anthers and male fertility in the material studied. |
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